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class="vector-toc-list"> </ul> </li> <li id="toc-Geometry" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Geometry"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.2</span> <span>Geometry</span> </div> </a> <ul id="toc-Geometry-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Curve_sight_distance" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Curve_sight_distance"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.3</span> <span>Curve sight distance</span> </div> </a> <ul id="toc-Curve_sight_distance-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Cross_section" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Cross_section"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Cross section</span> </div> </a> <button aria-controls="toc-Cross_section-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Cross section subsection</span> </button> <ul id="toc-Cross_section-sublist" class="vector-toc-list"> <li id="toc-Lane_width" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Lane_width"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.1</span> <span>Lane width</span> </div> </a> <ul id="toc-Lane_width-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Cross_slope" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Cross_slope"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.2</span> <span>Cross slope</span> </div> </a> <ul id="toc-Cross_slope-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Safety_effects_of_road_geometry" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Safety_effects_of_road_geometry"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Safety effects of road geometry</span> </div> </a> <button aria-controls="toc-Safety_effects_of_road_geometry-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Safety effects of road geometry subsection</span> </button> <ul id="toc-Safety_effects_of_road_geometry-sublist" class="vector-toc-list"> <li id="toc-Design_consistency" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Design_consistency"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1</span> <span>Design consistency</span> </div> </a> <ul id="toc-Design_consistency-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Safety_effects_of_alignment" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Safety_effects_of_alignment"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.2</span> <span>Safety effects of alignment</span> </div> </a> <ul id="toc-Safety_effects_of_alignment-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Safety_effects_of_cross_section" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Safety_effects_of_cross_section"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.3</span> <span>Safety effects of cross section</span> </div> </a> <ul id="toc-Safety_effects_of_cross_section-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Sight_distance" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Sight_distance"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>Sight distance</span> </div> </a> <button aria-controls="toc-Sight_distance-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Sight distance subsection</span> </button> <ul id="toc-Sight_distance-sublist" class="vector-toc-list"> <li id="toc-Stopping_sight_distance" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Stopping_sight_distance"> <div class="vector-toc-text"> <span class="vector-toc-numb">6.1</span> <span>Stopping sight distance</span> </div> </a> <ul id="toc-Stopping_sight_distance-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Decision_sight_distance" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Decision_sight_distance"> <div class="vector-toc-text"> <span class="vector-toc-numb">6.2</span> <span>Decision sight distance</span> </div> </a> <ul id="toc-Decision_sight_distance-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Intersection_sight_distance" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Intersection_sight_distance"> <div class="vector-toc-text"> <span class="vector-toc-numb">6.3</span> <span>Intersection sight distance</span> </div> </a> <ul id="toc-Intersection_sight_distance-sublist" class="vector-toc-list"> <li id="toc-Corner_sight_distance" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Corner_sight_distance"> <div class="vector-toc-text"> <span class="vector-toc-numb">6.3.1</span> <span>Corner sight distance</span> </div> </a> <ul id="toc-Corner_sight_distance-sublist" class="vector-toc-list"> <li id="toc-Uncontrolled_and_yield_controlled_intersections" class="vector-toc-list-item vector-toc-level-4"> <a class="vector-toc-link" href="#Uncontrolled_and_yield_controlled_intersections"> <div class="vector-toc-text"> <span class="vector-toc-numb">6.3.1.1</span> <span>Uncontrolled and yield controlled intersections</span> </div> </a> <ul id="toc-Uncontrolled_and_yield_controlled_intersections-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Two-way_stop_control" class="vector-toc-list-item vector-toc-level-4"> <a class="vector-toc-link" href="#Two-way_stop_control"> <div class="vector-toc-text"> <span class="vector-toc-numb">6.3.1.2</span> <span>Two-way stop control</span> </div> </a> <ul id="toc-Two-way_stop_control-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-All-way_stop_control_and_signalized_intersections" class="vector-toc-list-item vector-toc-level-4"> <a class="vector-toc-link" href="#All-way_stop_control_and_signalized_intersections"> <div class="vector-toc-text"> <span class="vector-toc-numb">6.3.1.3</span> <span>All-way stop control and signalized intersections</span> </div> </a> <ul id="toc-All-way_stop_control_and_signalized_intersections-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> </ul> </li> <li id="toc-Effects_of_insufficient_sight_distance" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Effects_of_insufficient_sight_distance"> <div class="vector-toc-text"> <span class="vector-toc-numb">6.4</span> <span>Effects of insufficient sight distance</span> </div> </a> <ul id="toc-Effects_of_insufficient_sight_distance-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>See also</span> </div> </a> <button aria-controls="toc-See_also-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle See also subsection</span> </button> <ul id="toc-See_also-sublist" class="vector-toc-list"> <li id="toc-Road_standards_setting_bodies" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Road_standards_setting_bodies"> <div class="vector-toc-text"> <span class="vector-toc-numb">7.1</span> <span>Road standards setting bodies</span> </div> </a> <ul id="toc-Road_standards_setting_bodies-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Notes" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Notes"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>Notes</span> </div> </a> <ul id="toc-Notes-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">9</span> <span>References</span> </div> </a> <button aria-controls="toc-References-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle References subsection</span> </button> <ul id="toc-References-sublist" class="vector-toc-list"> 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<div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><p class="mw-empty-elt"> </p> <div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Geometry of road design</div> <style data-mw-deduplicate="TemplateStyles:r1251242444">.mw-parser-output .ambox{border:1px solid #a2a9b1;border-left:10px solid #36c;background-color:#fbfbfb;box-sizing:border-box}.mw-parser-output .ambox+link+.ambox,.mw-parser-output .ambox+link+style+.ambox,.mw-parser-output .ambox+link+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+style+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+link+.ambox{margin-top:-1px}html body.mediawiki .mw-parser-output .ambox.mbox-small-left{margin:4px 1em 4px 0;overflow:hidden;width:238px;border-collapse:collapse;font-size:88%;line-height:1.25em}.mw-parser-output .ambox-speedy{border-left:10px solid #b32424;background-color:#fee7e6}.mw-parser-output .ambox-delete{border-left:10px solid #b32424}.mw-parser-output .ambox-content{border-left:10px solid #f28500}.mw-parser-output .ambox-style{border-left:10px solid #fc3}.mw-parser-output .ambox-move{border-left:10px solid #9932cc}.mw-parser-output .ambox-protection{border-left:10px solid #a2a9b1}.mw-parser-output .ambox .mbox-text{border:none;padding:0.25em 0.5em;width:100%}.mw-parser-output .ambox .mbox-image{border:none;padding:2px 0 2px 0.5em;text-align:center}.mw-parser-output .ambox .mbox-imageright{border:none;padding:2px 0.5em 2px 0;text-align:center}.mw-parser-output .ambox .mbox-empty-cell{border:none;padding:0;width:1px}.mw-parser-output .ambox .mbox-image-div{width:52px}@media(min-width:720px){.mw-parser-output .ambox{margin:0 10%}}@media print{body.ns-0 .mw-parser-output .ambox{display:none!important}}</style><table class="box-Globalize plainlinks metadata ambox ambox-content ambox-globalize" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><span><img alt="Globe icon." src="//upload.wikimedia.org/wikipedia/commons/thumb/b/bd/Ambox_globe_content.svg/48px-Ambox_globe_content.svg.png" decoding="async" width="48" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/bd/Ambox_globe_content.svg/73px-Ambox_globe_content.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/bd/Ambox_globe_content.svg/97px-Ambox_globe_content.svg.png 2x" data-file-width="350" data-file-height="290" /></span></span></div></td><td class="mbox-text"><div class="mbox-text-span">The examples and perspective in this article <b>deal primarily with the United States and do not represent a <a href="/wiki/Wikipedia:WikiProject_Countering_systemic_bias" title="Wikipedia:WikiProject Countering systemic bias">worldwide view</a> of the subject</b>.<span class="hide-when-compact"> You may <a class="external text" href="https://en.wikipedia.org/w/index.php?title=Geometric_design_of_roads&action=edit">improve this article</a>, discuss the issue on the <a href="/wiki/Talk:Geometric_design_of_roads" title="Talk:Geometric design of roads">talk page</a>, or <a href="/wiki/Wikipedia:Article_wizard" title="Wikipedia:Article wizard">create a new article</a>, as appropriate.</span> <span class="date-container"><i>(<span class="date">April 2009</span>)</i></span><span class="hide-when-compact"><i> (<small><a href="/wiki/Help:Maintenance_template_removal" title="Help:Maintenance template removal">Learn how and when to remove this message</a></small>)</i></span></div></td></tr></tbody></table> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Autovia_olivar.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/08/Autovia_olivar.jpg/230px-Autovia_olivar.jpg" decoding="async" width="230" height="153" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/08/Autovia_olivar.jpg/345px-Autovia_olivar.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/08/Autovia_olivar.jpg/460px-Autovia_olivar.jpg 2x" data-file-width="900" data-file-height="599" /></a><figcaption>The <i>Autovía del Olivar</i> which unites <a href="/wiki/%C3%9Abeda" title="Úbeda">Úbeda</a> with <a href="/wiki/Estepa" title="Estepa">Estepa</a> in <a href="/wiki/Andalucia" class="mw-redirect" title="Andalucia">Andalucia</a> in southern <a href="/wiki/Spain" title="Spain">Spain</a>. A geometric design saved on construction costs and improved visibility with the intention to reduce the likelihood of traffic incidents</figcaption></figure> <p>The <b>geometric design of roads</b> is the branch of <a href="/wiki/Highway_engineering" title="Highway engineering">highway engineering</a> concerned with the positioning of the physical elements of the roadway according to standards and constraints. The basic objectives in geometric design are to optimize efficiency and safety while minimizing cost and environmental damage. Geometric design also affects an emerging fifth objective called "livability", which is defined as designing roads to foster broader community goals, including providing access to employment, schools, businesses and residences, accommodate a range of travel modes such as walking, bicycling, transit, and automobiles, and minimizing fuel use, emissions and environmental damage.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p><p>Geometric roadway design can be broken into three main parts: alignment, profile, and cross-section. Combined, they provide a three-dimensional layout for a roadway. </p> <ul><li>The <b>alignment</b> is the route of the road, defined as a series of horizontal tangents and curves.</li></ul> <ul><li>The <b>profile</b> is the vertical aspect of the road, including crest and sag curves, and the straight grade lines connecting them.</li></ul> <ul><li>The <b>cross section</b> shows the position and number of vehicle and bicycle lanes and sidewalks, along with their cross slope or <a href="/wiki/Banked_turn" title="Banked turn">banking</a>. Cross sections also show drainage features, pavement structure and other items outside the category of geometric design.</li></ul> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Design_standards">Design standards</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=1" title="Edit section: Design standards"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Roads are designed in conjunction with design guidelines and standards. These are adopted by national and sub-national authorities (e.g., states, provinces, territories and municipalities). Design guidelines take into account <a href="/wiki/Speed" title="Speed">speed</a>, vehicle type, <a href="/wiki/Grade_(slope)" title="Grade (slope)">road grade</a> (slope), view obstructions, and <a href="/wiki/Stopping_distance" class="mw-redirect" title="Stopping distance">stopping distance</a>. With proper application of guidelines, along with good engineering judgement, an engineer can design a roadway that is comfortable, safe, and appealing to the eye.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (November 2013)">citation needed</span></a></i>]</sup> </p><p>The primary US guidance is found in <i>A Policy on Geometric Design of Highways and Streets</i> published by the <a href="/wiki/American_Association_of_State_Highway_and_Transportation_Officials" title="American Association of State Highway and Transportation Officials">American Association of State Highway and Transportation Officials</a> (AASHTO).<sup id="cite_ref-Garber_2-0" class="reference"><a href="#cite_note-Garber-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> Other standards include the Australian <a rel="nofollow" class="external text" href="http://www.austroads.com.au/interest_design.html">Guide to Road Design</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20111109001229/http://www.austroads.com.au/interest_design.html">Archived</a> 2011-11-09 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>, and the British <a rel="nofollow" class="external text" href="http://www.dft.gov.uk/ha/standards/dmrb/index.htm">Design Manual for Roads.</a> An open source version of the green book is published online by <a rel="nofollow" class="external text" href="http://www.csir.co.za/">The Council for Scientific and Industrial Research (CSIR)</a> office in <a href="/wiki/Zimbabwe" title="Zimbabwe">Zimbabwe</a>.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Profile">Profile</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=2" title="Edit section: Profile"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The profile of a road consists of road slopes, called grades, connected by <a href="/wiki/Parabola" title="Parabola">parabolic</a> vertical curves. Vertical curves are used to provide a gradual change from one road slope to another, so that vehicles may smoothly navigate grade changes as they travel. </p><p>Sag vertical curves are those that have a tangent slope at the end of the curve that is higher than that of the beginning of the curve. When driving on a road, a sag curve would appear as a valley, with the vehicle first going downhill before reaching the bottom of the curve and continuing uphill or level. </p><p>Crest vertical curves are those that have a tangent slope at the end of the curve that is lower than that of the beginning of the curve. When driving on a crest curve, the road appears as a hill, with the vehicle first going uphill before reaching the top of the curve and continuing downhill. </p><p>The profile also affects <a href="/wiki/Storm_sewer" class="mw-redirect" title="Storm sewer">road drainage</a>. </p> <div class="mw-heading mw-heading3"><h3 id="Symbols_used">Symbols used</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=3" title="Edit section: Symbols used"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1126788409">.mw-parser-output .plainlist ol,.mw-parser-output .plainlist ul{line-height:inherit;list-style:none;margin:0;padding:0}.mw-parser-output .plainlist ol li,.mw-parser-output .plainlist ul li{margin-bottom:0}</style><div class="plainlist"> <ul><li>BVC = beginning of vertical curve</li> <li>EVC = end of vertical curve</li> <li><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle g_{1}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>g</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>1</mn> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle g_{1}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3755e3e04ec295992b2b5331655ef83a500a05c1" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.163ex; height:2.009ex;" alt="{\displaystyle g_{1}}"></span> = initial roadway grade, expressed in percent</li> <li><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle g_{2}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>g</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle g_{2}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/f0261c34f2ad1e1b5317708b7f98ae13ee70ff1b" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.163ex; height:2.009ex;" alt="{\displaystyle g_{2}}"></span> = final roadway grade, expressed in percent</li> <li><i>A</i> = absolute value of the difference in grades (initial minus final), expressed in percent</li> <li><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle h_{1}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>h</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>1</mn> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle h_{1}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/14e8880a2e4243a2fe5157e574a0547ef3d5d373" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.393ex; height:2.509ex;" alt="{\displaystyle h_{1}}"></span> = height of eye above roadway, measured in meters or feet</li> <li><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle h_{2}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>h</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle h_{2}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/56d2d1733d09f02f33694f72b6da94681021e0f0" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.393ex; height:2.509ex;" alt="{\displaystyle h_{2}}"></span> = height of object above roadway, measured in meters or feet</li> <li><i>L</i> = curve length (along the <i>x</i>-axis)</li> <li>PVI = point of vertical interception (intersection of initial and final grades)</li> <li><i>S</i> = headlight sight distance</li> <li>Tangent elevation = elevation of a point along the initial tangent</li> <li><i>x</i> = horizontal distance from BVC</li> <li><i>Y</i> (offset) = vertical distance from the initial tangent to a point on the curve</li> <li><i>Y<span class="nowrap" style="padding-left:0.05em;">′</span></i> = curve elevation = tangent elevation — offset <sup id="cite_ref-Garber_2-1" class="reference"><a href="#cite_note-Garber-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup></li></ul> </div> <div class="mw-heading mw-heading3"><h3 id="Sag_curves">Sag curves</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=4" title="Edit section: Sag curves"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Sag vertical curves are curves which, when viewed from the side, are concave upwards. This includes vertical curves at valley bottoms, but it also includes locations where an uphill grade becomes steeper, or a downhill grade becomes less steep. </p><p>The most important design criterion for these curves is headlight sight distance.<sup id="cite_ref-Garber_2-2" class="reference"><a href="#cite_note-Garber-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> When a driver is driving on a sag curve at night, the sight distance is limited by the higher grade in front of the vehicle. This distance must be long enough that the driver can see any obstruction on the road and stop the vehicle within the headlight sight distance. The headlight sight distance (S) is determined by the angle of the headlight and angle of the tangent slope at the end of the curve. By first finding the headlight sight distance (S) and then solving for the curve length (L) in each of the equations below, the correct curve length can be determined. If the <span class="nowrap">S < L</span> curve length is greater than the headlight sight distance, then this number can be used. If it is smaller, this value cannot be used. Similarly, if the S>L curve length is smaller than the headlight sight distance, then this number can be used. If it is larger, this value cannot be used.<sup id="cite_ref-Homburger_4-0" class="reference"><a href="#cite_note-Homburger-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p> <table class="wikitable"> <tbody><tr> <th>Units </th> <th>Sight distance < curve length (<i>S</i> < <i>L</i>) </th> <th>Sight distance > curve length (<i>S</i> > <i>L</i>) </th></tr> <tr> <td>Metric<br />(<i>S</i> in metres) </td> <td><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle L={\frac {AS^{2}}{120+3.5S}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>L</mi> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mi>A</mi> <msup> <mi>S</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> </mrow> <mrow> <mn>120</mn> <mo>+</mo> <mn>3.5</mn> <mi>S</mi> </mrow> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle L={\frac {AS^{2}}{120+3.5S}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/adf59f24322f1c4eb489141efb2c66dcd639d489" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.171ex; width:16.316ex; height:6.009ex;" alt="{\displaystyle L={\frac {AS^{2}}{120+3.5S}}}"></span> </td> <td><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle L=2S-{\frac {120+3.5S}{A}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>L</mi> <mo>=</mo> <mn>2</mn> <mi>S</mi> <mo>−</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mn>120</mn> <mo>+</mo> <mn>3.5</mn> <mi>S</mi> </mrow> <mi>A</mi> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle L=2S-{\frac {120+3.5S}{A}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3b3f1320c9d0d1186bd013a2f2e188988d75f1e4" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.005ex; width:21.818ex; height:5.509ex;" alt="{\displaystyle L=2S-{\frac {120+3.5S}{A}}}"></span> </td></tr> <tr> <td>US customary<br />(<i>S</i> in feet) </td> <td><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle L={\frac {AS^{2}}{400+3.5S}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>L</mi> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mi>A</mi> <msup> <mi>S</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> </mrow> <mrow> <mn>400</mn> <mo>+</mo> <mn>3.5</mn> <mi>S</mi> </mrow> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle L={\frac {AS^{2}}{400+3.5S}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/8e136bcdce5c4a6f3c3d0ef336369d14e6bcb975" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.171ex; width:16.316ex; height:6.009ex;" alt="{\displaystyle L={\frac {AS^{2}}{400+3.5S}}}"></span> </td> <td><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle L=2S-{\frac {400+3.5S}{A}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>L</mi> <mo>=</mo> <mn>2</mn> <mi>S</mi> <mo>−</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mn>400</mn> <mo>+</mo> <mn>3.5</mn> <mi>S</mi> </mrow> <mi>A</mi> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle L=2S-{\frac {400+3.5S}{A}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/cd0571ca21ec6fb12f2e5e66e4541c4b6bbd95fa" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.005ex; width:21.818ex; height:5.509ex;" alt="{\displaystyle L=2S-{\frac {400+3.5S}{A}}}"></span> </td></tr></tbody></table> <p>These equations assume that the headlights are 600 millimetres (2.0 ft) above the ground, and the headlight beam diverges 1 degree above the longitudinal axis of the vehicle.<sup id="cite_ref-Green_Book_5-0" class="reference"><a href="#cite_note-Green_Book-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Crest_curves">Crest curves</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=5" title="Edit section: Crest curves"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Crest vertical curves are curves which, when viewed from the side, are convex upwards. This includes vertical curves at hill crests, but it also includes locations where an uphill grade becomes less steep, or a downhill grade becomes steeper. </p><p>The most important design criterion for these curves is <a href="/wiki/Stopping_sight_distance" title="Stopping sight distance">stopping sight distance</a>.<sup id="cite_ref-Garber_2-3" class="reference"><a href="#cite_note-Garber-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> This is the distance a driver can see over the crest of the curve. If the driver cannot see an obstruction in the roadway, such as a stalled vehicle or an animal, the driver may not be able to stop the vehicle in time to avoid a crash. The desired stopping sight distance (S) is determined by the speed of traffic on a road. By first finding the stopping sight distance (S) and then solving for the curve length (L) in each of the equations below, the correct curve length can be determined. The proper equation depends on whether the vertical curve is shorter or longer than the available sight distance. Normally, both equations are solved, then the results are compared to the curve length.<sup id="cite_ref-Homburger_4-1" class="reference"><a href="#cite_note-Homburger-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Green_Book_5-1" class="reference"><a href="#cite_note-Green_Book-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p><p><b>sight distance > curve length (<i>S</i> > <i>L</i>)</b> </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle L=2S-{\frac {200({\sqrt {h_{1}}}+{\sqrt {h_{2}}})^{2}}{A}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>L</mi> <mo>=</mo> <mn>2</mn> <mi>S</mi> <mo>−</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mn>200</mn> <mo stretchy="false">(</mo> <mrow class="MJX-TeXAtom-ORD"> <msqrt> <msub> <mi>h</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>1</mn> </mrow> </msub> </msqrt> </mrow> <mo>+</mo> <mrow class="MJX-TeXAtom-ORD"> <msqrt> <msub> <mi>h</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msub> </msqrt> </mrow> <msup> <mo stretchy="false">)</mo> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> </mrow> <mi>A</mi> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle L=2S-{\frac {200({\sqrt {h_{1}}}+{\sqrt {h_{2}}})^{2}}{A}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/5a8c72496e973e1b8006f19eb47040ee6730f9a7" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.005ex; width:29.645ex; height:6.343ex;" alt="{\displaystyle L=2S-{\frac {200({\sqrt {h_{1}}}+{\sqrt {h_{2}}})^{2}}{A}}}"></span></dd></dl> <p><b>sight distance < curve length (<i>S</i> < <i>L</i>)</b> </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle L={\frac {AS^{2}}{200({\sqrt {h_{1}}}+{\sqrt {h_{2}}})^{2}}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>L</mi> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mi>A</mi> <msup> <mi>S</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> </mrow> <mrow> <mn>200</mn> <mo stretchy="false">(</mo> <mrow class="MJX-TeXAtom-ORD"> <msqrt> <msub> <mi>h</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>1</mn> </mrow> </msub> </msqrt> </mrow> <mo>+</mo> <mrow class="MJX-TeXAtom-ORD"> <msqrt> <msub> <mi>h</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msub> </msqrt> </mrow> <msup> <mo stretchy="false">)</mo> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> </mrow> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle L={\frac {AS^{2}}{200({\sqrt {h_{1}}}+{\sqrt {h_{2}}})^{2}}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/af58074d5c74574d3ecfe2008564164d27a5aef4" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -3.171ex; width:24.143ex; height:7.009ex;" alt="{\displaystyle L={\frac {AS^{2}}{200({\sqrt {h_{1}}}+{\sqrt {h_{2}}})^{2}}}}"></span></dd></dl> <p>US standards specify the height of the driver's eye is defined as 1080 mm (3.5 ft) above the pavement, and the height of the object the driver needs to see as 600 mm (2.0 ft), which is equivalent to the taillight height of most passenger cars.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p><p>For bicycle facilities, the cyclist's eye height is assumed to be at 1.4 m (4.5 ft), and the object height is 0 inches, since a pavement defect can cause a cyclist to fall or lose control.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Alignment">Alignment</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=6" title="Edit section: Alignment"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Horizontal alignment in road design consists of straight sections of road, known as tangents, connected by <a href="/wiki/Circle" title="Circle">circular</a> horizontal curves.<sup id="cite_ref-Garber_2-4" class="reference"><a href="#cite_note-Garber-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> Circular curves are defined by radius (tightness) and deflection angle (extent). The design of a horizontal curve entails the determination of a minimum radius (based on speed limit), curve length, and objects obstructing the view of the driver.<sup id="cite_ref-Homburger_4-2" class="reference"><a href="#cite_note-Homburger-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p><p>Using AASHTO standards, an engineer works to design a road that is safe and comfortable. If a horizontal curve has a high speed and a small radius, an increased superelevation (bank) is needed in order to assure safety. If there is an object obstructing the view around a corner or curve, the engineer must work to ensure that drivers can see far enough to stop to avoid an accident or accelerate to join traffic. </p> <div class="mw-heading mw-heading3"><h3 id="Terminology">Terminology</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=7" title="Edit section: Terminology"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Horizontal_Curve.JPG" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/b/b9/Horizontal_Curve.JPG/220px-Horizontal_Curve.JPG" decoding="async" width="220" height="220" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/b/b9/Horizontal_Curve.JPG 1.5x" data-file-width="300" data-file-height="300" /></a><figcaption></figcaption></figure> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409"><div class="plainlist"> <ul><li>BC = beginning of curve</li> <li>EC = end of curve</li> <li>R = radius</li> <li>PC = point of curvature (point at which the curve begins)</li> <li>PT = point of tangent (point at which the curve ends)</li> <li>PI = point of intersection (point at which the two tangents intersect)</li> <li><i>T</i> = tangent length</li> <li><i>C</i> = long chord length (straight line between PC and PT)</li> <li><i>L</i> = curve length</li> <li><i>M</i> = middle ordinate, now known as HSO – horizontal sightline offset (distance from sight-obstructing object to the middle of the outside lane)</li> <li><i>E</i> = external distance</li> <li><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle f_{s}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>s</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle f_{s}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/34f933ad7a8dc310b3fa8e9f7b0b2558cba136db" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.143ex; height:2.509ex;" alt="{\displaystyle f_{s}}"></span> = coefficient of side friction</li> <li><i>u</i> = vehicle speed</li> <li><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \Delta }"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi mathvariant="normal">Δ</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \Delta }</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/32769037c408874e1890f77554c65f39c523ebe2" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.936ex; height:2.176ex;" alt="{\displaystyle \Delta }"></span> = deflection angle <sup id="cite_ref-Garber_2-5" class="reference"><a href="#cite_note-Garber-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup></li></ul> </div> <div class="mw-heading mw-heading3"><h3 id="Geometry">Geometry</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=8" title="Edit section: Geometry"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle T=R\tan \left({\frac {\Delta }{2}}\right)}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>T</mi> <mo>=</mo> <mi>R</mi> <mi>tan</mi> <mo>⁡</mo> <mrow> <mo>(</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mi mathvariant="normal">Δ</mi> <mn>2</mn> </mfrac> </mrow> <mo>)</mo> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle T=R\tan \left({\frac {\Delta }{2}}\right)}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/f2cb0b5623add778e7f035113ab59e9f204df8ca" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:16.439ex; height:6.176ex;" alt="{\displaystyle T=R\tan \left({\frac {\Delta }{2}}\right)}"></span></dd></dl> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle C=2R\sin \left({\frac {\Delta }{2}}\right)}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>C</mi> <mo>=</mo> <mn>2</mn> <mi>R</mi> <mi>sin</mi> <mo>⁡</mo> <mrow> <mo>(</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mi mathvariant="normal">Δ</mi> <mn>2</mn> </mfrac> </mrow> <mo>)</mo> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle C=2R\sin \left({\frac {\Delta }{2}}\right)}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7aa46fd3a1a5fd3f727bcf9f4a908e453a8fc5c3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:17.227ex; height:6.176ex;" alt="{\displaystyle C=2R\sin \left({\frac {\Delta }{2}}\right)}"></span></dd></dl> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle L=R\pi {\frac {\Delta }{180}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>L</mi> <mo>=</mo> <mi>R</mi> <mi>π</mi> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mi mathvariant="normal">Δ</mi> <mn>180</mn> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle L=R\pi {\frac {\Delta }{180}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ebdb8d9a326dc6ca992dce0af080e4d3ecd31ac8" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:12.101ex; height:5.343ex;" alt="{\displaystyle L=R\pi {\frac {\Delta }{180}}}"></span> <sup id="cite_ref-Garber_2-6" class="reference"><a href="#cite_note-Garber-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup></dd></dl> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle M=R\left(1-\cos \left({\frac {\Delta }{2}}\right)\right)}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>M</mi> <mo>=</mo> <mi>R</mi> <mrow> <mo>(</mo> <mrow> <mn>1</mn> <mo>−</mo> <mi>cos</mi> <mo>⁡</mo> <mrow> <mo>(</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mi mathvariant="normal">Δ</mi> <mn>2</mn> </mfrac> </mrow> <mo>)</mo> </mrow> </mrow> <mo>)</mo> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle M=R\left(1-\cos \left({\frac {\Delta }{2}}\right)\right)}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/1202049db1b20c3b36a3ec9aa4e8e99c7a88f299" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:24.42ex; height:6.176ex;" alt="{\displaystyle M=R\left(1-\cos \left({\frac {\Delta }{2}}\right)\right)}"></span></dd></dl> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle E=R\left({\frac {1}{\cos \left({\frac {\Delta }{2}}\right)}}-1\right)}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>E</mi> <mo>=</mo> <mi>R</mi> <mrow> <mo>(</mo> <mrow> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mn>1</mn> <mrow> <mi>cos</mi> <mo>⁡</mo> <mrow> <mo>(</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mi mathvariant="normal">Δ</mi> <mn>2</mn> </mfrac> </mrow> <mo>)</mo> </mrow> </mrow> </mfrac> </mrow> <mo>−</mo> <mn>1</mn> </mrow> <mo>)</mo> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle E=R\left({\frac {1}{\cos \left({\frac {\Delta }{2}}\right)}}-1\right)}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ca496afb27fd51eb8ab20b94db8a01012bcf423e" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -4.505ex; width:24.023ex; height:10.176ex;" alt="{\displaystyle E=R\left({\frac {1}{\cos \left({\frac {\Delta }{2}}\right)}}-1\right)}"></span></dd></dl> <p>The quantity <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle 1-\cos \theta }"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mn>1</mn> <mo>−</mo> <mi>cos</mi> <mo>⁡</mo> <mi>θ</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle 1-\cos \theta }</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3ac74155023b33a315077117b39b787c47a627e7" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.505ex; width:8.592ex; height:2.343ex;" alt="{\displaystyle 1-\cos \theta }"></span> is the <a href="/wiki/Versine" title="Versine">versine</a> and <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle 1/\!\cos \theta -1}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mn>1</mn> <mrow class="MJX-TeXAtom-ORD"> <mo>/</mo> </mrow> <mspace width="negativethinmathspace" /> <mi>cos</mi> <mo>⁡</mo> <mi>θ</mi> <mo>−</mo> <mn>1</mn> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle 1/\!\cos \theta -1}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/eea0aa60fe47ee88d664664dae5d295977d2335a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:10.916ex; height:2.843ex;" alt="{\displaystyle 1/\!\cos \theta -1}"></span> is the <a href="/wiki/Exsecant" title="Exsecant">exsecant</a>. </p> <div class="mw-heading mw-heading3"><h3 id="Curve_sight_distance">Curve sight distance</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=9" title="Edit section: Curve sight distance"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle M=R\left(1-\cos \left({\frac {28.65{\text{?}}}{R}}\right)\right)}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>M</mi> <mo>=</mo> <mi>R</mi> <mrow> <mo>(</mo> <mrow> <mn>1</mn> <mo>−</mo> <mi>cos</mi> <mo>⁡</mo> <mrow> <mo>(</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mn>28.65</mn> <mrow class="MJX-TeXAtom-ORD"> <mtext>?</mtext> </mrow> </mrow> <mi>R</mi> </mfrac> </mrow> <mo>)</mo> </mrow> </mrow> <mo>)</mo> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle M=R\left(1-\cos \left({\frac {28.65{\text{?}}}{R}}\right)\right)}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/41f14df78d6ee78be8fe63ee6635077afddb9eb0" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:28.878ex; height:6.176ex;" alt="{\displaystyle M=R\left(1-\cos \left({\frac {28.65{\text{?}}}{R}}\right)\right)}"></span></dd></dl> <div class="mw-heading mw-heading2"><h2 id="Cross_section">Cross section</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=10" title="Edit section: Cross section"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Typical_roadway_cross-section_sheet_in_transportation_engineering.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/a/a1/Typical_roadway_cross-section_sheet_in_transportation_engineering.jpg/220px-Typical_roadway_cross-section_sheet_in_transportation_engineering.jpg" decoding="async" width="220" height="142" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/a/a1/Typical_roadway_cross-section_sheet_in_transportation_engineering.jpg/330px-Typical_roadway_cross-section_sheet_in_transportation_engineering.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/a/a1/Typical_roadway_cross-section_sheet_in_transportation_engineering.jpg/440px-Typical_roadway_cross-section_sheet_in_transportation_engineering.jpg 2x" data-file-width="10200" data-file-height="6600" /></a><figcaption>A <a href="/wiki/Cross_section_(geometry)" title="Cross section (geometry)">typical cross-section drawing</a> of a roadway.</figcaption></figure> <p>The cross section of a roadway can be considered a representation of what one would see if an excavator dug a trench across a roadway, showing the number of lanes, their widths and cross slopes, as well as the presence or absence of shoulders, curbs, sidewalks, drains, ditches, and other roadway features. The cross-sectional shape of a road surface, in particular in connection to its role in managing <a href="/wiki/Runoff_(water)" class="mw-redirect" title="Runoff (water)">runoff</a>, is called "<style data-mw-deduplicate="TemplateStyles:r1238216509">.mw-parser-output .vanchor>:target~.vanchor-text{background-color:#b1d2ff}@media screen{html.skin-theme-clientpref-night .mw-parser-output .vanchor>:target~.vanchor-text{background-color:#0f4dc9}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .vanchor>:target~.vanchor-text{background-color:#0f4dc9}}</style><span class="vanchor"><span id="crown"></span><span class="vanchor-text">crown</span></span>". </p> <div class="mw-heading mw-heading3"><h3 id="Lane_width">Lane width</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=11" title="Edit section: Lane width"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The selection of lane width affects the safety, maximum capacity, and cost, of a highway. </p><p>Safety is best at a width of 3.0 to 3.1 metres (9.8 to 10.2 ft) in urban settings, where both narrow (less than 2.8 metres (9 ft 2 in)) and wide (over 3.1 metres (10 ft)) lanes have higher crash risks. Lanes wider than 3.3~3.4m (10.8-11.2 ft)) are also associated with 33% higher impact speeds and more severe collisions, as well as higher crash rates.<sup id="cite_ref-Dewan_Masud_Karim_8-0" class="reference"><a href="#cite_note-Dewan_Masud_Karim-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p><p>Carrying capacity is also optimal at a width of 3.0 to 3.1 metres (9.8 to 10.2 ft), both for motor traffic and for bicycles.<sup id="cite_ref-Dewan_Masud_Karim_8-1" class="reference"><a href="#cite_note-Dewan_Masud_Karim-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> Throughput is maximal at 18 miles per hour (29 km/h); as lane width decreases to 3.0 to 3.1 metres (9.8 to 10.2 ft), traffic speed diminishes, and so does the interval between vehicles.<sup id="cite_ref-Dewan_Masud_Karim_8-2" class="reference"><a href="#cite_note-Dewan_Masud_Karim-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> </p><p>Pedestrian volume also increases as lanes narrow, and intersections with narrower lanes provide higher capacity for bicycles.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p><p>Narrow lanes typically cost less to build and maintain.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> They lessen the time needed to walk across, and reduce stormwater <a href="/wiki/Surface_runoff" title="Surface runoff">runoff</a>. </p><p>Lane widths in Northern America are typically greater than optimum, ranging from 3 metres (9.8 ft) to 3.6 metres (12 ft). Wider lanes and shoulders are usually used on roads with higher speed and higher volume traffic, and with significant numbers of trucks and other large vehicles. </p> <div class="mw-heading mw-heading3"><h3 id="Cross_slope">Cross slope</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=12" title="Edit section: Cross slope"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">See also: <a href="/wiki/Cant_(road/rail)" class="mw-redirect" title="Cant (road/rail)">Cant (road/rail)</a></div> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Ellerker_Ave,_Doncaster_-_from_the_ground.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/a/a9/Ellerker_Ave%2C_Doncaster_-_from_the_ground.jpg/250px-Ellerker_Ave%2C_Doncaster_-_from_the_ground.jpg" decoding="async" width="250" height="188" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/a/a9/Ellerker_Ave%2C_Doncaster_-_from_the_ground.jpg/375px-Ellerker_Ave%2C_Doncaster_-_from_the_ground.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/a/a9/Ellerker_Ave%2C_Doncaster_-_from_the_ground.jpg/500px-Ellerker_Ave%2C_Doncaster_-_from_the_ground.jpg 2x" data-file-width="3264" data-file-height="2448" /></a><figcaption>Steeper cants or cambers are common on residential streets, allowing water to drain into the gutter</figcaption></figure> <p>Cross slope describes the slope of a roadway perpendicular to the centerline. If a road were completely level, water would drain off it very slowly. This would create problems with <a href="/wiki/Aquaplaning" title="Aquaplaning">hydroplaning</a>, and ice accumulation in cold weather. </p><p>In tangent (straight) sections, the road surface cross slope is commonly 1—2% to enable water to drain from the roadway. Cross slopes of this size, especially when applied in both directions of travel with a crown point along the centerline of a roadway are commonly referred to as "normal crown" and are generally unnoticeable to traveling motorists. </p><p>In curved sections, the outside edge of the road is <i>superelevated</i> above the centerline. Since the road is sloped down toward the inside of the curve, gravity draws the vehicle toward the inside of the curve. This causes a greater proportion of <a href="/wiki/Centripetal_force" title="Centripetal force">centripetal force</a> to supplant the tyre friction that would otherwise be needed to negotiate the curve. </p><p>Superelevation slopes of 4 to 10% are applied in order to aid motorists in safely traversing these sections, while maintaining vehicle speed throughout the length of the curve. An upper bound of 12% was chosen to meet the demands of construction and maintenance practices, as well as to limit the difficulty of driving a steeply cross-sloped curve at low speeds. In areas that receive significant snow and ice, most agencies use a maximum cross slope of 6 to 8%. While steeper cross slope makes it difficult to traverse the slope at low speed when the surface is icy, and when accelerating from zero with warm tyres on the ice, lower cross slope increases the risk of loss-of-control at high speeds, especially when the surface is icy. Since the consequence of high speed skidding is much worse than that of sliding inward at a low speed, sharp curves have the benefit of greater net safety when designers select up to 8% superelevation, instead of 4%.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (December 2012)">citation needed</span></a></i>]</sup> A lower slope of 4% is commonly used on urban roadways where speeds are lower, and where a steeper slope would raise the outside road edge above adjacent terrain.<sup id="cite_ref-Green_Book_5-2" class="reference"><a href="#cite_note-Green_Book-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p><p>The equation for the desired radius of a curve, shown below, takes into account the factors of speed and superelevation (e). This equation can be algebraically rearranged to obtain desired rate of superelevation, using input of the roadway's designated speed and curve radius. </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle R={\frac {u^{2}}{15(e+f_{s})}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>R</mi> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <msup> <mi>u</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> <mrow> <mn>15</mn> <mo stretchy="false">(</mo> <mi>e</mi> <mo>+</mo> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>s</mi> </mrow> </msub> <mo stretchy="false">)</mo> </mrow> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle R={\frac {u^{2}}{15(e+f_{s})}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/b62428fac31a89427106a41c766dd9f8bf3c350f" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.671ex; width:15.899ex; height:6.509ex;" alt="{\displaystyle R={\frac {u^{2}}{15(e+f_{s})}}}"></span></dd></dl> <p>The American Association of State Highway and Transportation officials (AASHTO) provides a table from which desired superelevation rates can be interpolated, based on the designated speed and radius of a curved section of roadway. This table can also be found in many state roadway design guides and manuals in the U.S. </p><p>Recent research has shown that, considering rollover risk for heavy vehicles (semitrailers & buses), which have a relatively high centre-of-gravity, the above equation yields cross slope values which are too low.<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Safety_effects_of_road_geometry">Safety effects of road geometry</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=13" title="Edit section: Safety effects of road geometry"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The geometry of a road influences its safety performance. While studies of contributing factors to road accidents show that human factors predominate, roadway factors are the second most common category, with vehicle factors last. </p> <div class="mw-heading mw-heading3"><h3 id="Design_consistency">Design consistency</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=14" title="Edit section: Design consistency"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Collisions tend to be more frequent in locations where a sudden change in road character violates the driver's expectations. A common example is a sharp curve at the end of a long tangent section of road. The concept of <i>design consistency</i> addresses this by comparing adjacent road segments and identifying sites with changes the driver might find sudden or unexpected. Locations with large changes in the predicted operating speed are likely to benefit from additional design effort. A horizontal curve with a significantly smaller radius than those before it may need enhanced curve signs.<sup id="cite_ref-IHSDM_DCM_13-0" class="reference"><a href="#cite_note-IHSDM_DCM-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> This is an improvement on the concept of <a href="/wiki/Design_speed" title="Design speed">design speed</a>, which only sets a lower limit for geometric design. In the example given above, a long tangent followed by a sharp curve would be acceptable if a 30 mph design speed was chosen. Design consistency analysis would flag the decrease in operating speed at the curve. </p> <div class="mw-heading mw-heading3"><h3 id="Safety_effects_of_alignment">Safety effects of alignment</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=15" title="Edit section: Safety effects of alignment"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The safety of a horizontal curve is affected by the length of the curve, the curve radius, whether spiral transition curves are used, and the superelevation of the roadway. For a given curve deflection, crashes are more likely on curves with a smaller radius. Spiral transitions decrease crashes, and insufficient superelevation increases crashes. </p><p>A safety performance function to model curve performance on two-lane roads is:<sup id="cite_ref-2-lane_14-0" class="reference"><a href="#cite_note-2-lane-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle AMF={\frac {1.55L_{c}+{\frac {80.2}{R}}-0.012S}{1.55L_{c}}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>A</mi> <mi>M</mi> <mi>F</mi> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mn>1.55</mn> <msub> <mi>L</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>c</mi> </mrow> </msub> <mo>+</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mn>80.2</mn> <mi>R</mi> </mfrac> </mrow> <mo>−</mo> <mn>0.012</mn> <mi>S</mi> </mrow> <mrow> <mn>1.55</mn> <msub> <mi>L</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>c</mi> </mrow> </msub> </mrow> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle AMF={\frac {1.55L_{c}+{\frac {80.2}{R}}-0.012S}{1.55L_{c}}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/a12d5e020e1e23286abcbc7d68d24d6784f3fb69" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.338ex; width:32.758ex; height:7.009ex;" alt="{\displaystyle AMF={\frac {1.55L_{c}+{\frac {80.2}{R}}-0.012S}{1.55L_{c}}}}"></span></dd></dl> <p>where </p> <dl><dd>AMF = Accident modification factor, a multiplier that describes how many more crashes are likely to occur on the curve compared to a straight road</dd> <dd><i>L</i><sub>c</sub> = Length of the horizontal curve in miles.</dd> <dd><i>R</i> = Radius of the curve in feet.</dd> <dd><i>S</i> = 1 if spiral transition curves are present <dl><dd>= 0 if spiral transition curves are absent</dd></dl></dd></dl> <div class="mw-heading mw-heading3"><h3 id="Safety_effects_of_cross_section">Safety effects of cross section</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=16" title="Edit section: Safety effects of cross section"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Cross slope and lane width affect the safety performance of a road. </p><p>Certain types of crashes, termed "lane departure crashes", are more likely on roads with narrow lanes. These include <a href="/wiki/Run-off-road_collision" class="mw-redirect" title="Run-off-road collision">run-off-road collisions</a>, sideswipes, and <a href="/wiki/Head-on_collision" title="Head-on collision">head-on collisions</a>. For two-lane rural roads carrying over 2000 vehicles per day, the expected increase in crashes is: </p> <table class="wikitable"> <tbody><tr> <th>Lane width</th> <th>Expected increase in crashes </th></tr> <tr> <td>12 feet (3.7 m)</td> <td>0% </td></tr> <tr> <td>11 feet (3.4 m)</td> <td>5% </td></tr> <tr> <td>10 feet (3.0 m)</td> <td>30% </td></tr> <tr> <td>9 feet (2.7 m)</td> <td>50% </td></tr></tbody></table> <p>The effect of lane width is reduced on urban and suburban roads<sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> and low volume roads.<sup id="cite_ref-2-lane_14-1" class="reference"><a href="#cite_note-2-lane-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> </p><p>Insufficient superelevation will also result in an increase in crash rate. The expected increase is shown below:<sup id="cite_ref-2-lane_14-2" class="reference"><a href="#cite_note-2-lane-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> </p> <table class="wikitable"> <tbody><tr> <th rowspan="2">Superelevation deficiency</th> <th colspan="2">Expected increase in crashes<sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> </th></tr> <tr> <th>Cars</th> <th>Heavy trucks </th></tr> <tr> <td><0.01</td> <td>0%</td> <td>< 5% </td></tr> <tr> <td>0.02</td> <td>6%</td> <td>10% </td></tr> <tr> <td>0.03</td> <td>9%</td> <td>15% </td></tr> <tr> <td>0.04</td> <td>12%</td> <td>20% </td></tr> <tr> <td>0.05</td> <td>15%</td> <td>25% </td></tr></tbody></table> <div class="mw-heading mw-heading2"><h2 id="Sight_distance">Sight distance</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=17" title="Edit section: Sight distance"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="thumb tright" style=""><div class="thumbinner" style="width:-moz-fit-content; width:fit-content;"><div class="thumbimage noresize" style="width:auto;"> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1251242444"><table class="box-Notice plainlinks metadata ambox ambox-notice" role="presentation" style="width:100%;margin:0;"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/1/1d/Information_icon4.svg/40px-Information_icon4.svg.png" decoding="async" width="40" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/1/1d/Information_icon4.svg/60px-Information_icon4.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/1/1d/Information_icon4.svg/80px-Information_icon4.svg.png 2x" data-file-width="620" data-file-height="620" /></span></span></div></td><td class="mbox-text" style="text-align: left;"><div class="mbox-text-span">Graphs are unavailable due to technical issues. There is more info on <a href="https://phabricator.wikimedia.org/T334940" class="extiw" title="phab:T334940">Phabricator</a> and on <a href="https://www.mediawiki.org/wiki/Extension:Graph/Plans" class="extiw" title="mw:Extension:Graph/Plans">MediaWiki.org</a>.</div></td></tr></tbody></table></div><div class="thumbcaption"><div class="center" style="width:auto; margin-left:auto; margin-right:auto;"><b>Sight Distance, by Type</b><sup id="cite_ref-CA_HDM_17-0" class="reference"><a href="#cite_note-CA_HDM-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup></div></div></div></div> <p>Road geometry affects the sight distance available to the driver. Sight distance, in the context of road design, is defined as "the length of roadway ahead visible to the driver".[1] Sight distance is how far a road user (usually a vehicle driver) can see before the line of sight is blocked by a hill crest, or an obstacle on the inside of a horizontal curve or intersection. Insufficient sight distance can adversely affect the safety or operations of a roadway or intersection. </p><p>The sight distance needed for a given situation is the distance travelled during the two phases of a driving maneuver: perception-reaction time (PRT), and maneuver time (MT). Perception-reaction time is the time it takes for a road user to realize that a reaction is needed to a road condition, decided what maneuver is appropriate, and start the maneuver. Maneuver time is the time it takes to complete the maneuver. The distance driven during perception-reaction time and maneuver time is the sight distance needed. </p><p>During highway design and traffic safety investigations, highway engineers compare the available sight distance to how much sight distance is needed for the situation. Depending on the situation, one of three types of sight distances will be used: </p> <div class="mw-heading mw-heading3"><h3 id="Stopping_sight_distance">Stopping sight distance</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=18" title="Edit section: Stopping sight distance"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Stopping_sight_distance" title="Stopping sight distance">Stopping sight distance</a></div> <p>Stopping sight distance is the distance traveled during perception-reaction time (while the vehicle driver perceives a situation requiring a stop, realizes that stopping is necessary, and applies the brake), and maneuver time (while the driver decelerates and comes to a stop). Actual stopping distances are also affected by road conditions, the mass of the car, the incline of the road, and numerous other factors. For design, a conservative distance is needed to allow a vehicle traveling at design speed to stop before reaching a stationary object in its path. Typically the design sight distance allows a below-average driver to stop in time to avoid a collision.<sup id="cite_ref-18" class="reference"><a href="#cite_note-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> <sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Decision_sight_distance">Decision sight distance</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=19" title="Edit section: Decision sight distance"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Decision sight distance is used when drivers must make decisions more complex than stop or don't stop. It is longer than stopping sight distance to allow for the distance traveled while making a more complex decision. The decision sight distance is "distance required for a driver to detect an unexpected or otherwise difficult-to-perceive information source or hazard in a roadway environment that may be visually cluttered, recognize the hazard or its threat potential, select an appropriate speed and path, and initiate and complete the required maneuver safely and efficiently".<sup id="cite_ref-AASHTO_20-0" class="reference"><a href="#cite_note-AASHTO-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> Ideally, roads are designed for the decision sight distance, using 6 to 10 seconds for perception-reaction time and 4 to 5 seconds to perform the right maneuver. </p> <div class="mw-heading mw-heading3"><h3 id="Intersection_sight_distance">Intersection sight distance</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=20" title="Edit section: Intersection sight distance"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Intersection sight distance is the sight distance needed to safely proceed through an intersection. The distance needed depends on the type of traffic control at the intersection (uncontrolled, yield sign, stop sign or signal), and the maneuver (left turn, right turn, or proceeding straight). <a href="/wiki/All-way_stop" title="All-way stop">All-way stop</a> intersections need the least, and uncontrolled intersections require the most. Intersection sight distance is a key factor in whether no control or yield control can be safely used, or more restrictive control in needed.<sup id="cite_ref-AASHTO_ISD_21-0" class="reference"><a href="#cite_note-AASHTO_ISD-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading4"><h4 id="Corner_sight_distance">Corner sight distance</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=21" title="Edit section: Corner sight distance"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Corner sight distance (CSD) is the road alignment specification which provides a substantially clear line of sight so that the driver of a vehicle, bicyclist or pedestrian waiting at the crossroad may safely anticipate the driver of an approaching vehicle. Corner sight provides an adequate time for the waiting user to either cross all lanes of through traffic, cross the near lanes and turn left, or turn right, without requiring through traffic to radically alter their speed. </p> <div class="mw-heading mw-heading5"><h5 id="Uncontrolled_and_yield_controlled_intersections">Uncontrolled and yield controlled intersections</h5><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=22" title="Edit section: Uncontrolled and yield controlled intersections"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Uncontrolled and yield (give way) controlled intersections require large sight triangles clear of obstructions in order to operate safely. At uncontrolled intersections, the basic right-of-way rules apply (either yield to the vehicle on the right, or the <a href="/wiki/Boulevard_rule" title="Boulevard rule">boulevard rule</a>, depending on the location). Vehicle drivers must be able to see traffic approaching on the intersecting road at a point where they can adjust their speed, or stop if need be, to yield to the other traffic before reaching the intersection. It isn't the only criterion for allowing these types of intersection control. Changing an intersection to stop control is a common response to poor safety performance. </p> <div class="mw-heading mw-heading5"><h5 id="Two-way_stop_control">Two-way stop control</h5><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=23" title="Edit section: Two-way stop control"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>When determining corner sight distance, a set back distance for the vehicle waiting at the crossroad must be assumed. Set back for the driver of the vehicle on the crossroad has been standardized by some state MUTCDs and design manuals to be up to a minimum of 10 feet plus the shoulder width of the major road but not less than 15 feet.<sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> However, the Federal MUTCD requires that a stop line, if used, shall be at least 4 feet from the nearest travel lane.<sup id="cite_ref-23" class="reference"><a href="#cite_note-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> Line of sight for corner sight distance is to be determined from a 3 and 1/2-foot eye height at the vehicle driver's location on the minor road to a 4 and 1/4-foot object height in the center of the approaching lane of the major road.<sup id="cite_ref-24" class="reference"><a href="#cite_note-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-25" class="reference"><a href="#cite_note-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> Corner sight distance, <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle D_{CSD}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>D</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>C</mi> <mi>S</mi> <mi>D</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle D_{CSD}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/faadddda53ab2527c34d333e86a58ead233736c7" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:5.826ex; height:2.509ex;" alt="{\displaystyle D_{CSD}}"></span>, is equivalent to a specified time gap, <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle t_{g}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>t</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>g</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle t_{g}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/fb06b4e7f223c17fb775d9458e2d34957b062351" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:1.861ex; height:2.676ex;" alt="{\displaystyle t_{g}}"></span>, at the <a href="/wiki/Design_speed" title="Design speed">design speed</a>, <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle V_{DS}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>V</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>D</mi> <mi>S</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle V_{DS}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/a488a4f852224b35e336088ce5a1132563cc1e22" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:4.008ex; height:2.509ex;" alt="{\displaystyle V_{DS}}"></span>, required for a stopped vehicle to turn right or left: </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle D_{CSD}=V_{DS}t_{g}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>D</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>C</mi> <mi>S</mi> <mi>D</mi> </mrow> </msub> <mo>=</mo> <msub> <mi>V</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>D</mi> <mi>S</mi> </mrow> </msub> <msub> <mi>t</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>g</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle D_{CSD}=V_{DS}t_{g}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/5c4f483ec7c2927b697d8d0139bb398b966df495" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:14.794ex; height:2.843ex;" alt="{\displaystyle D_{CSD}=V_{DS}t_{g}}"></span></dd></dl> <p>For passenger vehicles at two lane intersections, this time gap equivalence is commonly a distance 7.5 seconds away at the design speed. Longer gaps are required for trucks and buses, and for multilane roads.<sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> Generally, the <a href="/wiki/Right-of-way_(transportation)" class="mw-redirect" title="Right-of-way (transportation)">public right-of-way</a> should include and maintain this line-of-sight. </p> <div class="mw-heading mw-heading5"><h5 id="All-way_stop_control_and_signalized_intersections">All-way stop control and signalized intersections</h5><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=24" title="Edit section: All-way stop control and signalized intersections"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Drivers at intersections with all-way stop control or traffic signals need the least sight distance. At all-way stops, drivers need to be able to see vehicles stopped at other approaches. At signals, drivers approaching the intersections need to see the signal heads. In jurisdictions that allow <a href="/wiki/Right_turn_on_red" class="mw-redirect" title="Right turn on red">right turn on red</a>, drivers in the right lane stop control need the same sight distance as two-way stop control. Although not needed during normal operations, additional sight distance should be provided for signal malfunctions and power outages.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (August 2013)">citation needed</span></a></i>]</sup> </p> <div class="mw-heading mw-heading3"><h3 id="Effects_of_insufficient_sight_distance">Effects of insufficient sight distance</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=25" title="Edit section: Effects of insufficient sight distance"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Many roads were created long before the current sight distance standards were adopted, and the financial burden on many jurisdictions would be formidable to: <a href="/wiki/Eminent_domain" title="Eminent domain">acquire</a> and maintain additional <a href="/wiki/Right-of-way_(transportation)" class="mw-redirect" title="Right-of-way (transportation)">right-of-way</a>; redesign roadbeds on all of them; or implement future projects on rough terrain, or environmentally sensitive areas. In such cases, the bare minimum corner sight distance should be equal to the <a href="/wiki/Stopping_sight_distance" title="Stopping sight distance">stopping sight distance</a>.<sup id="cite_ref-27" class="reference"><a href="#cite_note-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> While a corner sight distance which far exceed the <a href="/wiki/Braking_distance" title="Braking distance">braking distance</a> at the <a href="/wiki/Design_speed" title="Design speed">design speed</a> should be afforded to the driver, he or she is still generally required to maintain such control and <a href="/wiki/Assured_clear_distance_ahead#Safe_speed" title="Assured clear distance ahead">safe speed</a> as to be able to stop within the <a href="/wiki/Assured_clear_distance_ahead" title="Assured clear distance ahead">assured clear distance ahead</a> (ACDA),<sup id="cite_ref-28" class="reference"><a href="#cite_note-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-NY_Jur_29-0" class="reference"><a href="#cite_note-NY_Jur-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Leibowitz&Herschel_30-0" class="reference"><a href="#cite_note-Leibowitz&Herschel-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup> and the <a href="/wiki/Speed_limit#Basic_rule" title="Speed limit">basic speed rule</a> always applies. Jurisdictions often provide some level of design immunity against government claims actions, in such cases.<sup id="cite_ref-Liability_31-0" class="reference"><a href="#cite_note-Liability-31"><span class="cite-bracket">[</span>Note 1<span class="cite-bracket">]</span></a></sup> </p><p><a href="/wiki/Warning_signs" class="mw-redirect" title="Warning signs">Warning signs</a> are often used where sight distance is insufficient. The <a href="/wiki/Manual_on_Uniform_Traffic_Control_Devices" title="Manual on Uniform Traffic Control Devices">Manual on Uniform Traffic Control Devices</a> requires Stop Ahead, Yield Ahead or Signal Ahead signs at intersections where the traffic control device is not visible from a distance equal to the stopping sight distance at speed of approaching traffic. Hill Blocks View signs can be used where crest vertical curves restrict sight distance.<sup id="cite_ref-32" class="reference"><a href="#cite_note-32"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup> However, many jurisdictions still expect drivers to use <a href="/wiki/Ordinary_care" class="mw-redirect" title="Ordinary care">ordinary care</a> regarding conditions readily apparent to a driver, without the prompting of a sign.<sup id="cite_ref-"Liability_for_unregulated_conditions_readily_apparent_33-0" class="reference"><a href="#cite_note-"Liability_for_unregulated_conditions_readily_apparent-33"><span class="cite-bracket">[</span>Note 2<span class="cite-bracket">]</span></a></sup> The care and focus ordinarily required of a driver against certain types of hazards may be somewhat amplified on roads with lower <a href="/wiki/Functional_classification" title="Functional classification">functional classification</a>.<sup id="cite_ref-34" class="reference"><a href="#cite_note-34"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-35" class="reference"><a href="#cite_note-35"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup> The <a href="/wiki/Probability" title="Probability">probability</a> of spontaneous traffic increases proportionally to the density of access points, and this density should be readily apparent to a driver even when a specific access point is not.<sup id="cite_ref-36" class="reference"><a href="#cite_note-36"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> For this reason, full corner sight distance is almost never required for individual driveways in urban high-density residential areas, and street parking is commonly permitted within the <a href="/wiki/Right-of-way_(transportation)" class="mw-redirect" title="Right-of-way (transportation)">right-of-way</a>. </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=26" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1184024115">.mw-parser-output .div-col{margin-top:0.3em;column-width:30em}.mw-parser-output .div-col-small{font-size:90%}.mw-parser-output .div-col-rules{column-rule:1px solid #aaa}.mw-parser-output .div-col dl,.mw-parser-output .div-col ol,.mw-parser-output .div-col ul{margin-top:0}.mw-parser-output .div-col li,.mw-parser-output .div-col dd{page-break-inside:avoid;break-inside:avoid-column}</style><div class="div-col" style="column-width: 23em;"> <ul><li><a href="/wiki/Cognitive_ergonomics" title="Cognitive ergonomics">Cognitive ergonomics</a></li> <li><a href="/wiki/Degree_of_curvature" title="Degree of curvature">Degree of curvature</a></li> <li><a href="/wiki/Design_speed" title="Design speed">Design speed</a></li> <li><a href="/wiki/Human_factors" class="mw-redirect" title="Human factors">Human factors</a></li> <li><a href="/wiki/Road_traffic_safety" title="Road traffic safety">Road traffic safety</a></li> <li><a href="/wiki/Stopping_sight_distance" title="Stopping sight distance">Stopping sight distance</a></li> <li><a href="/wiki/Track_geometry" title="Track geometry">Track geometry</a></li> <li><a href="/wiki/Traffic_psychology" title="Traffic psychology">Traffic psychology</a></li> <li><a href="/wiki/Transition_curve" class="mw-redirect" title="Transition curve">Transition curve</a></li> <li><a href="/wiki/Structural_road_design" title="Structural road design">Structural road design</a></li></ul> </div> <div class="mw-heading mw-heading3"><h3 id="Road_standards_setting_bodies">Road standards setting bodies</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=27" title="Edit section: Road standards setting bodies"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/American_Association_of_State_Highway_and_Transportation_Officials" title="American Association of State Highway and Transportation Officials">American Association of State Highway and Transportation Officials</a></li> <li><a href="/wiki/National_Cooperative_Highway_Research_Program" title="National Cooperative Highway Research Program">National Cooperative Highway Research Program</a></li> <li><a href="/wiki/Transportation_Research_Board" title="Transportation Research Board">Transportation Research Board</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="Notes">Notes</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=28" title="Edit section: Notes"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist reflist-lower-alpha"> </div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239543626"><div class="reflist"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-Liability-31"><span class="mw-cite-backlink"><b><a href="#cite_ref-Liability_31-0">^</a></b></span> <span class="reference-text">For example, see <a rel="nofollow" class="external text" href="http://www.leginfo.ca.gov/cgi-bin/displaycode?section=gov&group=00001-01000&file=815-818.9">California Government Claims Act</a> and <a rel="nofollow" class="external text" href="https://web.archive.org/web/20100531182754/http://www.dmv.ca.gov/pubs/vctop/d11/vc22358_5.htm">Vehicle Code Section 22358.5</a>.</span> </li> <li id="cite_note-"Liability_for_unregulated_conditions_readily_apparent-33"><span class="mw-cite-backlink"><b><a href="#cite_ref-"Liability_for_unregulated_conditions_readily_apparent_33-0">^</a></b></span> <span class="reference-text">For example, the <a href="/wiki/California_Tort_Claims_Act" title="California Tort Claims Act">California Government Claims Act's</a> <a rel="nofollow" class="external text" href="http://law.onecle.com/california/government/830.4.html">CGC § 830.4</a>: "A condition is not a dangerous condition within the meaning of this chapter merely because of the failure to provide regulatory traffic control signals, stop signs, yield right-of-way signs, or speed restriction signs..." and <a rel="nofollow" class="external text" href="http://law.onecle.com/california/government/830.8.html">CGC § 830.8</a>: "Neither a public entity nor a public employee is liable under this chapter for an injury caused by the failure to provide traffic or warning signals, signs, markings or devices described in the Vehicle Code. Nothing in this section exonerates a public entity or public employee from liability for injury proximately caused by such failure if a signal, sign, marking or device (other than one described in Section 830.4) was necessary to warn of a dangerous condition which endangered the safe movement of traffic and which would not be reasonably apparent to, and would not have been anticipated by, a person exercising due care." See also <a rel="nofollow" class="external text" href="http://www.dmv.ca.gov/pubs/vctop/d11/vc22350.htm">Cal Veh. Code § 22350</a>, <a rel="nofollow" class="external text" href="https://web.archive.org/web/20100531182754/http://www.dmv.ca.gov/pubs/vctop/d11/vc22358_5.htm">Cal Veh. Code § 22358.5</a>, <a rel="nofollow" class="external text" href="http://law.onecle.com/california/government/831.html">Cal Gov. Code § 831</a>, and <a rel="nofollow" class="external text" href="http://www.justia.com/trials-litigation/docs/caci/1100/1120.html">CACI Form 1120</a>. </span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=29" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239543626"><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.fhwa.dot.gov/livability/state_of_the_practice_summary/research00.cfm">"The Role of FHWA Programs in Livability: State of the Practice Summary"</a>. Federal Highway Administration<span class="reference-accessdate">. Retrieved <span class="nowrap">16 April</span> 2012</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=The+Role+of+FHWA+Programs+in+Livability%3A+State+of+the+Practice+Summary&rft.pub=Federal+Highway+Administration&rft_id=https%3A%2F%2Fwww.fhwa.dot.gov%2Flivability%2Fstate_of_the_practice_summary%2Fresearch00.cfm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span></span> </li> <li id="cite_note-Garber-2"><span class="mw-cite-backlink">^ <a href="#cite_ref-Garber_2-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Garber_2-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Garber_2-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Garber_2-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-Garber_2-4"><sup><i><b>e</b></i></sup></a> <a href="#cite_ref-Garber_2-5"><sup><i><b>f</b></i></sup></a> <a href="#cite_ref-Garber_2-6"><sup><i><b>g</b></i></sup></a></span> <span class="reference-text">Garber, N.J., and Hoel, L., A., Traffic and Highway Engineering, 3rd Edition. Brooks/Cole Publishing, 2001</span> </li> <li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20130520110949/http://geometricdesign.csir.co.za/">"SANRAL Geometric Design Guideline"</a>. The Council for Scientific and Industrial Research (CSIR) in South Africa. Archived from <a rel="nofollow" class="external text" href="http://geometricdesign.csir.co.za/">the original</a> on 2013-05-20<span class="reference-accessdate">. Retrieved <span class="nowrap">2013-07-28</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=SANRAL+Geometric+Design+Guideline&rft.pub=The+Council+for+Scientific+and+Industrial+Research+%28CSIR%29+in+South+Africa&rft_id=http%3A%2F%2Fgeometricdesign.csir.co.za%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span></span> </li> <li id="cite_note-Homburger-4"><span class="mw-cite-backlink">^ <a href="#cite_ref-Homburger_4-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Homburger_4-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Homburger_4-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text">Homburger, W.S., Hall, J.W., reilly, W.R. and Sullivan, E.C., Fundamentals of Traffic Engineering (15th ed), ITS Course Notes UCB-ITS-CN-01-1, 2001</span> </li> <li id="cite_note-Green_Book-5"><span class="mw-cite-backlink">^ <a href="#cite_ref-Green_Book_5-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Green_Book_5-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Green_Book_5-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation book cs1"><i>A Policy on Geometric Design of Highways and Streets</i>. Washington D.C.: American Association of State Highway and Transportation Officials. 2004.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=A+Policy+on+Geometric+Design+of+Highways+and+Streets&rft.place=Washington+D.C.&rft.pub=American+Association+of+State+Highway+and+Transportation+Officials&rft.date=2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span></span> </li> <li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://dotapp7.dot.state.mn.us/edms/download?docId=1062355">"MnDOT Road Design Manual"</a>. MnDOT<span class="reference-accessdate">. Retrieved <span class="nowrap">6 September</span> 2012</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=MnDOT+Road+Design+Manual&rft.pub=MnDOT&rft_id=http%3A%2F%2Fdotapp7.dot.state.mn.us%2Fedms%2Fdownload%3FdocId%3D1062355&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span></span> </li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text">Minnesota Department of Transportation, Bikeway Facility Design Manual, section 5-3.5.1, <a rel="nofollow" class="external free" href="http://www.dot.state.mn.us/bike/pdfs/Chapter5_Bw.pdf">http://www.dot.state.mn.us/bike/pdfs/Chapter5_Bw.pdf</a><sup class="noprint Inline-Template"><span style="white-space: nowrap;">[<i><a href="/wiki/Wikipedia:Link_rot" title="Wikipedia:Link rot"><span title=" Dead link tagged May 2024">permanent dead link</span></a></i><span style="visibility:hidden; color:transparent; padding-left:2px">‍</span>]</span></sup>, retrieved 4/20/2010</span> </li> <li id="cite_note-Dewan_Masud_Karim-8"><span class="mw-cite-backlink">^ <a href="#cite_ref-Dewan_Masud_Karim_8-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Dewan_Masud_Karim_8-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Dewan_Masud_Karim_8-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text">Dewan Masud Karim. <a rel="nofollow" class="external text" href="https://www.researchgate.net/publication/277590178_Narrower_Lanes_Safer_Streets"><i>Narrower Lanes, Safer Streets.</i></a> June 2015 Conference: Canadian Institute of Transportation Engineers, Regina 2015, accessed 14th March 2022</span> </li> <li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://safety.fhwa.dot.gov/geometric/pubs/mitigationstrategies/chapter3/3_lanewidth.cfm">"Lane Width"</a>. <i>Chapter 3: The 13 Controlling Criteria</i>. US Department of Transportation Federal Highway Administration. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20130513042602/http://safety.fhwa.dot.gov/geometric/pubs/mitigationstrategies/chapter3/3_lanewidth.htm">Archived</a> from the original on May 13, 2013<span class="reference-accessdate">. Retrieved <span class="nowrap">June 3,</span> 2013</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Chapter+3%3A+The+13+Controlling+Criteria&rft.atitle=Lane+Width&rft_id=https%3A%2F%2Fsafety.fhwa.dot.gov%2Fgeometric%2Fpubs%2Fmitigationstrategies%2Fchapter3%2F3_lanewidth.cfm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span></span> </li> <li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.pedbikeinfo.org/data/library/details.cfm?id=4348">"Theo Petrisch, "The Tite about Lane Widths," The Pedestrian and Bicycle Information Center, accessed April 12, 2013"</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20170405073638/http://www.pedbikeinfo.org/data/library/details.cfm?id=4348">Archived</a> from the original on April 5, 2017.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Theo+Petrisch%2C+%22The+Tite+about+Lane+Widths%2C%22+The+Pedestrian+and+Bicycle+Information+Center%2C+accessed+April+12%2C+2013&rft_id=http%3A%2F%2Fwww.pedbikeinfo.org%2Fdata%2Flibrary%2Fdetails.cfm%3Fid%3D4348&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span></span> </li> <li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text">Theodore A. Petritsch, "<a rel="nofollow" class="external text" href="http://nacto.org/docs/usdg/lane_widths_on_safety_and_capacity_petritsch.pdf">The Influence of Lane Widths on Safety and Capacity: A Summary of the Latest Findings</a>", n.d., Sprinkle Consulting</span> </li> <li id="cite_note-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-12">^</a></b></span> <span class="reference-text">Granlund et al. (2014). 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Retrieved <span class="nowrap">6 March</span> 2012</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Interactive+Highway+Design+Model+Engineer%27s+Manual&rft.atitle=Design+Consistency+Module+Engineers+Manual&rft_id=http%3A%2F%2Fwww.ihsdm.org%2Fpublic%2Fhtml%2Fuser%2Fdcm%2Fdcm_em.1.html%23overview_dcm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span></span> </li> <li id="cite_note-2-lane-14"><span class="mw-cite-backlink">^ <a href="#cite_ref-2-lane_14-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-2-lane_14-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-2-lane_14-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFD.W._HarwoodF.M._CouncilE._HauerW.E._Hughes2000" class="citation book cs1">D.W. Harwood; F.M. Council; E. Hauer; W.E. Hughes; A. Vogt (2000). <a rel="nofollow" class="external text" href="https://www.fhwa.dot.gov/publications/research/safety/99207/99207.pdf"><i>Prediction of the Expected Safety Performance of Rural Two-Lane Highways</i></a> <span class="cs1-format">(PDF)</span>. Washington, D.C.: Federal Highway Administration.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Prediction+of+the+Expected+Safety+Performance+of+Rural+Two-Lane+Highways&rft.place=Washington%2C+D.C.&rft.pub=Federal+Highway+Administration&rft.date=2000&rft.au=D.W.+Harwood&rft.au=F.M.+Council&rft.au=E.+Hauer&rft.au=W.E.+Hughes&rft.au=A.+Vogt&rft_id=https%3A%2F%2Fwww.fhwa.dot.gov%2Fpublications%2Fresearch%2Fsafety%2F99207%2F99207.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span></span> </li> <li id="cite_note-15"><span class="mw-cite-backlink"><b><a href="#cite_ref-15">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFPotts2007" class="citation book cs1">Potts, Ingrid B. (2007). <a rel="nofollow" class="external text" href="http://www.completestreets.org/webdocs/resources/lanewidth-safety.pdf"><i>Relationship of Lane Width to Safety for Urban and Suburban Arterials</i></a> <span class="cs1-format">(PDF)</span>. Transportation Research Board.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Relationship+of+Lane+Width+to+Safety+for+Urban+and+Suburban+Arterials&rft.pub=Transportation+Research+Board&rft.date=2007&rft.aulast=Potts&rft.aufirst=Ingrid+B.&rft_id=http%3A%2F%2Fwww.completestreets.org%2Fwebdocs%2Fresources%2Flanewidth-safety.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span></span> </li> <li id="cite_note-16"><span class="mw-cite-backlink"><b><a href="#cite_ref-16">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMillikende_Pont2004" class="citation web cs1">Milliken, Paul; de Pont, John (2004). <a rel="nofollow" class="external text" href="http://www.nzta.govt.nz/resources/research/reports/263/docs/263.pdf">"The Effect of Cross-Sectional Geometry on Heavy Vehicle Performance and Safety"</a> <span class="cs1-format">(PDF)</span>. Transfund New Zealand.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=The+Effect+of+Cross-Sectional+Geometry+on+Heavy+Vehicle+Performance+and+Safety&rft.pub=Transfund+New+Zealand&rft.date=2004&rft.aulast=Milliken&rft.aufirst=Paul&rft.au=de+Pont%2C+John&rft_id=http%3A%2F%2Fwww.nzta.govt.nz%2Fresources%2Fresearch%2Freports%2F263%2Fdocs%2F263.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span></span> </li> <li id="cite_note-CA_HDM-17"><span class="mw-cite-backlink"><b><a href="#cite_ref-CA_HDM_17-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.dot.ca.gov/design/manuals/hdm/chp0200.pdf">"Chapter 200 Geometric Design and Structure Standards, Topic 201 - Sight Distance"</a> <span class="cs1-format">(PDF)</span>. <i>Highway Design Manual</i>. California Department of Transportation. pp. 200_1<span class="reference-accessdate">. Retrieved <span class="nowrap">12 July</span> 2018</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Highway+Design+Manual&rft.atitle=Chapter+200+Geometric+Design+and+Structure+Standards%2C+Topic+201+-+Sight+Distance&rft.pages=200_1&rft_id=http%3A%2F%2Fwww.dot.ca.gov%2Fdesign%2Fmanuals%2Fhdm%2Fchp0200.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span> Stopping Sight Distance[:]...the distance required by the user, traveling at a given speed, to bring the vehicle or bicycle to a stop after an object <style data-mw-deduplicate="TemplateStyles:r1154941027">.mw-parser-output .frac{white-space:nowrap}.mw-parser-output .frac .num,.mw-parser-output .frac .den{font-size:80%;line-height:0;vertical-align:super}.mw-parser-output .frac .den{vertical-align:sub}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}</style><span class="frac"><span class="num">1</span>⁄<span class="den">2</span></span>-foot high on the road becomes visible. Stopping sight distance for motorists is measured from the driver's eyes, which are assumed to be <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1154941027"><span class="frac">3<span class="sr-only">+</span><span class="num">1</span>⁄<span class="den">2</span></span> feet above the pavement surface, to an object <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1154941027"><span class="frac"><span class="num">1</span>⁄<span class="den">2</span></span>-foot high on the road. ... Decision Sight Distance[:] sight distance greater than stopping sight distance is desirable to allow drivers time for decisions without making last minute erratic maneuvers...<a rel="nofollow" class="external text" href="http://www.dot.ca.gov/design/manuals/hdm.html">Read more types at CA Highway Design Manual</a></span> </li> <li id="cite_note-18"><span class="mw-cite-backlink"><b><a href="#cite_ref-18">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation book cs1 cs1-prop-long-vol"><a rel="nofollow" class="external text" href="http://www.dot.ca.gov/hq/oppd/hdm/hdmtoc.htm"><i>Highway Design Manual</i></a>. Vol. 6th Ed. California Department of Transportation. 2012. p. 200.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Highway+Design+Manual&rft.pages=200&rft.pub=California+Department+of+Transportation&rft.date=2012&rft_id=http%3A%2F%2Fwww.dot.ca.gov%2Fhq%2Foppd%2Fhdm%2Fhdmtoc.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span> See <a rel="nofollow" class="external text" href="http://www.dot.ca.gov/hq/oppd/hdm/pdf/english/chp0200.pdf">Chapter 200 on Stopping Sight Distance</a></span> </li> <li id="cite_note-19"><span class="mw-cite-backlink"><b><a href="#cite_ref-19">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFNational_Cooperative_Highway_Research_Program1997" class="citation book cs1">National Cooperative Highway Research Program (1997). <a rel="nofollow" class="external text" href="http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_400.pdf"><i>NCHRP Report 400: Determination of Stopping Sight Distances</i></a> <span class="cs1-format">(PDF)</span>. Transportation Research Board (National Academy Press). p. I-13. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-309-06073-7" title="Special:BookSources/0-309-06073-7"><bdi>0-309-06073-7</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=NCHRP+Report+400%3A+Determination+of+Stopping+Sight+Distances&rft.pages=I-13&rft.pub=Transportation+Research+Board+%28National+Academy+Press%29&rft.date=1997&rft.isbn=0-309-06073-7&rft.au=National+Cooperative+Highway+Research+Program&rft_id=http%3A%2F%2Fonlinepubs.trb.org%2Fonlinepubs%2Fnchrp%2Fnchrp_rpt_400.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span></span> </li> <li id="cite_note-AASHTO-20"><span class="mw-cite-backlink"><b><a href="#cite_ref-AASHTO_20-0">^</a></b></span> <span class="reference-text">American Association of State Highway and Transportation Officials (1994) <i>A Policy on Geometric Design of Highways and Streets</i> (pp. 117—118)</span> </li> <li id="cite_note-AASHTO_ISD-21"><span class="mw-cite-backlink"><b><a href="#cite_ref-AASHTO_ISD_21-0">^</a></b></span> <span class="reference-text">American Association of State Highway and Transportation Officials (1994) <i>A Policy on Geometric Design of Highways and Streets</i> (pp. 650—679)</span> </li> <li id="cite_note-22"><span class="mw-cite-backlink"><b><a href="#cite_ref-22">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation book cs1 cs1-prop-long-vol"><a rel="nofollow" class="external text" href="http://www.dot.ca.gov/hq/oppd/hdm/hdmtoc.htm"><i>Highway Design Manual</i></a>. Vol. 6th Ed. California Department of Transportation. 2012. pp. 400–14.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Highway+Design+Manual&rft.pages=400-14&rft.pub=California+Department+of+Transportation&rft.date=2012&rft_id=http%3A%2F%2Fwww.dot.ca.gov%2Fhq%2Foppd%2Fhdm%2Fhdmtoc.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span> See <a rel="nofollow" class="external text" href="http://www.dot.ca.gov/hq/oppd/hdm/pdf/english/chp0400.pdf">Chapter 405.1 on Sight Distance</a></span> </li> <li id="cite_note-23"><span class="mw-cite-backlink"><b><a href="#cite_ref-23">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://mutcd.fhwa.dot.gov/">"Manual on Uniform Traffic Control Devices (MUCTD)"</a>. United States Department of Transportation – Federal Highway Administration. Part3 – Markings –Section 3B.16(10).</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Manual+on+Uniform+Traffic+Control+Devices+%28MUCTD%29&rft.pages=Part3--+Markings--Section+3B.16%2810%29&rft.pub=United+States+Department+of+Transportation+%E2%80%93+Federal+Highway+Administration&rft_id=https%3A%2F%2Fmutcd.fhwa.dot.gov%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span></span> </li> <li id="cite_note-24"><span class="mw-cite-backlink"><b><a href="#cite_ref-24">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation book cs1 cs1-prop-long-vol"><a rel="nofollow" class="external text" href="http://www.dot.ca.gov/hq/oppd/hdm/hdmtoc.htm"><i>Highway Design Manual</i></a>. Vol. 6th Ed. California Department of Transportation. 2012. p. 200.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Highway+Design+Manual&rft.pages=200&rft.pub=California+Department+of+Transportation&rft.date=2012&rft_id=http%3A%2F%2Fwww.dot.ca.gov%2Fhq%2Foppd%2Fhdm%2Fhdmtoc.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span> See <a rel="nofollow" class="external text" href="http://www.dot.ca.gov/hq/oppd/hdm/pdf/english/chp0400.pdf">Chapter 405.1 on Sight Distance</a></span> </li> <li id="cite_note-25"><span class="mw-cite-backlink"><b><a href="#cite_ref-25">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation book cs1 cs1-prop-long-vol">"300". <a rel="nofollow" class="external text" href="http://www.transportation.org"><i>A Policy on Geometric Design of Highways and Streets</i></a>. Vol. 4th Ed. <a href="/wiki/American_Association_of_State_Highway_and_Transportation_Officials" title="American Association of State Highway and Transportation Officials">American Association of State Highway and Transportation Officials</a>. 2004.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=300&rft.btitle=A+Policy+on+Geometric+Design+of+Highways+and+Streets&rft.pub=American+Association+of+State+Highway+and+Transportation+Officials&rft.date=2004&rft_id=http%3A%2F%2Fwww.transportation.org&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span></span> </li> <li id="cite_note-26"><span class="mw-cite-backlink"><b><a href="#cite_ref-26">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation book cs1 cs1-prop-long-vol">"300". <a rel="nofollow" class="external text" href="http://www.transportation.org"><i>A Policy on Geometric Design of Highways and Streets</i></a>. Vol. 4th Ed. <a href="/wiki/American_Association_of_State_Highway_and_Transportation_Officials" title="American Association of State Highway and Transportation Officials">American Association of State Highway and Transportation Officials</a>. 2004.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=300&rft.btitle=A+Policy+on+Geometric+Design+of+Highways+and+Streets&rft.pub=American+Association+of+State+Highway+and+Transportation+Officials&rft.date=2004&rft_id=http%3A%2F%2Fwww.transportation.org&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span> See Exhibit 9-54. Time Gap for Case B1—Left Turn from Stop</span> </li> <li id="cite_note-27"><span class="mw-cite-backlink"><b><a href="#cite_ref-27">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation book cs1 cs1-prop-long-vol"><a rel="nofollow" class="external text" href="http://www.dot.ca.gov/hq/oppd/hdm/hdmtoc.htm"><i>Highway Design Manual</i></a>. Vol. 6th Ed. California Department of Transportation. 2012. pp. 400–22.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Highway+Design+Manual&rft.pages=400-22&rft.pub=California+Department+of+Transportation&rft.date=2012&rft_id=http%3A%2F%2Fwww.dot.ca.gov%2Fhq%2Foppd%2Fhdm%2Fhdmtoc.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span> See <a rel="nofollow" class="external text" href="http://www.dot.ca.gov/hq/oppd/hdm/pdf/english/chp0400.pdf">Chapter 405.1 on Sight Distance</a></span> </li> <li id="cite_note-28"><span class="mw-cite-backlink"><b><a href="#cite_ref-28">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://definitions.uslegal.com/a/assured-clear-distance-ahead/">"Assured Clear Distance Ahead Law & Legal Definition"</a>. US Legal, Inc<span class="reference-accessdate">. Retrieved <span class="nowrap">2018-07-12</span></span>. <q>ACDA or "assured clear distance ahead" requires a driver to keep his motor vehicle under control so that he can stop in the distance in which he can clearly see.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Assured+Clear+Distance+Ahead+Law+%26+Legal+Definition&rft.pub=US+Legal%2C+Inc.&rft_id=http%3A%2F%2Fdefinitions.uslegal.com%2Fa%2Fassured-clear-distance-ahead%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span></span> </li> <li id="cite_note-NY_Jur-29"><span class="mw-cite-backlink"><b><a href="#cite_ref-NY_Jur_29-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLawyers_Cooperative_Publishing" class="citation book cs1">Lawyers Cooperative Publishing. <a rel="nofollow" class="external text" href="http://legalsolutions.thomsonreuters.com/law-products/Legal-Encyclopedias/New-York-Jurisprudence-2d/p/100029357"><i>New York Jurisprudence</i></a>. Automobiles and Other Vehicles. Miamisburg, OH: LEXIS Publishing. p. § 720. <a href="/wiki/OCLC_(identifier)" class="mw-redirect" title="OCLC (identifier)">OCLC</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/oclc/321177421">321177421</a>. <q>It is negligence as a matter of law to drive a motor vehicle at such a rate of speed that it cannot be stopped in time to avoid an obstruction discernible within the driver's length of vision ahead of him. This rule is known generally as the 'assured clear distance ahead' rule * * * In application, the rule constantly changes as the motorist proceeds, and is measured at any moment by the distance between the motorist's vehicle and the limit of his vision ahead, or by the distance between the vehicle and any intermediate discernible static or forward-moving object in the street or highway ahead constituting an obstruction in his path. Such rule requires a motorist in the exercise of due care at all times to see, or to know from having seen, that the road is clear or apparently clear and safe for travel, a sufficient distance ahead to make it apparently safe to advance at the speed employed.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=New+York+Jurisprudence&rft.place=Miamisburg%2C+OH&rft.series=Automobiles+and+Other+Vehicles&rft.pages=%C2%A7+720&rft.pub=LEXIS+Publishing&rft_id=info%3Aoclcnum%2F321177421&rft.au=Lawyers+Cooperative+Publishing&rft_id=http%3A%2F%2Flegalsolutions.thomsonreuters.com%2Flaw-products%2FLegal-Encyclopedias%2FNew-York-Jurisprudence-2d%2Fp%2F100029357&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span></span> </li> <li id="cite_note-Leibowitz&Herschel-30"><span class="mw-cite-backlink"><b><a href="#cite_ref-Leibowitz&Herschel_30-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLeibowitzOwensTyrrell1998" class="citation journal cs1">Leibowitz, Herschel W.; Owens, D. Alfred; Tyrrell, Richard A. (1998). "The assured clear distance ahead rule: implications for nighttime traffic safety and the law". <i>Accident Analysis & Prevention</i>. <b>30</b> (1): 93–99. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2FS0001-4575%2897%2900067-5">10.1016/S0001-4575(97)00067-5</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/9542549">9542549</a>. <q>The assured clear distance ahead (ACDA) rule holds the operator of a motor vehicle responsible to avoid collision with any obstacle that might appear in the vehicle's path.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Accident+Analysis+%26+Prevention&rft.atitle=The+assured+clear+distance+ahead+rule%3A+implications+for+nighttime+traffic+safety+and+the+law&rft.volume=30&rft.issue=1&rft.pages=93-99&rft.date=1998&rft_id=info%3Adoi%2F10.1016%2FS0001-4575%2897%2900067-5&rft_id=info%3Apmid%2F9542549&rft.aulast=Leibowitz&rft.aufirst=Herschel+W.&rft.au=Owens%2C+D.+Alfred&rft.au=Tyrrell%2C+Richard+A.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span></span> </li> <li id="cite_note-32"><span class="mw-cite-backlink"><b><a href="#cite_ref-32">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://mutcd.fhwa.dot.gov/">"Manual on Uniform Traffic Control Devices (MUCTD)"</a>. United States Department of Transportation – Federal Highway Administration. Part2c –Warning signs.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Manual+on+Uniform+Traffic+Control+Devices+%28MUCTD%29&rft.pages=Part2c--Warning+signs&rft.pub=United+States+Department+of+Transportation+%E2%80%93+Federal+Highway+Administration&rft_id=https%3A%2F%2Fmutcd.fhwa.dot.gov%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span></span> </li> <li id="cite_note-34"><span class="mw-cite-backlink"><b><a href="#cite_ref-34">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://law.justia.com/cases/california/calapp2d/22/636.html">"Riggs v. Gasser Motors, 22 Cal. App. 2d 636"</a>. Official California Appellate Reports (2nd Series Vol. 22, p. 636). September 25, 1937<span class="reference-accessdate">. Retrieved <span class="nowrap">2013-07-27</span></span>. <q>It is common knowledge that intersecting streets in cities present a continuing hazard, the degree of hazard depending upon the extent of the use of the intersecting streets and the surrounding circumstances or conditions of each intersection. Under such circumstances the <a href="/wiki/Speed_limit#Basic_rule" title="Speed limit">basic law</a>...is always governing.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Riggs+v.+Gasser+Motors%2C+22+Cal.+App.+2d+636&rft.pub=Official+California+Appellate+Reports+%282nd+Series+Vol.+22%2C+p.+636%29&rft.date=1937-09-25&rft_id=http%3A%2F%2Flaw.justia.com%2Fcases%2Fcalifornia%2Fcalapp2d%2F22%2F636.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span> See <a rel="nofollow" class="external text" href="http://courts.ca.gov/opinions-slip.htm">Official Reports Opinions Online</a></span> </li> <li id="cite_note-35"><span class="mw-cite-backlink"><b><a href="#cite_ref-35">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.lexisnexis.com/clients/CACourts/">"Reaugh v. Cudahy Packing Co., 189 Cal. 335"</a>. Official California Reports, Vol. 189, p. 335, (California Supreme Court reporter). July 27, 1922<span class="reference-accessdate">. Retrieved <span class="nowrap">2013-07-27</span></span>. <q>motor vehicles, must be specially watchful in anticipation of the presence of others at places where other vehicles are constantly passing, and where men, women, and children are liable to be crossing, such as corners at the intersections of streets or other similar places or situations where people are likely to fail to observe an approaching automobile.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Reaugh+v.+Cudahy+Packing+Co.%2C+189+Cal.+335&rft.pub=Official+California+Reports%2C+Vol.+189%2C+p.+335%2C+%28California+Supreme+Court+reporter%29&rft.date=1922-07-27&rft_id=http%3A%2F%2Fwww.lexisnexis.com%2Fclients%2FCACourts%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span> See <a rel="nofollow" class="external text" href="http://www.lexisnexis.com/clients/CACourts/">Official Reports Opinions Online</a></span> </li> <li id="cite_note-36"><span class="mw-cite-backlink"><b><a href="#cite_ref-36">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://law.justia.com/cases/california/calapp2d/139/65.html">"Leeper v. Nelson, 139 Cal. App. 2d 65"</a>. Official California Appellate Reports (2nd Series Vol. 139, p. 65). Feb 6, 1956<span class="reference-accessdate">. Retrieved <span class="nowrap">2013-07-27</span></span>. <q>The operator of an automobile is bound to anticipate that he may meet persons or vehicles at any point of the street, and he must in order to avoid a charge of negligence, keep a proper lookout for them and keep his machine under such control as will enable him to avoid a collision with another automobile driven with care and caution as a reasonably prudent person would do under similar conditions.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Leeper+v.+Nelson%2C+139+Cal.+App.+2d+65&rft.pub=Official+California+Appellate+Reports+%282nd+Series+Vol.+139%2C+p.+65%29&rft.date=1956-02-06&rft_id=http%3A%2F%2Flaw.justia.com%2Fcases%2Fcalifornia%2Fcalapp2d%2F139%2F65.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span> See <a rel="nofollow" class="external text" href="http://law.justia.com/cases/california/calapp2d/91/142.html">Huetter v. Andrews, 91 Cal. App. 2d 142</a>, <a rel="nofollow" class="external text" href="http://www.lexisnexis.com/clients/CACourts/">Berlin v. Violett, 129 Cal.App. 337</a>, <a rel="nofollow" class="external text" href="http://www.lexisnexis.com/clients/CACourts/">Reaugh v. Cudahy Packing Co., 189 Cal. 335 </a>, and <a rel="nofollow" class="external text" href="http://courts.ca.gov/opinions-slip.htm">Official Reports Opinions Online</a></span> </li> </ol></div></div> <div class="mw-heading mw-heading3"><h3 id="Law_reviews">Law reviews</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geometric_design_of_roads&action=edit&section=30" title="Edit section: Law reviews"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><span class="anchor" id="34_ALR_3d_1008"></span><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation book cs1">"Liability of highway authorities arising out of motor vehicle accident allegedly caused by failure to erect or properly maintain traffic control device at intersection". <i>American Law Reports—Annotated, 3rd Series</i>. Vol. 34. The Lawyers Co-operative Publishing Company; Bancroft-Whitney; West Group Annotation Company. p. 1008.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Liability+of+highway+authorities+arising+out+of+motor+vehicle+accident+allegedly+caused+by+failure+to+erect+or+properly+maintain+traffic+control+device+at+intersection&rft.btitle=American+Law+Reports%E2%80%94Annotated%2C+3rd+Series&rft.pages=1008&rft.pub=The+Lawyers+Co-operative+Publishing+Company%3B+Bancroft-Whitney%3B+West+Group+Annotation+Company&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span></li> <li><span class="anchor" id="50_ALR_6th_95"></span><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation book cs1">"Comment Note: Governmental Liability for Failure to Reduce Vegetation Obscuring View at Railroad Crossing or at Street or Highway Intersection". <i>American Law Reports—Annotated, 6th Series</i>. Vol. 50. The Lawyers Co-operative Publishing Company; Bancroft-Whitney; West Group Annotation Company. p. 95.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Comment+Note%3A+Governmental+Liability+for+Failure+to+Reduce+Vegetation+Obscuring+View+at+Railroad+Crossing+or+at+Street+or+Highway+Intersection&rft.btitle=American+Law+Reports%E2%80%94Annotated%2C+6th+Series&rft.pages=95&rft.pub=The+Lawyers+Co-operative+Publishing+Company%3B+Bancroft-Whitney%3B+West+Group+Annotation+Company&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeometric+design+of+roads" class="Z3988"></span></li></ul>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" 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