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<div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Traffic light override system</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-More_citations_needed plainlinks metadata ambox ambox-content ambox-Refimprove" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><a href="/wiki/File:Question_book-new.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/50px-Question_book-new.svg.png" decoding="async" width="50" height="39" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/75px-Question_book-new.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/100px-Question_book-new.svg.png 2x" data-file-width="512" data-file-height="399" /></a></span></div></td><td class="mbox-text"><div class="mbox-text-span">This article <b>needs additional citations for <a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">verification</a></b>.<span class="hide-when-compact"> Please help <a href="/wiki/Special:EditPage/Traffic_signal_preemption" title="Special:EditPage/Traffic signal preemption">improve this article</a> by <a href="/wiki/Help:Referencing_for_beginners" title="Help:Referencing for beginners">adding citations to reliable sources</a>. Unsourced material may be challenged and removed.<br /><small><span class="plainlinks"><i>Find sources:</i> <a rel="nofollow" class="external text" href="https://www.google.com/search?as_eq=wikipedia&q=%22Traffic+signal+preemption%22">"Traffic signal preemption"</a> – <a rel="nofollow" class="external text" href="https://www.google.com/search?tbm=nws&q=%22Traffic+signal+preemption%22+-wikipedia&tbs=ar:1">news</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.google.com/search?&q=%22Traffic+signal+preemption%22&tbs=bkt:s&tbm=bks">newspapers</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.google.com/search?tbs=bks:1&q=%22Traffic+signal+preemption%22+-wikipedia">books</a> <b>·</b> <a rel="nofollow" class="external text" href="https://scholar.google.com/scholar?q=%22Traffic+signal+preemption%22">scholar</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.jstor.org/action/doBasicSearch?Query=%22Traffic+signal+preemption%22&acc=on&wc=on">JSTOR</a></span></small></span> <span class="date-container"><i>(<span class="date">September 2019</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> <p><b>Traffic signal preemption</b> (also called <b>traffic signal prioritisation</b>) is a system that allows an operator to override the normal operation of <a href="/wiki/Traffic_light" title="Traffic light">traffic lights</a>. The most common use of these systems manipulates traffic signals in the path of an <a href="/wiki/Emergency_vehicle" title="Emergency vehicle">emergency vehicle</a>, halting conflicting traffic and allowing the emergency vehicle right-of-way, thereby reducing <a href="/wiki/Emergency_service#Response_time" title="Emergency service">response times</a> and enhancing traffic safety. Signal preemption can also be used on <a href="/wiki/Tram" title="Tram">tram</a>, <a href="/wiki/Light_rail" title="Light rail">light-rail</a> and <a href="/wiki/Bus_rapid_transit" title="Bus rapid transit">bus rapid transit</a> systems, to allow <a href="/wiki/Public_transportation" class="mw-redirect" title="Public transportation">public transportation</a> priority access through intersections, and by <a href="/wiki/Level_crossing" title="Level crossing">railroad systems at crossings</a> to prevent collisions. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Implementation">Implementation</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Traffic_signal_preemption&action=edit&section=1" title="Edit section: Implementation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Traffic preemption is implemented in a variety of ways. Traffic light activation devices can be installed on road vehicles, integrated with transport network management systems, or operated by remote control from a fixed location, such as a <a href="/wiki/Fire_station" title="Fire station">fire station</a>, or by an <a href="/wiki/Dispatcher#Emergency_dispatchers" title="Dispatcher">emergency call dispatcher</a>. Traffic lights are equipped to receive an activation signal which interrupts the normal cycle. Traffic signals not equipped to receive a traffic preemption signal will not recognize an activation, and will continue to operate on the normal cycle. </p><p>Vehicular devices can be switched on or off as needed, but in the case of emergency vehicles, they are frequently integrated with the vehicle's <a href="/wiki/Emergency_vehicle_lighting" title="Emergency vehicle lighting">emergency warning lights</a>. When activated, the traffic preemption device will cause appropriately equipped traffic lights in the path of the vehicle to cycle immediately, granting right-of-way in the desired direction, after allowing programmed time delays for the necessary signal changes and for <a href="/wiki/Pedestrian_crossing" title="Pedestrian crossing">pedestrian crosswalks</a> to clear. </p><p>Traffic signal preemption systems integrated with <a href="/wiki/Train" title="Train">train</a> transportation networks typically extend their control of traffic from the typical <a href="/wiki/Grade_crossing_signals" class="mw-redirect" title="Grade crossing signals">crossarms</a> and warning lights to one or more nearby traffic intersections, to prevent excessive <a href="/wiki/Road_traffic" class="mw-redirect" title="Road traffic">road traffic</a> from approaching the crossing, while also obtaining the <a href="/wiki/Traffic#Passage_Priority_(right_of_way)" title="Traffic">right-of-way</a> for road traffic to quickly clear the crossing. That also allows <a href="/wiki/Bus" title="Bus">buses</a> and vehicles transporting <a href="/wiki/Dangerous_goods" title="Dangerous goods">dangerous goods</a> to proceed through the intersection without stopping on the railroad tracks. </p><p>Fixed-location systems can vary widely, but a typical implementation is for a single traffic signal in front of or near a fire station to stop traffic and allow emergency vehicles to exit the station unimpeded. Alternatively, an entire corridor of traffic signals along a street may be operated from a fixed location, such as to allow fire apparatus to quickly respond through a crowded <a href="/wiki/Downtown" title="Downtown">downtown</a> area, or to allow an <a href="/wiki/Ambulance" title="Ambulance">ambulance</a> faster access when transporting a <a href="/wiki/Medical_state" title="Medical state">critical patient</a> to a <a href="/wiki/Hospital" title="Hospital">hospital</a> in an area with dense traffic. </p><p>Traffic signal preemption systems sometimes include a method for communicating to the operator of the vehicle that requested the preemption (as well as other drivers) that a traffic signal is under control of a preemption device, by means of a notifier. This device is commonly referred to in the industry as a "confirmation beacon". It is usually an additional light located near the traffic signals. It may be a single <a href="/wiki/LED_light_bulb" class="mw-redirect" title="LED light bulb">LED light bulb</a> visible to all, which flashes or stays on, or there may be a light aimed towards each direction from which traffic approaches the intersection. In the case of multiple notifier lights at a controllable intersection, they will either flash or stay on depending on the local configuration, to communicate to all drivers from which direction a preempting signal is being received. This informs regular drivers which direction may need to be cleared, and informs activating vehicle drivers if they have control of the light (especially important when more than one activating vehicle approaches the same intersection). A typical installation would provide a solid notifier to indicate that an activating vehicle is approaching from behind, while a flashing notifier would indicate the emergency vehicle is approaching laterally or oncoming. There are variations of notification methods in use, which may include one or more colored lights in varying configurations. Some of the newer high tech systems have a display in the cab, which will eliminate the necessity of a confirmation beacon. This can also reduce the cost of a preemption project considerably. </p><p>Events leading up to an activation and notification are not experienced by drivers on a daily basis, and driver education and awareness of these systems can play a role in how effective the systems are in speeding response times. Unusual circumstances can also occur which can confuse operators of vehicles with traffic preemption equipment who lack proper training. For example, on January 2, 2005, a <a href="/wiki/Fire_engine" title="Fire engine">fire engine</a> successfully preempted a traffic light at an intersection which included a <a href="/wiki/Light_rail" title="Light rail">light rail</a> train (LRT) crossing in <a href="/wiki/Hillsboro,_Oregon" title="Hillsboro, Oregon">Hillsboro, Oregon</a>, yet the fire engine was hit by an LRT at the crossing. A subsequent inquiry determined that the LRT operator was at fault. The accident occurred in the middle of a network of closely spaced signalized intersections where the signs and signals granted right-of-way to the LRT simultaneously, at ALL intersections. The LRT operator was viewing right-of-way indications from downstream signals and failed to realize that preemption had occurred at the nearest intersection. The fire engine, granted the green light before it arrived at the intersection, proceeded through while the LRT operator, failing to notice the unexpected signal to stop, ran into the fire engine and destroyed it.<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. (March 2023)">citation needed</span></a></i>]</sup> </p> <div class="mw-heading mw-heading2"><h2 id="Vehicular_device_types">Vehicular device types</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Traffic_signal_preemption&action=edit&section=2" title="Edit section: Vehicular device types"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="Acoustic">Acoustic</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Traffic_signal_preemption&action=edit&section=3" title="Edit section: Acoustic"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Some systems use an <a href="/wiki/Microphone" title="Microphone">acoustic sensor</a> linked to the preemption system. This can be used alone or in conjunction with other systems. Systems of this type override the traffic signal when a specific pattern of tweets or wails from the siren of an emergency vehicle is detected. Advantages of a system like this are that they are fairly inexpensive to integrate into existing traffic signals and the ability to use siren equipment already installed in emergency vehicles – thus dispensing with the need for special equipment. A major disadvantage is that sound waves can easily be reflected by buildings or other large vehicles present at or near an intersection, causing the "reflected" wave to trigger a preemption event in the wrong direction. Reflected waves can also create unnecessary collateral preemption events alongside streets near the emergency vehicle's route. Yet another disadvantage is that the acoustic sensors can sometimes be sensitive enough to activate the preemption in response to a siren from too far away, or from an unauthorized vehicle with a horn exceeding 120 <a href="/wiki/Decibel" title="Decibel">dB</a> (many truck and bus horns exceed this threshold ‘at close range’).<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> <div class="mw-heading mw-heading3"><h3 id="Line-of-sight">Line-of-sight</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Traffic_signal_preemption&action=edit&section=4" title="Edit section: Line-of-sight"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div><p> A vehicle that uses a line-of-sight traffic signal preemption system is equipped with an emitter which typically sends a narrowly directed signal forward, towards <a href="/wiki/Traffic_light" title="Traffic light">traffic lights</a> in front of the vehicle, in an attempt to obtain right-of-way through a controllable intersection prior to arrival. These line-of-sight systems will generally use an invisible <a href="/wiki/Infrared" title="Infrared">infrared</a> signal, or a visible <a href="/wiki/Strobe_light" title="Strobe light">strobe light</a> as an emitter. In the case of a strobe light, it may also serve a dual purpose as an additional warning light. To communicate to the traffic light, the emitter transmits visible flashes of light or invisible infrared pulses at a specified <a href="/wiki/Frequency" title="Frequency">frequency</a>. Traffic lights must be equipped with a compatible traffic signal preemption <b><a href="/wiki/Receiver_(radio)" class="mw-redirect" title="Receiver (radio)">receiver</a></b> to respond. Once the vehicle with the active emitter has passed the intersection, the receiving device no longer senses the emitter's signal, and normal operation resumes. Some systems can be implemented with varying frequencies assigned to specific types of uses, which would then allow an intersection's preemption equipment to differentiate between a fire engine and a bus sending a signal simultaneously, and then grant priority access first to the fire engine.</p><figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Millersville_opticom.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/73/Millersville_opticom.jpg/220px-Millersville_opticom.jpg" decoding="async" width="220" height="142" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/73/Millersville_opticom.jpg/330px-Millersville_opticom.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/73/Millersville_opticom.jpg/440px-Millersville_opticom.jpg 2x" data-file-width="2575" data-file-height="1660" /></a><figcaption>A notifier and receiver mounted between <a href="/wiki/Traffic_light" title="Traffic light">traffic lights</a>.</figcaption></figure> <p>Drawbacks of line-of-sight systems include obstructions, lighting and <a href="/wiki/Weather" title="Weather">environmental conditions</a>, and undesired activations. Obstructions may be buildings on a curving road that block visual contact with a traffic signal until very close, or perhaps a large <a href="/wiki/Freight_truck" class="mw-redirect" title="Freight truck">freight truck</a>. In the case of a police car, such a blockage would serve to prevent the traffic signal from receiving the police car's emitter signal. Modifying the position of the receiver or even locating it separate from the traffic signal equipment can sometimes correct this problem. Direct sunlight into a receiver may prevent it from detecting an emitter, and severe environmental conditions, such as heavy rain or snow, may reduce the distance at which a line-of-sight system will function. Undesired activations may occur if an emitter's signal is picked up by many traffic lights along a stretch of road, all directed to change to red in that direction, prior to the activating vehicle turning off the road, or being parked without its emitter being deactivated. </p><p>Line of sight emitters can use IR diodes. They are pulsed with a low-priority signal (10 Hz) or a high-priority signal (14 Hz).<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Localized_radio_signal">Localized radio signal</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Traffic_signal_preemption&action=edit&section=5" title="Edit section: Localized radio signal"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Radio_wave" title="Radio wave">Radio</a>-based traffic-preemption systems using a local, short-range radio signal in the <a href="/wiki/33-centimeter_band" title="33-centimeter band">900MHz band</a>, can usually avoid the weaknesses of line-of-sight systems (<a href="/wiki/List_of_2.4_GHz_radio_use" class="mw-redirect" title="List of 2.4 GHz radio use">2.4 GHz</a> and <a href="/wiki/Optics" title="Optics">optical</a>). A radio-based system still uses a directional signal transmitted from an emitter, but being radio-based, its signal is not blocked by visual obstructions, lighting or weather conditions. Until recently, the major drawback of radio-based traffic signal preemption systems was the possibility of interference from other devices that may be using the same frequency at a given time and location. The advent of FHSS (Frequency Hopping Spread Spectrum) broadcasting has allowed radio-based systems to not only overcome this limitation, but also the aforementioned limitations associated with acoustic and line of sight (optical) systems. It was not until recently that cost effective GPS preemption systems were introduced, supplanting FHSS radio-based preemption as the preemption method of choice, particularly for cities that had experienced the myriad of issues associated with other (acoustic and optical) preemption systems. </p><p>Radio-based systems also began to offer some additional benefits — adjustable range and collision avoidance. The operating range was adjusted by varying the radio signal strength so that traffic lights could be activated only nearby (if desired), or at greater distances. The downside to these preemption systems (which also performed collision avoidance) was that they would display the direction of impending collisions, but not be able to effectively (or accurately) calculate the distance to collision by any method other than RF signal strength, which was only a rough estimate at best. </p> <div class="mw-heading mw-heading3"><h3 id="Global_Positioning_System">Global Positioning System</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Traffic_signal_preemption&action=edit&section=6" title="Edit section: Global Positioning System"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>With the advent of widespread <a href="/wiki/Global_Positioning_System" title="Global Positioning System">Global Positioning System</a> (GPS) applications came the introduction of a GPS-based traffic preemption system capable of collision avoidance. Recently some GPS preemption systems have found a way to overcome the nagging problem that "blinds" many GPS systems: how to prevent the system from being "blinded" by the loss of a GPS signal. In dense cities with tall buildings, GPS receivers may have difficulty obtaining the four required GPS satellite signals, required for <a href="/wiki/Trilateration" title="Trilateration">trilateration</a> to determine location. If the vehicle systems are not designed with a backup "IMU" (Inertial Measurement Unit), lack of GPS availability may adversely affect the system's performance. Extremely heavy cloud cover or severe weather can also adversely impact the ability of the GPS receiver from obtaining the four required satellites. </p><p>Some systems offer an Optical Compatible GPS system with features that also include an <a href="/wiki/Inertial_measurement_unit" title="Inertial measurement unit">Inertial measurement unit</a> (IMU). The price point of some compare to Optical Systems. Therefore, cities that do not have preemption can get a GPS based system for the price of Optical Systems (typically 1/3 the price of many GPS systems). Additionally, cities that have existing optical systems can start upgrading to a GPS-based system while maintaining compatibility with their existing Optical vehicle emitters. These systems also come with Collision Avoidance. </p><p>GPS systems typically convey their information in one of three ways - via 900 MHz FHSS, via 2.4 GHz FHSS, or by way of cellular modem. Each of these methodologies has a different set of advantages/disadvantages. 900 MHz FHSS appears to be the best option, because it is capable of the greatest range (often over 4.8 km or 3 mi for a 1 watt transceiver). 2.4 GHz is able to communicate more data, but is typically considered more "directional" or "line-of-sight". It only has a maximum range of about <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>1.2 km (<span class="frac"><span class="num">3</span>⁄<span class="den">4</span></span> mi). This can often preclude the system from preempting soon enough to ensure a clear intersection upon arrival. Cellular overcomes the "distance" issue, but can be quite costly when cellular fees are taken into consideration. During an area-wide emergency, it is also well known to those in the industry that the cellular network often will go down. This can make preemption difficult (unless there are other backup systems in place) during a time (of crisis) when preemption may be needed most. Cellular also brings with it a certain amount of "latency". It has been documented that it can sometimes take cellular based preemption systems 10 seconds or more to release the preemption of a traffic signal, even though the emergency vehicle has already cleared the intersection. </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=Traffic_signal_preemption&action=edit&section=7" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Bus_priority" class="mw-redirect" title="Bus priority">Bus priority</a></li> <li><a href="/wiki/Bus_rapid_transit_creep" title="Bus rapid transit creep">Bus rapid transit creep</a></li> <li><a href="/wiki/Mobile_Infrared_Transmitter" class="mw-redirect" title="Mobile Infrared Transmitter">Mobile Infrared Transmitter</a></li></ul> <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=Traffic_signal_preemption&action=edit&section=8" title="Edit section: References"><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"> <div class="mw-references-wrap"><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://web.archive.org/web/20081006031044/https://ntl.bts.gov/lib/jpodocs/repts_te/14097_files/14097.pdf">"Traffic Signal Preemption for Emergency Vehicles: A Cross-cutting Study"</a> <span class="cs1-format">(PDF)</span>. Federal Highway Administration. 2006. Archived from <a rel="nofollow" class="external text" href="https://ntl.bts.gov/lib/jpodocs/repts_te/14097_files/14097.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 2008-10-06<span class="reference-accessdate">. Retrieved <span class="nowrap">February 13,</span> 2019</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Traffic+Signal+Preemption+for+Emergency+Vehicles%3A+A+Cross-cutting+Study&rft.pub=Federal+Highway+Administration&rft.date=2006&rft_id=https%3A%2F%2Fntl.bts.gov%2Flib%2Fjpodocs%2Frepts_te%2F14097_files%2F14097.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATraffic+signal+preemption" class="Z3988"></span></span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</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.tech-faq.com/how-do-traffic-lights-work.html">"How Traffic Lights Work"</a>. <i>TECH-FAQ</i><span class="reference-accessdate">. Retrieved <span class="nowrap">February 13,</span> 2019</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=TECH-FAQ&rft.atitle=How+Traffic+Lights+Work&rft_id=http%3A%2F%2Fwww.tech-faq.com%2Fhow-do-traffic-lights-work.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATraffic+signal+preemption" class="Z3988"></span></span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Traffic_signal_preemption&action=edit&section=9" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a rel="nofollow" class="external text" href="https://www.usfa.fema.gov/downloads/pdf/publications/fa_336.pdf">"U.S. Fire Administration, Emergency Vehicle Safety Initiative, FA-336/February 2014"</a></li> <li><a rel="nofollow" class="external text" href="http://tti.tamu.edu/documents/1439-9.pdf"><i>Guide for Traffic Signal Preemption near Railroad Grade Crossing</i></a> (<a href="/wiki/PDF" title="PDF">PDF</a>) (from the <a href="/wiki/Texas_Transportation_Institute" class="mw-redirect" title="Texas Transportation Institute">Texas Transportation Institute</a>)</li> <li><a rel="nofollow" class="external text" href="https://mutcd.fhwa.dot.gov/HTM/2003r1/part4/part4d.htm#section4D13">Section 4D.13</a> of the U.S. <a href="/wiki/Manual_on_Uniform_Traffic_Control_Devices" title="Manual on Uniform Traffic Control Devices">Manual on Uniform Traffic Control Devices</a></li> <li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20060128221925/http://www.its.umn.edu/sensor/2003/spring/signals.html">University of Minnesota Intelligent Transportation Systems Institute report on Dynamic route clearance</a></li> <li><a rel="nofollow" class="external text" href="http://www.tmcnet.com/usubmit/2006/04/13/1571945.htm">"Hackers target traffic lights" at TMCnet</a></li></ul> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist ol ul,.mw-parser-output .hlist ul dl,.mw-parser-output .hlist ul ol,.mw-parser-output .hlist ul ul{display:inline}.mw-parser-output .hlist .mw-empty-li{display:none}.mw-parser-output .hlist dt::after{content:": "}.mw-parser-output .hlist dd::after,.mw-parser-output .hlist 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class="navbox-title" colspan="2"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><style data-mw-deduplicate="TemplateStyles:r1239400231">.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:"[ "}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:" ]"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}}</style><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Road_types" title="Template:Road types"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Road_types" title="Template talk:Road types"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Road_types" title="Special:EditPage/Template:Road types"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Road_hierarchy" style="font-size:114%;margin:0 4em"><a href="/wiki/Road" title="Road">Road</a> <a href="/wiki/Road_hierarchy" title="Road hierarchy">hierarchy</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Types_of_road" title="Types of road">Types of road</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Limited-access_road" title="Limited-access road">Limited-access</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Bicycle_highway" title="Bicycle highway">Bicycle highway</a></li> <li><a href="/wiki/Controlled-access_highway" title="Controlled-access highway">Freeway / Motorway</a></li> <li><a href="/wiki/Dual_carriageway" title="Dual carriageway">Dual carriageway / Divided highway / Expressway</a></li> <li><a href="/wiki/Elevated_highway" title="Elevated highway">Elevated highway</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Category:Limited-access_roads_by_country" title="Category:Limited-access roads by country">By country</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Highways_in_Australia" title="Highways in Australia">Australia</a></li> <li><a href="/wiki/Transport_in_Belgium#Road_transport" title="Transport in Belgium">Belgium</a></li> <li><a href="/wiki/Brazilian_Highway_System" title="Brazilian Highway System">Brazil</a></li> <li><a href="/wiki/Roads_in_Canada" title="Roads in Canada">Canada</a></li> <li><a href="/wiki/Expressways_of_China" title="Expressways of China">China</a></li> <li><a href="/wiki/Highways_in_Croatia" title="Highways in Croatia">Croatia</a></li> <li><a href="/wiki/Highways_in_the_Czech_Republic" title="Highways in the Czech Republic">Czech Republic</a></li> <li><a href="/wiki/Autobahn" title="Autobahn">Germany</a></li> <li><a href="/wiki/Highways_in_Greece" title="Highways in Greece">Greece</a></li> <li><a href="/wiki/List_of_streets_and_roads_in_Hong_Kong" title="List of streets and roads in Hong Kong">Hong Kong</a></li> <li><a href="/wiki/Roads_in_India" title="Roads in India">India</a></li> <li><a href="/wiki/High-quality_dual_carriageway" title="High-quality dual carriageway">Ireland</a></li> <li><a href="/wiki/Roads_in_Italy" title="Roads in Italy">Italy</a></li> <li><a href="/wiki/List_of_roads_in_Nepal" title="List of roads in Nepal">Nepal</a></li> <li><a href="/wiki/Roads_in_Pakistan" title="Roads in Pakistan">Pakistan</a></li> <li><a href="/wiki/Highways_in_Poland" title="Highways in Poland">Poland</a></li> <li><a href="/wiki/Roads_in_Portugal" title="Roads in Portugal">Portugal</a></li> <li><a href="/wiki/Highways_in_Spain" title="Highways in Spain">Spain</a></li> <li><a href="/wiki/Highway_system_in_Taiwan" title="Highway system in Taiwan">Taiwan</a></li> <li><a href="/wiki/Roads_in_the_United_Kingdom" title="Roads in the United Kingdom">United Kingdom</a></li> <li><a href="/wiki/Numbered_highways_in_the_United_States" title="Numbered highways in the United States">United States</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Main roads</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Arterial_road" title="Arterial road">Arterial road</a></li> <li><a href="/wiki/Collector_road" title="Collector road">Collector road</a></li> <li><a href="/wiki/County_highway" title="County highway">County highway</a></li> <li><a href="/wiki/Local%E2%80%93express_lanes" title="Local–express lanes">Express–collector setup</a></li> <li><a href="/wiki/Farm-to-market_road" title="Farm-to-market road">Farm-to-market road</a></li> <li><a href="/wiki/Highway" title="Highway">Highway</a></li> <li><a href="/wiki/Link_road" title="Link road">Link road</a></li> <li><a href="/wiki/Two-lane_expressway" title="Two-lane expressway">Two-lane expressway</a></li> <li><a href="/wiki/2%2B1_road" title="2+1 road">2+1 road</a></li> <li><a href="/wiki/2%2B2_road" title="2+2 road">2+2 road</a></li> <li><a href="/wiki/Parkway" title="Parkway">Parkway</a></li> <li><a href="/wiki/Ring_road" title="Ring road">Ring road</a></li> <li><a href="/wiki/Super_two" title="Super two">Super two</a></li> <li><a href="/wiki/Trunk_road" title="Trunk road">Trunk road</a></li> <li><a href="/wiki/Highway_systems_by_country" title="Highway systems by country">Highway systems by country</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Local roads</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li>Alley</li> <li><a href="/wiki/Avenue_(landscape)" title="Avenue (landscape)">Avenue</a></li> <li><a href="/wiki/Back_road" title="Back road">Back road</a></li> <li><a href="/wiki/Bicycle_boulevard" title="Bicycle boulevard">Bicycle boulevard</a></li> <li><a href="/wiki/Boulevard" title="Boulevard">Boulevard</a></li> <li><a href="/wiki/Country_lane" title="Country lane">Country lane</a></li> <li><a href="/wiki/Dead_end_street" title="Dead end street">Dead end</a></li> <li><a href="/wiki/Driveway" title="Driveway">Driveway</a></li> <li><a href="/wiki/Frontage_road" title="Frontage road">Frontage road</a></li> <li><a href="/wiki/Green_lane_(road)" title="Green lane (road)">Green lane</a></li> <li><a href="/wiki/Main_Street" title="Main Street">Main street</a></li> <li><a href="/wiki/Primitive_road" title="Primitive road">Primitive road</a></li> <li>Road</li> <li><a href="/wiki/Side_road" title="Side road">Side road</a></li> <li><a href="/wiki/Single_carriageway" title="Single carriageway">Single carriageway</a></li> <li><a href="/wiki/Single-track_road" title="Single-track road">Single-track road</a></li> <li>Street</li> <li><a href="/wiki/Sunken_lane" title="Sunken lane">Sunken lane</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Other terms</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Concurrency_(road)" title="Concurrency (road)">Concurrency</a></li> <li><a href="/wiki/Detour" title="Detour">Detour</a></li> <li><a href="/wiki/Road_hierarchy" title="Road hierarchy">Road hierarchy</a></li> <li><a href="/wiki/Private_highway" title="Private highway">Private highway</a></li> <li><a href="/wiki/Route_number" title="Route number">Route number</a> <ul><li><a href="/wiki/Special_route" title="Special route">special route</a></li> <li><a href="/wiki/Business_route" title="Business route">business route</a></li></ul></li> <li><a href="/wiki/Street_hierarchy" title="Street hierarchy">Street hierarchy</a></li> <li><a href="/wiki/Stroad" title="Stroad">Stroad</a></li> <li><a href="/wiki/Toll_road" title="Toll road">Toll road</a></li> <li><a href="/wiki/Winter_road" title="Winter road">Winter road</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Road_junction" title="Road junction">Road junctions</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="/wiki/Interchange_(road)" title="Interchange (road)">Interchanges</a><br /><span class="nobold">(<a href="/wiki/Grade_separation" title="Grade separation">grade-separated</a>)</span></div></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Cloverleaf_interchange" title="Cloverleaf interchange">Cloverleaf</a></li> <li><a href="/wiki/Diamond_interchange" title="Diamond interchange">Diamond</a></li> <li><a href="/wiki/Free-flow_interchange" title="Free-flow interchange">Free-flow</a></li> <li><a href="/wiki/Interchange_(road)#Directional_T_interchange" title="Interchange (road)">Directional T</a></li> <li><a href="/wiki/Diverging_diamond_interchange" title="Diverging diamond interchange">Diverging diamond</a></li> <li><a href="/wiki/Partial_cloverleaf_interchange" title="Partial cloverleaf interchange">Parclo</a></li> <li><a href="/wiki/Raindrop_interchange" class="mw-redirect" title="Raindrop interchange">Raindrop</a></li> <li><a href="/wiki/Roundabout_interchange" title="Roundabout interchange">Roundabout</a></li> <li><a href="/wiki/Single-point_urban_interchange" title="Single-point urban interchange">Single-point urban (SPUI)</a></li> <li><a href="/wiki/Stack_interchange" title="Stack interchange">Stack</a></li> <li><a href="/wiki/Three-level_diamond_interchange" title="Three-level diamond interchange">Three-level diamond</a></li> <li><a href="/wiki/Interchange_(road)#Trumpet_interchange" title="Interchange (road)">Trumpet</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="/wiki/Intersection_(road)" title="Intersection (road)">Intersections<br /><span class="nobold">(at-grade)</span></a></div></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Three-way_junction" title="Three-way junction">3-way junction</a></li> <li><a href="/wiki/Bowtie_(road)" title="Bowtie (road)">Bowtie</a></li> <li><a href="/wiki/Box_junction" title="Box junction">Box junction</a></li> <li><a href="/wiki/Channelization_(roads)" title="Channelization (roads)">Channelization</a></li> <li><a href="/wiki/Continuous-flow_intersection" title="Continuous-flow intersection">Continuous flow</a></li> <li><a href="/wiki/Hook_turn" title="Hook turn">Hook turn</a></li> <li><a href="/wiki/Jughandle" title="Jughandle">Jughandle</a></li> <li><a href="/wiki/Michigan_left" title="Michigan left">Michigan left</a></li> <li><a href="/wiki/Offset_T-intersection" title="Offset T-intersection">Offset T-intersection</a></li> <li><a href="/wiki/Protected_intersection" title="Protected intersection">Protected intersection</a></li> <li><a href="/wiki/Quadrant_roadway_intersection" title="Quadrant roadway intersection">Quadrant roadway</a></li> <li><a href="/wiki/Right-in/right-out" title="Right-in/right-out">Right-in/right-out (RIRO)</a></li> <li><a href="/wiki/Roundabout" title="Roundabout">Roundabout</a></li> <li><a href="/wiki/Seagull_intersection" title="Seagull intersection">Seagull intersection</a></li> <li><a href="/wiki/Split_intersection" title="Split intersection">Split intersection</a></li> <li><a href="/wiki/Superstreet" title="Superstreet">Superstreet</a></li> <li><a href="/wiki/Texas_U-turn" title="Texas U-turn">Texas U-turn</a></li> <li><a href="/wiki/Turnaround_(road)" title="Turnaround (road)">Turnaround</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Road_surface" title="Road surface">Surfaces</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Asphalt_concrete" title="Asphalt concrete">Asphalt concrete</a></li> <li><a href="/wiki/Bioasphalt" title="Bioasphalt">Bioasphalt</a></li> <li>Brick</li> <li><a href="/wiki/Chipseal" title="Chipseal">Chipseal</a></li> <li><a href="/wiki/Cobblestone" title="Cobblestone">Cobblestone</a></li> <li><a href="/wiki/Concrete#Roads" title="Concrete">Concrete</a> <ul><li><a href="/wiki/Reinforced_concrete" title="Reinforced concrete">Reinforced concrete</a></li></ul></li> <li><a href="/wiki/Corduroy_road" title="Corduroy road">Corduroy</a></li> <li><a href="/wiki/Crocodile_cracking" title="Crocodile cracking">Crocodile cracking</a></li> <li><a href="/wiki/Crushed_stone" title="Crushed stone">Crushed stone</a></li> <li><a href="/wiki/Diamond_grinding_of_pavement" title="Diamond grinding of pavement">Diamond grinding of pavement</a></li> <li><a href="/wiki/Dirt_road" title="Dirt road">Dirt</a></li> <li><a href="/wiki/Full_depth_recycling" title="Full depth recycling">Full depth recycling</a></li> <li><a href="/wiki/Glassphalt" title="Glassphalt">Glassphalt</a></li> <li><a href="/wiki/Gravel_road" title="Gravel road">Gravel</a></li> <li><a href="/wiki/Ice_road" title="Ice road">Ice</a></li> <li><a href="/wiki/Macadam" title="Macadam">Macadam</a></li> <li><a href="/wiki/Pavement_milling" title="Pavement milling">Pavement milling</a></li> <li><a href="/wiki/Permeable_paving" title="Permeable paving">Permeable</a></li> <li><a href="/wiki/Plank_road" title="Plank road">Plank</a></li> <li><a href="/wiki/Plastic_road" title="Plastic road">Plastic</a></li> <li><a href="/wiki/Rubberized_asphalt" title="Rubberized asphalt">Rubberized asphalt</a></li> <li><a href="/wiki/Sealcoat" title="Sealcoat">Sealcoat</a></li> <li><a href="/wiki/Sett_(paving)" title="Sett (paving)">Sett</a></li> <li><a href="/wiki/Stamped_asphalt" title="Stamped asphalt">Stamped asphalt</a></li> <li><a href="/wiki/Tarmacadam" title="Tarmacadam">Tarmac</a></li> <li><a href="/wiki/Road_texture" title="Road texture">Texture</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Road_traffic_safety" title="Road traffic safety">Road safety<br />factors</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%">Road and<br />environment</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Aquaplaning" title="Aquaplaning">Aquaplaning</a></li> <li><a href="/wiki/Avalanche" title="Avalanche">Avalanche</a></li> <li><a href="/wiki/Black_ice" title="Black ice">Black ice</a></li> <li><a href="/wiki/Bleeding_(roads)" title="Bleeding (roads)">Bleeding</a></li> <li><a href="/wiki/Crosswind" title="Crosswind">Crosswind</a></li> <li><a href="/wiki/Dead_Man%27s_Curve" title="Dead Man's Curve">Dead Man's Curve</a></li> <li><a href="/wiki/Expansion_joint" title="Expansion joint">Expansion joint</a></li> <li><a href="/wiki/Fog" title="Fog">Fog</a></li> <li><a href="/wiki/Ford_(crossing)" title="Ford (crossing)">Ford</a></li> <li><a href="/wiki/Hairpin_turn" title="Hairpin turn">Hairpin turn</a></li> <li><a href="/wiki/Level_crossing" title="Level crossing">Level crossing</a></li> <li><a href="/wiki/Manhole_cover" title="Manhole cover">Manhole cover</a></li> <li><a href="/wiki/Oil_spill" title="Oil spill">Oil spill</a></li> <li><a href="/wiki/Oversize_load" title="Oversize load">Oversize load</a></li> <li><a href="/wiki/Pothole" title="Pothole">Pothole</a></li> <li><a href="/wiki/Road_debris" title="Road debris">Road debris</a></li> <li><a href="/wiki/Road_slipperiness" title="Road slipperiness">Road slipperiness</a></li> <li><a href="/wiki/Road_train" title="Road train">Road train</a></li> <li><a href="/wiki/Roadkill" title="Roadkill">Roadkill</a></li> <li><a href="/wiki/Rockfall" title="Rockfall">Rockfall</a></li> <li><a href="/wiki/Rut_(roads)" title="Rut (roads)">Rut</a></li> <li><a href="/wiki/Speed_bump" title="Speed bump">Speed bump</a></li> <li><a href="/wiki/Storm_drain" title="Storm drain">Storm drain</a></li> <li><a href="/wiki/Traffic_light" title="Traffic light">Traffic light</a></li> <li><a href="/wiki/Traffic_sign" title="Traffic sign">Traffic sign</a></li> <li><a href="/wiki/Washboarding" title="Washboarding">Washboarding</a></li> <li><a href="/wiki/Washout_(erosion)" title="Washout (erosion)">Washout</a></li> <li><a href="/wiki/Whiteout_(weather)" title="Whiteout (weather)">Whiteout</a></li> <li><a href="/wiki/Snow_squall" title="Snow squall">Snow squall</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Traffic_psychology" title="Traffic psychology">Human factors</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Driver%27s_education" title="Driver's education">Driver's education</a></li> <li><a href="/wiki/Driving_under_the_influence" title="Driving under the influence">Driving under the influence</a></li> <li><a href="/wiki/Drowsy_driving" title="Drowsy driving">Drowsy driving</a></li> <li><a href="/wiki/Road_rage" title="Road rage">Road rage</a></li> <li><a href="/wiki/Single-vehicle_crash" class="mw-redirect" title="Single-vehicle crash">Single-vehicle crash</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Vehicles</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Airbag" title="Airbag">Airbag</a></li> <li><a href="/wiki/Automotive_safety" title="Automotive safety">Automotive safety</a></li> <li><a href="/wiki/Seat_belt" title="Seat belt">Seat belt</a></li> <li><a href="/wiki/Risk_compensation#Road_transport" title="Risk compensation">Risk compensation (road transport)</a></li> <li><a href="/wiki/Underride_guard" class="mw-redirect" title="Underride guard">Underride guard</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Traffic#Rules_of_the_road" title="Traffic">Space and<br />time allocation</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Barrier_transfer_machine" title="Barrier transfer machine">Barrier transfer machine</a></li> <li><a href="/wiki/Bike_lane" title="Bike lane">Bike lane</a></li> <li><a href="/wiki/Climbing_lane" title="Climbing lane">Climbing lane</a></li> <li><a href="/wiki/Complete_streets" title="Complete streets">Complete streets</a></li> <li><a href="/wiki/Contraflow_lane" title="Contraflow lane">Contraflow lane</a></li> <li><a href="/wiki/Contraflow_lane_reversal" title="Contraflow lane reversal">Contraflow lane reversal</a></li> <li><a href="/wiki/High-occupancy_toll_lane" title="High-occupancy toll lane">High-occupancy toll lane</a></li> <li><a href="/wiki/High-occupancy_vehicle_lane" title="High-occupancy vehicle lane">High-occupancy vehicle lane</a></li> <li>Lane</li> <li><a href="/wiki/Living_street" title="Living street">Living street</a></li> <li><a href="/wiki/Managed_lane" title="Managed lane">Managed lane</a></li> <li><a href="/wiki/Median_strip" title="Median strip">Median / Central reservation</a></li> <li><a href="/wiki/Motorcycle_lane" title="Motorcycle lane">Motorcycle lane</a></li> <li><a href="/wiki/Passing_lane" title="Passing lane">Passing lane</a></li> <li><a href="/wiki/Pedestrian_crossing" title="Pedestrian crossing">Pedestrian crossing</a></li> <li><a href="/wiki/Pedestrian_zone" title="Pedestrian zone">Pedestrian zone</a></li> <li><a href="/wiki/Refuge_island" title="Refuge island">Refuge island</a></li> <li><a href="/wiki/Reversible_lane" title="Reversible lane">Reversible lane</a></li> <li><a href="/wiki/Road_diet" title="Road diet">Road diet</a></li> <li><a href="/wiki/Road_verge" title="Road verge">Road verge</a></li> <li><a href="/wiki/Runaway_truck_ramp" title="Runaway truck ramp">Runaway truck ramp</a></li> <li><a href="/wiki/Shared_space" title="Shared space">Shared space</a></li> <li><a href="/wiki/Sidewalk" title="Sidewalk">Sidewalk / Pavement</a></li> <li><a href="/wiki/Shoulder_(road)" title="Shoulder (road)">Shoulder</a></li> <li><a href="/wiki/Street_running_train" title="Street running train">Street-running railway</a></li> <li><a href="/wiki/Traffic_calming" title="Traffic calming">Traffic calming</a></li> <li><a href="/wiki/Left-_and_right-hand_traffic" title="Left- and right-hand traffic">Traffic directionality</a></li> <li><a href="/wiki/Traffic_island" title="Traffic island">Traffic island</a></li> <li><a href="/wiki/Traffic_lanes" class="mw-redirect" title="Traffic lanes">Traffic lanes</a></li> <li><a class="mw-selflink selflink">Traffic signal preemption</a></li> <li><a href="/wiki/Truck_bypass" title="Truck bypass">Truck bypass</a></li> <li><a href="/wiki/Unused_highway" title="Unused highway">Unused highway</a></li> <li><a href="/wiki/Wide_outside_lane" title="Wide outside lane">Wide outside lane</a></li> <li><a href="/wiki/Woonerf" title="Woonerf">Woonerf</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Demarcation</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Bollard" title="Bollard">Bollard</a></li> <li><a href="/wiki/Botts%27_dots" title="Botts' dots">Botts' dots</a></li> <li><a href="/wiki/Cable_barrier" title="Cable barrier">Cable barrier</a></li> <li><a href="/wiki/Cat%27s_eye_(road)" title="Cat's eye (road)">Cat's eye (road)</a></li> <li><a href="/wiki/Concrete_step_barrier" title="Concrete step barrier">Concrete step barrier</a></li> <li><a href="/wiki/Constant-slope_barrier" title="Constant-slope barrier">Constant-slope barrier</a></li> <li>Curb</li> <li><a href="/wiki/F-shape_barrier" title="F-shape barrier">F-shape barrier</a></li> <li><a href="/wiki/Guard_rail" title="Guard rail">Guard rail</a></li> <li><a href="/wiki/Jersey_barrier" title="Jersey barrier">Jersey barrier</a></li> <li><a href="/wiki/Kassel_kerb" title="Kassel kerb">Kassel kerb</a></li> <li><a href="/wiki/Noise_barrier" title="Noise barrier">Noise barrier</a></li> <li><a href="/wiki/Raised_pavement_marker" title="Raised pavement marker">Raised pavement marker</a></li> <li><a href="/wiki/Road_surface_marking" title="Road surface marking">Road surface marking</a></li> <li><a href="/wiki/Rumble_strip" title="Rumble strip">Rumble strip</a></li> <li><a href="/wiki/Traffic_barrier" title="Traffic barrier">Traffic barrier</a></li> <li><a href="/wiki/Traffic_cone" title="Traffic cone">Traffic cone</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Structures</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li>Bridge</li> <li><a href="/wiki/Causeway" title="Causeway">Causeway</a></li> <li><a href="/wiki/Overpass" title="Overpass">Overpass / Flyover</a></li> <li><a href="/wiki/Tunnel" title="Tunnel">Underpass / Tunnel</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Performance<br />indicators</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Pavement_condition_index" title="Pavement condition index">Pavement condition index</a></li> <li><a href="/wiki/International_roughness_index" title="International roughness index">International roughness index</a></li> <li><a href="/wiki/Present_serviceability_index" title="Present serviceability index">Present serviceability index</a></li> <li><a href="/wiki/Pavement_performance_modeling" title="Pavement performance modeling">Pavement performance modeling</a></li> <li><a href="/wiki/Granular_base_equivalency" title="Granular base equivalency">Granular base equivalency</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <ul><li><a href="/wiki/Glossary_of_road_transport_terms" title="Glossary of road transport terms">Glossary of road transport terms</a></li> <li><a href="/wiki/List_of_road_types_by_features" class="mw-redirect" title="List of road types by features">Road types by features</a></li></ul> </div></td></tr></tbody></table></div>    </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" href="https://en.wikipedia.org/w/index.php?title=Traffic_signal_preemption&oldid=1238663514">https://en.wikipedia.org/w/index.php?title=Traffic_signal_preemption&oldid=1238663514</a>"</div></div> <div 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