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Curb extension
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<h2 id="uses">Uses</h2> <p>Curb extensions are used to: </p> <ul><li>Increase the visibility of pedestrians by enforcing the "daylighting" of the intersection and encouraging pedestrians to wait in a more visible area.</li> <li>Reduce crossing distances for pedestrians.</li> <li>Provide space for ramps on the sidewalk where it would otherwise be too narrow.</li> <li>Slow down traffic by visually narrowing the roadway and reducing the turning radius of drivers. This is especially useful for calming fast traffic turning from a major to a minor road.</li> <li>Shield <a href="/facts/Parallel_parking/A1wKe26P">parallel parked</a> vehicles from oncoming traffic.</li> <li>Protect passengers embarking and particularly disembarking from <a href="/facts/Tram/gSaKExyR">trams</a>, <a href="/facts/Bus/AgUM7Tab">buses</a>, and level-grade urban <a href="/facts/Light_rail/5Sr1FjHu">light rail</a> systems, particularly when <a href="/facts/Retrofitting/GHG2n0Vr">retrofitting</a> existing <a href="/facts/Street/cCpWWXtB">streets</a>. In other words, curb extensions prevent buses from needing to pull over to side of the road to release and receive passengers.</li> <li>Provide protection for pedestrians, possibly by including a <a href="/facts/Traffic_barrier/eYynyFKs">pedestrian barrier</a>, preventing pedestrians from <a href="/facts/Running/h09J9jtb">running</a> straight from the premises over the road.</li> <li>Provide room for <a href="/facts/U-turn/2wnePkEv">U-turns</a> on <a href="/facts/Superstreet/513CdAgk">superstreets</a>.<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a></li></ul> <p>Curb extensions are also used when <a href="/facts/Retrofit/GHG2n0Vr">retrofitting</a> existing streets to accommodate <a href="/facts/Congestion_charging/KmzLms3G">congestion charging</a> schemes - hitherto wide (sometimes multi-<a href="/facts/Lane/EQUR8gAD">lane</a>) roads are deliberately narrowed to ensure that the charging equipment can see passing vehicles, and the charging equipment (and often bollards or other barrier devices) are placed in the expanded sidewalk area (to prevent drivers from circumventing the charging system's <a href="/facts/Camera/j4uqsfJQ">cameras</a> and detectors). </p> <h2 id="design-advantages-and-disadvantages">Design, advantages and disadvantages</h2> <p>The Pedestrian and Bicycle Information Center, a body funded by the US Federal Highway Administration,<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> advises that curb extensions ought not encroach on travel lanes, bicycle lanes, or shoulders, and should not extend more than 1.8 m (6 ft) from the curb.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> Some curb extensions are built with the bike lane passing through (making the extension an island, separated from the main sidewalk by a narrow bike lane). </p><p>One study has found that pedestrians crossing at curb extensions have to wait for fewer vehicles to pass before a motorist yields to allow them to cross. The study was too small to determine whether other measures of effectiveness were significant, such as percent of pedestrians crossing after a motorist yields.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> </p><p>Poorly designed curb extensions can pose a hazard to <a href="/facts/Cyclist/XH6EKjAF">cyclists</a>, as they force cyclists from their position at the road side (or in a roadside <a href="/facts/Segregated_cycle_facilities/zGukC0gj">bike lane</a>) into the narrowed gap. They can also damage vehicles if the curbs extend too close to traffic lanes.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> </p><p>Author <a href="/facts/Randal_O%2527Toole/abpDElwA">Randal O'Toole</a> argues that curb extensions are used to discourage the use of automobiles by reducing the number of lanes available for automobiles. In particular, curb extensions can be used to block turn lanes, forcing turning vehicles to remain with the forward moving traffic.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> Curb extensions do prevent drivers from using parking lanes or shoulders as right turn lanes. </p><p>However, reducing the crossing distance also reduces the time needed to cross the street. This allows a reduction in the length of the pedestrian phase at signalized intersection, and reduces the time needed to yield to pedestrians at stop sign controlled intersections. This at least partially compensated for any loss in vehicle capacity.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> </p><p>Curb extensions complicate drainage. They obstruct the gutter, so a catch basin is needed at the uphill end to keep a puddle from forming. An alternate solution is placing a gap in the curb, allowing the stormwater in the gutter to irrigate a <a href="/facts/Rain_garden/g4YCHr6o">rain garden</a> or <a href="/facts/Bioswale/0mFPo1Au">bioswale</a> in the curb extension.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> </p> <p>To facilitate <a href="/facts/Street_sweeper/NEboqFED">street sweeping</a>, the internal and external curvatures of the extended curb section are moderately graduated. </p><p>Retroactively adding curb extensions to older, established communities has been controversial in some instances, due to the installation of the extensions reducing the availability of on-street parking for some properties, particularly in cases where the curb extension has been installed on its own and not in conjunction with a crosswalk. </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Bus_bulb/um1Q8gFC">Bus bulb / border</a>, a specific type of curb extension that is used as a bus stop</li> <li><a href="/facts/Sneckdown/uWu13WhR">Sneckdown</a>, a temporary curb extension caused by snowfall</li> <li><a href="/facts/Intersection_daylighting/I3KLFkd5">Intersection daylighting</a></li></ul> <h2 id="external-links">External links</h2> <ul><li><a href="http://www.transport.sa.gov.au/safety/road/road_use/ped_facilities.asp#03">Transport SA (South Australia) explanation of curb extensions</a></li> <li><a href="https://web.archive.org/web/20160519045826/http://www.portlandoregon.gov/transportation/article/83921">Portland Dept. of Transportation</a> - document showing curb extensions and the circumstances of their use.</li> <li><a href="https://web.archive.org/web/20100910193250/http://www.walkinginfo.org/engineering/crossings-enhancements.cfm#curb-extensions">WalkingInfo.org's detailed discussion of curb extensions</a></li> <li><a href="https://archive.today/20130115094029/http://www.cityofkingston.ca/residents/transportation/streets/trafficcalming/curbextension.asp">Information and policy from Kingston, Ontario</a></li> <li><a href="https://nacto.org/publication/urban-street-design-guide/street-design-elements/curb-extensions/">National Association of City Transportation Officials Urban Street Design Guide</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Plemmons, Mark (April 30, 2016). "Neighbors fear speeding traffic on new section of George Liles Parkway". Independent Tribune. Retrieved April 30, 2016. <a href="https://www.independenttribune.com/news/neighbors-fear-speeding-traffic-on-new-section-of-george-liles/article_4c7d25a8-0ef4-11e6-968a-e71a8e18014e.html" target="_blank">https://www.independenttribune.com/news/neighbors-fear-speeding-traffic-on-new-section-of-george-liles/article_4c7d25a8-0ef4-11e6-968a-e71a8e18014e.html</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>"About". PedBikeInfo. Retrieved 27 June 2023. <a href="https://www.pedbikeinfo.org/about.cfm" target="_blank">https://www.pedbikeinfo.org/about.cfm</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Pedestrian and Bicycle Information Center, "Crossing Enhancements," http://www.walkinginfo.org/engineering/crossings-enhancements.cfm Archived 2010-09-10 at the Wayback Machine, retrieved 23 June 2010 <a href="http://www.walkinginfo.org/engineering/crossings-enhancements.cfm" target="_blank">http://www.walkinginfo.org/engineering/crossings-enhancements.cfm</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Randal S. Johnson (July 2005). "Pedestrian Safety Impacts of Curb Extensions: a Case Study" (PDF). Retrieved 5 August 2011. <a href="http://www.oregon.gov/ODOT/TD/TP_RES/docs/Reports/PedestrainSafetyCurbExt.pdf?ga=t" target="_blank">http://www.oregon.gov/ODOT/TD/TP_RES/docs/Reports/PedestrainSafetyCurbExt.pdf?ga=t</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Albany Times Union "MOTORISTS TAKE HIT ON ROAD PROJECT" July 19, 2004, [1] retrieved 29 June 2010 <a href="https://web.archive.org/web/20120306101527/http://albarchive.merlinone.net/mweb/wmsql.wm.request?oneimage&imageid=6245046" target="_blank">https://web.archive.org/web/20120306101527/http://albarchive.merlinone.net/mweb/wmsql.wm.request?oneimage&imageid=6245046</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Randal O'Toole "Gridlock" <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>"Road Diets: Making Streets Slim Down Is Good For Pedestrians, Businesses And Even Traffic," Planetizen, http://www.planetizen.com/node/44645 <a href="http://www.planetizen.com/node/44645" target="_blank">http://www.planetizen.com/node/44645</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Sustainable Stormwater Management, http://www.portlandonline.com/BES/index.cfm?c=34598, retrieved 28 April 2010 <a href="http://www.portlandonline.com/BES/index.cfm?c=34598" target="_blank">http://www.portlandonline.com/BES/index.cfm?c=34598</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> </ol>