Editing Traffic calming (section)

=== Engineering measures ===
Engineering measures involve physically altering the road layout or appearance to actively or passively reduce traffic speeds by one of several means:
* increasing the [[cognitive load]] of driving (making driving more difficult)
* increasing the chance that an obstruction in the road will slow or momentarily stop motorists (such as replacing a bus pullout with a [[bus bulb]], causing transit vehicles to stop for passenger loading and unloading in the travel lane, rather than pulling off and letting cars pass)
* increasing the chance of passenger discomfort or even physical damage to a vehicle if speed limits are not observed (such as speed humps).{{Citation needed|date=May 2022}}
Measures include [[speed hump]]s, [[chicane]]s, [[curb extension]]s, [[modal filter]]s, and [[living street]] and [[shared space]] type schemes.  The town of [[Hilden]] in Germany has achieved a rate of 24% of trips being on two wheels, mainly via traffic calming and the use of 30&nbsp;km/h or 20&nbsp;mph zones.<ref>[http://homepage.ntlworld.com/pete.meg/wcc/report/Hilden.pdf Learning from Hilden’s Successes] {{Webarchive|url=https://web.archive.org/web/20081029100348/http://homepage.ntlworld.com/pete.meg/wcc/report/Hilden.pdf |date=29 October 2008 }}, Rod King, [[Warrington Cycle Campaign]], August 2004 (Accessed 24 January 2007)</ref>  In 1999, the Netherlands had over 6000 [[Woonerf|woonerven]] where cyclists and pedestrians have legal priority over cars and where a motorised "walking speed" limit applies.<ref>Home Zones briefing sheet, Robert Huxford, Proceedings, Institution of Civil Engineers, Transport, 135, 45-46, February 1999</ref> However, some [[United Kingdom|UK]] and [[Republic of Ireland|Irish]] "traffic calming" schemes, particularly involving road narrowings, are viewed as extremely hostile and have been implicated directly in death and injury to cyclists and pedestrians.<ref>[http://galwaycycling.org/archive/info/narrowings.html Road Narrowings and Pinch Points] {{Webarchive|url=https://web.archive.org/web/20071206130914/http://galwaycycling.org/archive/info/narrowings.html |date=6 December 2007 }} An Information Sheet, Galway Cycling Campaign, February 2001</ref><ref>[http://www.thebikezone.org.uk/thebikezone/campaigning/pinchpoints.html Cyclists at Road Narrowings] {{Webarchive|url=https://web.archive.org/web/20160609174239/http://www.thebikezone.org.uk/thebikezone/campaigning/pinchpoints.html |date=9 June 2016 }}, by Howard Peel, The Bike Zone. (Accessed 27 January 2007)</ref>

A number of '''visual changes''' to roads are being made to encourage more attentive driving, reduced speed, reduced crashes, and a greater tendency to yield to pedestrians. Visual traffic calming includes ''lane narrowings'' ({{cvt|9|–|10|ft|m|order=flip}}), ''road diets'' (reduction in lanes), use of trees next to streets, on-street parking, and buildings placed in urban fashion close to streets.
[[File:Dunbar_Spring_traffic_circle,_Tucson,_Arizona.jpg|thumb|Traffic calming roundabout and rainwater-harvesting infrastructure in Tucson, Arizona]]
Physical devices include speed humps, speed cushions and speed tables, sized for the desired speed. Such measures normally slow cars to between {{convert|10|and|25|mph|km/h|order=flip}}. Most devices are made of asphalt or concrete but rubber traffic calming products are emerging as an effective alternative with several advantages.

Physical traffic calming can include the following engineering measures, grouped by similarity of method:<ref>{{cite book|author1=Fitzgerald & Halliday, Inc|title=Traffic Calming Resource Guide|url=http://www.scrcog.org/documents/TrafficCalming_ResourceGuide_Final.pdf|publisher=South Central Regional Council of Governments|access-date=12 November 2014|archive-date=4 March 2016|archive-url=https://web.archive.org/web/20160304024816/http://www.scrcog.org/documents/TrafficCalming_ResourceGuide_Final.pdf|url-status=live}}</ref>
* Narrowing: [http://www.wri.org/blog/2016/12/bigger-isnt-always-better-narrow-traffic-lanes-make-cities-safer Narrowing traffic lanes] makes slower speeds seem more natural to drivers and are less intrusive than other treatments that limit speed or restrict route choice. Narrowing measures include:
** Lane narrowings can be created by extending sidewalks, adding bollards or planters, or adding a bike lane or on-street parking.<ref>{{cite web|url=http://thecityfix.com/blog/bigger-isnt-always-better-narrow-traffic-lanes-make-cities-safer-subha-ranjan-banerjee-ben-welle/|title=Bigger Isn't Always Better: Narrow Traffic Lanes Make Cities Safer {{!}} TheCityFix|website=TheCityFix|language=en-US|access-date=2017-04-17|date=6 December 2016|archive-date=18 April 2017|archive-url=https://web.archive.org/web/20170418000130/http://thecityfix.com/blog/bigger-isnt-always-better-narrow-traffic-lanes-make-cities-safer-subha-ranjan-banerjee-ben-welle/|url-status=live}}</ref>
** [[Curb extension]]s (also called bulbouts) narrow the width of the roadway at [[pedestrian crossing]]s
** Chokers are curb extensions that narrow roadways to a single lane at certain points<ref>[http://www.ite.org/traffic/choker.asp single lane choker] {{Webarchive|url=https://web.archive.org/web/20180404221853/http://www.ite.org/traffic/choker.asp |date=4 April 2018 }} ITE</ref>
** [[Road diet]]s remove a lane from the street. For example, allowing parking on one or both sides of a street to reduce the number of driving lanes.
** [[Pedestrian refuge]]s or small islands in the middle of the street can help reduce lane widths.
** Converting [[one-way street]]s into two-way streets forces opposing traffic into close proximity, which requires more careful driving. 
[[File:Construction of a crosswalk using polymer modified cement slurry.jpg|thumb|Construction of [[polymer cement overlay]] to change asphalt to brick texture and colour to indicate a high-traffic pedestrian crossing]]
* Vertical deflection: Raising a portion of a road surface can create discomfort for drivers travelling at high speeds. Both the height of the deflection and the steepness affect the severity of vehicle displacement. Vertical deflection measures include:
**[[Speed bumps]], sometimes split or offset in the middle to avoid delaying emergency vehicles
** [[Speed bumps#Speed humps|Speed humps]], parabolic devices that are less aggressive than speed bumps. 
** [[Speed bumps#Speed cushions|Speed cushions]], two or three small speed humps sitting in a line across the road that slow cars down but allows wider emergency vehicles to straddle them so as not to slow emergency response time.
** [[Speed bumps#Speed tables|Speed tables]], long flat-topped speed humps that slow cars more gradually than humps.
** Raised [[pedestrian crossing]]s, which act as speed tables, often situated at [[Road junction|junctions]].
** Raised [[intersection]]s, like raised pedestrian crossings, act as speed tables.
** Speed dips, sunken instead of raised (often seen as double dips in cycleways in The Netherlands).<ref>{{cite news |title=Speed bumps on the cycle-path |author=David Hemebrew |date=22 November 2011 |work=A view from the cycle path |url=http://www.aviewfromthecyclepath.com/2011/11/speedbumps-on-cycle-path.html |access-date=16 December 2022}}</ref>
** Changing the surface material or texture (for example, the selective use of [[brick]], [[cobblestone]], or [[Decorative concrete|polymer cement overlay]]). Changes in texture may also include changes in color to highlight to drivers that they are in a pedestrian-centric zone.
** [[Rumble strip]]s, when placed perpendicular to traffic in the travel lane (rather than placed between lanes parallel to traffic) act as speed bumps as they produce unpleasant sounds and vibration when crossed at higher speeds. 
* Horizontal deflection, i.e. make the vehicle swerve slightly. These include:
**[[Chicane]]s, which create a horizontal deflection that causes vehicles to slow as they would for a curve.
** [[Pedestrian refuge]]s again can provide horizontal deflection, as can [[curb extension|kerb extension]]s and chokers.
**[[Roundabout]]s and traffic circles provide another source of horizontal deflection especially when integrated within intersecting roads
[[File:Diagonalsperre.jpg|thumb|Diagram of an intersection divided by a median diverter]]
* Block or restrict access. Such traffic calming means include:
** [[Modal filter|Median diverter]]s to prevent left turns or through movements into a residential area.
** Converting an intersection into a [[cul-de-sac]] or dead end.
** [[Boom barrier]], restricting through traffic to authorised vehicles only.
** Closing of streets to create [[pedestrian zone]]s.
* Other means
Quite often residents have used a variety of homemade devices ranging from faux enforcement camera signs and even faux speed cameras and including dummy police.
Some Canadian communities erect flexible [[bollard]]s in the middle of the street in [[school zone]]s. The bollards have a sign affixed indicating a 40&nbsp;km/h speed limit.