Editing Traffic calming (section)

== Measures ==
Traffic engineers refer to three "E's" when discussing traffic calming: [[engineering]], (community) [[education]], and (police) [[enforcement]].  Because neighborhood traffic management studies have shown that residents often contribute to the perceived speeding problem within their neighborhoods, instructions on traffic calming (for example in Hass-Klau et al., 1992<ref>{{cite book|last=Hass-Klau|first=Carmen|title=Civilised Streets: A Guide to Traffic Calming|year=1992|publisher=Environmental and Transport Planning|location=Brighton, UK|isbn=0-9519620-0-0|page=223}}</ref>) stress that the most effective traffic calming plans entail all three components—that engineering measures alone will not produce satisfactory results.

=== 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.

===Implementation strategies===
There are primarily two implementation options for the creation of traffic calming measure: capital reconstruction versus operational changes.{{Citation needed|date=June 2021}}
* Capital reconstruction is rebuilding a street, which may involve moving infrastructure (such as sewers, water lines, electrical equipment) and adjusting the location, size and path of the roadway. Typically, capital reconstruction involves years of planning and design, and millions of dollars of investment.
* Operational changes to a road have to do with more short-term changes that typically implement minor adjustments within the existing curbline or that do not require rebuilding the road. These treatments range from a very temporary use of safety cones or other safety-approved traffic management devices, such as flexible bollards, that test a traffic-calming initiative for a few days to longer-term operational changes that may include restriping a street, which is best to plan around any routine maintenance resurfacing.

=== Enforcement and education measures ===
Enforcement and education measures for traffic calming include:
* Reducing speed limits near institutions such as [[school zone|schools]] and hospitals (see below)
* [[Vehicle activated sign|Vehicle activated signs]] and [[Radar speed sign|radar speed feedback signs]], signs which react with a message if they detect a vehicle exceeding a pre-determined speed.
* [[Embedded pavement flashing-light system]]s which react to pedestrian presence at crossings to signal drivers and increase awareness.
* [[Watchman camera|Watchman]], traffic calming system

==== Speed limits ====
{{main|Speed limit}}
Speed reduction has traditionally been attempted by the introduction of statutory [[speed limit]]s.  Traffic speeds of 30&nbsp;km/h (20&nbsp;mph) and lower are said to be more desirable on urban roads with mixed traffic.<ref>Speed reduction, traffic calming or cycling facilities: a question of what best achieves the goals?, Michael Yeates, Convenor, Cyclists Urban Speed limit Taskforce, Bicycle Federation of Australia, Velomondial Conference Proceedings, Amsterdam 2000</ref>  The Austrian city of [[Graz]], which has achieved steady growth in cycling, has applied 30&nbsp;km/h limits to 75% its streets since 1994.<ref>The Graz traffic calming model and its consequences for cyclists, Manfred Hoenig, Department of transportation, City Council Graz, Velomondial Conference Proceedings, Amsterdam 2000</ref>  Zones where speeds are set at [[20 mph zone|30 km/h]] (or 20&nbsp;mph) are preferred by some<ref>{{cite web |url=http://www.streetfilms.org/no-need-for-speed-20s-plenty-for-us/ |title=No Need for Speed: 20s Plenty for Us |publisher=Streetfilms |date=30 August 2010 |access-date=9 September 2013 |archive-date=14 June 2013 |archive-url=https://web.archive.org/web/20130614093436/http://www.streetfilms.org/no-need-for-speed-20s-plenty-for-us/ |url-status=live }}</ref> as they are found to be effective at reducing crashes and increasing community cohesion.<ref>{{cite web |url=http://www.walk21.com/papers/Josua_Hart.pdf |title=Driven To Excess: A Study of Motor Vehicle Impacts on Three Streets in Bristol UK |first=Joshua|last=Hart|access-date=2011-11-27 |url-status=dead |archive-url=https://web.archive.org/web/20120426002544/http://www.walk21.com/papers/Josua_Hart.pdf |archive-date=26 April 2012 |df=dmy-all }}</ref> Speed limits which are set below [[85th percentile speed|the speed that most motorists perceive to be reasonable]] for the given road require additional measures to improve compliance.  Attempts to improve speed limit observance are usually by either education, enforcement or road engineering. "Education" can mean [[Public service announcement|publicity campaigns]] or targeted road user training.

[[Speed limit enforcement]] techniques include: direct police action, automated systems such as [[speed camera]]s or [[vehicle activated sign]]s or traffic lights triggered by traffic exceeding a preset speed threshold. One cycling expert argues for placing direct restrictions on motor-vehicle speed and acceleration performance.<ref>[http://www.camcycle.org.uk/campaigning/talks/agm1999/ Enabling and encouraging people to cycle] {{Webarchive|url=https://web.archive.org/web/20081122043029/http://www.camcycle.org.uk/campaigning/talks/agm1999/ |date=22 November 2008 }}, John Franklin, Paper presented to the Cambridge Cycling Campaign AGM, 5 October 1999</ref>  An EU report on promoting walking and cycling specifies as one of its top measures comprehensive camera-based speed control using mainly movable equipment at unexpected spots.<ref>How to enhance WALking and CYcliNG instead of shorter car trips and to make these modes safer, Deliverable D6 WALCYNG Contract No: UR-96-SC.099, Department of Traffic Planning and Engineering, University of Lund, Sweden 1999</ref>  The [[Netherlands]] has an estimated 1,500 speed/red-light camera installations and has set a target for 30&nbsp;km/h limits on 70% of urban roads.  The UK has more than 6,000 speed cameras, which took more than [[£]]100 million in fines in 2006/07.<ref>{{cite news |title=Speed cameras collect over £100m in fines |author=Gary Cleland |date=14 March 2008 |work=The Daily Telegraph |url=https://www.telegraph.co.uk/news/main.jhtml?xml=/news/2008/03/14/nspeed114.xml |archive-url=https://web.archive.org/web/20080316074842/http://www.telegraph.co.uk/news/main.jhtml?xml=/news/2008/03/14/nspeed114.xml |url-status=dead |archive-date=16 March 2008 |access-date=18 March 2008}}</ref>