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Traffic calming

Evidence Rating

Scientifically Supported

Traffic calming measures such as speed bumps, speed humps, pedestrian refuge islands, and roundabouts strategically modify the built environment to affect traffic speed and patterns. Traffic calming measures can be implemented independently or as a component of larger efforts to improve streetscape design (US DOT-Traffic calming). Traffic calming measures are used in urban, suburban, and rural areas (Gulden 2016); in rural communities, such efforts often reduce speeds as drivers transition from high-speed roads into lower-speed zones (Hallmark 2013).

Expected Beneficial Outcomes (Rated)

  • Reduced traffic speed

Other Potential Beneficial Outcomes

  • Increased pedestrian and cyclist safety

  • Increased active transportation

  • Reduced crashes

Evidence of Effectiveness

There is strong evidence that traffic calming measures reduce traffic speed and redistribute traffic (, Rothman 2015, , Retting 2003). Traffic calming measures can also increase pedestrian and cyclist safety (CG-Physical activity) and increase bicycling and walking (Winters 2010, Morrison 2004). Additional evidence is needed to determine which measures are most effective.

Traffic calming measures such as speed bumps, single-lane roundabouts, and reduced speed limit zones reduce traffic speed (, ). Speed humps are particularly effective ways to reduce pedestrian-vehicle crashes that involve children (Rothman 2015). Single-lane roundabouts can reduce crashes and fatal crashes (, Qin 2013). Area-wide traffic calming measures have been shown to reduce traffic injuries, as well as the frequency and severity of crashes (, ).

Traffic calming measures implemented with broader streetscape design efforts have been shown to reduce crashes (Retting 2003, Zegeer 2017). Pedestrian refuge islands, sidewalks, crosswalks, advanced yield signs and markings, exclusive pedestrian signal phasing (Zegeer 2017, , Retting 2003), and increased lighting (, Retting 2003), for example, can reduce the risk of pedestrian-vehicle crashes. Red light cameras and speed cameras have been shown to reduce casualty crashes (, ).

Single-lane roundabouts can improve traffic performance (e.g., reduce intersection delay, queue lengths, and idling), which may reduce fuel consumption and greenhouse gas emissions (). Midblock crosswalks enhanced with rectangular rapid flash beacons may increase the likelihood that drivers yield to pedestrians ().

Costs for infrastructure improvements vary significantly both by locale and type of improvement; for example, the median cost is $1,670 for a speed bump, $10,460 for a pedestrian refuge island, and $27,190 for a traffic circle/roundabout (UNC-Bushell 2013).

Impact on Disparities

No impact on disparities likely

Implementation Examples

Traffic calming programs are in place in urban, suburban, and rural areas around the country (US DOT-Traffic calming).

Implementation Resources

US DOT-Traffic calming - US Department of Transportation (US DOT), Federal Highway Administration (FHWA). Safety: Traffic calming ePrimer.

ITE-Traffic calming library - Institute of Transportation Engineers (ITE). Traffic calming library.

UNC-Bushell 2013 - Bushell MA, Poole BW, Zegeer CV, Rodriguez DA. Costs for pedestrian and bicyclist infrastructure improvements: A resource for researchers, engineers, planners, and the general public. Chapel Hill: University of North Carolina, Chapel Hill, Highway Safety Research Center; 2013.

PFPS-Traffic calming - Project for Public Spaces (PFPS). Traffic calming 101: Toolbox outlining how to alter streets and parking, add roundabouts/traffic circles/raised medians/speed humps, and create an environment friendly to people on foot.

PALTA-Traffic calming - Pennsylvania Land Trust Association (PALTA). Conservationtools.org. Traffic calming: purpose, planning & approval process, and case studies.

WA DOT-Roundabout - Washington State Department of Transportation (WA DOT). What is a roundabout.

Citations - Evidence

* Journal subscription may be required for access.

Morrison 2003* - Morrison DS, Petticrew M, Thomson H. What are the most effective ways of improving population health through transport interventions? Evidence from systematic reviews. Journal of Epidemiology and Community Health. 2003;57(5):327-33.

Retting 2003 - Retting RA, Ferguson SA, McCartt AT. A review of evidence-based traffic engineering measures designed to reduce pedestrian-motor vehicle crashes. American Journal of Public Health. 2003;93(9):1456-63.

CG-Physical activity - The Guide to Community Preventive Services (The Community Guide). Physical activity.

Cochrane-Bunn 2003* - Bunn F, Collier T, Frost C, et al. Area-wide traffic calming for preventing traffic related injuries. Cochrane Database of Systematic Reviews. 2003;(1):CD003110.

Cochrane-Beyer 2009* - Beyer FR, Ker K. Street lighting for preventing road traffic injuries. Cochrane Database of Systematic Reviews. 2009;(1):CD004728.

Cochrane-Aeron-Thomas 2005* - Aeron-Thomas A, Hess S. Red-light cameras for the prevention of road traffic crashes. Cochrane Database of Systematic Reviews. 2005;(2):CD003862.

Mountain 2005* - Mountain LJ, Hirst WM, Maher MJ. Are speed enforcement cameras more effective than other speed management measures? The impact of speed management schemes on 30 mph roads. Accident Analysis & Prevention. 2005;37(4):742–54.

Morrison 2004 - Morrison DS, Thomson H, Petticrew M. Evaluation of the health effects of a neighbourhood traffic calming scheme. Journal of Epidemiology and Community Health. 2004;58(10):837-40.

Winters 2010 - Winters M, Brauer M, Setton EM, Teschke K. Built environment influences on healthy transportation choices: Bicycling versus driving. Journal of Urban Health. 2010;87(6):969–93.

UNC-Bushell 2013 - Bushell MA, Poole BW, Zegeer CV, Rodriguez DA. Costs for pedestrian and bicyclist infrastructure improvements: A resource for researchers, engineers, planners, and the general public. Chapel Hill: University of North Carolina, Chapel Hill, Highway Safety Research Center; 2013.

Zegeer 2017 - Zegeer C, Lyon C, Srinivasan R, et al. Development of crash modification factors for uncontrolled pedestrian crossing treatments. Transportation Research Record: Journal of the Transportation Research Board. 2017;2636:1-8.

Foster 2014a* - Foster N, Monsere CM, Carlos K. Evaluating driver and pedestrian behaviors at enhanced, multilane, midblock pedestrian crossings. Transportation Research Record: Journal of the Transportation Research Board. 2014;2464:59-66.

Rothman 2015 - Rothman L, Macpherson A, Buliung R, et al. Installation of speed humps and pedestrian-motor vehicle collisions in Toronto, Canada: A quasi-experimental study. BMC Public Health. 2015;15(1):774.

Hu 2014* - Hu W, McCartt AT, Jermakian JS, Mandavilli S. Public opinion, traffic performance, the environment, and safety after construction of double-lane roundabouts. Transportation Research Record: Journal of the Transportation Research Board. 2014;2402:47-55.

Qin 2013 - Qin X, Bill A, Chitturi M, Noyce DA. Evaluation of roundabout safety. Transportation Research Board 92nd Annual Meeting. 2013.

Citations - Implementation Examples

* Journal subscription may be required for access.

US DOT-Traffic calming - US Department of Transportation (US DOT), Federal Highway Administration (FHWA). Safety: Traffic calming ePrimer.

Date Last Updated

May 30, 2017