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Traffic Calming to Slow Vehicle Speeds

The Institute of Transportation Engineers defines traffic calming as the combination of measures that reduce the negative effects of motor vehicle use, alter driver behavior, and improve conditions for non-motorized street users. Traffic calming consists of physical design and other measures put in place on existing roads to reduce vehicle speeds and improve safety for pedestrians and cyclists. For example, vertical deflections (speed humps, speed tables, and raised intersections), horizontal shifts, and roadway narrowing are intended to reduce speed and enhance the street environment for non-motorists. Closures that obstruct traffic movements in one or more directions, such as median barriers, are intended to reduce cut-through traffic. Traffic calming measures can be implemented at an intersection, street, neighborhood, or area-wide level.

“Road diets” are one approach to traffic calming. Road diets involve a reduction in the width or number of vehicular travel lanes and reallocate that space for other uses such as bicycle lanes, pedestrian crossing islands, left turn lanes, or parking. Safety and operational benefits for vehicles and pedestrians include

  • decreasing vehicle travel lanes for pedestrians to cross,
  • providing room for a pedestrian crossing median,
  • improving safety for bicyclists when bicycle lanes are added,
  • providing an opportunity for on-street parking (which also serves as a buffer between pedestrians and vehicles),
  • reducing rear-end and side-swipe crashes,
  • improving speed limit compliance, and
  • decreasing crash severity when crashes do occur.

Implementation of traffic calming measures can reduce traffic speed, reduce motor-vehicle collisions, and improve safety for pedestrians and cyclists. These measures can also increase pedestrian and bicycling activity.

Related Transportation and Heath Tool Indicators

How can this strategy result in health benefits?

  • Address chronic disease (e.g., asthma, diabetes, heart disease)
  • Improve equity
  • Increase physical activity
  • Improve safety
  • Reduce motor vehicle-related injuries and fatalities
  • Reduce transportation's contribution to air pollution

How has this worked in practice?

Lafayette, LA Traffic Calming Program

The Lafayette Consolidated Government (LCG) adopted Traffic Calming Policies and Procedures in 2009. City and parish residents can apply for consideration for traffic calming measures through the LCG Department of Traffic and Transportation. A petition signed by more than half of area residents is required. Conditions considered include traffic volumes, proportion of non-local traffic, crash types, and speeding. Staff members collect data and conduct an intensive design meeting to develop a traffic calming plan. If the petition distributed with the proposed plan is signed by more than 66% of area residents, then the measures in the plan are implemented when funding is made available. Procedures are also in place for pursuing privately funded traffic calming measures and removal of traffic calming measures. Traffic calming devices implemented under the program include speed humps, “mini” roundabouts, and chokers. Evaluation by LCG staff of traffic calming projects along five corridors found a drop of more than 10% in total traffic volumes. On one corridor, Yvette Marie Drive, traffic decreased, more vehicles were traveling less than 23 miles per hour, and fewer vehicles were traveling 23 miles per hour or faster.

Seattle, WA, Neighborhood Traffic Calming

Between 2007 and 2010, more than 54,000 traffic-related crashes occurred on Seattle’s streets, where speed contributed to 42% of the city’s fatal crashes. The Seattle Department of Transportation (SDOT) set a goal of zero traffic-related fatalities by 2030 in its 2012 Road Safety Action Plan. The agency identified speed reduction as one of the priority areas to reach that goal. As part of the speed reduction strategy, SDOT has made changes to the roadway environment. These include improving placement and visibility of speed limit signs, engaging neighborhood organizations and community associations in implementing SDOT’s Arterial and Neighborhood Traffic Calming Programs, and upgrading speed-related signage in school zones. Various partners have contributed to the success of the program, including major employers in Seattle, AAA Washington, local schools and universities, advocacy groups, and city neighborhood councils. Preliminary evidence suggests that these speed reduction efforts are reducing crashes and improving traffic safety in Seattle.

Where can I learn more?

The Institute of Transportation Engineers Traffic Calming Website, which is supported by the Federal Highway Administration, includes a library of traffic calming resources, fact sheets of traffic calming measures, case studies, presentations, and a discussion group.

The Urban Traffic Calming and Health Literature Review, compiled by the National Collaborating Centre for Healthy Public Policy, includes research on the effects of traffic calming in urban environments on the number and severity of road collisions, air quality, environmental noise, and physical activity associated with active transportation.

County Health Rankings and Road Maps has information on methods for making communities healthier, including a description of the connection between traffic calming and health.

The FHWA Speed Management Program website has information about traffic calming.

The National Collaborating Centre for Healthy Public Policy (Canada) developed a report on Urban Traffic Calming and Health that includes a comprehensive literature review.

Evidence base

Bunn F, Collier T, Frost C, Ker K, Steinbach R, Roberts I, Wentz R. Area-wide traffic calming for preventing traffic related injuries. Cochrane Database of Systematic Reviews 2003;(1):CD003110.

Institute of Transportation Engineers (ITE). The City of Monterey Neighborhood Traffic Calming Program. Washington DC; 2009.

Institute of Transportation Engineers (ITE). Traffic Calming Measures. Washington, DC; 2014.

Jones SJ, Lyons RA, John A, Palmer SR. Traffic calming policy can reduce inequalities in child pedestrian injuries: Database study. Injury Prevention 2005;11(3):152–6.

Lockwood I. ITE Traffic Calming Definition. ITE Journal; 1997.

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.

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.

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.