What Is Traffic Calming? Definition and Examples

A woman seen crossing the UK's first '3D' zebra which has...
3D crosswalk in Westminster, UK, designed to give the impression that approaching vehicles are about to drive over a ramp, forcing them to slow down.

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Traffic calming is a combination of measures implemented by local governments that reduce the negative effects of vehicle use by altering driver behavior and improving road conditions for cyclists and pedestrians. The main goal is to increase a community’s quality of life and safety, but there are added environmental benefits—such as promoting pedestrian, cycle, and public transit use and lowering CO2 emissions—that can come from traffic calming as well.

Traffic Calming Definition

Traffic calming mainly consists of physical measures aimed at creating safe streets, including slowing drivers down, reducing collision frequency and severity, reducing the need for police enforcement, and increasing access for different modes of transport. By creating attractive streets and increasing the perception of safety for pedestrians, non-motorized users, and those who work, play, and reside near those streets, traffic calming has the potential to inspire more residents to use eco-friendly modes of transportation.

Traffic Light for Bicycle in City
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The slower a motor vehicle is moving, the greater the chances of survival for a pedestrian involved in an accident. At speeds at or below 20 miles per hour, a pedestrian is less likely to be permanently injured, but if the vehicle is traveling at a speed of 36 miles per hour or more, a pedestrian-involved accident is usually fatal, according to the Federal Highway Administration. In 2018, there were 9,378 crash fatalities where the driver was speeding, accounting for 26% of total traffic fatalities for the year, as shown by National Highway Traffic Safety Administration (NHTSA) data.

According to a Department of Energy-sponsored study published in 2021, driving faster costs drivers significantly more when it comes to fuel prices and, consequently, carbon emissions. Driving at 60 miles per hour is 25% more efficient than traveling at 75 miles per hour, which can burn more fuel due to wind resistance.

Traffic calming has become a tried and true element of sustainable urban mobility management all around the world. In Slovenia, the Urban Planning Institute found that a comprehensive traffic calming redesign of a residential neighborhood between 2014 and 2017 had nothing but positive effects. Around a third of the residents said that they walked, cycled, and socialized more than before the redesign, and around two-thirds said that the quality of life in the neighborhood had improved. What’s more, overall vehicle speeds, flows, and peak-hour flows decreased and road safety improved.

Measures and Tools

Twenty's Plenty 20 Mph speed limit sign
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So, what types of methods are implemented when it comes to traffic calming? Traffic engineers typically look to the three E’s: engineering measures, education, and enforcement.

Engineering measures involve altering the road layout physically, such as by narrowing lanes, extending sidewalks or curbs, minimizing the size of a corner radius to reduce turning speeds, adding trees to distinguish urban environments from highways, adding chicanes or lane shifts (forming the road into an S-shaped to lower vehicle speeds), raising center medians or creating pedestrian refuge islands, adding mini roundabouts or speed bumps, and many more. Sometimes, local residents take matters into their own hands by erecting their own signs to reduce traffic speeds in their neighborhoods.

Enforcement and education methods may mean reducing speed limits near schools or hospitals and installing electronic signs designed to activate when a vehicle drives by at a predetermined speed. Engineers may also include flashing lights embedded into the pavement to indicate pedestrian crosswalks or local law enforcement may introduce publicity campaigns, training, or residential education programs. These flashing beacons and area lightings tend to be solar-powered, so they come at no cost to local energy resources.

While speed bumps may be the most familiar (and obvious) speed-reducing measure, research shows that they may actually increase particulate matter air pollution. One study published in the journal Measurement found that when vehicles pass through speed bumps, their cars emit more pollution as they brake and speed back up. While measuring speed bump structures in residential areas, air pollution with particulate matter increased by 58.6% near plastic circular speed bumps. Although they have been proven to reduce speed and make neighborhoods safer, some municipalities are moving away from speed bumps as they can also cause damage to vehicles and increase emergency response time.

Examples of Successful Traffic Calming

Although traffic calming evolved in Europe (specifically in the Netherlands, “woonerf” refers to streets that are shared among pedestrians, bicyclists, and motor vehicles, or areas where pedestrians have priority over cars), it is now a regular practice in the United States. And while we definitely have a long way to go, speeding-related fatalities declined by 12% between 2009 and 2018, according to NHTSA statistics.

Oakland, California

The city’s Harrison Street had a bad reputation as a high injury corridor due to the wide six-lane design and a difficult left turn from the neighboring 23rd Street. The intersection is also next to one of the city’s oldest and largest senior centers, and after the death of 68-year-old Robert Bennett by a driver turning left, the city implemented several traffic calming measures in response. This included purple pedestrian sidewalk extensions and a median to make pedestrians more visible, as well as additional bicycle lanes in both directions. As a result, speeding decreased by 7% along the corridor and drivers yielding to pedestrians increased by 82%-89%. Next steps include installing a two-way, concrete median-protected bikeway, buffered bike lanes, parking protected bikeways, and several more pedestrian safety improvements.

Burgos, Spain

In 2016, researchers in Spain compared street sections in the city of Burgos with different types of traffic calming measures against other street sections of similar characteristics where traffic calming had not been implemented. They found the best overall results in streets with more than one calming measure, while the best speed lowering improvements were seen in streets with raised crosswalks and lane narrowing.

Portland, Oregon

A study published in the journal Regional Science and Urban Economics examined over 1,000 traffic calming measures in the city of Portland to find that traffic calming reduced 85th percentile speeds by 20% and traffic volumes by 16%.