cars parked on a tree lined street

January 17, 2023 /
Christina Hester

Trees for Traffic Calming

Last week we discussed a study that showed how street trees may be saving lives. Aside from the physical health benefits that trees provide, research shows that street trees can also be effective in making our roads safer.

During the COVID-19 pandemic, regional and national trends showed a sharp increase in vehicle-related fatalities – so much so that 2021 was the deadliest year on D.C. roads in over a decade. Since 2015, D.C. has participated in the U.S. Department of Transportation’s Mayor’s Challenge for Safer People and Safer Streets, resulting in Mayor Bowser’s Vision Zero DC plan – which aims to reduce roadway injuries and achieve zero traffic deaths by next year (2024).

When used in concert with other solutions that reduce injuries and deaths on our roadways, trees can help make city streets safer – and D.C.’s Vision Zero a reality – through traffic calming.

Traffic calming is the use of mainly physical measures (speed bumps, horizontal shifts, roadway narrowing, etc.) that reduce the negative effects of motor vehicle use, alter driver behavior, and improve conditions for pedestrians and cyclists. And among the methods to calm and control city traffic, the addition of trees to a city street has been proven to slow traffic, reduce accidents, and create safer streets for all – for those who walk, bike, drive, ride transit, exercise, play, dine, or any of the many other activities that take place on or near our streets.

Studies have shown that when a street is lined with trees, they act as a visual barrier between drivers and pedestrians. A study from 2019 found that a higher urban tree cover is associated with increased feelings of safety. The study states: “High coverage and dispersion of trees are needed for increased perceived safety.”

The amazing thing is that areas with street trees not only feel safer, but they’ve been proven to be safer. Trees have been shown to calm traffic and reduce vehicle speeds by appearing to narrow the width of the roadway. Without trees, the open space gives drivers the illusion that they have more control to drive faster – when in reality, that’s exactly how accidents occur. Reminder: If a street looks like a highway, people will treat it like a highway. In an area where streets were widened and trees were not present, accidents increased by almost 500% within an 8-year period.

Another unexpected benefit of using street trees for traffic calming is that drivers feel more relaxed in the presence of trees. This has shown to result in less road rage and accidents caused by frustration. Unlike other traffic calming devices, trees are multi-faceted – not only do they help make roads safer, but they also save energy, increase property value, reduce stormwater runoff, and generally make our lives more comfortable and beautiful!