Skip to Content
Streetsblog USA home
Streetsblog USA home
Log In
Pedestrian safety

3 Graphs That Explain Why 20 MPH Should Be the Limit on City Streets

Graph: ProPublica
A still from ProPublica's interactive graph.
Graph: ProPublica

Speed kills, especially on city streets teeming with pedestrians and cyclists.

The investigative news nonprofit ProPublica has produced an interactive graph that deftly conveys how just a few miles per hour can spell the difference between life and death when a person is struck by a motorist. ProPublica's Lena Groeger used data from the AAA Safety Foundation to chart the plummeting likelihood of survival as motorist speed increases.

The average pedestrian struck by a driver traveling at 20 mph has a 93 percent chance of surviving. For a 70-year-old, the chances are somewhat lower but still a robust 87 percent.

As Groeger puts it:

Once cars reach a certain speed (just above 20 mph), they rapidly become more deadly. According to [AAA's Brian] Tefft's data, a person is about 70 percent more likely to be killed if they’re struck by a vehicle traveling at 30 mph versus 25 mph.

In collisions at 30 miles per hour, about one in five pedestrians will not survive. For older pedestrians, the odds are significantly worse:

Graph: ProPublica
Graph: ProPublica
Graph: ProPublica

The risk of death continues to rise dramatically as speeds exceed 30 mph. At 40 mph, most older pedestrians will not survive:

Graph: ProPublica
Graph: ProPublica
Graph: ProPublica

In addition to much higher survival rates in the event of a collision, driving at slower speeds reduces stopping distances, making it easier for drivers to avoid hitting people in the first place.

These graphs are a compelling visualization of the data that undergirds campaigns like "20's Plenty" in the UK, where residents have demanded 20 mph streets to protect the most vulnerable. As of last fall, more than 14 million people in the UK lived on streets with 20 mph speed limits, according to 20's Plenty founder Rod King, and the campaign is now focused on extending the 20 mph limit to most streets in the country:

Stay in touch

Sign up for our free newsletter

More from Streetsblog USA

The ‘One Big Beautiful Bill’ Is About Our Transportation Future, Too

Transportation didn't get a lot of mention in the public discussion of the One Big Beautiful Bill Act. But it's everywhere.

July 8, 2025

Tuesday’s Headlines of Many Colors

Transportation Secretary Sean Duffy called rainbow crosswalks "a distraction" and called on cities to eliminate them.

July 8, 2025

Form-Based Codes Mean More Sustainable Cities

New research shows that prioritizing building "form" over their use leads to more sustainable cities.

July 8, 2025

Monday’s Headlines Are Big and Beautiful

The ginormous GOP tax and spending bill President Trump signed on July 4 will make the air dirtier, a lot of it from tailpipe emissions.

July 7, 2025

The Single Most Important Element In Creating Good Cities

A lot of U.S. cities are getting their "right of way" all wrong — and urbanists can help by getting to know this poorly-understood concept.

July 7, 2025

Reclaiming Streets from ICE with Music, Dance, Altars, Mutual Aid, Community, and Resistance

The Mariachi Plaza event was one of four held across LA. Tuesday night. The June 19 abduction of street vendor Emma de Paz from the Hollywood Home Depot was a touchstone of the Eastside gathering.

July 4, 2025
See all posts