Speed cameras lower speeds and prevent crashes, new research confirms

By Chris McCahill 

The Safe System approach to preventing traffic deaths and serious injuries requires us to rethink every aspect of our transportation system, from road and vehicle design to our pervasive car culture. Many communities have found that automated traffic enforcement is one valuable step along the way. As more of these systems are deployed, researchers continue building knowledge about how they work and where they are most effective.  

For one recent study in Curitiba, Brazil, researchers monitored 13 drivers in a vehicle outfitted with cameras and sensors. They drove a total of 116 trips involving 16 speed cameras. The study found that as drivers approach areas with cameras, their speeds drop by around 1.4%, then increase again when they leave the zone. The most notable exceptions were uphill segments and weekends. 

The researchers note many other comparable studies have found considerably more significant effects. In nine of the 13 studies they looked at, the mean speed reduction is around 10% or more, and as high as 25% in two cases. 

More importantly, these speed reductions can translate into meaningful safety improvements, as another recent study in Philadelphia found. Roosevelt Boulevard—one of the most dangerous roads in the U.S.—runs through the city’s north end, carrying as many as 12 lanes of traffic at posted speeds between 40 and 45 miles per hour. The researchers explain: 

“Between 2016 and 2022, 100 people died in car crashes on Roosevelt Boulevard. Another 17 people died on the local roads immediately surrounding Roosevelt Boulevard. In total, around 12% of total traffic fatalities and around 6% of crashes involving injury, property damage, or a towed vehicle in Philadelphia occurred on Roosevelt Boulevard.”

Speed cameras were installed at eight locations in 2020 and another two locations in 2022. The researchers conclude that the cameras prevented what would have been a major increase in serious crashes. On similar roads without cameras, they found, the increase was 1.5 times larger for crash rates, 1.7 times larger for injury rates, and 2.1 times larger for death rates. The difference was even larger for pedestrian crashes. The increase was 1.8 times larger for pedestrian injury rates and 2.5 times larger for pedestrian death rates (although with a lower level of confidence). 

Overall, the researchers estimate the cameras prevented roughly 15 to 20 crashes per month and around 0.9 to 1.4 monthly deaths. They also note that speeding infractions dropped by more than 90% after the cameras were installed, which means most drivers changed their behavior to avoid paying citations of $100 to $150. 

This is important to consider since automated enforcement programs can risk having a disproportionate impact on disadvantaged communities—a topic we discussed at our Community of Practice meeting in 2019. Like Roosevelt Boulevard, many of the nation’s most dangerous corridors pass through Black and Hispanic neighborhoods, or neighborhoods with lower household incomes. 

Not only must traffic experts deploy speed cameras thoughtfully and with an eye toward equity, but they also need to consider automated enforcement as just one of many tools for taming dangerous roads. The researchers in Philadelphia note: 

“Despite the safety improvements, there remain important limits to the current speed enforcement program. Roosevelt Boulevard remains and will likely continue to remain Philadelphia’s most deadly arterial. In 2021 and 2022, 19 people lost their lives on and around the treated sections of Roosevelt Boulevard. That is just under 7% of the city’s total traffic fatalities. The roadway remains a dangerous combination of high-speed highway that intersects with local streets in densely populated neighborhoods.” 

They recommend several potential interventions, including an option to “redesign the Boulevard to operate as a lower speed and lower-capacity boulevard that looks and behaves more like Philadelphia’s other urban arterials.” 

Photo Credit: Denny Müller via Unsplash, unmodified. License