Like the data from Bellevue, studies on traffic enforcement cameras show conflicting results, especially for red-light cameras. Some show a positive impact: reducing red-light running as much as 21% and decreasing collisions by 29%. Other researchers found a change in the type of crash, often from angle to rear-end, but no evidence the cameras reduced total crashes or injuries.
Cameras in school zones seem to have more success at modifying driver behavior, according to studies, most of which found vehicle speeds dropped outside schools when comparing data before and after installation. They also tend to be the most priciest tickets issued by the cameras.
“There’s a lot of research on the impact of traffic enforcement cameras and results have been conflicting,” said Yinhai Wang, a civil and environmental engineering professor at the University of Washington. “It’s a great tool, but must be used carefully, and properly.”
The cameras need to be placed in areas where there are a lot of vehicles violating traffic rules, he added.
“If these cameras truly work, people will change their driving behavior,” Wang said. “In the initial stage when the system is installed, you may see a high number of citations, but with the years [they’re] supposed to be reducing down.”
Is the future automated enforcement?
Amid COVID and struggles to fully staff the police department, Seattle relies even more on traffic enforcement cameras than just a few years ago. In 2021, officers handed out 5 percent of tickets.
Some of that increase in citations is linked to just one location Seattle added last year. Cameras now issue tickets to unauthorized vehicles using the Spokane Street Bridge which is reserved for emergency vehicles, transit riders and a few other select groups while the West Seattle Bridge is closed for repairs. Those without permission must use the First Avenue Bridge detour or risk a $75 ticket.
In recent years, fewer officers have been dedicated to traffic enforcement as focus shifted to priority and 911 calls, said Sgt. Randy Huserik, a public affairs officer with the Seattle Police Department.
The flashing signs and the pricey school zone ticket that starts at $237 seems to be a good reminder for drivers in Seattle as fewer and fewer tickets are issued outside school buildings. After all the school zone cameras came online in 2016 in Seattle, citation numbers dropped by 19% the next year. And they continue to drop, according to city data.
Collisions also decreased.
Benefits of the red-light system seem a bit more nebulous for Seattle. Despite both crashes and citations trending up between 2013 to 2019, Venu Nemani, a traffic engineer for Seattle Department of Transportation, argued that the cameras at red lights and in school zones were improving safety.
He also pointed to growth as one factor in the increasing number of red-light citations issued year over year. A 2017 study analyzing three years of crashes before and after the cameras were installed also showed a 40% reduction in angle collisions. This reduction could have an overall impact on injuries, as angle collisions often result in more serious crashes than rear-end ones.
Automatic enforcement is a critical safety tool, Nemani said. “Behavior modification is our primary goal; we approach it from that perspective.”