The growth of automatic emergency braking systems undercuts a common gripe about red light safety cameras by preventing rear-end crashes that can occur when drivers stop short, a new study from the Insurance Institute for Highway Safety shows.
Red light safety cameras reduce the dangerous right-angle crashes that often cause injuries or fatalities when drivers run red lights. But the devices are also associated with an increase in less severe rear-end crashes due to a rise in sudden stops at equipped intersections.
The new IIHS study shows that the increasing prevalence of automatic emergency braking (AEB) will mitigate that unfortunate side effect.
“Red light running causes extremely dangerous, high-speed side crashes, so red light safety cameras are an essential intervention,” IIHS President David Harkey said. “This study illustrates that AEB helps address one of their few downsides, which hopefully can help accelerate their deployment in intersections across the country.”
In 2023, more than a thousand people were killed and more than 136,000 were injured in crashes that involved a driver running a red light. Ensuring that the duration of the yellow signal is sufficient can reduce red light running. But the addition of red light safety cameras has a more dramatic effect. An IIHS study conducted in Philadelphia, for example, showed that a longer yellow reduced red light violations by 36%, while adding a camera boosted the effect by another 96%.
Despite those benefits, only 343 communities across the United States were operating red light safety cameras as of this month, and the number of places using them has declined by more than a third since 2012.
Community opposition is often among the reasons given for turning cameras off, and opponents often use studies showing that cameras are associated with an increase in rear-end crashes to argue against deploying them.
To be sure, rear-end crashes are costly and can sometimes cause serious or debilitating injuries. But severe rear impacts are rare enough that the benefits of red light safety cameras outweigh that downside.
AEB boosts camera benefits
Even if no vehicles were equipped with AEB, the new study shows, red light safety cameras would slash injury crashes by as much as a fifth and result in a net reduction in crashes of all types. As more and more of the vehicles in the U.S. fleet come equipped with AEB, rear impacts are expected to shrink, and the overall crash reductions associated with red light safety cameras will grow.
To determine the effects of red light safety cameras on crashes without the influence of AEB, IIHS researchers performed a meta-analysis of 35 studies of red light safety camera interventions, paying special attention to their influence on rear-end crash rates.
To estimate the mitigating effects of AEB, they then analyzed police-reported crashes from 19 states over several years, comparing the rates of rear-end crashes at signalized intersections in which the striking vehicle had AEB with those in which the striking vehicle was not equipped with the crash avoidance feature.
They combined those findings and used statistical analysis to extrapolate the overall effects of AEB systems on crash rates at intersections with red light safety cameras assuming different percentages of the fleet were equipped with the technology.
If no vehicles on the road had AEB, the researchers found, red light safety cameras would be associated with a 7% decrease in all crashes at the intersections where they are used.
However, since 2023, more than 28% of the U.S. fleet has been equipped with AEB, according to analyses conducted by the Highway Loss Data Institute. With that many AEB-equipped vehicles on the road, the reduction in crashes ticks up to 8%.
In 2045, when virtually all vehicles in the fleet will have AEB, red light safety cameras will reduce all crashes by nearly 10%, presuming no other advancements take place that make them more effective.
Not all crashes are equal
In an important way, though, those numbers fail to capture the full benefits of red light safety cameras. The small net reductions reflect much larger decreases in the more dangerous right-angle crashes that tend to occur when drivers run red lights. In the net numbers, those reductions are offset by increases in comparatively minor rear-end crashes that happen when drivers stop suddenly to avoid getting fined.
The net 7% reduction that would occur if no vehicles had AEB includes a 21% increase in rear-end crashes. At the current AEB-installation rate, that increase in rear-end crashes narrows to 19%. If every vehicle had AEB, it would drop further to 14%.
As the increases in those less-dangerous crashes get smaller and the reductions in overall crashes get larger, the reductions in crashes that cause injuries — the obvious safety benefit of red light safety cameras — remain comparatively constant at 19%-20%.
“This is a great example of a vehicle technology and an infrastructure solution working in tandem to produce better results,” said IIHS Senior Transportation Research Engineer Wen Hu, the lead author of the study. “As advanced driver assistance features become more common, researchers will need to revisit other tried and true safety measures to see how their effectiveness has changed.”
SOURCE: IIHS
