A new Chicago-focused study links red light cameras to a coinciding rise in rear-end collisions, casting doubts on claims that the mounted cameras improve safety at intersections.

The study’s findings, published by the Chicago Tribune Friday, found that while traffic cameras appeared to reduce injuries by 15% for collisions at right angles, where one car crashes head-on into the side of another car, those improvements were overshadowed by a 22% increase in injuries from rear-end accidents. Taken together, the study shows a statistically insignificant increase of injuries by 5%.

The results come amid Chicago mayor Rahm Emmanuel’s push to mount cameras on traffic lights city wide. The programs have attracted a growing backlash from critics who question its safety benefits and worry the program will lead to a swelling of ticket payments.

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