Turns out in Virginia they actually increased the amount of accidents, or redistributed them, instead of decreasing accidents/injuries as proponents had hoped. It's of interest here in Houston; the city govt will install them at key locations. story here.

A brand new, exhaustive study of all seven Virginia red light camera programs shows an overall increase in injury accidents has occurred where the devices are installed. The study was performed by The Virginia Transportation Research Council at the request of the state transportation secretary. The report also notes a fatal flaw in the Virginia's camera law -- motorists can ignore any ticket received in the mail. Only tickets that are personally served matter (the same thing happened in Arizona).

Despite a distinct sympathy in favor of camera enforcement, the researchers found a "definite" increase in rear-end accidents and only a "possible" decrease in angle accidents. Most importantly, the net effect was that more injuries happened after cameras are installed. Camera proponents explain this away by asserting angle accidents are more serious, but this claim has not been scientifically studied according to this report. The rear end collisions caused by the cameras still produce injuries -- the original promise of camera proponents was that they would reduce accidents and injuries, not rearrange them.

This study agrees with long-term findings in Australia and North Carolina.