One red light camera study cited in the Institute's review was conducted in Oxnard, California. A question was raised at California state hearings about the study's findings of 7 percent fewer crashes overall and 29 percent fewer injury crashes at signalized intersections after red light cameras were introduced. A state senator said the Institute researchers who conducted the study should have taken into account what police said about the causes of the intersection crashes — whether they were or weren't caused by red light running.
The problem is that the California data about crash causation at intersections include violations other than red light running. Still, most violations at signalized intersections are likely to involve red light running, so the researchers followed the senator's suggestion and re-analyzed the Oxnard data. This time the findings showed even greater effects of cameras — 20 percent fewer crashes and 46 percent fewer injury crashes that police said involved violations at signalized intersections. So any way you look at it, red light cameras cut crashes and prevent injuries.
Reductions in intersection crashes in Oxnard, as first reported by the Institute
and according to a re-analysis suggested by a California legislator