Some statistical funny business is going on in a new Insurance Institute for Highway Safety report claiming to prove that camera-enforced red lights reduce the overall number of accidents. Turns out that the study excluded an increase in rear-end crashes (often caused by a sudden stop at a red light) simply by defining the "intersection" to mean only the zone between crosswalks. A man named Kadison, who reexamined the data, came to a different conclusion:

Over this enlarged zone, rear-end crashes increased by 33 after red-light cameras were installed. At the same time, side impacts dropped 25 percent. Kadison concludes that the cameras merely trade one type of crash for another.

IIHS's claim of safety from cameras is flatly contradicted by a number of cities that have tried them. "At some intersections [with cameras] we saw no change at all, and at several intersections we actually saw an increase in traffic accidents," admitted San Diego police chief David Bejarano on ABC News's Nightline.

In Charlotte, North Carolina, station WBTV had this to say, "Three years, 125,000 tickets, and $6 million in fines later, the number of accidents at intersections in Charlotte has gone down less than one percent. And the number of rear-end accidents, which are much more common, has gone up 15 percent."

This should come as no surprise to anyone familiar with the principle of unintended consequences -- try to fix one problem (red light violations) and likely as not you worsen another (rear end crashes).