Des Moines’ red light cameras cost motorists at least $32,000 per accident “prevented” in the last six months of 2011, according to a lame statistics release by the Des Moines Police yesterday reported by the Des Moines Register:

Des Moines police reported Tuesday the use of red light cameras in Des Moines from July through December last year reduced accidents at five major intersections by an average of some 33 percent, compared to the same six-month period at the same locations over the previous four years.

The cameras at these intersections resulted in 4,473 $65 tickets, costing drivers $290,745 — all to prevent 9 accidents — and that assumes that the entire reduction in accidents is attributable to the revenue cameras. Considering that this winter so far has been mild and almost snow-free, while the prior three winters were anything but, that’s a shaky assumption. It would be worthwhile to know what the city-wide accident statistics were for the same period. In real life, the cost per accident “prevented” may be much higher.

Police and city officials are defensive about this tax on normally harmless behavior, like not quite stopping before making a right turn at an empty intersection or not quite beating the yellow light before it turns red. That’s why they feel the need to justify it, even with this batch of cherry-picked statistics.
A more complete disclosure would include the nature of the accidents “prevented.” We know of one high-speed wreck the cameras didn’t prevent. It would also be worthwhile to compare these intersections to a control group of other intersections where revenue cameras weren’t installed, but other means, like extended yellows and all-red phases, were tried. But as these alternatives pick no pockets, the police and the city aren’t interested.
UPDATES:
“Extensive, two-year study finds red-light cameras don