http://www.fhwa.dot.gov/publications/research/safety/05049/
April 2005
"...the lesser severities and generally lower unit costs for rear end injury crashes together ensure that the increase in rear end crash frequency does not negate the decrease in the right-angle crashes targeted by red-light-camera systems."
"This analysis, which was based on an aggregation of rear end and right-angle crash costs for various severity levels, showed that RLC systems do indeed provide a modest aggregate crash-cost benefit."
"...this economic analysis represents the first attempt in the known literature to combine the positive effects of right-angle crash reductions with the negative effects of rear end crash increases and identify factors that might further enhance the effects of RLC systems. ... Even though the positive effects on angle crashes of RLC systems is partially offset by negative effects related to increases in rear end crashes, there is still a modest to moderate economic benefit of between $39,000 and $50,000 per treated site year... The modest benefit per site is an average over all sites. As the analysis of factors showed, this benefit can be increased through careful selection of the sites to be treated ... and program design..."
The study's conclusion does point out that red light cameras are not a cure-all for every intersection -- "RLC systems would be most beneficial at intersections where there are relatively few rear end crashes and many right-angle ones." But think about it -- would you rather be in a rear-end collision or a right-angle collision?