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New Evidence on Red-Light Cameras

+ Brandon Fuller

Eric Jaffe writes about useful new research on the effectiveness of red-light cameras:

In 2005, the Virginia legislature allowed the state law permitting the cameras to expire…The researchers focused on eight intersections in southeast Virginia: four in Virginia Beach with red-light cameras that would expire with the law, and four others…where cameras didn’t exist. They recorded the light status of the final car to cross through an intersection — documenting only those cars that went straight — with a particular focus on the period just before and after the cameras turned off.

In nearly 2,800 light cycles, about a quarter of all last cars to enter the intersection went through on green, and 63 percent on yellow. The remaining 12 percent crossed on red — but when the cameras were still on, that rate was only 3 percent. (At intersections that never had cameras, the last-driver-through crossed on red 14 to 15 percent of the time.)

So we have some evidence that red-light cameras work. And while the researchers were surprised by how quickly people reverted to their red-light running ways once the cameras went dark, the finding that the cameras deter red-light violations is not terribly surprising. Nor will it do much to shift the debate about cameras. As Jaffe points out, the opposition to traffic safety cameras has never really stemmed from a conjecture that they don’t work. Instead, people tend to oppose the cameras because they believe the motivation for their installation is based more on a desire to generate revenue than a desire to improve traffic safety.

Because of this, city officials would be wise to think hard about how to structure the rules around the use of the cameras. One idea we’ve blogged about before is the notion that better measurement of traffic behavior should be accompanied by lower stakes. If the odds of getting caught go up significantly, the punishment for violations can come down.

Jaffe mentions another pitfall that cities should avoid: structuring contracts with camera operators that actually incentivize the issuance of more tickets. If the point of the cameras is to shift drivers to a low-violation equilibrium then it disingenuous when cities sign contracts with private firms that include clauses for minimum ticketing or ticket revenue sharing.

The cameras appear to be working. But it’s not enough to simply say “if you violate the law, you get punished” and leave it at that. Cities now need to take care to introduce the new technology in a way that doesn’t undermine the legitimacy of their enforcement strategies.

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