More on Traffic Cameras

Glen Whitman doubts my assertion that lengthening yellow lights will stave off red-light runners. Glen suspects longer yellows might deter motorists for a bit, but that they'll soon become acclimated to the longer yellow lights, and adjust their sense of risk appropriately.

It's an intuitive theory. But the available evidence suggests otherwise. In 2001, the National Motorists Association persuaded the Virginia DOT to lengthen the yellow light at one particularly egregious intersection in Faifax by 1.5 seconds -- from 4.0 seconds to 5.5. A camera installed at the intersection monitored the number of infractions. About 70 days after the yellow was increased, infractions fell from 52.1 per day less than one per day -- or about 96%.

That was three years ago. NMA reports that infractions at that intersection have remained at about .80 per day in the three years since.

NMA also lists four studies (though, unfortunately, they aren't available online) discrediting the notion that motorist adaptation offsets the safety benefits of longer yellows.

There's also a 2003 study from two Texas A&M professors which concludes that while there may be some driver adaptation, a 1.5 second increase in yellow time generally produces about a 50% long-term reduction in red light running at the intersections in question.

Whatever the case, I can't conceive of an argument where shortening yellows without warning -- as Bethesda, Maryland did -- could in any way improve the safety of motorists.

Still other studies have shown that other structural improvements (see page 3) at problem intersections, such as installing magnifying lenses on traffic lights, or allowing 1-2 seconds of" clearence reds" (where all lanes stay red for a moment), do more to prevent red-light runners than cameras.

More importantly, all of these alternate adjustments protect motorists without creepy surveilance systems and perverse adjudication processes. When D.C. and San Diego first installed cameras, for example, the private corporations running the cameras got a cut of every ticket issued. Not only that, but if you challenged a ticket, you were sent to a" court" run not by the city, but by the very corporation that gets money from every ticket issued!

When cities grow reliant on revenue from tickets, and the corporations running them profit from more red light runners, not less, you've incentivized your public officials to encourage law breaking. Any structural adjustment that might improve the safety of an intersection will by definition decrease the revenue generated by traffic fines.

Indeed, a 1995 study from Australia (the first country to implement traffic cameras on a large scale) suggests that cameras might increase accidents and injuries.

As D.C. Mayor Anthony Williams conceded (then later recanted after public outcry), cities install these cameras to generate revenue.

Protecting motorists is an ancillary concern, if it's a concern at all.