Friday, March 27, 2009

The difference between red light & speed cameras

State Sen. Terry Link (D. Waukegan) has made quite a splash recently with a proposal to allow cameras to catch speeders and issue tickets. Jon Hilkevitch writes about the proposal in yesterday's Chicago Tribune; you can find the text of SB 1852 by following the link embedded in this sentence.

In the City of Chicago and certain Illinois counties the law already permits the erection of 'red light cameras' that automatically spit out tickets to violators. (For the state statute, see §11-208.6 of the Motor Vehicle Code, 625 ILCS 5/11-208.6.) These cameras seem to work: Where signs warn of camera enforcement, even at intersections where a red light was previously taken as little more than a suggestion, motorists seem to have modified their behavior. More of them actually stop when they're supposed to. (In one sense these cameras may have worked too well: Complaints have surfaced in some quarters about the cameras failing to generate promised revenues.)

But determining who is a speeder is fundamentally different from determining whether someone has, or has not, blown a red light. Running a red light is an either/or proposition. An unthinking, unblinking camera can reasonably make that call. But can it really decide when someone is really "speeding"?

What is a "speed limit" anyway? On most arterial streets, at rush hour, it's an impossible dream; at non-peak hours, though, on those same streets, a speed limit is more like a posted minimum. A "speed limit" is not a "limit" at all. A limit is an absolute: Try buying three items when the store says "limit two." Watch what happens when you exceed your credit limit. A speed limit is more a target average.

A police officer observing traffic may see that traffic is moving safely and smoothly at 40 mph... and choose not to enforce a 35 mph limit. A police officer observing traffic on an icy Winter's day may see that it is unsafe to drive at even 20 mph and pull over a motorist who tries. A driver can be ticketed under §11-601(a) of the Motor Vehicle Code for "driving too fast for conditions." ("The fact that the speed of a vehicle does not exceed the applicable maximum speed limit does not relieve the driver from the duty to decrease speed... when special hazard exists with respect to pedestrians or other traffic or by reason of weather or highway conditions.")

A police officer has training, judgment and discretion. The most advanced unthinking, unblinking eye has none of these.

Well, says the Tribune editorial this morning, in Arizona cameras are set to catch only those traveling 11 mph over the posted limit. An article by William M. Bulkeley in today's Wall Street Journal notes the same assertion.

But there's no guarantee that an 11 mph cushion would remain in place for long. It all depends on whether the cameras generate the anticipated revenue.

Don't blame me for a cynical assertion. Bulkeley's article cites "a study in last month's Journal of Law and Economics [which] concluded that, as many motorists have long suspected, 'governments use traffic tickets as a means of generating revenue.' The authors, Thomas Garrett of the St. Louis Fed and Gary Wagner of the University of Arkansas at Little Rock, studied 14 years of traffic-ticket data from 96 counties in North Carolina. They found that when local-government revenue declines, police issue more tickets in the following year." Thin the cushion, fatten the revenues.

The Tribune thinks that cameras will make the highways safer. But Bulkeley reports that studies are mixed on whether speed cameras enhance safety:
Some research indicates they may increase rear-end collisions as drivers slam on their brakes when they see posted camera notices. A 2005 Federal Highway Administration study of six cities' red-light cameras concluded there was a "modest" economic benefit because a reduction in side crashes due to less red-light running offset the higher costs of more rear-end crashes.

A study of crash causes released by the National Highway Traffic Safety Administration last July found about 5% of crashes were due to traveling too fast and 2% were from running red lights. Driving off the side of the road, falling asleep at the wheel and crossing the center lines were the biggest causes identified.
Speed cameras are about revenue, not safety. Unless we're going to make speed limits into real limits -- top end speeds beyond which no one can travel safely at any time, under any conditions -- discretion is always going to play a role in determining what constitutes speeding. Machines just can't do this job.


Bulkeley's WSJ article discusses countermeasures some citizens have taken in response to unthinking, unblinking eyes. The funniest of these is shown in a YouTube video and you can watch that on page two.