Friday, December 20, 2019

Traffic Cameras?

I like to get home in one piece, thank you.
First full day of winter ride, 2019.
 There is a discussion underway in Santa Fe to deploy traffic cameras to catch speeders. This has been met with the usual resistance such as offered in the Letters section of today's New Mexican. Speed cameras are an imperfect solution to a real problem: speeding.

Although motorists may feel safe while speeding in a 5000 lb vehicle equipped with air bags, crumple zones, seat belts, and a lot of mass, its tough to be a pedestrian or bicyclist hit by a car. Several studies are readily available (Science Direct here and the AAA Foundation version here) indicating the rapid rise in mortality suffered by those hit by cars as vehicle speeds increase. Quoting from one paper, "...The average risk of death reaches 10% at an impact speed of 24.1 mph, 25% at 32.5 mph, 50% at 40.6 mph, 75% at 48.0 mph, and 90% at 54.6 mph. Risks varied by age. For example, the average risk of death for a 70-year-old pedestrian struck at any given speed was similar to the average risk of death for a 30-year-old pedestrian struck at a speed 11.8 mph faster...."

Yet major arterials in Santa Fe (Cerrillos, St. Francis, St. Michaels) are typically posted at 35 mph or higher. Actual travel speeds are likely in excess of posted speeds, giving pedestrians hit by cars a fifty fifty chance of ending up in the morgue.  This is a social justice and traffic justice issue, if we wish to promote alternative transportation (biking, walking, mass transit). Of course these are state roads and not subject to traffic cameras.

Cameras, however, are a tricky solution for several reasons. One, they perpetually lead to assertions that they are forms of "policing for profit", since cities often contract with for-profit companies to run the cameras rather than manage the systems themselves. Policing for profit is big business in some jurisdictions that are under-capitalized and which rely on fines to balance their budget. Balancing the budget with fines often puts the costs on the backs of the poor and minorities. The death of Philando Castile during a botched traffic stop is one of the worst examples of worst case outcomes.

Cameras are also problematic because motorists are getting mixed signals. We design roads to be wide, fast, and efficient for motorist travel.  You cannot then post a speed limit inconsistent with design and ticket drivers for what comes naturally to them.  There is ample literature saying that wide roads that look like highways will be driven like highways and this encourages speeding. You can post a road at a low speed limit but this conflicts with that old "85th percentile rule" that says if 85 percent of motorists think a road should be driven fast, it should be posted fast. For example, St. Francis Drive or the SW section of Cerrillos.

The best way to lower traffic speeds is to engineer roads so they look like they should be driven slowly. Unfortunately, this is a costly transition and subject to a budgetary process. Maybe in the future we can, in addition, mandate that all motor vehicles be equipped with GPS-linked speed limiters. But like making "smart guns", making "smart cars" that don't speed is a tough sell and made even tougher since the average life of a car is now about a decade.

For now, we use a patchwork of enforcement mechanisms. If we are to use traffic cameras, the first thing to do is make sure the city owns and operates them. That takes away the biggest accusation against the city, to wit, that we are not interested in safety so much as in lining the pockets of a for profit traffic camera company.

Stay tuned.

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