What the Dog Saw [80]
4.
A few miles northwest of the old YMCA in downtown Denver, on the Speer Boulevard off-ramp from I-25, there is a big electronic sign by the side of the road, connected to a device that remotely measures the emissions of the vehicles driving past. When a car with properly functioning pollution-control equipment passes, the sign flashes “Good.” When a car passes that is well over the acceptable limits, the sign flashes “Poor.” If you stand at the Speer Boulevard exit and watch the sign for any length of time, you’ll find that virtually every car scores “Good.” An Audi A4 — “Good.” A Buick Century — “Good.” A Toyota Corolla — “Good.” A Ford Taurus — “Good.” A Saab 9-5 — “Good,” and on and on, until after twenty minutes or so, some beat-up old Ford Escort or tricked-out Porsche drives by and the sign flashes “Poor.” The picture of the smog problem you get from watching the Speer Boulevard sign and the picture of the homelessness problem you get from listening in on the morning staff meetings at the YMCA are pretty much the same. Auto emissions follow a power-law distribution, and the air-pollution example offers another look at why we struggle so much with problems centered on a few hard cases.
Most cars, especially new ones, are extraordinarily clean. A 2004 Subaru in good working order has an exhaust stream that’s just .06 percent carbon monoxide, which is negligible. But on almost any highway, for whatever reason — age, ill repair, deliberate tampering by the owner — a small number of cars have carbon-monoxide levels in excess of 10 percent, which is almost two hundred times higher. In Denver, 5 percent of the vehicles on the road produce 55 percent of the automobile pollution.
“Let’s say a car is fifteen years old,” Donald Stedman says. Stedman is a chemist and automobile-emissions specialist at the University of Denver. His laboratory put up the sign on Speer Avenue. “Obviously, the older a car is, the more likely it is to become broken. It’s the same as human beings. And by broken we mean any number of mechanical malfunctions — the computer’s not working anymore, fuel injection is stuck open, the catalyst died. It’s not unusual that these failure modes result in high emissions. We have at least one car in our database which was emitting seventy grams of hydrocarbon per mile, which means that you could almost drive a Honda Civic on the exhaust fumes from that car. It’s not just old cars. It’s new cars with high mileage, like taxis. One of the most successful and least publicized control measures was done by a district attorney in L.A. back in the nineties. He went to LAX and discovered that all of the Bell Cabs were gross emitters. One of those cabs emitted more than its own weight of pollution every year.”
In Stedman’s view, the current system of smog checks makes little sense. A million motorists in Denver have to go to an emissions center every year — take time from work, wait in line, pay $15 or $25 — for a test that more than 90 percent of them don’t need. “Not everybody gets tested for breast cancer,” Stedman says. “Not everybody takes an AIDS test.” On-site smog checks, furthermore, do a pretty bad job of finding and fixing the few outliers.