Most cars do indeed meet emissions regulations. From the essay Million Dollar Murray [0]:
> In Denver, five per cent of the vehicles on the road produce fifty-five per cent of the automobile pollution.
> 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.”
When I moved to Denver, there were inspections (I think annually). Later, they were eliminated and now there are remote sensors set up along side various onramps. The main sensor is on one side, a box about the size of a suitcase, and the other side is a mirror, since the sensor aims a laser and measures the absorption lines of what comes out of the exhaust (and takes a photo of your license plate). If your car is a gross polluter, you get a letter from the DMV telling you to get it checked.
Anecdotally, I used to have a late 80s Geo Spectrum. When it failed emissions, after attempting to repair it, it turned out that the reason the oxygen sensor failed was due to a crack in the exhaust manifold. The way the engine was arranged, if left untreated, the crack in the manifold would direct exhaust gases into the radiator which is why there were so many engine fires (resulting in a total loss of the vehicle).
Notes:
0 - Written by Malcolm Gladwell, this essay is about "power law distributions", where a few percent produce wildly different results:
Most cars do indeed meet emissions regulations. From the essay Million Dollar Murray [0]:
> In Denver, five per cent of the vehicles on the road produce fifty-five per cent of the automobile pollution.
> 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.”
When I moved to Denver, there were inspections (I think annually). Later, they were eliminated and now there are remote sensors set up along side various onramps. The main sensor is on one side, a box about the size of a suitcase, and the other side is a mirror, since the sensor aims a laser and measures the absorption lines of what comes out of the exhaust (and takes a photo of your license plate). If your car is a gross polluter, you get a letter from the DMV telling you to get it checked.
Anecdotally, I used to have a late 80s Geo Spectrum. When it failed emissions, after attempting to repair it, it turned out that the reason the oxygen sensor failed was due to a crack in the exhaust manifold. The way the engine was arranged, if left untreated, the crack in the manifold would direct exhaust gases into the radiator which is why there were so many engine fires (resulting in a total loss of the vehicle).
Notes:
0 - Written by Malcolm Gladwell, this essay is about "power law distributions", where a few percent produce wildly different results:
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