[Zak]

I wonder how many years a car eligible for that program would need to be driven to equal the environmental impact of building a new car and driving it for the same number of years.

I lack the expertise to offer a useful estimate, but I'm guessing that number is not small.

[buildsjets]

That’s totally beside the point. Breathing smog is disgusting, regardless of the economic balance. It removed an incredible number of local point-source polluters from high population density areas. Cash 4 Clunkers was so successful that Seattle completed eliminated emissions testing, because not enough crapboxes were failing the test after they weeded out the vast majority of the clunkers.

[bluGill]

Most clunkers were not eliminated. It only covered if you bougt a more fuel efficien vehicle so small cars didn't get covered and people who couldn't afford new cars were not covered.

emmisions were already improving and tests rarely found anything so this was used as an excuse to eliminate waste

[Zak]

I did not say anything about economics; I wrote only about environmental impact.

It's hard to compare different kinds of environmental impact, but building a new car involves several, often with effects far away from the place where the car is used.