That this would be a new idea surprises me. In 2009, the US had the Car Allowance Rebate System (aka Cash for Clunkers) program which likely helped reduce emissions even it was more of an economic program. Further back, twenty years ago Ventura County offered money to get old clunkers off the road strictly for emissions reasons. In 1995 per the article I link below, "More than 50% of the smog comes from vehicle emissions and a large percentage of that comes from older, pre-1974 clunkers." If you look at the distribution of cars, many are late model, well-maintained, and operating at or very near their peak. But as cars age and lose value, newer cars are built to higher emissions (and safety) standards, the parts get worn, routine maintenance gets done but many repairs aren't done because it isn't worth it based on the value of the vehicle. In areas without emissions testing, there is absolutely zero incentive to worry about it with an older vehicle. I realize this every time I get behind a vehicle that is smoking or burns my eyes because it is in such bad shape. This is not even about zero or low emissions, it is simply about getting extreme polluters off the road.
Bottom line: Encourage people to replace clunkers and keep their vehicle well-maintained.
As an odd aside, there are articles that show a similar distribution of costs in emergency room. A small number of patients dominate ER costs in the US because they have no insurance and chronic conditions. Google that one for yourself.
Ventura County Reference: http://articles.latimes.com/19...