Thanks for your comment. Older vehicles (>10 years) that are poorly maintained contribute a higher volume of emissions than a new vehicle. New cars and trucks have improved fuel economy, pollution controls (eg. particulate filters to take advantage of ultra-low sulphur diesel fuel), and advanced on-board diagnostics for alerting the driver and technicians of problems. Emission testing has shown that the older vehicles have higher emission rates of hydrocarbons, carbon monoxide, and particulate matter. Programs like Drive Clean in Ontario and AirCare in BC target older vehicles that do not meet acceptable exhaust standards.

You raise a good point about the net environmental impact of building new vehicles to replace old. There are air emission and energy consumption impacts resulting from manufacturing. I used to estimate the air emission impacts per vehicle when I worked at GM so I’ll see if I can find some data. It would be interesting to see the net impact. My hunch is that if an older polluting vehicle is driven for a long period of time there will be a net benefit to replacing with new. That all being said, I don’t think people should be replacing their cars every few years. Proper maintenance and reducing reliance on driving will go a long way.

Carbon dioxide emissions are primarily fuel dependent (based on carbon content of gas or diesel) and reduce with fuel economy improvements and engine technologies that rely less on fossil fuels like hybrids.

Whew, long answer! Thanks.

I am a layman in this area, but I do have a gut reaction to the idea that retiring old cars early results in a net pollution reduction. Granted that new cars produce less pollution per km, but does that offset the environmental cost of building the new car before the old car was truly not drivable?

Also, though new cars produce much less of some pollutants, such as sulphur oxides, how much improvement is there concerning the main bad guy (so far as I understand) which is carbon dioxide?

I heard one environmentalist throw cold water on the notion. The suspicion regarding the whole RYR program is that auto companies are looking for any reason for the government to subsidize sales.

Cheers,
Michael