I think we need a system solution that greatly reduces emissions. So the idea is to create some sort of trade of carbon emission limits. This among private car owners.
Careful considerations have to be made. I think short time rules are necessary to adapt to the current climate change and progress towards electric cars. Total emissions are not the only important target. This means that emissions wherever the need to go down the most. Actually go down. Like smog affected areas.
Perhaps we could have smart area limits so no place can get overrun with too much emissions.
Another idea would be to give private citizens with ideas that generate research breakthroughs rewords like tax refunds.