My idea is to create a fairer system of vehicle registration.
Instead of paying a flat fee for vehicle registration, the fees would be gathered by adding a tax to the price of fuel. This system would be more fair-- ie, the little old lady who drives to the shop and goes to her daughter's place once a week would not be paying the same registration as the salesman who drives 100,000 km a year. It would also encourage the use smaller, more fuel efficient cars and would also encourage people to use public transport.
This would obviously help the environment and lead to saving in other areas, such as road maintenence, medical cost from accidents, insurance, etc.
If we use a fuel efficiency of 9 litres/100 km is the standard we could add about 20c a litre to the price of fuel. This would result in a yearly payment of approximately $400 for someone travelling 20,000km (apparently seen as standard for manufacturer's warranties). (Other people might have different ideas for the standards used.)