The simplest way to incentivize the consumer to drive smaller more efficient vehicles is to raise fuel taxes. As much as I personnally dislike taxes, an energy tax would provide:
1. An economic decision for new vehicle buyers making the decision more about what I can afford to drive than what I can afford to buy.
2. It will provide an environment in which car companies can provide vehicles consumers want to buy and not make auto companies responsible for selling the government mileage policy.
3. It will reduce fuel useage and therefore reduce dependence on foriegn oil.
4. If all fuel for all reasons is taxed the same, there would be no exceptions for special useage, enforcement is easier and there is no need for governemental regulatory agencies.
5. An alternative fuel policy and required incentives would not be necessary, the market would support new fuel sources and auto companies would exploit the technologies for the consumer.
6. Mass transit would be incentivized due to the willingness of people to consider alternative travel arrangements, currently 2 or more people can tarvel by car cheaper than by mass transit.
7. Taxes would be used to pay for the crumbling infrastructure.
There have been several articles quoting auto company executives endorsing this approach. Again, I hate the T word. A rational fuel taxing policy would "fix" a lot of "bads" without increasing government costs.