The new issue of Democracy: A Journal of Ideas (registration, but easy and free) is very interesting. Here is one proposal, from Jason Bordoff:

Drivers who are

similar in all respects–age, gender, driving record–pay roughly the

same premiums whether they drive 5,000 or 50,000 miles per year, even

though the likelihood of a collision increases with each mile. This

“all-you-can-drive” pricing scheme imposes significant costs on

society: more traffic accidents, congestion, air pollution, greenhouse

gas emissions, and dependence on oil.

…the effect of PAYD on miles traveled and gasoline

consumption would be significant: a 6.5 percent reduction under

conservative estimates, and others suggest the reduction could be as

high as 10 percent. To put that in perspective, it would take an

81-cent-per-gallon increase in the gas tax to achieve a 6.5 percent

reduction in miles driven.