Here's an article by a conservative think tank guy on the costs of highway congestion including health costs: Free the freeways - Economics - AEI

He presents evidence that highway congestion may cause health problems in nearby residents due to the excess exhaust produced by idling in traffic, or that simply living near a highway has health costs. (in other words your driving hurts my health - you heard it from the American Enterprise Institute) He tosses out a few ideas for correcting the problem:

We could build more roads, increase tolls during rush hour, add more fast-passes to avoid tollbooth traffic, and improve public transportation. While members of the different political parties might favor different combinations, the key point is that pricing road use could help solve the problem, and provide a double dividend as revenues are used in other ways.

Now it seems to me that "building more roads" would not be ideal, as simply living near a highway harms your health, and more roads would expose more people to risk. Ultimately though, he sees "pricing road use" as the solution. I can certainly get behind that idea.