The NY Times magazine ran an article by the authors of "Freakonomics"
Crux being that cars are subsidized by way of "negative externalities" (economist speak for "passing the pain to someone else") in three ways:
1. Congestion: $78 Billion/year
2. Pollution: $20 Billion/year
3. Accidents: $220 Billion/year
They cede the first two as near impossible to combat, but cite Progressive Insurance for attempting a pilot program on a pay per mile basis -- thus rewarding those who ride bikes, for example.
Not sure how to translate this into direct action such as what brought State Farm around on their ads, but certainly would be interested in ideas. . .