OK, but given that they both work, the question of which works better becomes important.
For example:
An increase in gasoline tax devoted to public transit and R&D would reduce gasoline consumption.
Tighening the CAFE standards, increasing mileage requirements, and plugging the SUV and light truck loopholse would reduce gasoline consumption.
Environmental groups have limited resources and political capital. Right now they are focusing on the CAFE standards for good reason. As the data
I posted indicates, while both are effective, regulattion is more effectivie. That is cutting the gasoline a trip requires will save more gas than reducing the number of trips. In addition tighter regulations are nearer to poltically possible. Nathan pointed out that both a majority of the public, and even a majority of the UAW suppport tighter regulation. I doubt the same is true for higher gasoline taxes. So the fact the regulation works better than price, in this particular case, is significant. Which brings me back my original statement which you questioned, that higher gas taxes are not the best way to reduce gasoline consumption.