I just read about a contest going on in the North Texas area about trying to get people to car pool. They estimated about 3 million people driving to and from work everyday and 9 out of 10 are driving alone. The contest is at http://www.tryparkingit.com/. "Only" 235,512 miles have been saved thus far.
My problem with this is though people care about the environment and people talk about trying to carpool, people don't and won't do this. People in North Texas have pride in their cars and they want others seeing them driving their cars. People can't see the prestige if it's sitting in a parking lot for DART (the transit system here).
I work from home, so I don't have this problem. But more and more, when I'm showing properties, people assume they'll just follow me in their car. I'm like, ummm, no, we'll be taking one car. Why drive two cars around when we all fit in one. But that's different than driving to work together. Emergencies come up. If I had kids, I would be worried about getting a call from the day care or from school saying I needed to rush and pick up my kid from an accident or something. If I didn't have a car with me, what would I do? I would spend wasted minutes trying to coordinate a ride.
Though I think it's a good effort to get people to carpool, I don't think it's going to work as a whole.