There is a study that finds that building freeways just makes for more traffic congestion because of the subrban flight phenomena. A highway is built in a relatively unpopulated area, and then developers biuld all around the highway and people buy houses there because they think they will have an easy commute. The first ones to buy do have an easy commute for a while, but then the sprawl takes over and the new highway becomes a parking lot during rush hour.

Another study showed that if you completely paved over every inch of an urban area so that cars could travel on it, there would be no decrease in traffic congestion.

Americans will not give up their cars until the inconvenience and cost of driving is so huge, they will switch to mass transit. And from what I can see, Americans will put up with huge cost and inconvenience because the only places that mass transit is popular is in very dense urban areas of the notheast.