Here's a great video that explains the relationships between transportation infrastructure, subsidies and behavior.
Arlington has done some of the best work in the country at keeping traffic under control by using a multiple strategy approach and understanding how the various aspects of our transportation system interact. It's a constant effort, however.
One big difference between what we see in the video and the United States is the % of people who use cars as their primary form of transport. According to the video, in Mexico it is only 30%. Since the majority of the population do not use cars, getting political support for more transit/bike/ped infrastructure should--in theory--be easier there than here.
Steve Offutt, Arlington