You can see it in any major East Coast city: you need to get 1 million people from the suburbs into the city center between 7 and 9am and the only reliable way to do it is subways and rail.
In Boston, which has a hub-and-spoke transit system that is oriented towards getting people downtown to an almost absurd degree, the numbers bear out that the T takes about as many people in and out of downtown as the freeways do by car. The report below states about 500,000 cars enter Boston via its main highways, and about 500,000 people take the T, daily.
