As I've discussed numerous times, if we want clean air and water, safer streets, more sustainable energy use and better societies, it's not enough for people to use transit. We need people to stop using cars. To do that, most transit advocates try to run transit from existing residential neighborhoods to existing job centers. That's a good start.
Many advocates understand, though, that transit is much more efficient, and much more competitive with car travel, when it connects dense urban residential neighborhoods with dense urban job centers. Transit subsidy dollars can go farther this way, even if on paper they are accessible to smaller numbers of people.
So if we don't subsidize transit from sprawly residential areas to sprawly office parks, how do we get the people who live and work in those areas out of their cars? Simple: we get them to move.
As I wrote regarding freight transportation, development follows the transportation network. Invest in transit, and people will want to live and work near it. Invest in roads, and people will want to live and work near them.
The key is, of course, that you have to reduce government investment in roads, so that you're not setting up the transit service for failure. And of course you have to change the regulations so that you can get enough people and/or jobs and/or shopping to make the place walkable.
Rather than running inefficient transit to where the housing, shopping and jobs currently are, we need to run efficient transit to where we want the people to be, and stop building inefficient roads to where they currently are.