Whenever I have the opportunity, I am a consumer of public transportation. The fact that it reduces my carbon footprint is immaterial to me, really I just find it cheaper and more convenient.
Consider a Washington Metro trip from Vienna/Fairfax to Farragut West during rush hour. The cost is $2.35 (or less if you buy weekly passes and even just use them for commuting on weekdays), and it takes about half an hour. During that half hour you leisurely listen to your iPod, read a newspaper, and the only real inconvenience of the experience is the crowding.
Now consider driving into DC from Fairfax the time is already into the hours. Parking is going to be a minimum of $10, and that doesn't include the costs of gas, wear and tear on your auto, or the disutility of the maddening fury that dealing with DC traffic causes.
So as a consumer the choice is clear. But I wonder, is it efficient?
A rail system undoubtedly requires an immense capital outlay as well as significant maintenance expenditures, and with fares like these, when do they recoup the investment? Washington DC doesn't seem to. Although rail ridership in Fiscal Year 2007 was almost 208 million, fares and other revenue (like advertising) provide only about 60% of the Metro's funding. In addition to fares and advertising revenues, the system receives money from each jurisdiction is serves [source (PDF)].
State and local taxpayers are funding a significant portion of the Washington Metro system. The Metro essentially operates at a loss (typical public program), which is disconcerting. It doesn't have to. The fare prices are extremely low compared to the cost of driving into and throughout DC. They could be doubled and it would still make rational sense to use the metro. Even if fare prices start to exceed the cost of commuting, the extra traffic into the city is going to raise parking prices and increase the psychological cost of driving (more commuters = more frustration). So before long, the metro would still be the more economical choice.
Perhaps, you think of the positive externalities, most significantly the reduction of the environmental impact of the daily commute into our nation's capitol. One can make an argument that the because of the tragedy of the commons and the public good problem of the environment, environmentally friendly enterprises such as mass transit should be subsidized. I don't quite buy it because as I pointed out above, there isn't really a market failure here: the market isn't for the environmental benefits, but for the transportation space. Transportation space is not a public good: it both is rivalrous and excludable, and a mass transit system can be operated for a profit. The positive externality of reducing emissions per commuter is just that: external to the market considerations at work here. It's gravy.
It doesn't make sense that public transit should be public in that it is owned and operated by the government. If it is operated at a loss, it is inefficient and then it is subsidized by taxpayers who may or may not use it. Further, in most cases could be operated at a profit. If it is operated at a profit then the private sector is better suited to own and operate it. Why should the government get profits in addition to the taxes they steal from us?