"This research is all discussed in a new policy brief (pdf) by the American Public Transportation Association, which notes that the United States appears to have entered a new era of oil volatility. (They're not alone in thinking so!) And that means that demand for public transportation is likely to keep surging. If gas prices spike, more people will try to ride the bus or train to work. If gas prices then settle down again, many of those people will stick with transit."
The problem, pointed out by Plumer, is that America's transit agencies are ill equipped to handle increased demands. In fact, 71 percent of metropolitan transit agencies have had to cut services in the past year or are currently considering it.
Of course the catch-22 in this equation is the federal government's reliance on gasoline taxes for transit funding. "Transit is funded through a dedicated fraction of the gas tax. And that can create havoc: Whenver [sic] oil volatility pushes people away from driving and toward transit, that means there's less gas-tax revenue available. We've seen this during the current recession - driving has plunged, which means gas-tax collections have fallen, which means Congress is bickering about whether to cut money for transit systems."