Something I hear often when I try to convince people that the prevalence of the automobile has everything to do with its below-market cost is that it wouldn't matter how much it costs, people like riding in cars. Today, though, comes a study by the American Public Transportation Association (reported by Yahoo, here's the original report) that shows that mass transit ridership has increased about 2% in the US over the last year, and about 4.5% in Canada over the same period. Population growth, I believe, is lower than this, which indicates an overall increase in mass transit ridership over the same time period as the cost of gasoline has risen about 20%.
Though I'm not up for it right now, it would be interesting to calculate the total cost of travel by car (which surely rose by much less than 20%, given that gasoline is only one of the costs), and then calculate the price elasticity of demand for car travel. Unlike most, I'd be willing to bed that its elasticity is closer to 1 than to 0.