A good overview of the cost of cars in terms of money, space, and time at Planetizen. Transportation costs are already unaffordable (>20% of household income) for the lowest income 40% of the US, and drivers only pay a minority of automotive costs directly. Over the last half of the 20th century, the proportion of household income dedicated to transportation doubled. Cars use ~20x as much spacetime (s*m^2) as bikes for the same commute, and ~200x as much as a pedestrian. Interestingly the direct car costs mentioned are only about half what AAA estimates ($4100 vs. $8500 per year).