I put the equivalent gasoline fuel efficiency of the major modes of transportation in one graph to get a feel for where they fall relative to one another. The loading assumption makes a big difference, but I think this is a reasonable approximation.
Typical loads are roughly:
Car = 1.5 passengers
Subway = 95% full
Airplane = 80% full
Train = 80% full
Bus = 70% full
:: Wikipedia :: James Strickland
