Efficiency

I was reading Wendell Cox's recent attack on the Center for Neighborhood Technology's affordability calculations, and was struck by one thing he wrote:“transportation costs will be reduced in the future by the far more fuel efficient vehicles being required by Washington.”* 

In other words, don't worry about Americans being impoverished by the cost of a car for every man, woman, and 16-year old in the House: the technological miracle of fuel efficiency will save us. 

Every so often, one sees an article arguing that one mode of transportation is cheaper, more efficient, or less dangerous than another because it uses less energy/kills more people/costs more per passenger-mile. (1)

It seems to me, however, that per passenger-mile comparisions are flawed in one key respect: they assume that trips on any mode of transportation will involve the same mileage, so that if the average driver lives 20 miles from work, the average bus rider will also live 20 miles from work.