Perhaps, but let me throw in an additional consideration. Per-passenger-mile statistics treat a mile driven within a city (which involves complex interactions w

Perhaps, but let me throw in an additional consideration. Per-passenger-mile statistics treat a mile driven within a city (which involves complex interactions with pedestrians/cyclists/other drivers) the same as a mile driven on a freeway (relatively uncomplicated). If you happen to be in a position right now to be able to walk to work at all, most of your driving is probably intra-city, because you probably both live and work in the same city. However, I suspect per-passenger-mile stats weigh freeway driving more heavily than city driving: on a typical car commute into a city from the suburbs, most of your mileage is not within the city proper, but on the freeways surrounding it.