A curmudgeonly friend writes: Do you live in a mid-sized city with poor public transit, a taxi fleet choked with vested interests, and a risible bicycle system? Do you fear there will never be a day when folks can get around your city efficiently, emitting a minimum of greenhouse gases? If so, then the family sedan may be the answer. That’s crazy talk, of course. Buses are far more efficient, right? But how many times have you driven behind a bus containing two, one or zero passengers. Do you really believe the greenhouse gas emissions from your trusty Corolla are more than those...