DOOMSDAY FORECASTS of crippling traffic jams now dominate discussions of urban development and form the basis of some very expensive transportation proposals. The Southern California Association of Governments, for instance, recently forecast that by the year 2000 the average rush-hour freeway speed for the Los Angeles area will fall from 35 mph to 17 mph. Under the banner “$42 Billion Needed to Avoid Future Gridlock, Report Says,” the Los Angeles Times recently wrote that...