We can drone on about fuel economy standards and miles per gallon, but the next big deal is Vehicle Miles Travelled, or VMT, because it is as much of a problem. in the 25 years from 1977 to 2001 the number of miles driven each year went up by 151%. Joseph White writes in the Wall Street Journal:
The reasons for the big growth in miles traveled are pretty obvious if you don't live in the center of a big city endowed with functioning public transport. To make space for ever larger suburban homes, housing developers pushed further and further from city centers and shopping areas. New neighborhoods often had street layouts cluttered with cul de sacs that forced people to drive farther to get to main roads or stores. Local zoning laws -- reflecting the preferences of residents -- tended to separate commercial and residential uses, and single family from multi-family dwellings.
Meanwhile, the bulk of the money spent on transportation infrastructure was directed to building more and bigger highways. We could have subsidized bullet trains and more light rail systems, but we didn't.
It is possible that gas prices, urban redevelopment and just being sick of commuting will bring empty nester boomers back into town and reverse this, but the Department of Energy doesn't think so, and is predicting another 59% increase in VMT by 2030. ::Wall Street Journal via ::Planetizen