Trends in Vehicle Miles Traveled

The number of vehicle miles traveled increased after World War II, but over the past 20 years, the number of miles Americans drive every year has increased at four times the rate of population growth. Pollutants associated with atmospheric deposition from automobile emissions and runoff from roads are recognized as an increasingly significant source of water pollution. As this pattern of development has eliminated transportation options for many Americans, related impacts on quality of life such as time lost in traffic congestion, longer commuting times, more aggressive driving and more accidents have worsened.

One study concludes that the number of miles traveled per household falls by 35 percent when residential densities move from 2 units per acre to 10 units per acre (Holtzclaw 1994). Studies of transit usage establish seven to eight residential units per acre as the minimum housing density necessary to support regular transit service (Pushkarev and Zupan 1977).