NCPA - National Center for Policy Analysis

Higher Urban Density Brings More Pollution

February 15, 2001

"New urbanism" proponents say American urban areas are sprawling out of control and are too reliant on the automobile. They contend that increasing the population density of those areas would force people to abandon their cars and use public transit, bicycles or walking as an alternative. In a Goldwater Institute issue analysis, Wendell Cox systematically compares this policy ideal with actual experience in cities outside the United States and concludes that densifying urban areas only worsens traffic congestion and pollution.

European urban areas tend to have population densities more than four times that of U.S. urban areas. Canadian urban areas are more than two times as dense, and Asian urban areas are more than 14 times as dense. Public transportation carries a higher percentage of urban travel in Europe, Canada and Asia.

However, these factors do not translate into reduced traffic congestion and air pollution because of the simple problem of too many cars in too small a space.

  • Traffic volumes per square mile in European urban areas are more than 50 percent higher than in the United States, 20 percent higher in Canadian urban areas and 80 percent higher in dense Asian urban areas.
  • Traffic speeds are slower in denser areas -- the average in U.S. urban areas is 32 miles per hour compared with less than 20 mph in Europe, 25 mph in Canada and 16 mph in Asia.
  • Air pollution levels are also considerably lower in U.S. urban areas compared to urban areas in Europe, Canada and Asia.

Cox rejects the ideological -- if not theological -- view among urban planners that no new highways are necessary. He contends that roadway expansions will be necessary; newly developed areas need adequate roadway capacity and improved traffic management systems are needed.

Source: Wendell Cox, "How Urban Density Intensifies Traffic Congestion and Air Pollution," Arizona Issue Analysis 162, October 2000, Goldwater Institute.

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