Monday, October 17, 2011

Population, Traffic Density and Air Pollution in Large Cities

Smart Growth (Livability), Air Pollution and Public Health (Wendell Cox, NewGeography, Sep. 29, 2011)

Today’s focus is on the links between population density, traffic intensity and higher levels of pollution intensity based on an analysis of traffic and EPA pollutant data from 51 cities in the USA with more than 1 M population. The conclusion proposed is that the objective of urban planners toward urban population densification to reduce infrastructure costs and sprawl may result in higher pollution in the city core and that allowing sprawl allows vehicle emissions to dissipate over a larger area. While there is no argument against the link between heavy traffic, vehicle emissions and health risk, it seems that the author does not consider the fact that a sprawled city results in more vehicle travel and emissions from people commuting to work downtown than one with a high population density- aside from the added cost to provide municipal services such as fire, police, water and sewage to a larger area.

Key Quotes:

“higher population densities are strongly associated with higher levels of automobile travel and more intense air pollution emissions from cars and other highway vehicles”

“more intense traffic congestion and the consequent higher air pollution emissions are negative externalities of smart growth and densification”

“Seven of the 10 counties with the highest NOx emissions concentration (annual tons per square mile) in major metropolitan areas are also among the top 10 in population density (2008).”

“Virtually all urban areas of Western Europe, North America and Oceania principally rely on cars for their mobility and there is no indicate that this will change. The air is less unhealthful for residents where traffic intensity is greater. As the air pollution intensity data shows, cars need space”
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