Congestion’s Effect on Greenhouse Gases Seen in NYC

Published October 1, 2009

Perhaps the best indication of the strong correlation between traffic congestion and greenhouse gas emissions is a comparison of Environmental Protection Agency “driving cycles,” tests used to estimate some emissions, although not greenhouse gases, and fuel economy.

Under the New York City Cycle, average speeds are two-thirds less than they are under the average urban cycle. This reduction in speed and increase in congestion results in a 50 percent decrease in fuel economy, according to an Argonne National Laboratory study.

On average, vehicle travel in New York City is approximately eight miles per capita per day. In the average large urban area outside New York City—such as the Phoenix, Arizona urban area, or the suburbs of New York City—vehicle travel is approximately 24 miles per capita per day.

That means per-capita driving in New York City is 67 percent less than in Phoenix. However, because of the loss in fuel efficiency caused by congestion, the greenhouse gas emissions from cars per capita are only 31 percent less.

Thus the data indicate nearly one-half of the greenhouse gas emissions difference between New York City driving rates and Phoenix driving rates are cancelled out by the impacts of slower speeds and increased congestion.

Wendell Cox ([email protected]) is a visiting professor at the Conservatoire National des Arts et Metiers in Paris, France. This article was originally published in New Geography and is reprinted with permission.