Quick Note on Air Pollution

Yesterday’s USA Today carried a story about a study from the Harvard Center for Risk Analysis coming up with a huge figure for excess mortality, 2,200 nationwide just from the extra gas consumption caused by traffic congestion. Such a figure is almost certainly too high.

On page 4, the study compares the costs of congestion in terms of wasted time, wasted gas, and excess mortality due to pollution. In 2020, the cost of excess mortality is given as just under $20 billion in the largest 83 urban areas. Since the total amount of fuel wasted due to congestion according to the TTI, on whose data the study is based, is about 3.5 billion gallons, this corresponds to more than $5 per gallon.

With this figure in hand, we can compare the study to studies of car pollution and not just congestion pollution. American studies tend to find much lower costs of pollution and lower percentages of pollution coming from cars than foreign studies, and foreign studies find costs in the $2-3/gallon range. For examples, see here for Toronto and compare with fuel consumption figures coming from carbon emissions figures in the same study; here for Sydney and compare with fuel consumption figures from here; and here for Auckland sourced to this New Zealand study and compare with these fuel consumption numbers. Note that in the US, such figures are considered high-end estimates – see anything on social costs by Mark Delucchi.

The most likely reason for the factor-of-2 discrepancy we obtain is funding sources. The study under discussion was sponsored by the transportation construction industry, and was conducted by a research institute that had ties to the tobacco industry in the 1990s.

The study’s content indeed suggests such interest conflicts. The methodology estimates pollution per unit of VMT; it could just as well have posted figures for total car pollution. And the conclusion, far from suggesting regulations or pollution pricing, is:

long-term policy alternatives for addressing congestion such as traffic management through congestion pricing, traffic light synchronization and more efficient response to traffic incidents, and adding new highway and public transit capacity.

Adding more transit capacity is reasonable, since it displaces car trips. But adding highway capacity means people drive more, which increases rather than reduces pollution. And nowhere does the study recommend a tax on gas, which is what causes this pollution in the first place. This is not serious public health research; it’s lobbying for construction.

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