Beyond the tailpipe.

Neil Kolwey ("Planes, Trains, and Automobiles," March/April 2009) provided a good analysis of tailpipe emissions from transportation from an individual family perspective. However, looking only at tailpipe emissions means missing about one-third of transport emissions and results in an inadequate analysis for decision making.

For example, the 2006 Hydro Quebec study Greenhouse Gas Emissions from Transportation Options found that transport tailpipe emissions account for 31 percent of total Canadian GHG emissions but more than 50 percent of lifecycle emissions. Similarly, researchers from the UC Berkeley Center for Future Urban Transport estimated last year that total emissions for a typical U.S. passenger car are 57 percent higher than tailpipe emissions.

The lifecycle emissions from transportation include not only the obvious upstream emissions from extracting and refining petroleum, but also the emissions from manufacturing and maintaining vehicles, and building and maintaining roads and parking facilities. When you look at lifecycle emissions, automobile ownership becomes almost as big an issue as how much each car is driven. A two-car family can do a lot more by selling one of their cars and reducing the distances they drive than by just reducing the amount they drive.

The individual or family is also not a particularly useful level of analysis for transportation emissions in urban areas. Automobile traffic volumes expand and contract to fill the available road and parking space, as do the resulting emissions. If an individual stops driving to work, in many cases someone else will make use of the road and parking space vacated (and this person might buy a new car to take advantage of the opportunity). Decisions about expanding freeways and parking supply, or instead re-allocating resources and road space to transit, cycling, and walking, are primarily societal decisions.

Looking at the full lifecycle emissions of transportation leads me to conclude that we need to slam the brakes on all urban roadway expansion and shift the resources to high-quality transit to get people out of their cars, fast. Then we need to start re-allocating road space to low-emissions transportation modes. Individual actions count, but in the case of urban transportation societal actions count for a lot more.

ERIC DOHERTY

Vancouver, British Columbia, Canada