Monday, November 05, 2007

Toward a Full Accounting of GHG Transport Emissions

Accounting for greenhouse gas emissions (GHG) is no simple matter in urban transport. It is not as simple as the GHG emissions from the vehicles themselves. For example, there is the vehicle manufacturing process. There is also vehicle maintenance and the energy used to keep stations and administrative facilities open. There is simply no central source of information for such data, a situation that is a serious “GHG omission.”

Three decades ago, BART, the San Francisco area rapid transit system, published estimates of the full energy requirements for operating public transport and cars, including such factors as vehicle maintenance, right of way maintenance, and stations. Generally, the analysis found that the rail mode required 41 percent more energy than is consumed in traction (transportation), buses 37 percent and cars 22 percent. These factors may be old, but they may be the only ones available (and it is possible that they are still valid).

If we assume the BART factors, then the comparison of GHG emissions between transport modes in Australia is even more favorable for cars. The average car would emit 229 grams of GHG per passenger kilometer, compared to 212 grams for buses and 148 grams for Sydney’s rail system. Cars meeting the 2010 National Average Fuel Consumption target would be better than both buses and rail in Sydney at 137 grams per passenger kilometer. The best hybrids could better buses by two-thirds and rail by one-half.

All of which points out the needed for objective, comprehensive analysis.

The previous post on GHG emissions by mode("Public Transport Greenhouse Emissions Similar to Cars", Wednesday, October 31, 2007) does not include any adjustment for vehicle maintenance, right of way maintenance, and stations. Its calculations apply only to direct transportation.

Posted by Demographia

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