Nic Lutsey and Dan Sperling, Institute of Transportation Studies, University of California, Davis

Transportation presents a substantial and growing worldwide greenhouse gas (GHG) emission challenge. GHG mitigation strategies can be grouped into three categories: vehicle efficiency, low carbon fuels, and travel reduction. Potential GHG reductions are very large, with varying levels of cost effectiveness. Virtually all provide large co-benefits, including energy cost savings, oil security, and pollution reduction.

Transportation accounts for about one-fifth of total greenhouse gas (GHG) emissions worldwide, but close to 30 per cent in most industrialised countries. Worldwide, transport GHG emissions are growing faster than those from any other sector. Most are associated with motor vehicles, but air transport is an increasingly important source. Studies of cost effectiveness generally find transportation GHG reductions more expensive than reductions in most other sectors. The high cost is due to: low fuel price elasticity by passenger car owners (and light trucks); strong demand for personal travel, air travel, and goods transport; the difficulty of introducing new low carbon fuels and new fuel efficient propulsion technologies; deteriorating quality of public transport virtually everywhere; and the increasing share of goods carried by truck. In addition, petroleum fuel use is becoming more carbon intense. As easily accessed and high quality reserves are depleted, more carbon intense and remote sources of fossil energy are tapped and additional refining is required to upgrade fuel quality.

The analysis here focuses on the two largest components of the transportation sector: passenger automobiles and commercial freight trucks. Together, these make up about two-thirds of transportation GHG emissions.