Suggested Citation:
Sperling, Daniel and Nicholas P. Lutsey (2009) Energy Efficiency in Passenger Transportation. The Bridge 39 (2), 22 - 30

Transportation accounts for approximately one-third of greenhouse gas (GHG) emissions in the United States, two-thirds of oil consumption, and about half of urban air pollution. In addition, GHG emissions are increasing faster in transportation than in any other sector, making it a prime target for changes in energy and climate policy. As a result of increased use of energy-intensive modes of transport, especially private cars and trucks, bus and rail transit now account for less than 3 percent of passenger travel in the United States.

Reducing oil use and GHG emissions in transportation is difficult for two basic reasons: (1) as a derived demand linked to almost all other economic activity, travel demand has proven to be both strong and inelastic; and (2) unlike other large energy-using sectors that can operate with a variety of commercial fuels, vehicles operate almost exclusively on oil-based fuel.

Introducing new fuel-efficient propulsion technologies and low-carbon fuels has been difficult because of poor coordination between fuel and vehicle industries, the necessity of large upfront investments in infrastructure, and entrenched consumer expectations and habits. To make matters worse, petroleum production is becoming more rather than less carbon intensive as easily accessed, high- quality reserves are depleted, and producers tap into remote sources of fossil energy that require additional refining to upgrade fuel quality.

Despite this rather bleak scenario, there are many attractive opportunities for reducing oil use and GHG emissions. In this article we focus on the largest component of the transportation sector, light-duty vehicles, which account for more than half of the oil consumption and almost a quarter of GHG emissions in the United States. In addition, we define energy efficiency to include: (1) improvements in conventional vehicles and the introduction of advanced, high-efficiency propulsion technologies based on non- petroleum fuels; (2) changes in “on-road” operational practices; and (3) system improvements that result in decreased vehicle use.