Environmental Impacts

Energy Use, Oil, and Greenhouse Gas Emissions

From shortly after the Arab oil embargo of 1974 until the fall in oil prices in the mid-1980s, U.S. energy policy was concerned with conserving energy and reducing oil use. Since about 1988, energy policy in the U.S. and Europe has increasingly focused on reducing emissions of so-called greenhouse gases, which are thought to be changing the global climate (IPCC 2007a, c). Analysts now routinely evaluate transportation plans for their energy use, oil use, and greenhouse gas emissions.

LLMs use much less energy and have much lower emissions than do conventional FHVs. Thus, the huge reduction in average kinetic energy throughout a town based on an LLM network translates directly (although not proportionately) into a large reduction in the total life cycle energy required for the manufacture, operation, and maintenance of vehicles and infrastructure. Because emissions of CO2 and other greenhouse gases are closely related to energy use, a large reduction in life cycle energy use results in large reductions in greenhouse gas emissions.

To analyze life cycle energy use and emissions of greenhouse gases, an expanded version of the life cycle emission model (LEM) developed by Delucchi (2003) was used. This model estimates emissions of urban air pollutants and greenhouse gases from the life cycle of fuels from feedstock production to end use and from the life cycle of materials from raw resource extraction to manufacture and assembly. It does this for a wide range of transportation modes, vehicle technologies and energy sources, including buses, trains, and electric vehicles.

For this analysis, conventional travel modes were compared with LLMs in the United States for the year 2010. Table 24.1 shows the life cycle CO2-equivalent emissions estimated by the LEM. The CO2-equivalent is a way of expressing the impact of emissions on global climate; it is equal to actual emissions of CO2, plus emissions of other gases expressed in terms of the amount of CO2 that would have the equivalent effect on climate. The other gases are CH4, CO, hydrocarbons, NOx, SOx, particulate matter, and refrigerants.

Table 24.1 Life cycle CO2-equivalent emissions from transportation modes in the U.S., in 2010. One passenger per vehicle is assumed for both fast, heavy (conventional) vehicle (FHVs) and light, low-speed mode (LLMs).


Mode technology

g/pass-km (gasoline FHV) % change vs. gasoline FHV Fuel cycle(a) Fuel + material(a)

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