Sustainable transportation: the road from Kyoto

Public Roads, March-April, 1998 by Kevin Heanue, Susan B. Petty

For the transportation community, the Kyoto Conference creates the opportunity - and the demand - to begin research and initiatives to work toward a sustainable transportation system. A sustainable transportation system will meet today's needs for access and economic growth without compromising the ability of future generations to meet their own needs. Motor vehicles emit 25 percent of the U.S. carbon dioxide (C[O.sub.2]) emissions. If worldwide transportation trends continue, along with energy use in other sectors, emissions will continue to increase and contribute to global climate change. This is not sustainable; changing the average temperatures and rainfall patterns around the world will create an irreversible impact on future generations.

Transportation is only one component of global climate change. Even if all transportation systems were sustainable, global warming would continue. However, transportation systems are not sustainable today, and the transportation community must do its part along with other consumers of fossil fuel if a solution is to be found.

Sustainability is a broader issue than global climate change. A transportation system cannot be sustainable and only address an environmental issue. A sustainable transportation system balances short- and long-term needs for the environment, economic growth, and community. To meet the global warming challenges of Kyoto and the broader issue of sustainable transportation, we must consider how transportation decisions that we make today may create longterm economic, environmental, and community changes.

This article has three purposes. One is to provide an overview of the global climate-change issue and transportation's role in it. The second is to describe the broader problem of sustainability. The third purpose is to begin to define the issues and challenges to the transportation community so that "the road from Kyoto" is an opportunity to create a sustainable transportation system for the future.

What Are the Options?

Global climate change is a central issue in sustainability and will lead much of the discussions. However, as previously mentioned, a sustainable transportation system requires more than simply addressing C[O.sub.2]; it must balance short- and long-term needs for the environment, economic growth, and equity - the "three E's" of sustainability. The strategies of the transportation community to address global climate change must be developed in the context of sustainability.

A number of studies and commissions have focused a worldwide, public policy debate on the basic tenants of sustainability. An important, recent publication is the Transportation Research Board's (TRB) Special Report 251: Toward a Sustainable Future. The TRB report is the work of 18 experts in environmental sciences, economics, transportation, and public policy. It is an excellent primer, providing background on the science and policy options to address three sustainability issues: global climate change, biodiversity, and habitat.

The United States contributes a disproportionate share of greenhouse gases and motor vehicle emissions. Carbon dioxide accounts for 85 percent of the U.S. greenhouse gas emissions. We have only 4 percent of the world's population, but we produce more than 23 percent of the global emissions of C[O.sub.2] produced from fossil fuel. Our per capita emissions of C[O.sub.2] are about 50 percent greater than the average for the other countries in the Organisation for Economic Co-operation and Development (OECD).

Figure 1 shows the dramatic increases in global energy-related emissions from carbon since 1900. The C[O.sub.2] emissions in 1995 in the United States came from three main sources: industrial production (34 percent); heating, cooling, and electrical power for buildings (35 percent); and transportation (31 percent). The transportation percentage included motor vehicle travel, production of fuels, manufacturing of vehicles, and construction of transportation facilities. Clearly, transportation is a significant part of the problem.

Emissions from motor vehicles in the United States account for most of the transportation-related greenhouse gas emissions. On average, the current car fleet in the United States gets 16.9 miles per gallon (7.1 kilometers per liter). Each gallon (3.8 liters) produces 19.5 pounds (8.85 kilograms) of C[O.sub.2] or 1.15 pounds of C[O.sub.2] per mile (0.33 kilograms per kilometer).

In 1995, the U.S. motor vehicle fleets used 143 billion gallons (541 billion liters) of motor fuel, creating [TABULAR DATA FOR TABLE 1 OMITTED] 2,800 billion pounds (1,270 kilograms) of C[O.sub.2]. All motor vehicles in the United States accounted for about 25 percent of the U.S. C[O.sub.2] emissions - about 5 percent to 6 percent of the worldwide C[O.sub.2] emissions.

Note that this is not carbon monoxide (CO), which is one of the toxic pollutants that cause smog and affect the quality of the air we breathe. Carbon dioxide (C[O.sub.2]) from natural sources is an essential part of the upper atmosphere. The global climate-change problem comes from the man-made production of C[O.sub.2].