Toward A Sustainable Future: Addressing the Long-Term Effects of Motor Vehicle Transportation on Climate and Ecology

TRB Special Report 251 - Toward A Sustainable Future: Addressing the Long-Term Effects of Motor Vehicle Transportation on Climate and Ecology identifies some of the challenges that lie ahead in managing transportation's long-term environmental effects and the kinds of research and preparations that are needed to inform policy and meet these challenges. Although the report does not recommend specific policies to pursue, it identifies some of the issues and uncertainties that will need to be addressed in evaluating them.

Recognition that humans may be influencing environmental systems and processes on a global and lasting basis has encouraged interest in the concept of sustainable development. The basic premise of this concept is that each generation should seek to provide for its own needs in ways that do not compromise the ability of later generations to meet their needs. International concern over the effects of current development patterns has spawned far-ranging debate about alternative policies and practices that can foster more sustainable forms of development and reduce the risk of detrimental long-term environmental changes.

Policies, technologies, and practices within the U.S. transportation sector have become part of this debate. A study conducted by a TRB committee examined a number of environmental disturbances due to motor vehicle transportation. The committee decided to focus on those disturbances having lasting and adverse environmental consequences that may not become fully manifest for decades and would be difficult, if not impossible, to rectify if left untreated. The premise of the committee’s report is that a significant risk of an adverse outcome is undesirable and, at a minimum, warrants taking early steps to better understand and reduce that risk.

The report considers two long-term environmental risks in particular: that of global climate change caused by the buildup of greenhouse gases in the atmosphere, including carbon dioxide; and that of losses in biological diversity and ecosystem functioning due to changes in air, water, and soil chemistry caused by the chemicals emitted into the atmosphere by motor vehicles, as well as the gradual changes in habitats and natural processes caused by pervasive road and other transportation infrastructure.

Abroad range of strategies could curb the growth in carbon emissions from transportation. Substantially higher fuel taxes would both curb demand and provide incentives to own and operate more fuel-efficient vehicles, but the level of taxation required lacks public support. Major breakthroughs in fuel-efficiency technologies could also substantially reduce carbon emissions from transportation over the long term. Without incentives or market demand for such technologies, however, they may not materialize. Reducing the ecological consequences of motor vehicle transportation will require developing a much better understanding of how emissions and infrastructure contribute to changes in soil and water chemistry and disrupt habitats. The committee recommended major research initiatives on the determinants of travel demand and on the long-term ecological damage from transportation, as well as long-range technology R&D.