As the concern for the effects of transportation on living quality and the environment grew, broader approaches to transportation planning were being developed. This concern was being expressed not only in the United State but worldwide. The term sustainable development became popularized in 1987 when the World Commission on Environment used it to describe a process of economic growth, with “the ability to ensure the needs of the present without compromising the ability of future generations to meet their own needs.” The global impact of transportation on the environment was reemphasized at the United Nations Conference on the Environment in Rio de Janeiro, Brazil, in 1992, which focused on global climate change.
To respond to those concerns, the Clinton administration developed The Global Climate Action Plan, which contained nearly 50 initiatives designed to return U.S. greenhouse emissions to their 1990 levels by the year 2000 (Clinton and Gore, 1993). In addition, President Clinton appointed a Council on Sustainable Development, which completed the report Sustainable Development: A New Consensus for Prosperity, Opportunity, and a Healthy Environment for the Future (The President’s Council on Sustainable Development, 1996).
Passage of the Intermodal Surface Transportation Efficiency Act of 1991 and the Clean Air Act Amendments of 1990 demonstrated the concern for the air pollution effects of increased motor vehicle travel. The acts created the “conformity” process to assure that transportation plans and projects contributed to the NAAQS. This process had a major impact on the urban transportation planning process, increasing its complexity and requiring greater accuracy and precision in the results.
The concern for environmental quality and sustainable development brought renewed interest in the relationship between land use development patterns and