do not know what the future might bring. Citizens need no experts to know that one does not cure obesity by loosening one's belt nor cure traffic-related problems by simply expanding highways.

Readers of this report should consider two closely related reports issued in 1994 by high-level study commissions in the United Kingdom. These considered a wider range of evidence and drew conclusions and judgments that contrast with the committee report and are generally more consistent with this minority statement. The Standing Advisory Committee on Trunk Road Assessment (SACTRA) report, Trunk Roads and the Generation of Traffic, is focused specifically on the strong evidence that highway capacity expansion spurs increased motor vehicle travel demand (SACTRA 1994). In the Royal Commission on Environmental Pollution (RCEP) report, Transport and the Environment, an overview is given of the broader challenge of making transportation more sustainable, including extensive discussion and recommendations regarding the role of road investment in contributing to environmental degradation (RCEP 1994).

The committee report does not give appropriate consideration to evidence related to the effects on energy use and the environment caused by a reduction of highway capacity—for example the effects of traffic calming and traffic cells—although such evidence is highly relevant to the issue at hand. While asserting that transportation pricing strategies are more important than changes in highway capacity in determining environmental performance, the report gives only limited consideration to evidence from outside the United States that might isolate the effects of highway capacity changes from the effects of transport pricing, levels of public transportation provision, and alternative land use and urban design patterns. Excluding this evidence, and in a tone that appears to subtly play to one side of current contentious domestic policy debates, the report concludes that our state of knowledge is insufficient to evaluate the effects of added highway capacity to support current federal environmental regulations.

It is intellectually inconsistent for the report to argue that on the one hand, current models cannot evaluate the effects of changes in highway capacity on the environment, while on the other hand asserting that alternative strategies, such as time-of-day tolls, will have known and larger effects on air pollution emissions. If we lack the ability to develop reasoned estimates of likely effects of changes in high-



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement