Highway administrators, engineers, and researchers often face problems for which information already exists, either in documented form or as undocumented experience and practice. This information may be fragmented, scattered, and unevaluated. As a consequence, full knowledge of what has been learned about a problem may not be brought to bear on its solution. Costly research findings may go unused, valuable experience may be overlooked, and due consideration may not be given to recommended practices for solving or alleviating the problem. There is information on nearly every subject of concern to highway administrators and engineers. Much of it derives from research or from the work of practitioners faced with problems in their day-to-day work. To provide a systematic means for assembling and evaluating such useful information and to make it available to the entire highway community, the American Association of State Highway and Transportation Officials–through the mechanism of the National Cooperative Highway Research Program–authorized the Transportation Research Board to undertake a continuing study. This study, NCHRP Project 20-5, “Synthesis of Information Related to Highway Problems,” searches out and synthesizes useful knowledge from all available sources and prepares concise, documented reports on specific topics. Reports from this endeavor constitute an NCHRP report series, Synthesis of Highway Practice. This synthesis series reports on current knowledge and practice, in a compact format, without the detailed directions usually found in handbooks or design manuals. Each report in the series provides a compendium of the best knowledge available on those measures found to be the most successful in resolving specific problems. As demand for transportation facilities outstrips our ability to provide new facilities or even maintain existing ones, decision makers are faced with hard choices. They must critically examine the most efficient use of transportation facilities and how to prepare for investment or disinvestment over time. This study focuses on macroeconomic effects, intermodal tradeoffs, and methods for broadly informing disinvestment decision making in an era of constrained resources. The study examines methods available to estimate disinvestment effects on transportation system integrity within and across modes in urban areas, regionally, and in non-metro areas, and the use of those methods by transportation agencies. This includes economic forecasting and travel demand models, risk or probability models, needs models, and benefit and impact models. Information for this report was gathered through a survey of state departments of transportation, a literature review, and interviews with transportation officials. Seven case examples illustrate different disinvestment scenarios. (Author/publisher)
Samenvatting