Lack of sufficient capacity to meet current and future travel demands is seen as a major obstacle to both passenger and freight movements in many transportation corridors throughout the United States. Indeed, there are serious concerns about preserving adequate corridor capacity to meet future increases in travel demand. Many major highways are congested and operate at or below acceptable service levels during most hours of the day. Traditional approaches to corridor preservation, including those for urban and intercity transportation corridors, have proven to be inadequate. Land acquisition has encountered severe stumbling blocks due to the high costs of land in urban areas, environmental regulations, physical barriers, and political and community opposition. The objective of NCHRP Project 8-31, `Long-Term Availability of Multimodal Corridor Capacity', is to characterize the nature, type, and extent of existing and potential capacity problems in many important corridors in the country. There is a need to measure the maximum possible throughput in these corridors in terms of person and freight movements, not just vehicle movements. While some corridors may have reached their capacities in terms of maximum vehicle throughput, there could still be excess capacities in terms of potential person and goods movement. For example, statistics on average highway vehicle occupancy rates indicate that there is an extraordinary amount of excess capacity even on the most crowded highways. Compared with vehicle capacity measured in passenger-car equivalents, heavily travelled highways currently have nearly four times their current capacity when measured as potential passenger throughput. Options to increase current physical capacities, utilize excess or unused capacities, or reduce travel demands need to be identified and evaluated. This `Multimodal Corridor and Capacity Analysis Manual' provides a comprehensive framework for dealing with capacity analysis, performance determination, needs and options identification, and alternatives evaluation for various elements comprising transportation corridors. It includes a typology of corridors that can help transportation analysts develop a specific approach for analysis. Four multimodal transportation corridors are used as examples to illustrate the procedures for establishing the scope of corridor analysis and to characterize the fundamental problem. Capacity analysis and determination methods for various transportation modes including highways, rail, air, pipeline, and waterways are discussed and supplemented with examples. A multimodal approach to capacity analysis is presented using the existing methods for individual modes, and specific measures of performance and level of service that are applicable to transportation corridors are identified. The `Multimodal Corridor and Capacity Analysis Manual' also provides a rather extensive summary and description of options that are available to enhance corridor capacity and performance either by providing additional capacity, freeing up unused capacity, or reducing travel demands. Methods to evaluate these options, including illustrative examples, help complete the manual. Transportation planners and analysts are encouraged to use the rich and valuable information contained in this manual in dealing with multimodal transportation corridors. (A)
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