The National Academies

NCHRP 03-37 [Final]

Capacity and Level of Service at Ramp-Freeway Junctions

  Project Data
Funds: $400,000
Research Agency: Polytechnic University
Principal Investigator: Dr. Roger P. Roess
Effective Date: 7/1/1990
Completion Date: 12/31/1993

This project produced a draft Chapter 5, "Ramps and Ramp Junctions," that was adopted by the TRB Highway Capacity and Quality of Service Committee and included in the third edition, second upgrade of the Highway Capacity Manual, released in 1994. A matching software module has been incorporated into the Highway Capacity Software.

Chapter 5 of the 1985 Highway Capacity Manual was based primarily on a Bureau of Public Roads study of lane distribution in the vicinity of merge and diverge areas conducted in the early 1960's. The procedure represented operating characteristics, such as vehicle fleet mix and driver and vehicle performance, that are no longer valid and did not include a number of geometric and traffic factors that influence capacity and level of service.

The objective of this research was to develop and validate an appropriate methodology for determining capacity and level of service at ramp-freeway junctions. This research has (1) evaluated the state of the art in operational analysis of ramp-freeway junctions, (2) developed and tested a new methodology for analyzing capacity and LOS at these junctions, and (3) verified the proposed method with an extensive field data-collection effort.

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