This paper reports on the results of the National Cooperative Highway Research Program (NCHRP) Project 3-37 `Capacity and Level of Service at Ramp-Freeway Junctions'. The objective of this research was the development and validation of an appropriate methodology for determining capacity and level of service (LOS) at freeway-ramp junctions. It included a nation-wide data base of over 60 sites. Using videotape technology, the data base included five-minute summaries of flow, average speed, and vehicle type distribution for each 500-foot section of each lane in the study site, including the ramp and acceleration or deceleration lane. Additional data included sample traces of ramp vehicles. Data Data collection generally covered a section of 2000 feet in length, beginning 500 feet upstream of an on-ramp junction and 1500 feet upstream of an off-ramp junction. Based upon the development of regression models, a new analysis methodology for ramp-freeway junctions was constructed and adopted for inclusion in the Highway Capacity Manual (HCM). (A)
Abstract