Headway Compression during Queue Discharge at Signalized Intersections under Mixed Traffic Condition

Abstract

The evaluation of capacity at signalized intersection is an important component in the planning, design, operation and management of transportation system. Presently, the methodologies available for the estimation of capacity of signalized intersections are based on the concept of saturation flow(s). Saturation flow is the steady maximum queue discharge rate after the green onset. According to the U.S. Highway Capacity Manual, this steady maximum rate is generally achieved after the fourth queuing vehicle enters the intersection. For the present work, data were collected at different signalized intersections of NH-2 and NH-5 under mixed traffic conditions. It has been found in the present study that the queue discharge headways show an unmistakable pattern of gradual compression as queuing vehicles are discharged in succession. Consequently, the average discharge headways become stable from position ninth at NH-2 intersections and from position eighth at NH-5 intersections. Saturation headway (hs) was calculated by averaging the headways of all the vehicles in the saturation flow region and it was 1.70 and 1.64 s for NH-2 and NH-5 respectively. The queue discharge characterizations of all the intersections of NH-2 were found to be similar to those observed at intersection of NH-5.