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60019-2 Report Abstract

Congress Avenue Regional Arterial Study: Variability of Departure Headways

Stilios Efstathiadis and Randy B. Machemehl, University of Texas at Austin, June 1995, 109 pp.

Virtually all aspects of arterial street performance are dominated by traffic signal operation. Efficiency of signal operations is synonymous with green intervals having exactly the correct duration. That is, greens that are too short or too long can significantly reduce operational efficiency by causing traffic delays to traffic streams using the intersection. Green interval duration is dependent upon many things, but two of the most significant are queue start-up time and intervehicle headways.

These two highly significant traffic flow parameters have been measured through a carefully designed field testing program. Estimates of appropriate parameter values are developed. Actual variation of both parameters across a wide range of geometric, traffic, and other conditions was captured. Predictive models are developed and their use in signal timing optimization is described.

Keywords: Signalized Intersections, Starting Reaction Time, Vehicle Performance, Departure Headways, Capacity, Queue Discharge Rate, Saturation Flow Value, Lane Position, Time of Day, Speed Limit, Time Spacing

ENTIRE REPORT (Adobe Acrobat File – 4 MB)