Citation

Majeed AA, Zephaniah SO, Mehta G, Jones S. Int. J. Traffic Transp. Eng. (Rosemead, Calif.) 2014; 3(5): 207-215.

Copyright

(Copyright © 2014, Scientific and Academic Publishing)

DOI

unavailable

PMID

unavailable

Abstract

Traffic signal planning for new installations involves the estimation of saturation headway for green time allocation to optimize intersection throughput. Hitherto, the Highway Capacity Manual (HCM) procedure is usually adopted in estimating this value. The HCM requires the estimation of a base saturation flow rate that is then adjusted by eleven input parameters that are often not readily available at the project development stage. Intersection planning analyses require reasonable approximations to actual saturation flows reflecting local conditions. This paper analyzes saturation headway data obtained from intersections in Huntsville, Birmingham and Montgomery cities of Alabama. The study compares the base saturation headway of 1.9s recommended in HCM with the saturation headways observed from these cities. A student t-test concludes that there exists a statistically significant difference between the saturation headways observed between the cities and HCM recommended value of 1.9s. This was necessary to allay the assumption of homogeneity of the application of HCM base flow rates and highlights the need for alternative saturation flow estimates. Hence, an empirical-based exponential model equation involving a limited number of readily available input parameters (number of through lanes, total number of vehicles clearing the intersection and the average effective green time per cycle), was developed for estimating actual saturation headway at intersections specific to the Alabama region.

Language: en