Abstract
Delay is an important factor in the optimization of traffic signals and the determination of the level of service of a signalized intersection. The paper proposes the modified Webster's formula to estimate the delay of vehicles at pre-timed signalized intersections under mixed traffic conditions. Traffic volumes approaching signalized intersections are classified into four groups: Motorized two-wheeler, Car, Minibus, and Bus. The passenger car unit is estimated by using the multiple regression analysis. Distributions of the saturation flow are developed and proved to follow the normal distributions at three studied intersections. The expectation function method and Taylor series expansion are then utilized to estimate the mean and variance of delay. A comparison between the proposed model and (i) the conventional Webster's model and (ii) observed delays are performed to present the improvements of this model.
