Delay Models for Mixed Platoon and Secondary Flows

Abstract

A mathematical model is described for estimating approach delays at pretimed, signalized, coordinated intersections. The delay models incorporate the size of and flow rate within the progression bandwidth. Platoon dispersion and secondary flows are considered via a simplified platoon‐dispersion algorithm calibrated from the TRANSYT‐7F model. The basic premise in this study is that traffic is assumed to arrive at the progressed approach in two average flow rates, one within the progression bandwidth, and another outside of it. This modeling concept represents a middle ground between bandwidth models that assume a constant flow rate in the dispersed platoon and TRANSYT‐like techniques where arrival flow rates vary in each time slice of the cycle length. The delay models are evaluated with Webster's delay formula for random arrivals and with simulated data in NETSIM; in both cases the results compare very favorably. Pending field validation of the delay estimates, an immediate application of the models is the development of progression adjustment factors, which can be readily estimated from system signal‐timing parameters and flow rates derived herein.