Traffic Performance Models for Unsignalised Intersections and Fixed-Time Signals

Abstract

New analytical models are presented for predicting various performance statistics for traffic in approach lanes controlled by give-way and stop signs and fixed-time signals. The models are also applicable to roundabouts. An integrated modelling framework is employed for consistency among different statistics and among models for different intersection types. The models have the traditional two-term form used for fixed-time signals, with additional calibration factors introduced for each term of each model. The additional factors help to allow for the effects of variations in arrival flow rates and cycle capacities. The models for unsignalised intersections were developed by converting the block and unblock periods in traditional gap acceptance modelling to effective red and green periods by analogy to traffic signal operations. This enabled the modelling of the average back of queue, proportion queued and queue move-up rates in a manner consistent with models for signal intersections. Data generated by a modified version of the microscopic simulation model MODELC were used for model calibration. Models were derived using a bunched exponential model of arrival headway distributions for all traffic streams.