Fundamental Relationships for Freeway Traffic Flows

This report presents findings of a study of fundamental characteristics of freeway traffic flows based on analysis of individual vehicle data collected on the Eastern Freeway in Melbourne under both saturated and unsaturated conditions using a two-loop presence detection system. The aim of the study was to assess data collection and analysis methods, and to develop analytical models to describe the relationships between traffic flow parameters. The traffic flow parameters considered include flow rate, speed, density, spacing, gap length, vehicle length, headway, occupancy and space time, gap time, vehicle passage time and occupancy ratios. Travel speeds were also measured using an instrumented car. Six analytical traffic flow models are presented including various single-regime and two-regime models. Model calibration results are summarised and the parameters representing the traffic characteristics at the survey site are given. Graphs showing fundamental relationships with measured data and model predictions are presented.