New speed-flow relationships for road links in Perth.

Speed-flow curves describe the characteristics of a road facility in the form of average speed or its inverse, travel time per unit distance, as a function of traffic flow. They are fundamental to traffic assignment modelling for a range of applications from strategic, long-term planning to short-term small area analysis. The Perth metropolitan road network previously used 124 speed-flow curves to represent different road types. This paper describes how a project was organised to develop a new set of speed-flow curves representing the current traffic conditions in Perth and suitable for a range of traffic assignment platforms. Travel times were collected using the floating-car technique. Traffic flow data was also collected on routes when the floating-cars passed by. The new set consists of 27 speed-flow curves for the modelling of link flow characteristics in the Perth metropolitan road network. The principle of harmonisation was fruitfully employed in developing the curves. This principle refers to the need to consider all speed-flow curves as a consistent set in the process of finding the best set of parameters to specify a speed-flow curve. (a) For the covering entry of this conference, please see ITRD abstract no. E214938.