Novel statistical analysis approach for free-flow speed on real-time traffic data

As a basic attribute of road traffic flow, free-flow speed is an indispensable parameter in most of transport research and management tasks. Employing the traditional freeflow speed definition method, it is hard to obtain a steady result with the real-time traffic data from Intelligent Transportation System (ITS). Based on analysis of real-time traffic data in Shanghai urban expressway, a statistical approach to determine the free-flow speed is proposed in this paper. The application sample for real-time data collection from the Advanced Traffic Management System (ATMS) of Shanghai urban expressway system is provided. The stability of results from free-flow speed statistical model is excellent. The influence factors for free-flow speed, such as junction location, route alignment and lane quantity, are also discussed in this paper.