Using expert system rules to establish data for intersections and turns in road networks

Delays and restrictions in intersections contribute significantly to the overall travel times in urban traffic networks and therefore also affect route choices. In practice, however, it is quite unusual to include intersection delays in traffic models, logistic models and route guidance systems. Time consuming and tedious data preparation together with the complexity of network updating is the main reason for this, as most transportation software applications can do the necessary calculations. In this paper, we report on the development of a procedure that can automate the task of adding data for intersection delay modelling to an existing network. The method requires a GIS-based network with link attributes as input data. The method has developed as an extension tool applicable to existing networks and therefore supply of additional data is normally not required. By a set of ‘expert system rules’, the intersections are classified into a number of groups – such as prioritised and signalised intersections, wedges and Y-junctions – and the required input data for turn delay models is established. The method has been tested on large-scale networks with good results. Most of the required data were satisfactorily estimated, although some edits had to be made manually. This was mainly the case for roundabouts and for intersections with a very special geometry. In conclusion, the method greatly reduced the burden in establishing data sets for intersection delay modelling in urban traffic networks.