Automatic Extraction of a Subnetwork for Dynamic Traffic Assignment

Dynamic traffic assignment (DTA) is a commonly used approach for the process of assigning traffic from origin–destination (OD) pairs to actual roadway paths. The amount of computational effort required by the typical DTA application is approximately proportional to the square of the number of OD pairs, so for large networks the level of effort is very large. however, many network questions only involve changing one or a small number of links and therefore do not involve a very large fraction of the whole network. The concept of using a subnetwork to replace a regional network has been often used as a solution to this problem. however, how to define the size of the subnetwork, how large subnetwork is appropriate and how to build a subnetwork have been the questions. This study reviewed the researches which focused on the above questions. Then, based on the literature review, we developed a programme that can automatically build an optimal size of the subnetwork with acceptable error in Visual Interactive System for Transportation algorithms (VISTA), a mesoscopic DTA simulator. This automatic programme makes the process of examining the subnetwork size easy and is expected to have important implications for future research on DTA.