ANALYSIS OF TOKYO METROPOLITAN EXPRESSWAY’S DEMAND USING ETC-OD DATA by Marc Miska**, Hiroshi Warita***, and Masao Kuwahara**** 1. Motivation To manage any kind of system, it is essential to understand the internal processes and limitations to avoid a collapse. Water, gas and energy supply are good examples. These systems have to be monitored constantly to ensure an undisrupted service for all users, even during high demand (e.g. increase of electricity usage during summer times). What is well known in such fields, is still quite a new approach for managing traffic networks. While we understand the traffic flow process, and often are able to find solutions for local bottlenecks, the more global view of a system for network wide strategic decisions is less explored. This paper explores the demand, Tokyo Metropolitan Expressway has to handle, using ETC-OD data. About three million vehicle records have been extracted from trips on Wednesdays in September 2006. The choice for Wednesdays is based on literature 1)-3) , where it is commonly stated that Wednesdays can be referred to as “normal” days without any influences from the weekend (i.e. high demand in evenings, more spread peak hours). The demand is generated by 186 on-ramps, from which 78 ramps generate a substantial input from more than 100 vehicles per hour with the maximum inflow of a single ramp being about 1800 vehicles per hour. During the study period, the Tokyo Metropolitan Expressway carried 665.000 to 721.000 vehicles with ETC on board units per day. That means that the demand variation, considering the whole network, is less than 10%. The value itself might not be surprising, but the fact that only 18% of the vehicles are regular users is, and raises the question who the majority of drivers are every day, why the demand remains relatively constant and what the implications for traffic management on the expressway are. To answer these questions we will first take a closer look at the data, to determine the facts on volumes, traffic sources, and traffic composition. 2. Temporal and Spatial Demand Analysis As mentioned before, the actual daily traffic demand on the Tokyo Metropolitan Expressway does not vary significantly. Figure 1 shows the network wide demand for four Wednesdays in September 2006. The figure shows for each day a morning and evening peak, with the evening peak being a bit more spread over time. Especially the morning peak’s shape is fairly regular and just shows some overall increase at the end of the month. One should remember that with the low percentage of regular users, this single observation can lead to wrong assumptions about the total network. Figure 1: Daily network wide traffic demand If we focus on one of the most used on-ramps to enter the Tokyo Metropolitan Expressway (Takaido) the traffic demand 6 a.m. can vary from around 350 vehicles/hour up to 2050 vehicles/hour. Figure 2 shows the demand for the same four Wednesdays as the total demand. Figure 2: Daily traffic demand from Takaido on-ramp ________________________________________________________________________________________________________________________ * Keywords: ETC OD data, demand, expressway ** Ph.D., Institute of Industrial Science, University of Tokyo (4-6-1 Komaba, Meguro-ku, Tokyo, Japan 153-8505 Tel: +81-3-5452-6419, Fax: +81-3-5452-6420) *** Member of JSCE, Dr. Eng., Tokyo Metropolitan Expressway Company Limited, Planning and Environmental Department (1-4-1 Kasumikaseki, Chiyoda-ku, 100-8930 Tokyo, Japan, Tel: +81 3 3539 9389, Fax +81 3 3502 2412) **** Member of JSCE, Professor, Institute of Industrial Science, University of Tokyo (4-6-1 Komaba, Meguro-ku, Tokyo, Japan 153-8505 Tel: +81-3-5452-6419, Fax: +81-3-5452-6420)