The Traffic-Control System on the Hanshin Expressway

In 1970, the Hanshin Expressway Public Corporation started operating an automated traffic control system to maximize the total traffic flowing into its expressway network. The corporation has been improving the system ever since. The system relies on two control methods. The first is to limit the cars coming onto the expressway at each entrance ramp to avoid congestion in any section. The system calculates the maximum allowable inflows by solving a linear programming problem once in every five minutes using data from detectors installed along the expressway and at all ramps. The second method is to give drivers the most recent and accurate traffic information about the expressway and its vicinity, including expected travel times and accidents, through various information channels so that they can decide what routes to take. This system is greatly appreciated by the corporation because it is extremely cost effective and also by drivers, who now consider it an indispensable service.