Countermeasure Strategies against Traffic Congestion on Motorways in Japan

摘要

Due to excess demand, we encounter traffic congestion on motorways quite often at bottlenecks in the vicinity of metropolitan areas in Japan, mainly on holidays. The administrators of motorways have tackled this issue for more than four decades. At the beginning, they just tried to increase the number of lanes; however, widening of motorways requires huge construction costs and long periods. After the collapse of the bubble economy in the early 1990s, it became so difficult to broaden the existing motorways. To alleviate traffic congestion, they have introduced comparatively costless innovative attempts; however, those could not eradicate traffic congestion completely.This paper describes the advantageous effects of innovative attempts, methodologies and applied cases, such as traffic information system providing location of the traffic bottleneck to drivers to activate them to gain speed on the upgrade, using the variable message signs, or traffic demand management disseminating real-time traffic information (e.g., travel time, length of the queue) to drivers, resulting in mitigation of traffic congestion on motorways.In recent years, toll discount has been introduced on motorways as a pilot program; the situation of traffic congestion is getting worse. This paper also mentions a quick overview of the countermeasure strategies against traffic congestion and of the state of the congestion on motorways for a couple of decades.