Concerning the Congestion Reduction Measures by Providing Driving Support Information on the Expressway

Speed factors reduction occurs frequently at the sag part of an expressway because of road structural factors. When the traffic density is high, this experience makes a shockwave at the rear of vehicles and causes traffic congestion. Most of the spots where traffic congestion frequently occurs in the management area of Kanto Regional Head Office of the East Nippon Expressway Company Limited (it is refer as “Kanto Regional Head Office,” in the rest of this article) are sag structure parts on the uninterrupted flow of the main track of an expressway. Concerning the measures to reduce traffic congestion at sag points, hardware side measures and software side measures can be considered. As a hardware side measure, traffic capacity would be increased physically by increasing traffic lanes, etc. As a software side measure, smooth traffic could be promoted by providing drivers suitable information such as road structure, congestion status and lane operation, etc., with LED information boards. Though the hardware side measure requires plenty of time and an operating budget to obtain land or for construction work, the software side measure can be carried out comparatively in a short period with a small budget. As software side measures, Kanto Regional Head Office conducts the driving support information streaming with LED signboards, which provide some alerts to balance the amount of traffic on each lane, a caution to prevent accidents and information for quick recovery from traffic congestion. Balancing the amount of traffic on each line to correct the unbalance of it, which is distributed more on the passing lane, it attempts to increase the amount of traffic in all the lanes to avoid or delay the occurrence of traffic congestion by balancing the utility rate of each lane. The signboard for the recovery of speed is a system to provide text information with LEDs which have great visibility. This is the software side measure to reduce the traffic congestion by providing information by installing the LED signboards, which have great visibility, at the points where heavy congestion is predicted. The signboards connect the driving speed, which is detected by vehicle sensors positioned before and after the signboards, and the data of the amount of traffic. It reminds drivers “the alert” before congestion, and accelerates “the recovery of driving speed” after the occurrence of congestion. This is a measure to reduce congestion by increasing traffic flow. The authors conduct this congestion countermeasure with the speed recovery signboard at 11 spots within the jurisdiction of Kanto Regional Head Office. They report the effect of the “speed recovery signboard” which they use in the sag points around the Hanazono IC on the KAN-ETSU Expressway.