REDUCTION OF TRAFFIC ACCIDENTS AND IMPROVEMENT OF ROAD TRAFFIC PRODUCED BY INTELLIGENT TRANSPORTATION SYSTEMS (ITS) DEPLOYMENT

Since 1966, Japanese Police have been promoting a project for installation and improvement of traffic safety facilities aiming at attainment of safe and smooth traffic. During the course of this project, it has been found out that increased installation of traffic signals and upgrading by computer control of already existing traffic signals are significantly effective for prevention of traffic accidents and the attainment of smoother traffic. This finding was made by an analysis based on a survey comparing number of occurrences of accidents involving human injuries and changes in the travel time before and after installation of traffic signals or implementation of upgrading, at intersections where traffic signals have been newly installed or computer controlled upgrading of existing signals has been newly implemented. According to the survey and its analysis, new installation and upgrading of traffic signals were found effective in reducing the number of occurrences of traffic accidents by some 90,000 per annum; and its economic benefits can be translated into a saving of one trillion yens per one year. Given below are examples of the effects of the new installation and upgrading of traffic signals for prevention of traffic accidents and the attainment of smoother traffic: 1. New installation of traffic signals works to reduce occurrence of traffic accidents by 75% or more. 2. Among computer controlled upgrading of existing traffic signals: 1) Most appropriate signal controls corresponding to the current traffic density works to reduce occurrence of sudden encounter collision accidents by some 78%. 2) Traffic adjustments by using blue arrow signaling works to reduce occurrences of right-turn accidents by 48%. 3. Offset adjustments for smoother vehicle travels improves the travel time by 10 to 20% and reduces traffic congestion time during the intersections by 15 to 28%.