REVIEWING THE CONTROL PARAMETERS OF TRAFFIC SIGNAL CONTROLLERS WITHIN A CONTROL AREA

The Traffic Control Center of the Shiga Prefectural Police Headquarters (SPPHQ) (Japan) began operation on April 1, 1979, with 48 traffic signal controllers for traffic control on National Highway Route 1 and arterial roads within the city of Otsu. Since then, the SPPHQ has been expanding its control area on a gradual basis and has been endeavoring to maintain and improve its traffic control system including upgrading these controllers for more advanced functions. During these years, along with fluctuations in traffic flow and road improvement works, SPPHQ took actions such as operational improvement of the traffic signal controllers and the like whenever required. To relieve chronic congestion within Otsu, a thorough investigation into travel time and traffic volume within the control area was conducted, problems were extracted that had never come to the surface before, and control parameters (offset, split, and control time in seconds) of all the segments and local controllers were reviewed. The investigation coincided with the upgrading of signal control-related central equipment in 1992. As a result of the review and based on improvements, SPPHQ has succeeded in shortening travel time, stop time, and reducing the number of stops. The economic effect of these reductions resulted in an annual saving of about 6.9 billion yen.