This study examined a traffic control system equipped with dynamic message signs (DMS) designed to provide real-time alternative-route travel time information to freeway travelers in the Osaka-Kobe area of Japan. This advanced traveler information system (ATIS) was designed to optimize traveler timesavings during periods of congestion on the Hanshin Expressway.

The DMS system was installed in November 1997. Each DMS unit provided travel time information for two or more competitive routes. Travel time was determined based on current vehicle speed measured by roadside vehicle detectors installed every 500 meters, and Automatic Vehicle Identification (AVI) units capable of matching corresponding license plate numbers at different points in the network.

Initially, the impact of the DMS signs on freeway traffic was measured by observing changes in traffic volume at two key alternative route divergence points before and after system deployment. The Hanshin Expressway Public Corporation (HEPC) conducted an investigation and found that divergence rates increased after DMS deployment.

RESULTS

• After introduction of DMS alternative route information at Maya/Route-3, the average divergence rate increased 3.7 percent during periods of congestion.
• Based on DMS data displayed at Maya/Route-3, detoured traffic saved an average of 9.8 minutes per vehicle during periods of congestion.
• Based on DMS data displayed at Ohmaha/Route-4, detoured traffic saved up to 38 minutes per vehicle during incident congestion.