Section4 Increasing the Efficiency of Administration and Road Management

At the mountain section in Nara Prefecture of the National Highway No. 25 (Meihan Route), a trunk road connecting Tenri City of Nara Prefecture and Kameyama City of Mie Prefecture, it is necessary to take swift actions such as imposing traffic restriction and closure to prevent accidents when it snows a lot or the road surface freezes in winter.

This requires the collection of correct meteorological information, so seven observation stations are built along the highway to obtain necessary data in real time. These observation stations, however, cover only a limited area and cannot continuously monitor the road surface conditions. To address this problem, optical fiber sensors (optical thermo radars) capable of measuring air and road surface temperatures at 5-m intervals were experimentally installed in 2000 along a 2-km section between Fukusumi and Ipponmatsu, which has the highest probability of road surface freezing.

In 2001, devices for the Frost Prediction System to Assist Measures against Snow Damage were deployed along the highway: the system uses data provided from the Nara Meteorological Observatory and those obtained by such devices as the above-mentioned optical fiber sensors, to assist the spreading of anti-freezing agent at the proper timing, ensure a safe driving environment, and facilitate road management activities. In parallel with activities to establish a method to predict the time of road surface freezing and to cope with snow damage by using these devices, this frost prediction system will be installed at the 25-km section, from Kono-guchi to Tenri-higashi, of the 32-km section in Nara Prefecture of the Meihan Route.