Volcanic ash impacts on railway signal facilities and utilizing of the volcanic ash fall forecast

Abstract

Ash fall affects various railway operations in a wide range. One of the most critical and likely impact of ash fall on railway is an obstacle to the train detection using track circuit. The track circuit, which is generally used in Japanese railway and controls the signal and level crossing security devices, detects the existence of train on rails when the rails are electrically shunted by the axles of the train. When volcanic ash is deposited on rails, the track circuit is failed because the volcanic ash interferes with the energization between the wheels and the rails. However, the thickness of the volcanic ash which prevents train detection is unknown so far. In this study, we examined the impact of volcanic ash on the shunting of track by running trains on rails which are artificially covered with volcanic ash. The experimental track used in this study simulates the track generally used in Japan. As a result, it is clarified that 0.025 mm thick volcanic ash can make the shunting unstable, and that over 0.05 mm thick volcanic ash causes the malfunction of shunting. Additionally, it is also clarified that the electronic train detector, which controls the operation of the level crossing, fails to detect the existence of trains when volcanic ash is deposited over 0.2mm thick on rails. Based on the results, we propose prevention actions at normal time and at the time of ash fall for railway companies to mitigate the impact, using public information on eruption. The Volcanic Ash Fall Forecast, for example, can be utilized for narrowing the range where inspection or cleaning of rails should be carried out according to the predicted thickness of volcanic ash.