An advanced on-board signaling and telecommunications system to supplement wayside signaling

To supplement the existing signaling system, devices that prevent head-on collisions, warn maintenance workers on the wayside of approaching trains, and prevent trains from operating over the allowable speed limit were produced by way of trial and error and their performance were evaluated. In the case of head-on collisions prevention, a train's running position is located by a tachometer generator to determine its position in relation to other trains and by a global positioning system (GPS) to determine its absolute position. In addition, train radios with multichannel UHF transmission are adopted to provide direct communication between trains without the use of control stations along the wayside. For controlling the train speed, constant comparisons between the allowable maximum speed and actual train speeds along a line are carried out using an IC-card that enables a train to judge for itself whether or not it is speeding. Judging from the test results, a stable distance for data transmission between trains is about 2,000 m in a plain area, which is sufficient for securing the minimum distance of 1200 m necessary to prevent the head-on collision of two trains. In addition, it was discovered that a maximum of 10 trains could be operated on one carrier wave of a train radio when the scanning time of the data transmission is fixed at 2 seconds.