Satdham Safety System

The present signal systems involve fixed optical signals and physical monitoring wherein track circuits and relays are used. These are further linked and net worked with complex logical paths and routes on which a train is to be received or dispatched. Physical wiring and very large number of relays with on / off status are combined and designs with layout plans for wiring are prepared laboriously to ensure interlocking of signals. Until recently, these systems were considered safe, proven, and relatively effective techniques for train control. However, these systems offer only limited functions and they require train operations on fixed blocks (fixed segmentation of track) rather than flexible or moving block. In the fixed block method, the track is divided into predetermined distances between wayside signals and, for safety reasons, the block lengths are established based on the required maximum stopping distance of worst case operations; that is, for long and heavy loaded trains operating at maximum authorized speeds, the operations are restricted both in the block which the train occupies and in the adjacent block or blocks. This also means that, in the fixed block method, trains are given access to each block only after the train ahead has left this block and, when additional margin is needed, after the following block is clear. From the standpoint of safety, the effectiveness of conventional track circuits methods in providing full train control is not high enough because its effectiveness depends on the resolution of the track circuits; feedback to the train (in the form of cab signal or wayside signal aspects); and human interpretation and actions taken by the locomotive engineers (train operators) in responding to signal indications. Conventional systems are also costly to install and maintain.