The document discusses anti-collision devices used in trains. It describes how anti-collision devices (ACD) use radio frequency and GPS to automatically brake trains 3 km ahead of a blockade to prevent collisions from human error or equipment failure. The ACD system was invented by Rajaram Bojji and installed on over 2,700 km of track in India, preventing 82% of accidents from 1997-2000. The ACD provides additional safety without replacing existing signaling and is a cost-effective solution without needing track cabling or inputs from train crews.