Kanchanjunga Express: Goods Train Crashes into Passenger Train 3D Animation Explained ! 

Mainak, this is a simulation depicting what happened; we're looking at the aspects of possible outcomes that led to the rear collision of two different trains. As far as I've received updates and information through the news, all signals failed, and T/A912 and T/D912 were issued to the train. For your kind information, T/A912 and T/D912 are given: "When the automated system fails, railway protocol mandates a written authority known as TA 912. This document authorizes train drivers to pass all red signals due to the signaling defect, provided they adhere to stringent safety measures.". Thanks for watching.