RailFanning is a gift you give yourself. - Varun

The reason for not taking the risk here is that it is a big risk. Diverting the runaway train through a loop line will undoubtedly cause a derailment at the switches. Basically, in this particular route, one can be 99.99% certain that any accident is going to be a major accident. You can check the gallery for Kadagaravalli station ( I've added some pics earlier when I trekked on this route) to get an idea about how precarious this route is!
Braking operations with the bankers and lead loco is very tricky. The crew usually communicate using walkie-talkies and coordinate their controlling. The train's original locomotive, and the bankers usually work together, but the braking controls...
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are usually left to the bankers. For example, on these ghats, they use locomotives with 'AEB' - Auto-emergency braking, which basically applies the brakes automatically when the locomotive goes beyond 30kmph. This feature is mandatory for banking operations.
The bankers and the train's main locomotive have different crews, but braking efforts have to be coordinated properly. Any imbalance in the braking efforts from the train's loco and the bankers can either lead to coaches getting crushed or coupling failures and train parting. So usually a strict set of operations are followed and absolutely nothing is left to luck.
Even if they manage to allow such operations, still not many passenger trains can be expected here. Most of the ghat section is very, very remote and not at all accessible. For the gangmen and the track maintenance crew, it is a very dangerous job. Asking them to patrol these sections in the dead of the night would be very, very dangerous for them. That is one of the reasons why SWR did not make any efforts to introduce a night train on this route for a very long time.