Coming back to the debate of Electrification.
I feel the trunk routes should be electrified and the non dense routes be left unelectrified. D-Locos offer you advantages that E-locos can't simply match
1. What if there is a power grid failure like what happened in 2010s? I remember a WDM2 rescuing 12314, the WAP7 behind was dead.
2. Incase of natural disasters or challenging...
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terrains, resulting in failed OHE wire/difficulty in installation, D-locos are the only hope.
3. Thirdly there is a huge misconception that D-locos cause pollution and E-locos are boy scouts. Nope, firstly pollutions can be of several types, sound, heat, light. E-locos are guilty of all of the above. Secondly, the power that is fed to the E-loco from the catenary is derived mostly from (around 70%) from thermal (coal based) plants. Coal has a really low thermal efficiency and factoring in the added power losses in transmission, E-locos ultimately cause the same amount of pollution as D-locos themselves. However coal is available in our country while fuel has to be imported.
So, you see there are arguments both in favour and against electrification.