Single Line Crossing | Twin KJM WDP-4B with #20030 in lead with 56913 SBC-UBL Fast Passenger waiting at BSN for 20652 TLGP-SBC Intercity Express to cross.
Twins cant get decoupled and run as split Loco for split rake for slip & regular rake (until they arnt coupled and run as different unit)!! Its easy to attach/detach one Rake with other (as in Freight Python Rake), without disturbing loco (to minimize hassle & time)!!
To decouple Locos (and to recouple when slip gets attached), is a complicated process (carried out at Loco Shed) & usually Twins remain stable for long period and attached to train, as per availability!!
Is the twins is a new loco
Because whenever a new d loco enters service the first run will be with an another loco attached to it
Both will be on duty
Twin locos are provided by KJM/UBL now a days to reduce idling time at shed
Production of diesel locos have been stopped 2 years back itself