Why does the engine of a passenger train parked on the platform keep running, does it not waste fuel or is there some other reason?

Often people think that a train engine is like a car or bus, which can be stopped whenever you want, but a railway locomotive is a very complex machine. Keeping it on sometimes proves to be safer and more economical than switching it off. Especially in diesel engine trains, this decision is taken thoughtfully.

Diesel locomotives need time to reach full capacity. After the engine is stopped, it may take about 15 to 20 minutes to start it again. A lot of diesel is consumed during this period. In many cases, the engine can run at low speed for hours with the amount of fuel required for starting. Therefore, switching off the engine at short stops does not save fuel but becomes a loss.