Most of us may not be aware of why trains have a sandbox.
There is a hopper (container) under the bogie of a train, close to wheels of locos. It contains fine sand. And its nozzle is open at the wheel-rail contact region.
Let’s understand what the use of this box in a train is.
All of us have heard of a kind of hissing sound produced by a train when its breaks are applied. When brakes are applied to stop the train, sand from this box is sprayed on rails. It improves braking system ensuring stoppage at a short distance without slipping from tracks. Compressed air is used to spray sand grains on rails. During winter and rainy seasons or if any oily substances fall on rails, wheels tend to lose grips. In that case too, the loco pilot goes for sand spraying.
And it is operated manually. This means, it depends on loco pilots when to use the buttons meant for sandbox and how long to be used.