Exactly what Mr Amit wrote, and I said he was right ! good wishes. It does mean Whistle Level Crossing ahead, manned, or unmanned. Manned means to an LP that the level crossing gates are properly closed, and if you notice there will be a signal before the manned level crossing, so normally on a dense traffic route, the whistle blowing will start much earlier and stay on for longer....
In the case of unmanned level crossings, there is long and sharp blast while passing through that unmanned level crossings...
The manned and...
more... unmanned level crossings are earmarked in what is known as the 'running/working time table' as opposed to the time table available to the general public...
Good wishes