WMATA Train horns?

[Chargerdodge9]

Why does everytime a train goes in or out of a tunnel, the conductor blows the horn? I always wondered this. Can anyone explain?

[NewFlyer9736BCT]

To warn anybody who's around the tunnel entrance that a train is coming. Could be a Metro track worker, a random person wandering around (least likely), or a random animal I guess...

[Chargerdodge9]

You'd think that the T/O would slow down if that's the case.