path_track

Spawnflag

SF_PATH_TELEPORT

16 (like path_corner, allows teleporting of a func_tracktrain and all objects attached to it)

m_iszFireFow	Target that is activated only when the train passes the path_track in the regular direction.
m_iszFireRev	Target that is activated only when the train passes the path_track in the reverse direction.

If no alternative path is specified, then activating a path_track causes it to turn off, simulating a broken track. If an alternative path is specified, activation causes switching to it or switching back. That said, this is regular behaviour for the object, and it does the same in Half-Life.