The Sunset Tunnel, known as the Duboce Tunnel (San Francisco).
There is not enough clearance between the train and the tunnel walls, so you *must* hide in a small alcove when you see a train coming. The light at the end of the tunnel on this photo is actually a muni train coming.
No trespassing! This is REALLY a DANGEROUS place!
For more information about this place, read: en.wikipedia.org/wiki/Sunset_Tunnel