A Muni light rail train (sort of metro-tramway) going fast in the Duboce Tunnel, also known as Sunset 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.
No trespassing! This is REALLY a DANGEROUS place!
For more information about this place, read: en.wikipedia.org/wiki/Sunset_Tunnel