> There are only two tracks (North and South) and there is no room to build more. The SP/Caltrain/Bayshore-Cutoff line into SF used to be partially quad-track

> There are only two tracks (North and South) and there is no room to build more. The SP/Caltrain/Bayshore-Cutoff line into SF used to be partially quad-tracked. It's easiest to see at Tunnel 2 just south of 22nd Street Station. The current two-track main uses one tunnel and there's a second tunnel portal blocked off next to it. Here are the north and south ends respectively: - https://upload.wikimedia.org/wikipedia/commons/9/90/Tunnel_number_2_from_23rd_Street_bridge%2C_November_2017.jpg https://upload.wikimedia.org/wikipedia/commons/9/90/Tunnel_n... - https://upload.wikimedia.org/wikipedia/commons/9/9f/South_portal_of_Bayshore_Cutoff_Tunnel_2%2C_August_2018.JPG https://upload.wikimedia.org/wikipedia/commons/9/9f/South_po... Ironically the Caltrain electrification project blocked it off even further by putting the supports for the overhead wires right where the other tracks used to be.