A sight to never be seen again. When the Battery Street Tunnel was built in the late Fifties along with the Alaskan Way Viaduct, the tunnel had a set of carbon monoxide sensors, and parking those idling vehicles was the way they were tested. Now, after the Alaskan Tunnel was finished, and the Alaskan Way Viaduct was knocked down and crushed, the tailings of that crushing were dumped into the Battery Street Tunnel (both sides) and very soon, concrete slurry will be pumped into the remaining tunnel space to finish filling them in.