This is my current pet subject as I've been researching the area for a while now. I hope the follwing doesn't bore anyone
The Goods avoiding line was the remnants of a once huge network of Lines throughout Carlisle. There was another goods line that left at Rome Street Jn giving access to trains to The Waverley route and the Silloth line which was closed in 1969. Part of the triangle had shut the previous year but was reinstated when the Lines around Carlisle where being resignalled and electrified in 1973/1974.
The Goods line was signalled with 3 aspect signals controlled from Carlisle PSB with permissive working available for freight trains. There was a connection to Metal Box company and Dentonholme goods yard on the branch.
The aforementioned accident happened in the early hours of 1st May 1984. A freightliner approaching Carlisle had problems with the brakes dragging and they where isolated. The coupling snatched upon restarting and the rear portion of the train ran out of control.
The front portion made it safely into Carlisle but the signalman realised he had a train running away and routed the train on the goods line where it derailed on the Caldew Bridge , destroying the southern part of it. I understand the payload was harmful to life in the Caldew.
I belive there was a passenger train in the station at the time and the consequences of a train derailing at high speed where unimaginable.
The signalman passed away not long after the accident. Somewhere on the station there is a plaque dedicated to his memory.
the southern part remained until the mid 90s to serve the metal box sidings but the rest was deemed beyond repair and the overhead wires cut back to Upperby. The bridge in that area have since been demolished. some of the signalling at Carlisle was later upgraded to help cope with the reduced capacity.
There was talk of re-opening a couple of years ago but this appears to have fallen by the wayside for the time being. Network Rail don't own the trackbed as far as I'm aware.