However locos (or at least older designs like the 56) have less brake force relative to their weight than passenger coaches. This is why loco-hauled trains shorter than about five coaches were subject to special speed restrictions. So two locos with four or five unbraked coaches would have to be subject to some pretty severe speed restrictions to be able to stop within signal braking distance.
I'd forgotten that. A very short formation is classified as a light engine movement, which is limited to 75mph I think where signal spacing normally allows 90mph or more.
Not all ROG locos have the brake translator equipment. The 37s that have ben modified with auto-couplers do (there's an extra socket on the nose to plug into the unit, I believe), but I don't believe the 57s have been so modified.
Or can be as low as 60mph depending on line speed.
That explains the single ROG 37 pulling a 9 car class 345 in the video below (08:40 mins in)
It would eventually, assuming the brakes didn't overheat, but how long it took would depend on speed and gradient. One hopes the brakes on the rear 57 were working (as noted there was a pipe through the train to control them) otherwise if a coupling failed the rear part would be totally unbraked.
The rear loco should have been braked; there was a through pipe run through the unit.
A loco can be braked off an external air supply without having to have the engine running. This may require certain valves to be changed from their normal settings - I don't know the specific case of a 57 but a few years ago it wasn't done correctly on a 66 and after a coupling broke it was rolling around south Manchester unbraked for some time (search RAIB for East Didsbury). No doubt RAIB will be looking into whether the rear loco was unbraked (in fact they should know this already) and if so why.
