Two long trains were both ascending a steep gradient with some difficulty, because their engines generated barely enough power to carry the load.

As it struggled up the gradient to Ais Gill summit, the highest point of the Settle-Carlisle line, the steam pressure steadily dropped to the point where the locomotive's ejectors were unable to generate enough vacuum to hold the train brakes "off", and so the train stopped one-half-mile (800 m) short of the summit.

As they cleaned out the grate and tried to build up steam pressure, the driver and fireman made the mistake of telling the guard that they would only be standing for a few minutes.

The guard therefore did not protect the train in the rear, which could be done by laying detonators on the rails or walking a considerable distance along the line with a lantern.

Just short of Mallerstang, a few miles north of Ais Gill, the driver left the cab, to walk round the outside framing and oil some of the working parts while the train was in motion.

As with many railway collisions in Britain about this time, flammable gas escaping from the cylinders for the gas-oil lighting system ignited and rapidly spread a fire.

Most concerned the enforcement of regulations on drivers, firemen, guards and signalmen to ensure closer attention to their primary duty; the care and safety of trains.

This would sound a siren in the cab to alert the crew of a train if they passed a signal at danger or caution and then automatically apply the brakes if they failed to acknowledge and cancel the warning.

Signalboxes should be fitted with detonator placers, to alert engine crews who missed signals or were unable to observe them in fog or thick weather.