Because of the combined risks of shortage of brake power and breaking couplings, the speed of freight trains was initially restricted to . The brake van was marshalled at the rear of the train, and served two purposes: Provided additional braking for 'unfitted' goods trains Put a man (the guard) at the rear of the train, who could take action in the event of a breakdown or accident While the UK railway system persisted until post-nationalisation in 1948 with "unfitted" (discontinuously braked) trains and loose couplings (the final unfitted trains ran in the 1990s), other systems, such as the North American adoption of the Janney coupler, overcame the same railway safety issues in a different manner. The guard's job On unfitted trains, the brake van has several purposes, and hence jobs for the guard. Firstly, and most importantly, the guard would use the brake van's brakes to assist with keeping the train under control on downwards gradients and whenever he could see that the locomotive's crew was attempting to slow the train. Route knowledge would allow the guard to initiate the braking before the driver. To aid in this, signalling regulations mandated that signals be left at clear until the entirety of a train (including guard's van) had passed, as the guard would immediately apply brakes upon seeing a signal at danger. Secondly, the wheel handbrake could be screwed down to keep the loose screw couplings taut between unfitted wagons, to minimise the risk of snapped broken couplings from the locomotive "snatching" or jerking, which was particularly a problem as locomotives became more powerful. As breaking couplings on unfitted trains when starting were a fairly common occurrence, train crews were given specific instruction. Upon starting a freight train, rules mandated the footplate crew to look back on their train towards the brake van, waiting for the guard to signal (by flag or lamp) that the entire train was moving and all couplings were taut, before accelerating to higher speeds. A later job of the guard was the provision of side lamps on brake vans. The white lamp is the tail lamp, whilst the grey lamps are the side lamps, along with the standard tail lamp (showing red to the rear and sides) required on the rear of every train. The side lamps showed a white light towards the front and a red light to the side/rear. The front-facing lamps were