This poster, Quickly Away, Thanks to Pneumatic Doors, promotes the air-operated doors on Tube trains. It describes how the doors operate, including the fact that the signal to start the train cannot be given whilst the doors are open. Air-operated doors were controlled by one or two guards, and speeded up the process of loading and unloading at stations. Their introduction also reduced staff costs since they replaced the need for manually operated end gates on the standard stock cars. The poster was designed by Laszlo Moholy-Nagy, a Hungarian artist and photographer known for his experimental work at the Bauhaus art school.