Tank
With World War II the multi-turreted tanks proved impracticable, and as the single turret on a low hull design became standard, crews became standardized around a crew of four or five. In those tanks with a fifth crew member, usually three were located in the turret (as described above) while the fifth was most often seated in the hull next to the driver, and operated the hull machine gun in addition to acting as a co-driver or radio operator. Well-designed crew stations, giving proper considerations to comfort and ergonomics, are an important factor in the combat effectiveness of a tank, as it limits fatigue and speeds up individual actions.
British heavy tanks of World War I
Steering was difficult, controlled by varying the speed of the two tracks. Four of the crew, two drivers (one of whom also acted as commander; he operated the brakes, the other the primary gearbox) and two "gearsmen" (one for the secondary gears of each track) were needed to control direction and speed, the latter never more than a walking pace. As the noise inside was deafening, the driver, after setting the primary gear box, communicated with the gearsmen with hand signals, first getting their attention by hitting the engine block with a heavy spanner. For slight turns, the driver could use the steering tail: an enormous contraption dragged behind the tank consisting of two large wheels, each of which could be blocked by pulling a steel cable causing the whole vehicle to slide in the same direction. If the engine stalled, the gearsmen would use the starting handle – a large crank between the engine and the gearbox. Many of these vehicles broke down in the heat of battle making them an easy target for German gunners. There was no wireless (radio); communication with command posts was by means of two pigeons, which had their own small exit hatch in the sponsons, or by runners. Because of the noise and vibration, early experiments had shown that radios were impractical, therefore lamps, flags, semaphore, coloured discs, and the carrier pigeons were part of the standard equipment of the various marks.