 In order to enable them to be operated by just the driver, they included an overhang of beyond the front axle, allowing the entrance door to be mounted just behind the windscreen, so that payment could be made to the driver when entering the vehicle.To cope with the steep gradients of the Coimbra system, they were fitted with 600-volt motors, and each trolleybus carried two compressors, normally designed to work together, but each capable of maintaining the air supply for braking and door operation if one should fail.The expanding trolleybus network in Perth, Western Australia, placed an order for 50 F4 vehicles in 1950/51.