Computer; Computer Automated Radio Location Aid (CARLA) control desk, circa 1973

CARLA was an experimental computer system used to display the live location of buses along their routes, using radio channels to transmit and receive data. Each bus was fitted with a hodometer - a device which recorded wheel revolutions. By working out the number of times the wheels had turned since the start of its journey, the buses current location could be calculated. The computer screen displayed the order of vehicles, indicating any early or late running.
Buses fitted with CARLA equipment could be easily recognised by the two flat circular aerials attached to the rear of the roof, known as 'blisters' by LT staff. One contained the radio transmitter, the other a receiver.