Abstract: A tachograph comprises a casing (1,2) which houses a speed indicator (4), an odometer (6) and styli (8a, 8b) for respectively recording speed and distance travelled. A stepper motor (22) drives the speed indicator (4) and speed recording stylus (8a). A stepper motor (23) drives the odometer (6) and distance recording stylus (8b). A pulse generator (25) provides an input, proportional to vehicle speed, to a microprocessor (16) which computes speed and distance on the basis of the pulse input and a correction factor (26) relating to vehicle characteristics in order to drive the stepper motors (22,23). The microprocessor (16) is also responsive to a preset maximum top speed reference (27) and a driver selected top speed reference (28) to provide an output to an actuator (30) in order to control the vehicle speed.