Article 3
The following device is prescribed for the purposes of section 20 of the Road Traffic Offenders Act 1988 (speeding offences etc: admissibility of certain offences), that is to say, a manually activated device designed or adapted for recording the measurement of the speed of a motor vehicle (“vehicle A”) from another motor vehicle (“vehicle B”) by—
measuring the time taken by vehicle A to pass two positions on the road either directly or by reference to the time taken by vehicle B to pass the same two positions on the road;
recording the distance between the two positions by counting the odometer pulses from vehicle B as it travels between the two positions; and
calculating the average speed of vehicle A over the distance between the two positions by reference to the time recorded in sub–paragraph (a) and the distance either calculated in accordance with sub–paragraph (b) or measured manually.