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Speedometers
Page 92
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REGULATION 13 in Part II of the Motor Vehicles (Construction and Use) Regulations 1966 requires that all motor vehicles first registered after October 1 1937, and all public service vehicles used as express carriages (irrespective of the date they were first registered) shall be fitted with a speedometer which is accurate within a margin of plus or minus 10 per cent when the vehicle is being driven over 10 mph.
There are a few minor exceptions to this regulation important to the commercial vehicle operator: (a) a vehicle with which it is unlawful at all times to exceed 12 mph; (b) a vehicle which is incapable by reason of its construction of exceeding 12 mph on the level under its own power; and (c) a works truck. Invalid carriages, motorcycles under 100 c.c. and pedestrian-controlled vehicles are also exempt.
Although if the gear ratio is known it is possible to calculate the speed of a vehicle from an engine revolution counter, it was held in Sellwood v Butt (1962) 106 S.J. 835 that prima facie such an instrument did not satisfy the requirements of this regulation.
It is often found in the C and U Regulations that Part II requires something to be fitted to a vehicle and Part III deals with its maintenance. Such is the case with speedometers as in Regulation 76 in Part III it is required that all speedometers shall be maintained in good working order and free from any obstruction which might prevent them from being easily read.
It is not generally realized that the same regulation provides a statutory defence for a person charged with this offence. It is a good defence to prove that the defect in the speedometer occurred in the course of the journey during which the contravention was detected or at the time contravention was detected steps had already been taken to have the defect remedied with all reasonable expedition.
Although it is not suggested that perjury should be committed, it would be very difficult for the prosecution to prove that a speedo meter had not failed just before the vehicle was stopped if the defence stoutly maintained that such was the case.
With regard to the second defence there appears to be no guidance as to what constitutes "reasonable expedition". One would think that if a part necessary to execute the repair was not obtainable locally and an order to the manufacturer had been sent by telephone, telegram or telex "all reasonable expedition" had been used and that one would be justified in using the vehicle without a speedometer while the arrival of the part was awaited.
On the other hand if one ordered the part by postcard or awaited the arrival of a normal stock order to the local dealer for that particular make of vehicle the requirements for the defence would not be fulfilled.