asked the Secretary of State for the Environment how many roadside spot checks have been carried out during each of the past 24 months on defective brakes; what are the nature of such tests; and what results and conclusions he has drawn therefrom.

The figures are available only on a quarterly basis as follows:

ROADSIDE SPOT CHECKS
Quarter Ending	No. of Tests	No. of Prohibitions
December 1973	14,042	637
March 1974	14,968	701
June 1974	38,044	1,801
September 1974	32,207	1,558
December 1974	11,197	550
March 1975	8,542	538
June 1975	34,448	1,738
September 1975	30,107	1,353

The percentage of defective vehicles indicated by these statistics must be viewed with caution because there is a natural tendency to pick out the apparently bad vehicles for testing.Roadside spot checks entail a detailed inspection of the vehicle which includes a test of the brake performance using a decelerometer. More tests take place in the summer months when the weather conditions are less likely to interfere with the test programme. Defective lorries are issued with prohibition notices; defects on private vehicles are notified to the driver.The number of vehicles warranting prohibition notices points to the need for continued vigilance by owners, drivers and examiners in order to ensure the road-worthiness of all vehicles.