Headlamp aim remains top reason for vehicle test failure

Trucks and passenger vehicles shared the same top three reasons for test failure: headlamp aim, lamps and brake system components – although all three of these were each in single figure percentages in 2013/14.

One explanation given for headlamp aim remaining the top reason for failure is human variation. Even if a vehicle is set up on the same equipment that it is tested on, individual variations in colour perceptions between the individual technician setting the vehicle up and the tester may be sufficient to cause a failure.

The top three reasons for trailer failures are service brake performance, parking brake performance and lamps.

Wiring faults have become the tenth most common reason for a truck test failure in 2013/14, replacing warning lamps. There were no changes in the top ten reasons for failure in the other vehicle classes.