HGV brake testing should be one of the most crucial components in your preventative maintenance systems. EVERY safety inspection must assess the braking performance of the vehicle or trailer. It is strongly advised that a calibrated roller brake tester is used at each safety inspection to measure individual brake performance and overall braking efficiencies.
It is also acceptable to use an approved and calibrated decelerometer to test vehicles without trailers to measure overall brake efficiency values.
Road tests are permitted – however if this is the only method of brake testing, it will be deemed inadequate. It is normally expected that a vehicle should complete at least three successful brake efficiency tests spread throughout the year in addition to the annual MOT test.
Guidance was issued by the DVSA in April 2016 which you can read here.