https://movingon.blog.gov.uk/2013/10/21/simplifying-the-heavy-vehicle-test/

Simplifying the heavy vehicle test

Simplification - not to jack

VOSA has completed our investigation into simplifying heavy vehicle test procedures. The aim is to reduce the burden on both operators and VOSA without compromising road safety or the environment.

Option to jack
We have concluded that the steered axles on trucks, buses and some trailers can be correctly assessed by using the heavy duty wheel play detectors and feeler gauges without jacking the axle – similar to the practice used by most of Europe.

But not every vehicle can be assessed this way, so where necessary, an examiner will have the option to jack the axle to make an assessment. We have also identified that some vehicles with independent front suspension can only be tested properly by jacking. So, for a small number of vehicles jacking will continue.

Emissions test
There is an extremely low failure rate for the emissions test.  Our investigation showed that in most cases a visual assessment would give exactly the same result. Current diesel smoke meter (DSM) technology struggles to cope with modern, clean engines. The European Commission is looking at new testing equipment for the future to test for smaller particulate matter and oxides of nitrogen.  So, until new equipment is available we will be restricting the use of DSMs to those vehicles where smoke levels appear marginal. Any vehicle that fails the visual emissions test will have a metered test. Vehicles submitted for reduced pollution or low emissions tests will always receive a DSM test.

Simplify
The conclusion of our investigation, and after consulting with manufacturers and trade bodies, is that we will simplify the test by allowing examiners the discretion not to jack steered axles or conduct a metered smoke test.

Making the change
We will monitor and analyse the introduction of these changes from 1 October 2013. The heavy vehicle inspection manuals were updated when these changes were introduced.