Additional technical information is now available at https://mattersoftesting.blog.gov.uk/adding-vehicl... .
New information covered includes: steering and suspension (designs and tolerances); special features (such as electromechanical parking brake bedding mode before roller brake testing); and the roller brake test itself (including whether a vehicle can be brake tested using a roller brake tester).
The web page also details: unusual features, such as testing certain vehicle types with the ignition off (ensuring the brake servo is charged); and relevant safety design features.
There are also technical tips, covering, for example, how to jack up some vehicles with air suspension.
This first version of the additional web page has advice on how to test around 20% of vehicles. However, DVSA says it will be regularly updated.
Information is available on a per-vehicle basis: clicking the link takes you to any relevant information held by the agency.