While you are on your test the Examiner will be watching for faults with your driving and will record those faults as they occur. Every departure from a standard of 'Perfect Driving' needs to be assessed on whether the fault is of car control, or road procedure. In assessing the degree of fault the Examiner will first ask themselves the following question as each fault is observed:-
'If this candidate's driving had been perfect up to this point, and this were the only fault made, would this fault be sufficiently serious enough to justify the failure of the Driving Test?' If the Examiner without doubt or hesitation answers '
NO' to the question then the fault is recorded as a
MINOR fault. Minor faults on there own will not not normally entail failure unless under the totting up procedure there are 16 minor faults or more made.
If the answer is '
YES' then he must assess whether it was a
SERIOUS or a
DANGEROUS fault.
Just one Serious or Dangerous fault will bring a failure. The main difference between these two is that a
Dangerous fault is a fault which actually causes another road user to brake, swerve, or take some form of evasive action. A
Serious fault is one that might have caused another road user to take action if there had been one present at the time.
http://www.learning2drive.co.uk/driving_test.htm