[wnut]

Originally Posted by Richard Casto

Can someone point to me any documentation as to the exact understanding of this rule? I know there is more to it than just a "cars width". See my concerns below...

Richard

I think this is what you are looking for Richard?

copied and posted relevant piece of Appendix L relating to river conduct as it is relevant to this thread.

Appendix L International Sporting Code
International Drivers’ Licences, medical examinations, drivers’ equipment and conduct – 2019
Chapter IV Section 2 pages 39 and 40
2. Overtaking, car control and track limits

a) A car alone on the track may use the full width of the said track, however, as soon as it is caught by a car which is about to lap it the driver must allow the faster driver past at the first possible opportunity.
If the driver who has been caught does not seem to make full use of the rear-view mirrors, flag marshals will display the waved blue flag to indicate that the faster driver wants to overtake. Any driver who appears to ignore the blue flags will be reported to the Stewards.

b) Overtaking, according to the circumstances, may be carried out on either the right or the left. A driver may not deliberately leave the track without justifiable reason. More than one change of direction to defend a position is not permitted. Any driver moving back towards the racing line, having earlier defended his position offline, should leave at least one car width between his own car and the edge of the track on the approach to the corner. However, manoeuvres liable to hinder other drivers, such as deliberate crowding of a car beyond the edge of the track or any other abnormal change of direction, are strictly prohibited. Any driver who appears guilty of any of the above offences will be reported to the Stewards.

c) Drivers must use the track at all times. For the avoidance of doubt, the white lines defining the track edges are considered to be part of the track but the kerbs are not.
Should a car leave the track for any reason, and without prejudice to 2(d) below, the driver may rejoin. However, this may only be done when it is safe to do so and without gaining any advantage. A driver will be judged to have left the track if no part of the car remains in contact with the track.

d) Causing a collision, repetition of serious mistakes or the appearance of a lack of control over the car (such as leaving the track) will be reported to the Stewards and may entail the imposition of penalties up to and including the exclusion of any driver concerned.

e) It is not permitted to drive any car unnecessarily slowly, erratically or in a manner deemed potentially dangerous to other drivers at any time.