The admissibility of the regulation depended upon its being relevant to the issue of negligence which the jury had to try. The appellant's case had necessarily to be considered as one of carelessness of the respondent in driving his semi-trailer across the centre line and on the portion of the carriageway south of the centre line. The appellant's argument must go as far as to say that as the respondent entered the southern portion of the carriageway the regulation applied to the situation and obliged him to stop, for the reason that the rear of the semi-trailer was still being drawn out from the northern boundary. We may assume, without deciding, that it is correct to describe the respondent as still, at that point of time, engaged in drawing his vehicle out from the northern boundary. The question is whether, on that assumption, the regulation obliged the respondent to stop when the danger of a collision with the appellant's vehicle arose. The answer, in our opinion, is that the regulation has to do only with a danger of collision arising from the special quality which the movement of a vehicle possesses when and because the point of departure is the boundary of a carriageway. The common case is that in which a vehicle which has been stationary at the boundary is being moved out so as to be in the way of traffic which could have passed it safely if it had stayed where it was. There may well be other cases. But the regulation plainly intends only to provide against the special dangers which may be due to a vehicle at the boundary of a carriageway being driven out from the boundary into road space which its position at the boundary may have led drivers of other vehicles to suppose was open for their use. It follows that in our opinion the regulation had no relevance in the present case. The danger which the appellant encountered was not of the kind referred to. Because of the width of the carriageway and the clear line of demarcation between the portions available for east-bound and west-bound traffic respectively a driver in the position of the appellant could not possibly be placed in any special danger from the respondent's vehicle by the fact that the latter had crossed the northern boundary. His complaint was of the drawing out of the semi-trailer from the centre line (if the manoeuvre can be so described) and onto the southern portion of the carriageway. In our opinion the trial Judge was clearly right in rejecting the tender of the regulation, and the appeal should be dismissed.