Driving on the M5 last week, a thought struck me as I was overtaking another car.
If you are in, say, the inside lane and want to overtake a car in the same lane as you, any car behind you in the 2nd lane should, in my opinion, give you priority once you have indicated your intention to move into the 2nd lane, depending on that car's distance behind you. However, they rarely do, believing that they have priority and that you should wait for them to pass you before you can move out into the 2nd lane. Priority remains with the car being overtaken, within reason, not the overtaking car - at least that's my understanding and there's logic behind it, as I will explain later.
The Highway Code is unclear on this matter and ChatGPT gave me two conflicting answers when asked - in one response it said the car intending to move to the right had priority, but in another it maintained the car wishing to move to the right had to give way to any car approaching from behind in the middle lane.
Rule 267 states; "Make sure that the lane you will be joining is sufficiently clear ahead and behind." This kind of fudges the issue - what is meant by 'sufficiently clear' in regard to the area behind you?
Given motorway driving plays no part in the driving test, it's not surprising there's confusion. Many are the times I have not been given priority by drivers coming up behind me in the next lane out, having to swerve to the left to avoid a collision as they unwaveringly maintain their direction and speed. It's especially prevalent when the car in the middle lane is boxed in by yet another car in the outside lane, believing they can't give way to you precisely because they're boxed in. They seem blissfully unaware that they can reduce their speed to allow you in.
The logic of which car is given priority is quite simple - the driver behind you has a much better view of the overall situation than you do. You have to crane your neck around while simultaneously keeping an eye on the car you're intent on overtaking and look in all your mirrors while hoping you haven't missed the blind spot. The driver behind you is not so encumbered, having an uninterrupted view of the unfolding situation, and is hence the car that should give way - at least in terms of logic and safety.
Rule 13 of the maritime "Rule of The Road" for ships at sea states the following, which supports my logic:
(a) Notwithstanding anything contained in the Rules of Part B, Sections I and II, any vessel overtaking any other shall keep out of the way of the vessel being overtaken.
(b) A vessel shall be deemed to be overtaking when coming up with a another vessel from a direction more than 22.5 degrees abaft her beam, that is, in such a position with reference to the vessel she is overtaking, that at night she would be able to see only the sternlight of that vessel but neither of her sidelights.
(c) When a vessel is in any doubt as to whether she is overtaking another, she shall assume that this is the case and act accordingly. (d) Any subsequent alteration of the bearing between the two vessels shall not make the overtaking vessel a crossing vessel within the meaning of these Rules or relieve her of the duty of keeping clear of the overtaken vessel until she is finally past and clear.
In the above rule, 22.5 degrees abaft the beam of the vessel being overtaken equates, approximately, to the blind spot of a car.
It's the same in warfare. How do you increase your chances of successfully attacking an enemy? By approaching him from behind, as you have the advantage and his attention is focused to his front.
However, when it comes to traffic joining the motorway from a slip road, the car joining the flow of traffic has to give way to traffic already on the motorway, despite the motorway traffic coming up from behind the car joining the motorway having a much better appreciation of the situational positioning than the car joining the motorway.
Why is there this disjoint in logic when the slip road is still a lane, but just one that peters out. In this aspect, it's no different to an inside or outside lane that closes ahead, forcing traffic to merge within the confines of the motorway and where the rule of an overtaking car giving priority to the overtaken car prevails, in my opinion.