That would be my interpretation of the law - I would have to watch the original video to confirm if that was the scenario - but I can't find anything that supersedes the keep left rule, so yes, if you are holding up traffic, you need to stop riding 2 abreast, and keep left.
The law is a little ambiguous - and I think in my first post I even conceded that a re-write is needed - I will further concede that I am not sure what the laws default position would be, I would feel that the onus would be on the person making the claim that practicable in their scenario meant not keeping left as opposed to the opposite (as the law states you must keep left as far as practicable, so any change to not keeping left must be confirmed in debate, not the other way around)
Well, the cyclist in the second video justified his actions under the guise of claiming the Lane, so I don't think it can be considered a true strawman. In that video however, he used the same justification you are attempting to use for his actions.
but neither of them were ticketed, which indicates both were at fault:
We know from the video that the Car driver clearly engaged in a dangerous move. If the cyclist was not at fault, we would expect further action to be taken. No further action was taken. Since no further action was taken, we can conclude that there most be a mitigating reason for no further action being taken. The most likely mitigating factor is that the cyclist was also at fault. (there is no logical fallacy in that reasoning, unless you believe the car driver didn't do a dangerous move)
Typically in incidents were one party is solely at fault, there are consequences, however when both parties equally contributed to the near miss (ie nothing major happened) then the default response is to not push forward with charges (since each sides lawyers will proceed to blame the other party)
Anecdotally - the only people who I have heard infer they have a right to claim the lane is road cyclists
From the KB forum - those that have participated in this debate actively are 3, Myself, yourself and Ocean1, 2 of us think you don't have a right to claim the lane, 1 of us does. Thats a 66.6% majority (666 \m/)
From observations of how the average Kiwi road user interacts with cyclists - overwhelming majority
Finally the reverse - Cyclists make up a small percentage of the population I don't have figures to hand, and TBH I can't be arsed since we know that those who commute via car far outweigh (both figuratively and literally

) the number of cyclists. Since Cyclists are the generally the only ones who hold the position that claiming the lane is okay, we know that only a minority holds this position - thus the Clapham Omnibus defence stands
Do I kow the scope in which it applies - well from my perspective, it never applies (this is my interpretation of practicable) from your interpretation it is when the lane/road conditions are such that in order to complete an overtaking move the car behind most cross the centreline into the oncoming lane (Have I got your interpretation of Practicable correct?)
And my point is that if he wasn't riding illegally, there is a reasonable expectation that there would be further action against the car driver from the police. There wasn't, so we can conclude that the rider was riding illegally.
Are you not doing the same? I hold to one definition of Practicable, you hold to another - we are both projecting (more or less) our definition of this rule and applying it to what we have watched.
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