Core: Weaving and zip merging: who yields to whom, and the 300/50-metre rule

Legally, mergers and exiters must give way to each other — it is a mutual rule on paper (Book p.153). But because mergers coming off the merge lane still drive more slowly than through traffic, and also have more room and overview to wait, in practice it is safer — and therefore self-evident — that MERGERS yield to EXITERS, not the other way around. Zip merging happens at a narrowing from two lanes to one, and follows a fixed rhythm with two distances (Book p.155): at about 300 metres before the narrowing you already adjust your speed to the traffic on the adjacent, through lane. Only at about 50 metres before the narrowing do you actually merge, without braking and without disrupting traffic — you slide into a space that is already there, you do not force your way through. There is also an agreement about the order (Book p.154): every driver on the through lane lets exactly ONE driver from the obstructed lane go first each time — not two or more in a row. That is what 'zip merging' literally means: the teeth of a zip also close one at a time. One final nuance the book itself names (Book p.155): you should indeed drive far along the lane that is ending — merging early is not a virtue here — but driving too far and only then claiming merge space at the last moment is irritating for other road users. Use the whole lane, but do not overdo it.