I see the same throughout the US: everyone knows to alternate when a merge is required - and will even call this ‘zippering’ - but does not consistently (or oft

I see the same throughout the US: everyone knows to alternate when a merge is required - and will even call this ‘zippering’ - but does not consistently (or often) do the throughput-maximizing practice of forcing this, by waiting until a merge is absolutely required. Rather, people often try to avoid the ‘phase transition’ to a forced-merge flow-state for as long as possible, by ad-hoc merging earlier. Partially that’s because the initial transition-to-zippering can be chaotic. Once established, zippering is easy to follow and well-respected. But, being the “first” to assert an alternating-right-to-merge depends on more judgement & recognition from a specific other driver.