In my experience there is no full stop if zipper merge is done right, but lots of angry people and a an inefficient use of the road leading to traffic jam miles before the merge needs to happen if people try to get into the one lane early.

If people all zip merge, there is no zooming possible on the closed lane and both lanes that merge get down to around 20mph at the choke point.

This only works in countries with civilized traffic participants as mentioned by OP. I have personally only seen 2 countries out of maybe 30 where that was the case. In cars many people behave like animals for some reason

Even odder when it comes to behavior, in my experience people in my current city routinely fail at navigating a zipper merge without significantly reducing their speed, even coming to a full stop.

But when it comes to freeway on ramps, even in busy interchanges, there s usually no issues, which is odd because they are more or less the same maneuver.

There must be some psychological factors at play.

So that sounds like a massive flaw in traffic management design.

It's more efficient to develop traffic rules that work in how people are not how they should ideally be.

Brawndo! it's what plants crave.

Where do you draw the line though when catering to the uniformed? There is a reason we hire SME's.

You design systems for the way nature works not how you wish nature worked ideally.

And you think nature made drivers in some countries behave different to drivers in other countries?

Technically yes. Humans are biological creatures.

Nature? we are talking about car infra here right?

I understand that my argument will lead to the inevitable 'well if everyone one followed all the rules all the time' type response, but there if people are leaving the appropriate following distance with perhaps a bit extra at the as they approach the zipper merge, than there is no reason the merge cannot take place at near highway speeds, certainly with no need to stop.

Its no different than how a freeway entry works.

I can't prove it, but I suspect (strongly) that whichever method you believe to be the correct one, following distances must shorten dramatically, or speeds must drop so low as to threaten traffic jams (which, perversely, leave everyone bumper to bumper). It's all about how many cars are trying to use that stretch of road for a period of time, and if all are to fit through within that window, there is both a minimum speed and a maximum following distance. Wish I wasn't a math flunky.

I think most people are just unaware of how much distance is required between to cars at highway speeds to considered safe. A proper buffer would leave lots of room to absorb the extra cars and loss of speed. That the point, its flexible and elastic.

> if people are leaving the appropriate following distance

The general rule is, no, they are not. Unfortunately there is really no penalty in the US if you're following to close unless you get in an accident. I quite often drive on I-35 and so often it's in conditions I call a fast moving traffic jam. People are traveling nearly 80MPH with 2 car distances between each other. Quite often this turns into multi car pileups because someone has to emergency break.