extensively. daily. anyone who picks up their kid at school inevitably has to flow through several. its generally not a problem unless someone isnt paying attention, or just being an ass.

I think it is the law in PA, but it is at the very least, posted to use both lanes to merge point and then alternate. It worked well in my experience. It was quite a shock when i moved to Maryland and merging was so lawless.

Where I live it's easily 50/50, nobody wants to wait their turn. You can tell who's gonna be problem too because they always have fancy rich people cars.

Honestly this is one of the few things that have improved in driving over the years. There's still the occasional douchecanoe who rides in between both lanes to keep anyone from getting by, but that is now the exception as far as I've seen.

In Georgia? 75% chance it works

In Florida? 0% chance of yes

I feel like it's hit-or-miss. A lot of people will zipper merge, but a lot of other people don't care and mess things up.

Yes, I see it happen successfully every day on my way home from work.

Like once, but generally naw.

If two cars from one of the queues go through without letting someone in, then the pattern just resumes right after that

I'd say it's pretty typical where I live in the US. Yeah, there's always a couple of assholes, but most people stick to it.

I've never seen a zipper merge work in high traffic, but I have seen "right lane ends" work more-or-less fine. Same effect, but people on the right lane drivers are a bit more likely to yield which makes people in the left lane slightly more likely to make room.

We're often not a smart species.

I think a lot of it is regional. In big city-center-compacted cities it works well, NYC being a great example. In suburbs it's sort of sloppy or depends on the area. In sprawling everyone-in-SUV-8-lane-highway cities, places like LA or Houston, it's an absolutely hopeless shit show of selfishness.

I have theories on why it's that way, but all I really know is that's what I have observed.

Yes and no. Some people think that the zipper merge would improve traffic flow, and eliminate backup at a merge point. I say that it's not failure to zipper-merge that causes backups, but it's backups the provide the conditions in which people fail to zipper-merge.

We can divide traffic at a 2-lane-to-1-lane merge into three conditions: Traffic volume that 1 lane can handle; traffic volume that's too much for 1 lane, but 2 lanes can handle; and traffic volume that's too much for 2 lanes. Obviously, too much traffic for 2 lanes, in 2 lanes, is already a traffic jam, and a zipper merge cannot fix it. Traffic volume appropriate for 1 lane, but that's spread out over 2 lanes can easily coalesce into 1 lane. The zipper merge is good and appropriate in this scenario, and this is where I've seen it work the way some people think it should. But that's not zipper-merge magic. Merging early works, too, because a volume of traffic that fits in 1 lane, well, fits in 1 lane.

It's the scenario in which there's traffic that fits in 2 lanes has to merge into 1 lane that's the problem. Just like how you can't fit a water buffalo in your carry-on bag, no matter what clever packing technique you employ, there are just too many cars for 1 lane, and there's going to be a backup. It's only after there's a backup that the conflict between the merge-early and zipper-merge people arises, so picking one or the other can't change the basic fact of the traffic backup. At best, the zipper merge reduces the spatial length of the queue of cars waiting to merge, but does not improve the throughput of vehicles at the merge point.

In Canada it seems to depend on the city. Calgary is good at zipper merging, Victoria doesn't seem to know what it is.

Yes. It definitely doesn’t work well in Chicago but it does in Denver. Different places have different driving cultures. Different stress cultures.

I see it all the time I think, but maybe my standards are low. Often what I see the traffic isn't quite equal in both lanes, so it's not abab, but people see the guy ahead find a space and they pick a space behind the next car and so on. It's there more to it? Like if someone doesn't get it, you just continue the zipper behind them, right?

I've gotten into some very amusing fights online about the difference between merge and yield, some people are just assholes when it comes to driving and refuse to accept they might be doing something wrong.

Never. It's fundamentally flawed.