Of course if you prevent further merging, the traffic unaffected by further merging will tend to flow better; that doesn’t demonstrate anything unless you also take into account of the ‘choke’ you created behind you
Two lanes of traffic have to go into one lane; that single lane will then tend to be crowded and this will always be a problem; the longer you make that crowded single-lane section (by moving the merge point back away from it), the more opportunities you create for poor flow conditions to occur.
It’s nothing to do with ‘suckers’ and ‘ass-clowns’. If everyone used both lanes for as long as possible, then merged to a single lane for as short a distance as possible, that’s the best possible way to use the space available and the least likely mode in which problems will occur. Nothing is perfect though, so merging two busy lanes into one is very likely to slow the traffic.
This isn’t even debatable. It’s been studied very extensively and the zipper merge is the least-worst solution, providing that everybody does it (which of course they won’t, because ego).
But arguing that its not effective in principle is like arguing that the earth is flat (which of course people also do, because morons).
It depends on the congestion. If it’s not congested, it’s best to merge early. Then everyone just drives on through at the speed limit… If you merge late, and really have to slow down, others will need to slow down for you because you where not paying attention.
Note, I’m talking about regular traffic flow that is not congested. And not a construction zone, but just a two lane road that goes down to one. Happens a lot in the Colorado mountains with passing lanes on hills.
We’ve got one of those near where I live. It works quite well, and I’ve never heard or read any significant grumbling over it. This may be because the local authorities and media did a good job of explaining it.
Far too many people are unaware of what the zipper merge is and how to do it correctly. From personal experience, it certainly wasn’t covered when I was in Driver’s Ed.
To the best of my knowledge, a successful zipper merge isn’t just “using both lanes,” but also:
matching speed with thru lane (closed lane)
staggering vehicle position (both lanes)
gradually allowing more space to allow the eventual merge without braking (thru lane).
While more nuanced signs can help, the mere fact that the zipper technique requires…
knowledge and experience
a requirement that drivers coordinate with each other in acts of selflessness, and
that the whole prospect can be screwed up by a single driver not cooperating,
…the zipper merge is a bit of an idealistic expectation, especially since there are so many drivers actually ignorant of the technique.
I fear for successful zipper merges to become commonplace may mean a requirement that it is incorporated into Drivers Ed across the country, and then waiting a generation for all the ignorant drivers to die off.
Oh, and the non-existence of selfish hotheads on the road.
I wonder if a small part of the problem with ‘zipper merge’ signage might be the assumption that everyone knows how a zipper works, and why it’s a metaphor for merging in turn
Sure, if the road is sufficiently quiet that all of the traffic can flow easily in one lane, it’s sort of moot. It might not even be much of a ‘merge’, in that nobody really needs to worry about finding gaps.
I think the problem is that zipper merges only work in areas of high congestion, as in California, where it is obvious that the merging is in turn.
If there aren’t areas of high congestion, and one person is in line in the busy lane, and sees someone else passing a line of cars in the other lane to go to the front, they don’t see it as merging in turn.
If there’s a slow moving line of cars in the merge-into lane, that is congestion.
It wouldn’t necessarily be vastly better if they merged later assuming they all merged in orderly fashion, but imo:
(edit: this is the generic ‘you’, not you personally)
If you decide to merge early, you yielded use of the remainder of the merge-from lane to anyone else who wants to use it. You could have used it. You chose not to. You’ve no business griping about people who made the other choice.
If you try to block people from passing by straddling the two merging lanes, you’re far more of a problem yourself than any possible problem you think you are ‘fixing’.
‘it’s my right of way’ should alway take second place to ‘is this safe?’ a very large proportion of the stupid incidents you see on dashcam compilations arise from people trying to assert their perceived right of way and pressing on beligerently into an obviously risky situation. If you can prevent a collision by yielding, it’s insanity not to.
In the case of merging, you don’t even have a right of way in a lane you already stopped driving in.
I don’t think the problem is signage. It’s that there are too many awful drivers who pay no attention to signs, other cars, impending hazards, etc. Where I live, it has gotten worse since the pandemic (not sure if that’s somehow the cause, or the timing is just a coincidence). I regularly see people run stop lights like they aren’t even there.
A zipper merge requires cooperation between drivers. Lots of people are either too selfish or too oblivious to cooperate.
Any single lane behind will be limited by any merges ahead.
You need to think on both directions or - commonly - a loop. If you’ve got a loop with two lanes for 99% of the circumference and just that one 1% where there’s a merge down to a single lane then traffic backup is going to hit sooner and last longer if people are acting like it’s a single lane for 80% of the full length rather than the actual 99%. You can comfortably fit an extra 19% of the road with cars before there should be any slowdown.
I don’t believe you’re imagining it.
I’ve noticed a change in social behaviours (or I suppose an increase in antisocial behaviours) more littering, more of people doing stuff like just parking their cars across other people’s driveways, more careless or thoughtless driving.
I believe the phenomenon has actually been formally documented and has been attributed to some sort of behavioural rebound by people who felt affronted by being locked down - like ‘why should I follow rules? Haven’t I suffered enough?’
Is that a goal? The purpose of a road isn’t to be a parking lot.
A good road needs to maintain a high throughput and a high average speed. The throughput will be limited by the bottleneck. The high speed mostly depends, I think, on maintaining a low density.
If a two-lane road is fed by a 1-lane, and merges back into 1 lane, then zipper merging might be a tad better. By lowering the per-lane density, people can speed up until the following distance hits the recommended 2 seconds.
Of course it also depends on how fast cars are going on the single lane. If they’re already at the speed limit, then the lowered density on the 2-lane part won’t help much. They might as well go 1-lane for the whole distance.
If the 1-lane is fed by a 2-lane that goes for a long ways back, then I think early merging is better. It doesn’t improve throughput, but it does prevent the 2-lane part from backing up over a larger distance. There are fewer cars in that section, but the throughput is the same and the cars can go faster.
The 1-lane section is where the problems happen; higher traffic density means it’s more prone to stop-start surges caused by braking phenomena - the car in front of you brakes a little; in dense traffic, you cannot brake less than them or you will collide, so it’s likely you brake a little bit more. The car behind you cannot brake less than you, so they probably brake a bit more - and so on, until it propagates backward to someone stopping completely, and everyone behind them.
The shorter you can make the 1-lane section, where the traffic is compressed, the less likely this is to happen, and the quicker it will clear when it does happen (because on longer sections, it happens repeatedly) - so the traffic clearing one braking-pulse runs right into the back of the next wave.
If the 1-lane section runs for miles and miles, it’s a bit moot; it’s gonna be crap regardless, but if it’s for a few hundred yards, then any extent to which you can shorten the 1-lane length by delaying the merge, is an advantage.
Obviously a severe, last-minute panic-merge is not ideal, and neither is it ideal when there is a mismatch between different people’s behaviours and expectations in the merging traffic, but making a 300 yard 1-lane bottleneck into a 700-yard single-lane queue, by (nearly) everyone merging 400 yards before the actual merge, just makes the single-lane section twice as prone to whatever issues would be happening in there naturally.
Why not a sign that simply says “Zipper Merge” with a stylized illustration of traffic merging in zipper formation (e.g. 3 black rectangle “cars” in each lane zippering into one lane).
It’s unambiguous and would be better than what they use today.
The biggest hurdle: inertia. I imagine getting a new Official Road Sign approved is far from easy, especially if it’s a very fundamental sign–“Turtle Crossing” signs might be easy to update, but something basic like “Merge” sign designs would encounter so much resistance.
That’s not been my experience. I’m in lane 1, because that’s the lane I’m travelling in. Lane 2 often has less traffic, so cars in lane 2 are passing those in lane 1.
What have I done wrong? I didn’t decide to merge early; I’m just travelling in the lane that my traffic pattern / destination dictates.
I don’t think signage is the problem - in the UK, we have signs that say ‘merge in turn’ (ie ‘take turns in merging’), often accompanied by ‘when queueing use both lanes’
The signage is pretty unambiguous, but these merges still have dangerous uppity people who merged very early* and who then try to block others from passing them to merge further on.
*like hundreds and hundreds of yards early - the merge is typically announced by signs saying at 800, 600, 400 and 200 yards, often also accompanied by ‘use both lanes until merge’.
Signs, regardless what they say, don’t make aggressive, selfish, entitled drivers stop behaving in aggressive, selfish and entitled ways. It’s the same ‘me first’ problem as people close-passing at high speed when they overtake cyclists and horses, overtaking on blind bends and hill crests, feeling compelled to overtake learners, tailgating, etc.
