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How Do You Merge? Early or Zipper?
Finally! Research that’s actually useful!
When you’re driving on the highway and you see a lane closed ahead, what do you do? Do you merge quickly into the other open lane? Or do you zoom ahead and try to merge at the last minute?
If you’re the former kind of person, the latter kind of person probably irritates you. Why don’t you just merge earlier, you may think, rather than being a jerk and trying to butt in?
Turns out, though, the rude mergers are (often) doing you a favor. From Ars Technica:
There’s a name for it: late merging, though advocates prefer the term “zipper merging” because it doesn’t have a negative connotation. According to Ken Johnson, a Minnesota State Work Zone, Pavement Marking, and Traffic Devices engineer, “We want people to merge at the point we’re asking them to, so it’s not ‘late,’ per se.”
It works as follows: in the event of an impending lane closure, drivers should fill in both lanes in equal measure. Within a few car lengths of a lane ending, both lanes’ cars should take turns filling in the open lane and resuming full speed.
If roads are clear enough that everyone is already driving close to the speed limit, zipper merging isn’t as effective, but in the case of congestion, Johnson said that this method reduces backups by a whopping 40 percent on average, since both lanes approach the merge with equal stake in maintaining speed. “When the queue backup is reduced, the access points behind a work zone, like signals or ways to get on and off the freeway, those aren’t blocked,” Johnson pointed out. “People have a better opportunity to get off or on the system at that point.
“I’ve been amazed at how consistent the flow is,” Johnson added. “You don’t have to put your foot on the brake at all. You just coast ahead and take turns at the merge point.”
Here’s the diagram, in case you need it:
So it turns out that all of those rude late mergers were actually making things better, making them move faster. Who knew?
Now can we have some research on the reasons why people — especially in Los Angeles — take roughly 45 minutes to pull out when the light turns green?
Published in General
I aspired to merge early, but, in stop-and-go traffic, I’ll now gladly wear the mantle of rudeness to reach my destination faster than misguided courtesy previously allowed me. It’s for the other drivers’ own good, after all.
Against my better judgement I am frequently a “zipper”. There is a highway exit (for those in the area, the exiting off the Northbound Dan Ryan onto the Westbound Eisenhower) where I have tried to be an “early” merger only to be at a standstill for 10 minutes watching dozens of cars fly by me at high-rates of speeds only to “zip” over, so now I just follow their lead.
I am, at times, ashamed of it, but as they say “When in Rome…”
How do I merge? Like a good conservative – Hostile Takeover!
?Why is this such a surprise. It ought to have been patently obvious. I have been a “zipper” merger since forever. It is only logical that 2 lanes taking turns will be quicker than one long, back-up lane while the other is open. That’s not courtesy; that’s dumb.
Enforce the zipper. Kill the faux politeness that is really just a mask for self-righteousness on the road.
Early merge, then tailgate to be a cog in the zipper.
I drive up to the point where traffic is actually stopped in both lanes. Then I partially merge at the first opportunity while making sure to block enough of the closing lane so some claimjumper doesn’t try to fly up and cut me off.
My rule is simple: I pick a lane and stay in it as long as possible. If the lane disappears, that means merging as close to the point where it disappears. If I am in the merge lane, I stay in it, and let one (or two cars) merge ahead of me at the merge point. Doing that is not politeness — it is common sense. It allows the use of two lanes for as long as possible.
What I do not do is switch from the merge lane to the closing lane and then back to the merge lane. Frequent lane changing slows traffic. Got that from my son with a Civil Engineering degree. He learned that in his traffic class.
Seawriter
EZ — 2 bzy txtng.
I call shenanigans on the video. The late mergers don’t run up to the end of their lane then slow down and merge when they can. They run up to the end of their lane, force their way in at speed, and cause the everyone else in the other lane to slow. A little courtesy goes a long way. Just let off the accelerator for a second, give enough room for others to merge, and everyone will move along more efficiently.
There is a 2-1 merge in my county that is notoriously bad, and it is bad because of the [expletives] trying to pass as many cars as possible and merge at the last moment. For their own selfish sakes they force everyone else to be delayed just so they can get a few inches farther down the asphalt. As soon as the dashed line goes away I move over and block the rest of those [expletives] from passing anyone else. I’m not the only one.
Rob, maybe this will help further explain the importance of the zipper merge:
There’s a spot on my evening commute where I have to deal with this. My strategy:
1) Slow down to the speed of the lane that isn’t ending.
2) Find a natural space in the traffic in which to merge. In front of a semi is normally a great spot, as the truck doesn’t speed up fast enough to ride the next person’s bumper.
3) When the lane begins to accelerate, do *not* match the acceleration of the person in front of you. Increase speed, but do so at a slower rate, so as to create space between the cars.
4) Other cars will merge into the space. DO NOT BE ANNOYED. It’s better to let them in now than wait for someone in the front of the line to brake to let them in up there.
5) Also, by increasing the space between cars, you won’t have to brake as often, if at all. Instead of stop-and-go traffic, you are creating slow-but-steady traffic. This is much more pleasant for folks who drive stick shifts (me) and people without air conditioning in their cars. (me).
I tend to skim first. Thought you were talking about being an “early zipper,” a practice I cannot recommend.
But, to the question about traffic, I’m a squish. I tend to merge when I find a hole to fit in. On the other hand, I tend not to be in as big a hurry as I was when I was younger.
In other words, “zipping” is not inherently more efficient. It depends on how one uses the zipper lane. If the zipper lane simply has a shorter line than the host lane, then there’s no problem. But when someone zooms in at high speed at the merge point, that person slows everyone down.
That applies not just to merging traffic but to highway traffic in general. Congestion is caused largely by people who do not conform to the speed of traffic around them. That’s when people have to use their brakes.
Merging would is most efficient when drivers simply alternate between one vehicle from the left lane and one vehicle from the right lane. But there are an equal amount of jerks who try to squeeze ahead and timid fools who leave a three-car gap in front of them.
As usual Prawn, you’ve nailed it. Regular drivers know when and where they should be moving over to the clear lane. They know where these lanes end. I say no mercy shall be given to these latecomers. I am happy to allow trucks and out of state vehicles to merge in front of me but those who decide to cram their vehicle in front of others aren’t doing it to be efficient, they are doing it because they think they deserve it.
I would love to get Dave’s insight on this story as well. As a trucker who has seen it all, he may offer the best opinion yet of how he sees things from inside the big rig.
Here’s my philosophy: I can either stop when someone at the front of the merge lane brakes for the jerks, or I can go slower — letting the jerks in and giving myself room to coast when everyone else is braking — and keep moving.
Self-righteous fury doesn’t keep me as cool as a 15 mph breeze in my car with no AC.
And all the people behind me cursing my slowness and timidity are then left in my dust when after the merge point I return to my normal highway cruising speed of 75 mph.
“. . . You just coast ahead and take turns at the merge point.”
If only it were so.
I can’t remember where in the East it was, but I once saw a highway construction sign that actually told drivers to use both lanes and then take turns at the merge point. It made so much sense to me that I’m not surprised I’ve never seen a second one.
It’s quite common to see “Use Both Lanes to Merge Point” on Pennsylvania signs, probably the only thing PennDOT has ever purchased that they received actual value for.
What I want to know, though, is this:
Why do the drivers of very large trucks so often take it upon themselves, to pull out and block both lanes, travelling side-by-side at exactly the same speed (slow, or stopped) from the first warning that a merge point is coming up in, say, a mile?
All this does is encourage “zooming ahead,” and people trying to get round the blockage (that has nothing to do with the actual merge point). And it makes the congestion worse, as well as infuriating the person who is behind the truck (in front of which there may be one or two, or several, hundred yards of empty road, before the lane is filled again.
It happens so often that it can’t be chance.
Does this happen elsewhere? Is it just a PA thing? Or are they just doing it to annoy ME?
Not being a trucker, I can’t say for certain, but my guess would be that truckers have an informal code where they will let each other over to merge. Given how most people don’t even leave room between cars to let other cars merge into the lane, if I were a trucker I certainly wouldn’t want to bet on there being a car in the merge lane willing to create the 100′ or so feet the truck will need to safely merge. Thus, you might as well stick close to someone who will probably let you get over.
Yeah, it’s a traffic merge … not a personal possession (“I will not let you in!”). If this was a sane world, all lanes would fill, but then both lanes would equally merge at the designated point. The killer is when you get huffy people who have already merged who feel that someone is butting in on their hard-earned space. After all, they merged when first commanded! They were obedient! They obeyed the law when they were commanded and therefore they deserve their place, and no one should … (potty training didn’t go well)
It’s a freakin’ traffic merge …
Game Theory talks about The Altruist’s Dilemma. It’s what happens when you think you’re being “generous” in letting other people go first … but since everyone else is expecting you to simply follow the right-of-way, traffic comes to a hesitating stop because the drivers no longer can predict what you’re going to do. Take your turn. Go when you’re supposed to go. If you call that being selfish, then by all means, be selfish. Being “generous” causes more harm than good.
Maybe I’m just a jerk but zipper merging has always been somewhat intuitive to me. Why merge 2 miles before the lane ends and stack up all the cars in one lane? Glad to see the “science” has vindicated my methods…
I’m an early merger… once I see a sign, I like to act on it immediately, so I don’t have to think about it later. Maybe I’m just a lazy driver. :)
I don’t necessarily zoom ahead but if I’m already in the lane that disappears I stay in it until I have to merge over. If I’m in the accomodating lane, I let one person over in front of me. One person (ping) only, Anatoly.
There’s no one behavior that is optimal always and everywhere. Drivers have to adapt to the personalities and road conditions around them.
But I think a lot of drivers fail to understand that they influence the expectations of drivers around them by the amount of space they leave ahead. There’s a difference between allowing other drivers ahead and encouraging impatient idiots. If you don’t have to brake, then you’re probably doing it right.
I should add that I *never* brake for late mergers. I will not accelerate as quickly to provide room to merge, but if they can’t figure out how to match speed and get over without crashing into me, tough. I could use a new car.
I used to be an early merger until I realized I spent more time in the longer lane & actually made the process take longer. If I’m in the lane that’s disappearing I drive at an appropriate speed (not zipping along), pay attention to other cars, & merge as the lanes come together.
That could be it. It certainly doesn’t improve the traffic flow though. And perhaps it’s a self-fulfilling prophecy–I’m certainly ticked off enough by the time I get to the actual merge point that if one of the truckers who’s been hogging the lane is trying to merge, I’m going to ‘zip!’
Very interesting. I don’t doubt the math, but I’ve been one to merge early, and then grit my teeth at the “cheaters” who cut in at the last minute. I also tell myself that they might just be knuckleheads who can’t think more than a few seconds ahead. In my state, I see this all the time, and am starting to wonder if there’s even a state law that requires this behavior.
Regardless, since I don’t doubt the math, I’ll start re-thinking this.