Merging 101

We’re about to head out for another summer weekend, and there’s plenty of road construction to encounter. The atmosphere is right to try out the “zipper merge.”

MnDOT, last month, created a video to try to get people to change the way they merge from two lanes to one…

Here’s the problem: People see “lane closed ahead” and they automatically change lanes. It’s like planning for retirement. You don’t wait until the last minute to do it, right? Why should merging be any different?

Then, once you merge, some jerk goes racing by in the soon-to-be closed lane and scoots ahead of everyone who had the good sense to plan ahead. Face it, you silently wish that whoever is up ahead won’t let them in.

But the “jerk” is the one who is merging correctly. And we early-adopters are the ones who are actually messing things up.

The problem is not enough people know this so in order to merge correctly, you have to be willing to absorb the grief from other drivers.

Try it out this weekend and report back here how it went.

  • Chris

    Perhaps the problem is the “Prepare to merge” signs?

    If MnDOT doesn’t want us merging too early, they might try changing their signage to something that doesn’t mention the word “merge” or that a lane is closing. Maybe the initial sign could be “Construction ahead” or something similarly vague?

    (Cue giant pile-up! I’m sure traffic engineers have more insight into this than I do…)

  • Gary

    If I am not suppose to but in line at the movie theater, why is it OK on the road?

  • Heather

    Oh, Bob. This post is a true public service. I don’t know how many times I’ve silently screamed, “It’s like a zipper, people!”

    Somehow, folks seem to see “Prepare to Merge” and read “Get Over Right Now, and Become Vindictive”.

  • @Gary: Your analogy is the problem. You’re thinking of a merge as a single line of cars that forms well in advance of the required merge, and anyone declining to be a part of that single line is “cheating.” What MNDOT (and every other DOT in the universe) is saying is that the most efficient way for everyone to get where they’re going is to use all available lanes of traffic until one of them disappears, at which point everyone takes turns merging. If everyone stacks themselves into a single lane a mile before the lane drop, backups are measurably worse as a result. It’s not butting in line – it’s moving large numbers of cars efficiently.

  • I agree with Sam. It’s not about being in a line and keeping your order. It’s more about filling the road capacity. The merge is going to happen anyway, whether it’s at the beginning of a single line or at the end just before the lane closure. Using both lanes will halve (approximately) the length of the backup.

  • Bob Collins

    The theory here, also, is that if you have just one merge point, it’s safer than if you have 50 different cars thinking “this is where I can squeeze in” (Think traffic coming off US61 onto I-94 WB at Mounds Blvd.).

    But you do have to be willing to take it all the way to the barrier and not try to merge one or two cars before the barrier.

    But have you ever noticed what happens in Minnesota (and elsewhere?) If you’ve got an empty lane because everyone else has merged early, sure as shootin’, some truck or driver is going to pull into the middle of the two lanes to try to block you.

    It’s a nightmare out there.

  • Quite some time ago, Atlanta – during all the highway construction to accommodate MARTA – used a convention I haven’t seen since:

    No warnings about lane closures, only warnings about “construction ahead.” Then, at the merge point, big flashing signs indicating the lane closure along with a simple “Give a space, take a space.”

    Seemed to work really well.

  • Tyler

    @ Sam:

    I will say – there was a project on I35 by Lakeville a few years ago, where the DOT indicated the merge 3-5 miles ahead, and via signage, encouraged everyone to start getting in the right lane. This method worked FAR better, and kept everyone going at highway speed through the 2-lane construction area. Unfortunately, this won’t work if you don’t have the lead time (3-5 miles of signage).

  • Chris

    My husband has always been a devoted zipper merge driver and I literally cannot look out either the front window to see the impending conflict nor out the side window to see people flipping him the bird, etc. even though I know he’s right – it just seems so very wrong.

  • Paul

    //If you’ve got an empty lane because everyone else has merged early, sure as shootin’, some truck or driver is going to pull into the middle of the two lanes to try to block you.

    I’ve gone so far as to drive in the ditch to get around these sanctimonious jerks. The only thing worse than being self-righteous is being self-righteous when you’re wrong.

  • Nathan


    I wish I had the guts to try this a year or so ago. I encountered a guy who zipped out in front to block me and the numerous other cars behind me who were using the mostly open lane. The most I did was to honk like crazy when we came up to a flashing sign telling drivers to use both lanes until the merge.

    This behavior is by far the most aggravating thing I’ve encountered on the freeway. I really like the “construction ahead” only warning idea.

  • andy


    I know exactly what you mean. Also, the big rigs love to pull up next to one another and granny-gear it as if drag racing in super slo-mo.

    After I do eventually merge, I’m the one who gives tons of space in front of me for those who are about to merge. You’re welcome world (me patting myself on the back…..)

  • matt

    What about placing a soft divider (cones, fabric stretched between pylons, or even a double line) at the first sign to merge. This commits cars to the lane that they are in until right before the merge.

  • Jay

    Am I correct in thinking that this doesn’t apply to exit ramps. You’re still a jerk if you wait until the last minute to cut into a line waiting for a slow-moving exit, right?

    I feel like people get these two issues confused.

  • Janelle

    FINALLY! I’ve been waiting for this to catch on! I lived in the Bay Area for awhile and I really miss California drivers. Everyone knows the zipper and no one is passive agressive.

    @Paul, Nathan, Andy

    I too hate the drivers who become the “merge patrol”!

  • Dave S.


    Yes, in most cases you’re still a jerk if you wait until the last minute to cut into a line waiting for a slow-moving exit. The difference is that with the construction merge, everyone ends up in one lane, so you’re not delaying anyone by slowing down to merge at the end. With an exit lane, unless you can cut quickly in line without slowing up the traffic behind you in the through lane, you’re actually creating a backup. Guilty.

  • David M

    @Jay, @Dave S

    I disagree about exits, mostly because of my experience exiting westbound 694 onto Rice St. Frequently traffic to northbound Rice backs up onto the freeway, however, southbound (where I’m headed) almost never has a back up. It is a two lane exit ramp- but I frequently get blocked, honked at, and worse when I try to drive up to the stop light to turn left. So don’t assume the guy driving around the back up is a jerk- he may not be going to the same place you are!

  • Gardog

    I have heard of the zipper merge technique. I’ve also simulated it against the “merge ahead” technique a couple of different ways with mathematical models. The zipper merge always causes more congestion, and lets fewer cars through overall. This is why it confuses me that DOT advocates the zipper merge.

    A number of the people working for DOT right now who figure out ideas like zipper merging are the same geniuses who tell us that traffic circles are a good idea, too. It does make me wonder.

  • Bob Collins

    //The zipper merge always causes more congestion, and lets fewer cars through overall.

    Interesting. Please explain

  • Jamie

    I think Gardog is wrong, and so do the researchers who have proven that “the zipper” works.

    I’ve been a zipper-merger for years, and have encountered those self-righteous lane-straddling jerks who try to thwart the efficient movement of traffic. Paul said it well: it’s even worse to be self-righteopus AND wrong. Those are probably the very people who will ignore or defy the efforts to promote the zipper.

  • ryanspublicfeed

    I’ll admit I’ve been the merge patrol but ONLY on the shoulder… there’s no lane there, you’re going to be stuck behind me.

    Zipper merge? I do it most of the time, but if I have time to kill I’ll let the rest of the world do it.

  • mitch

    I don’t buy this argument that the merge point is where the lane ends. It’s one thing if the two lanes (from three) are moving quickly, then fine, the zipper or just general merging works. But if the two lanes are backed up for a half mile and clearly the opportunity to merge has been announced and not taken, isn’t it butting in line? Flooring it to the front of the line (when clearly there is a line of cars waiting) in hopes of wedging in front of some compassionate or exasperated soul is butting in line, in my opinion.

    It would be far more courteous to try to merge somewhere in that backed-up stretch, and not at the front of the line. On the other hand, drivers need to be more generous in letting those people merge.

    I think the movie theater analogy works for all motor vehicle traffic. Just ask yourself: Would you attempt this maneuver if you were on foot?

  • Elizabeth T.

    If everyone all getting into one lane miles ahead of the merge was a Good Idea, there would be no reason to have more lanes. Traffic flows faster when there are more lanes. And, if drivers operate on the merge-miles-ahead principle, and kept driving at 65 mph, there would be less of a problem.

    re: traffic circles – I’ve used them often in other countries and found them to be good. Until I get back here – People are afraid of merging in/out so quickly and therefore don’t use them efficiently. Same thing with the Zipper merge.

  • Bill

    @Mitch. You don’t have to buy the argument. It’s a fact that the merge point is where the lane ends. Otherwise the traffic cones or whatever they are using to block the other lane would be used at an earlier point on the road. Until the lane is blocked, it is a legal lane of travel. Period.

  • Rick

    How about merging the lanes into a lane that takes up the inner most parts of both lanes. So in fact both lanes are ending and a new one is formed. The lanes would form more of a Y, like a real zipper.

    If both lanes end, then neither the people in the right lane or the left lane have already merged.

    And there would be no getting ahead . . .

  • Seth


    Hate to say it but you people are infinitley incorrect. If everyone would get in one lane and continue at the speed limit, or the max allowed speed jurisdicted by the construction zone then traffic would flow accordingly. The PROBLEM with your so called “lane liberators” is their inability to merge like everyone else causes a bottle neck effect, traffic has to slow to allow them over, causing a horridly slow driving experiance for everyone minus the ******* who is getting to bypass everyone who got in the appropriate lane.