Despite years of the Minnesota and Wisconsin Departments of Transportation trying to educate people on the "zipper merge" and why it is the better solution, the debate over these "rude" last-minute merging drivers continues to rage on each year - especially during road construction season.

Like clockwork each road construction season, memes, comments, and debates fire up on social media as people trench themselves in on the "pro-zipper merge" or "those drivers are jerks" sides of this debate.

I'll admit, I can understand how someone can feel a bit offended as they merge early, thinking they are being more efficient and aware, while zipper mergers might appear to some to be "cutting in line". We Midwesterners don't like people cutting in line. That's rude, and rude doesn't fly around these parts.

Even though I will readily admit there is some logic to that mindset, science continues to say otherwise.

As was pointed out by my colleague several years ago, zipper merging is the recommended method by Departments of Transportation in both Minnesota and Wisconsin. Despite this repeated recommendation to use all lanes until the merge point, there are still a lot of people that don't for whatever reason - and it turns out there may be some science behind why some people avoid zipper merging.

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So, if you're one of those people (or you know one of those people), here is why that seemingly "rude" zipper merging is the preferred way to merge in construction zones and other areas where the number of lanes reduce.

Why MNDOT & WISDOT say zipper merging is better

The Minnesota Department of Transportation actually has a page dedicated to explaining the zipper merge. So does the Wisconsin Department of Transportation. That's how much they prefer and recommend this method.

The two methods they describe are "early merging" and "zipper merging". As you might guess, early merging is the type of merge people do when they move into the appropriate lane before the merge point. Meanwhile, as you know, zipper merging is where drivers take turns merging at the merge point where the lane ends.

The benefits MNDOT offers include:

  • It reduces differences in speed in the two different lanes, which is an important safety thing for everyone involved - especially in construction zones
  • it reduces the overall length of a traffic backup by as much as 40%
  • It reduces congestion on freeway interchanges
  • It creates "a sense of fairness and equality" that all lanes are moving at the same rate

They explain that zipper merging is the better option on congested roads, maximizing road capacity in backups and optimizing safety.

As WISDOT explains, the only way a zipper merge lives up to its billing as a more efficient method is if all drivers practice it. That's the hitch. It is the better solution, but only truly works best if everyone does it.

Because not everyone does, often times there is some kind of a hybrid that turns out to be a lot less efficient than if everyone just took turns at the merge.

Is there ever a time it is okay to not zipper merge or merge early?

While traffic studies from the US Department of Transportation's Federal Highway Administration explain that the zipper merge is the most efficient way to keep traffic moving in bottleneck areas, there is an admission that early merging does have a place in the driving world.

As explained in a video produced by MNDOT in 2011, if all traffic is moving at highway speed and there is not heavy traffic or congestion, early merging can be a good idea.

The thought here is that if traffic is light and freely moving, it should be easier to move into the other lane safely without causing any major ripples in the flow of traffic. WISDOT backs this statement up on their website, stating it is perfectly fine when all lanes are moving freely to merge whenever is safe.

The science behind why some people don't zipper merge

As I mentioned off the top, there are a lot of people that always merge early, which creates issues in the flow of traffic. It turns out while zipper merging seems to make more sense from a purely scientific level, psychological research conducted (via Mental Floss) explains it might go against human nature - even if it is the better solution.

They detail something called "pre-crastinating" is an aspect of many people's approach to things in life. The concept is basically when someone tries to complete a task (like merging) as soon as possible, regardless of whether or not it is the best timing for the action. The research found that people were willing to do more work just to get something done in the tasks that were part of the study.

The translation is that "pre-crastinators" want to get the merge out of the way as soon as possible, so they try to slide into the other lane before the merge point. When traffic is heavier, this leads to longer lines of cars, slower-moving flow of traffic, and greater overall driver frustration. It may seem counterintuitive, but multiple studies continue to say that the truly most efficient way to keep traffic moving is by using both lanes and taking turns at the merge. Now we all just need to do it to keep the flow of traffic moving. ;)

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