Sunday, 21 July 2013

Zipper Merge

So I was driving recently on the freeway in Saskatoon and ... oh wait ... maybe I should explain for those of you who have never driven in a city besides Winnipeg: a "freeway" is a road with no stoplights where you can drive at highway speeds. Saskatoon, a city one third the population of Winnipeg, has one. It's called Circle Drive.

As I was saying ... I was driving on Circle Drive in Saskatoon when I approached a construction project to extend the freeway to the west. That's when I saw it: a sign that said "ZIPPER MERGE AHEAD".

The concept is simple: drivers are to stay in their lane until the point at which one of them ends, and then they are to take turn merging -- one from the left, one from the right -- like a zipper.

I quite like it.

It's a nice alternative to the situation that we normally encounter here in Winnipeg. That is, the majority of drivers all pile into the single lane that is continuing, causing a huge backup in traffic. Then a minority of drivers zip ahead and cut in at the front of the line or somewhere close to it.

There are a couple of problems with this, one being that it creates an unnecessarily long traffic queue, another being that it causes animosity among drivers. The drivers who get in line right at the start of the queue and wait patiently as the line trudges along resent the selfish nimrods who zip past them in the empty lane and cut in at the front.

But why should you get in line half a mile before the construction starts when there is a perfectly good lane that can legally take you right up to the merge zone? That isn't rational.

I've been on both sides. Sometimes I get in line, and when I do I get annoyed at those who don't. Depending on what kind of mood I'm in that day, I may even do my best to keep them from merging in front of me. Sometimes, if I'm in an unusually pissy mood, or if the guy trying to merge is driving a pickup truck with a license plate that says "GORJUS" and is wearing a ball cap backwards (I have seen this), I'll even tease them by leaving space for him to merge and then closing up to the car in front of me at the last second, and then I'll go extra slow to give the guy behind me a chance to close up behind me too.

That's how I roll.

However, sometimes I'm the douche bag who zips up the empty lane, although in my head I say to myself "Oops, is this lane closing off? Gosh, I hadn't noticed. I guess I ought to merge over here at some point." -- as if I can telepathically communicate to the drivers waiting in the queue that I didn't mean to drive up the empty lane, it's just that I didn't notice the construction signs. Silly me.

However, I won't drive right to the front of the line because that would be rude, and it would negate the little excuse that I made for myself that I only inadvertently failed to get in line.

This is all normal behaviour, right? Good. Just checking.

Sometimes those who set up the construction sites make it worse than it needs to be. For example, the signage for the construction on the Pembina overpass on the south Perimeter Highway in Winnipeg begins more than 2 kilometers in advance of the lane closure, with signs that warn you that there is a lane closure ahead and the speed limit is reducing to 70 km/h. As a result, most drivers pull over into the right hand lane and slow down to 70 km/h on the highway so far in advance of the construction that you can't even see where the construction begins.


In writing this blog post, I found out that the zipper merge is a new thing for Saskatoon. They only started to experiment with it in May, because, as one person put it, "People have been so bad historically in this city anyway on road construction and merging that anything might improve it".

Saskatoon borrowed the idea from the state of Minnesota, a pioneer in the zipper merge revolution, and so far they have found that it works quite well. My own experience with it was pretty good. I mean, about as good as merging at a road construction site can be. It's not comparable to, say, a full-body hot oil massage, but you know ... it wasn't painful.

The Minnesota Department of Transportation says that the zipper merge "has proven to help traffic flow by decreasing queue lengths as much as 35 percent" and "reduced lane-changing conflicts and sudden-stop crashes."

However, even in Minnesota not everyone is an advocate. One blogger: "I get how the zipper merge is supposed to work, the problem is the people who don’t. ... The zipper merge is going to be this century’s conversion to the metric system in the ’70s. Great idea, made perfect sense, and was dead on arrival."

Much like a roundabout, I don't know how you could fail to understand how it works. Having never experienced such a thing before, I found it exceedingly easy to understand. Mind you, I have underestimated the stupidity of other drivers before.

Even if some people don't catch on to the concept of a zipper, I think it's worth trying out here in Winnipeg because it eliminates the dilemma of deciding between two bad options: burn 5 minutes of your life in a line of cars, or be rude and selfish by cruising to the front of the queue.

Taking turns is something we're taught to do as little kids. As adults driving cars it shouldn't be that hard.


Glen said...

I agree, it's a nice idea (which city was it that actually used quick change traffic lights to control the zipper feeds?) but, like many people, I'm doubtful it will work.

Too many people don't see the "rush by others to get ahead" option as being rude or unfair - it's an opportunity that they've jumped at, and been rewarded for being aggressive & selfish.

The principles of democracy & capitalism that are taught in school trump any well intentions of turn-taking, unfortunately.

bgilchrist said...

It all depends on how it is managed. If everyone zipper merges, then it works fine. If ( as is the case on NB Pembina, you can zipper merge and get in without really causign someone to slam their brakes or cut someone off, fine.

But too often in this city, people blast to the front of the line then attempt to cut someone off in ofer to get in right at the front. And then people wonder why it doesn't work in this city.

Of course, nobody in this city knows what a merge is and how to use one anyway, so why should we expect people to know how to zipper merge?

cherenkov said...

@Glen: I need to re-read Adam Smith's chapter on merging traffic.

@Brian: even if some people do it, it's still an improvement.

Anonymous said...

Its not really that complicated. For a sample see Lions Gate Bridge, works everyday, all the time. Its called common courtesy with a dose of common sense.

Anonymous said...

Form even length lines. It should be basic human nature to go into the shortest line until they look pretty much equal. As a result there would be no 'cutting', no animosity nor passive aggressive, 'you're not getting in MY lane' BS.

Maybe stop putting up signs indicating *which* lane ends. Could work, could also be hilarious.

cherenkov said...

.. or instead of ending one lane, merge both into a middle lane. I.e., end the outside half of each lane so that both merge towards the middle. Both lane are equal. Should promote taking turns.

John Dobbin said...

At Kenaston right by the IKEA, there is a lane that proceeds past the turn off and over the rail tracks. It is a breeze past point where we see people zip past and then result in huge animosity as things narrow off to two lanes again. I should point out that traffic lights at IKEA has been smashed twice already,

cherenkov said...

That area was never designed properly.

Anonymous said...



Howard Dueck said...

good points. I especially appreciate the explanation of a freeway, as our government does not seem to understand those complexities!

Anonymous said...

It can work once people get used to it and can be relied upon. The Lower Mainland BC does not have Zipper Merge signs anywhere, but it is the unwritten rule at all major choke points such as bridges or tunnels. Works even when 4 lanes reduces to 1 over 200 meters in full rush hour. I suspect that if people get what zipper merge is supposed to mean, that second lane will fill right up and it will be the job of the dominant lane to let the next car in.

ColbyCramden said...

The zipper merge is brilliant! However, management of road construction warning and redirection signage in Winnipeg is not. On 23 July 2013 23:24 "cherenkov" [our blog host I believe] mentions "end the outside half of each lane so that both merge towards the middle." This solves the whole thing except needing one final tweak: the road work is usually needing access to one or another of the lanes, so the centre-lane would perform best as a short-run choke-point, which would then arc gently over to the single available lane for all. For those in the know [residents, frequent commuters] balancing line length would be the goal, and the shorter line would always get the next available car. Nice.

cherenkov said...

Colby: yes, that was the idea .. merge into the middle then the single flow could be directed left or right as needed. I think it would help.

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