
Washington, Minnesota officially endorse a “safer, faster” traffic merge - smacktoward
http://arstechnica.com/cars/2014/07/the-beauty-of-zipper-merging-or-why-you-should-drive-ruder/
======
malandrew
That video explanation made no sense to me. Basically the "interface"
presented to the drivers has not changed, so why would drivers deviate from
how they currently merge? Because the government said so? I don't see this
working.

However there are two solutions that could promote zipper merging:

(1) Force both lanes to the center before moving that center lane to the side
that is available ahead:

    
    
        ____________________________________________
                              \________/
        _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ________
                               ____________/
        ______________________/_____________________
    
    

(2) Present a long-barrier between both lanes well before the merge that only
permit late merging, so that those in the continuing lane feel morally
obligated to let those queued up in.

    
    
        ____________________________________________
                             
        _ _ _ _____________     ____________________
                               /
        ______________________/_____________________

~~~
Negitivefrags
In New Zealand we just have signs like this all over the place:

[http://i.imgur.com/AtaDOGX.jpg](http://i.imgur.com/AtaDOGX.jpg)

~~~
joelcollinsdc
Its pedantic, but I think this is sublty different than what is being dicussed
here. All over the US, there are situations where 2 lanes converge to 1 and
drivers "take turns" merging. But I think the scenario that is being discussed
is a little different, where there is 1 "working" lane and one "closed" lane,
the thought process of drivers in the lane that they know is 'closed' up ahead
is to merge early.

I wonder if cultures where queueing (like, in the grocery store) is not as
common as in the US have this problem? I suspect not.

~~~
JeanMertz
I live in the Netherlands, but drive through Belgium when driving home from
work.

There is one area where a permanent two-lane road merges into a single lane.
The funny thing is that (mostly) Belgians never use the second (left) lane
that eventually merges into the single right lane.

This always seems stupid to me, because it increases the length of the traffic
jam so much, that the traffic jam goes all the way over a roundabout, causing
stops for all drivers, even the ones not going in the same direction as us.

The worst thing is, whenever I use the left lane - which I do all the time
(and in return, pass 60 cars waiting in line), people sometimes get so angry
that I've had two trucks in the past few months hitting the gas and blocking
the left lane so no one can pass anymore.

Crazy people...

Last month a new sign was installed along the road "Please use both lanes,
drive all the way to the front and THEN start merging". Even now, people still
choose to wait in line at the right lane. It is as if people feel guilty when
they see a whole lane being empty and available to drive on.

~~~
vrikis
This is what it's like in Scotland!! People here get SO angry, thinking that
you have "skipped" all the other patiently waiting people... And then they
don't let you merge! And it makes absolutely no sense to me, because they
cause one reallllyyyy long traffic jam then...

------
molf
I'm surprised this is written like zipper merging is some kind of recently
discovered secret. Zipper merging (or weaving) has been standard practice in
parts of Europe for 20 years (maybe longer – I can't really remember anything
else). Since March 2014 it is even _mandatory_ in Belgium, and anyone merging
early may risk a €55 fine [1].

It has been repeatedly advocated and promoted by various governments in Europe
[2] and I doubt anyone questions its effectivity. Some experiments have been
done in the past with alternative methods like zipper merging with groups of
cars, but this is only applied when traffic can be regulated (with lights or
traffic controllers). The nice thing about zipper merging is that with enough
public knowledge, drivers can regulate merging themselves.

[1]:[http://www.vandaag.be/binnenland/145761_ritsen-verplicht-
van...](http://www.vandaag.be/binnenland/145761_ritsen-verplicht-
vanaf-1-maart.html)

[2]:[https://www.youtube.com/watch?v=TNhnLYI2Efw](https://www.youtube.com/watch?v=TNhnLYI2Efw)
– Dutch government TV ad from 1989 which explains and promotes zipper merging
(albeit very poorly, I must admit).

~~~
ChikkaChiChi
It's not the concept that is newsworthy, it's the decision to actively promote
it that is.

~~~
dubfan
More importantly, the decision by American transportation authorities to
promote it is newsworthy. It seems like Northern Europe takes a more
systematic and serious attitude towards driving, while the American attitude
is more "eat my breakfast while driving 50mph in the left lane, and give the
finger to everyone who passes me on the right"

------
notacoward
Zipper merging works great as long as everyone on both sides is willing to
alternate (or if strong enforcement requires them to do so). Otherwise,
letting "late mergers" scream past fifty "early mergers" often creates a
situation worse than simple early merge. There's plenty of blame to go around.

* The vast majority of the people blasting down the late-merge lane clearly have no interest in alternating or merging into the largest/safest gap at the end. They'll squeeze into the smallest latest gap that they think they can possibly get away with.

* Quite a few of the early mergers feel they've already done their part. Whether they're competitive, territorial, or sincerely concerned with traffic flow/safety, they're not much interested in alternating with the late mergers either.

So how does this play out _every effing day_ at construction projects and toll
booths? You end up with a few late mergers playing chicken with a few early
mergers at the chokepoint, jockeying for position inch by inch and degree by
degree as they try to cut each other off. That's where all the "vigilantes"
come from - they're people who are _already_ stuck in the aftermath, they know
how it happened, and they have decided that they'd rather settle for forced
early merge than botched zipper merge.

Without enforcing proper merge behavior _on both sides_ , zipper merge just
becomes a big Prisoners' Dilemma game with a few defectors screwing all of the
cooperators.

~~~
john_b
> _" Without enforcing proper merge behavior on both sides, zipper merge just
> becomes a big Prisoners' Dilemma game with a few defectors screwing all of
> the cooperators."_

Except unlike prisoner's dilemma, it's not a zero (or negative) sum game. The
entire traffic flow can speed up if zipper merging is done. The "late mergers"
don't have to risk losing their game of "chicken" while the "vigilantes" don't
have to deal with the reckless maneuvers of some of the former.

People don't do zipper merging because people are human and drive emotionally
[1]. The stereotypes of the conservative early merger claiming the moral high
ground and the reckless late merger doing anything to save a few minutes are
the cultural results of this mentality.

[1] Another example is the special breed of driver who stops the traffic flow
on a major road (which has the right of way) to let someone on a minor cross
road or parking lot exit onto the major road, thus inconveniencing everyone
behind them for the self satisfaction of having helped the one person they can
see.

~~~
ics
> [...] inconveniencing everyone behind them for the self satisfaction of
> having helped the one person they can see.

Or because you know that otherwise they'll be at that crossing for the next
hour if nobody's willing to let them by. Perhaps there are some funny
allusions to net neutrality to be made here...

~~~
dionidium
Just because you want to turn left, doesn't mean you have to sit helpless
waiting to do so. You're allowed to turn right and locate a safe place to turn
around.

~~~
ics
I have sympathy for left-turners in particularly busy intersections where
there is no turn light. Driving in NYC, you pretty much have to nudge as close
to the opposing lane as you can until the light turns yellow/red and you can
scoot yourself out of gridlock. Furthermore, you must account for streets
which are one way, too narrow, full, or active to stop and turn around.
However, this was not the situation I was really talking about at all.

The scenario I had in mind while writing my post is that of the local road
which crosses a major stretch of highway. Such highways might be an actual
interstate, a busy two-lane highway, etc. One of the worst types of road to
cross is the one that is far too wide for its own good– an ambitious 6-lane
road with not enough traffic to ever be full (Trenholm Road in SC, ahem), but
enough so that drivers spread out across all lanes and make crossing very
annoying sometimes. There are parts of the Taconic (NY) that pretty bad to
cross, though I'm usually the one on the highway. The local cross sometimes
gets backed up 5-10 cars, 2-3 of which are stuck in the median. Getting on the
highway or going around by going the next town can add 10+ miles. Letting
someone cross by slowing down a bit and changing lanes is not, in my opinion,
a smug assault on the efficiency of those driving on the highway... it's just
something a few people do when they recognize that nothing is very efficient
anyway. (Note that I haven't said much about safety because it was only a
small part of their comment, and not the part I was responding to. I hope it's
clear that I am _not_ advocating for people to test fate by slamming their
brakes to let someone curtsy across the pavement.)

------
ChikkaChiChi
In practice zipper merging works amazingly well. MNDOT has used signage to
tell drivers to maintain speed and stay in their lanes for the past few years
of construction in the northern Twin Cities. You wouldn't believe how much
faster traffic moves when these simple reminders are posted.

The problem is that without the signs (and enforcement) drivers in the Twin
Cities Metro regularly shoot to seal any gap that may allow someone signaling
to enter their lane, regardless of the distance to the merge point. This
behavior also occurs in on-ramp situations where drivers are entering the
highway and slow lane drivers refuse to move over, but don't want you in front
of them!

I have driven in many states and never has the mentality that you cannot, MUST
NOT, let someone ahead of you been as bad as it is here. Minnesota Nice,
indeed.

~~~
dusing
I live in the Twin Cities and "Minnesota nice" means merging incredibly early
when a lane is posted as closed. As a transplant I can always count on getting
and extra 1/2 - 1 mile ahead by staying in the closed lane.

It is getting better, but still 40% of the time the car at the end of the
zipper merge is NOT happy to see you, and thinks they are letting you in.

Signage is helping at the big construction areas.

~~~
tedsanders
The whole point of zipper merging is to minimize speed differences between
lanes for maximum efficiency and maximum safety.

The proper way to execute a late zipper merge is to match speeds and merge at
the end.

You are not correctly zipper merging if you are passing other cars before
merging at the end.

~~~
nhaehnle
dusing is probably talking about the (rather common in some places) situation
where one lane has half a kilometer of slow-to-standing vehicles, while the
other lane is entirely free.

In this situation, _of course_ you're going to pass those other cars (please
do so slowly and carefully if you pass them on the right). It would be
ridiculous to slow to a standstill with half a kilometer of empty road ahead
of you.

When zipper merging works correctly, you usually _cannot_ pass cars in the
other lane, because traffic automatically flows in the right way. So in a
sense you are right that if you pass cars in the other lane, _someone_ is
doing the merging wrong. That someone are the people in the crowded lane,
however, not the one of who is passing them in the empty lane.

~~~
tedsanders
Thank you for your charitable interpretation of my comment, but in fact I
don't think it is ridiculous to drive slowly in the right lane. I really do
think that's the correct strategy.

Even if the second lane is free, it's safer and more efficient to match speeds
with the first lane. And shouldn't we take actions that maximize safety and
efficiency? Note that there is no global gain from speeding down the right
lane, since the bottleneck is what controls the flow.

I suspect many of you will disagree with me, so let me address some possible
concerns.

Is it safer? Yes. Generally driving is safer when all vehicles are moving at
similar speeds. Relative speeds being low mean that there's plenty of time to
react to danger. It's also safer because other drivers are more predictable
when going at a single speed.

Is it more efficient? Yes. The bottleneck is constraining the flow, so gains
before the bottleneck end up being useless. The important thing is to make
sure that traffic is entering the bottleneck at a fast, consistent speed.
Predictable and uncontested merges are the best way to stop the traffic lane
from slowing. Going at the speed of the left lane offers two benefits here.
First, it's easier and more predictable to merge when you travel at the same
speed as other traffic. Second, if you travel at the same speed as other
drivers, they won't get annoyed at you and attempt block you out (to
everyone's detriment).

Is it weird? Yes. Driving below the speed limit with space in front of you is
an odd thing to do. But in this case, you're matching the speed of traffic and
there's no global opportunity cost because the bottleneck ahead is the
constraint, not your speed. It's weird, but it makes sense.

The reason that the zipper merge is recommended by so many travel departments
is not because it's straight-up more efficient than other merging strategies -
it's because it's more robust to defection.

But just because it is robust to defection, that doesn't mean the optimal
strategy is to defect.

For those of you who disagree, why? Could you point out where you feel my
logic fell short?

~~~
nhaehnle
Hmm, probably we don't disagree by much anyway. Perhaps it's clearer if we put
some numbers to it: Suppose that the occupied lane is doing stop-and-go (due
to the natural waves occurring in traffic), with a maximum speed of 20km/h.

What should the speed be for somebody in the unoccupied lane? Certainly 80km/h
is far too much. On the other hand, it also doesn't make sense (IMHO) to come
to a complete stop in the free lane just because cars in the occupied lane
have to stop. I feel that a steady 30km/h is a good compromise.

Does that sound reasonable to you?

~~~
tedsanders
If the left lane is going an average speed of 10 km/h, then I believe the
right lane should drive at 10 km/h. Doing otherwise is being selfish and
unsafe, with no global benefit. It feels weird, but it makes the most sense as
far as I can reason.

------
pwenzel
As a driver in the Twin Cities area, I can back the stereotype that
Minnesotans don't know how to zipper. It speaks so truly of the Minnesota
condition.

People begin often merge far too early, and get offended when folks like
myself "budge" at the front of the line.

Learn to zipper, darn it!

Edit: This TPT parody, How to Talk Minnesotan, shows how to drive in Minnesota
(scrub to 11:58):

[http://video.tpt.org/video/2365042610/](http://video.tpt.org/video/2365042610/)

If you ever lived in rural Minnesota, you know this is completely dead on.

~~~
jerf
People think they are being nice. Education can work very quickly and
efficiently on such people by showing them they aren't being nice after all.

I live in the US in a "nice driver" area with a number of traffic circles. On
a fairly routine basis I come up to a traffic circle and stop because there is
someone in it coming towards me, but then they try to "helpfully" stop and
wave me in, slowing down themselves, everyone behind them, and even slowing me
down as now I'm confused and less likely to move. Or I get stuck behind such a
person in the circle and have to stop gracelessly as they unexpectedly stop in
the middle. (This being a traffic circle it's not that dangerous due to lack
of speed, plus over time I've learned to predict who is going to do this based
on the car body language...) I haven't yet witnessed this causing an accident
but it's just a matter of time, it snarls things up that badly. They _think_
they're being friendly. If someone would explain that "friendly" is using the
traffic circles as designed, they'd probably do the right thing in the future,
but so far I haven't discovered the hand gestures that properly express that.

~~~
jrs235
Someone died today because someone didnt know how to merge (the on ramp is to
get up to speed) and probably because someone thought they'd be 'nice' and
slowed down. My guess is both vehicles at the merge point slowed drastically
and everyone on the interstate were too close to each other for the speed and
volume of traffic. Sad.
[http://www.wxow.com/story/26101450/2014/07/24/breaking-
part-...](http://www.wxow.com/story/26101450/2014/07/24/breaking-part-
of-i-90-closed-due-to-an-accident)

Edit: or perhaps we should fault inattentive driving on the truck driver.
Still sad.

~~~
jrs235
It sucks because the speed limit through there should probably be 40 not 55
when traffic is heavy. The problem then is people on the interstate still
tailgate and/or don't leave adequate room to allow zipper merging.

Edit: to clarify, the slower speed should be that low only now during
construction and lane closure.

------
barnwell5
"Optimal" means different things to different people. What the DoT may be
trying to maximize (safety, lack of frustration) is generally not what drivers
want to maximize (overall speed) and I think there's confusion about that when
zipper merge is discussed. The linked article uses the word 'faster' but the
Minnesota pdf they cite actually says "Our analysis has shown that the Zipper
System has no effect on travel time through the work zone."

Here is a Michigan DoT paper[1] from 2007 that analyzed zipper merge studies
in various states and countries. Only 1 out of 6 showed statistically
significant increase in throughput.

"It was found that the system did not increase the throughput or decrease the
length of the queue." (Netherlands)

"It was found that the throughput did not increase, but the queuing was more
efficient and there were less frustrated drivers." (UK)

"Beacher, Fontaine, and Garber (12) found that there was an increase in the
throughput and a decrease in the queue length; however, the difference was not
statistically significant." (Virginia)

"However, flow did not appear to be significantly affected by the dynamic late
lane merge system." (Kansas)

"The data from both of the studies shows that the typical queue length
decreased and the lane usage were nearly equal, but the throughput decreased
slightly." (Minnesota)

"The results from Maryland’s deployment show an increase in the overall
throughput, a reduction of the maximum queue length, and a more even
distribution of volume between lanes."

1:
[http://www.michigan.gov/documents/mdot/MDOT_Research_Report_...](http://www.michigan.gov/documents/mdot/MDOT_Research_Report_RC1500_Part1_209842_7.pdf)

------
justinpaulson
The problem is, there are two very different ways to merge based on the flow
of traffic. If traffic is moving, then early merge is the preferred method. If
traffic is not moving, then a late merge makes more sense.

The problem is people who do not merge early when traffic is flowing. These
people wait until the last second to merge instead of finding an opening while
traffic is flowing and force traffic to slow down in order to let them in.

And the really real problem is that the average driver in the USA has no idea
what they are doing and should probably not be driving at all. It would take a
huge change in the way we train drivers to get them to recognize when they
should use each type of merge. And forcing people into one way to merge or the
other is not really the "fastest/safest" way, because it varies on conditions.

------
joshstrange
I have to deal with such a merge almost daily as the main road I use is under
heavy construction. I am an "early merger" mainly because the people in the
left lane (right lane goes away) will not let you in if they have a choice and
it is widely seen as being a "douchbag" if you fly down the right hand lane
expecting to be let in at the end. I'm not saying that I disagree with this
article in fact I've sat in near standstill traffic in the lefthand land and
I've had plenty of time to wonder if merging at the merge point does make more
sense, which I think it does.

I personally wish they would have closed off the entire right lane as there is
only a couple hundred meter stretch where this road is 2 lanes and so I wish
they had just kept it a single lane all the way though while construction was
underway. Here is the road in question:
[http://s.joshstrange.com/oRq9.png](http://s.joshstrange.com/oRq9.png) From
where you see Louie Pl it turns into a 2 lane road then goes back to 1 lane at
Opportunity Way then back to 2 lane where you see it get fatter again. However
construction makes the road for a mile or two after Opportunity Way 1 lane
only so the 2 lanes for such a small stretch are almost more trouble than they
are worth.

------
beejiu
As a driver in the UK, I don't understand what exactly the difference between
a merge and an overtake is. It is quite common here for roads to change from 2
lanes to 1 lane. There's no signage telling you to merge. There's no rules
telling you what to do. You just operate by the same logic as an overtake, and
you'll find that, quite naturally, everybody 'zip merges'. Perhaps the reason
for the inefficiency is having rules in the first instance.

~~~
o0-0o
The difference is localized. The UK is much smaller, and therefore has less
regional tastes about merging. In the Midwest and Eastern seaboards of the US
you have polite and diverse people respectively. In California, you have
experienced drivers. California works like the zipper merge already, and the
rest of the US is flummoxed by what to do - depending on where you are.

~~~
teamonkey
I don't think it's so much about being smaller, more that there is only one
set of rules for the whole country and those rules are more strongly enforced.
Also, from what I can tell, the driving exam is far more rigorous in the UK.

~~~
bsder
Speeds in the UK are _way_ slower than the US, and cars are way more expensive
to run in the UK than the US.

Consequently, everybody and their dog doesn't expect to drive a car in the UK.

~~~
jameshart
Demonstrably and comically false (except on the running costs front - you're
spot on there). Not only are UK motorway speed limits 70mph (and traffic
speeds higher still), 70mph is also the limit on most dual carriageways, and
major undivided roads have a 60mph limit. In the US you'll rarely find a road
with no central divider with a limit above 45, and only major multilane
highways go to 65 and higher limits (depending on state).

------
bpdenimy
So Negitivefrags is probably right that the best top-down way to get this to
happen is to place signage. But it's sort of fun to think of the best bottom-
up way to get this to happen, assuming your local government isn't putting up
signs.

For example, I love going a constant speed in start-stop traffic (letting gaps
appear ahead of me then closing them as traffic stops) so as to smooth out the
ride of everyone behind me.

So what's the optimal way to get this behavior to spread? It's probably not
just to gun it to the front of the line and yell 'zipper!', everyone just
thinks you're an asshole.

VikingCoder suggests "If you want to show people how it's done, you go the
same speed as the cars next to you in the open lane, and zipper merge at the
end." I love it, because it's really awkward, and people will note it enough
to _maybe_ think through what's happening, what your logic is.

But I dunno, maybe there's something else more clever out there, too.

------
Brian-Puccio
Locally (metro NYC), I've heard this referred to as "alternate merge" and it's
usually mentioned in the context of someone saying something along the lines
of "there was a traffic jam due to an accident and then when it was MY TURN to
go, the person in the other lane didn't let me in". Usually there's a comment
about how the plates were from out of state, too.

This is not to be confused with, e.g., a road that splits and the left lane
split it moving fine and the right lane is backed up and a driver in the left
lane waits until the last possible second to move over, often times coming to
a complete stop, thus backing up what should be a free-flowing lane. No, in
that case you didn't move over in time, you don't get to slow down traffic,
you take the lane you're in and keep going, you'll have to take the next exit.

------
iLoch
This works pretty well where I live. Here in Vancouver, a major bridge that
takes traffic into the downtown core is only 3 undivided lanes. There's a huge
amount of traffic flowing over this bridge in the morning as it connects work
to home for somewhere in the range of 60,000 - 70,000 commuters daily. From
the residential side of the bridge, traffic zipper merges from 4 lanes into
either one or two depending on the time of day. The traffic is coming from two
different sources (west and east) so each source will zipper merge and then
the zipper merged lanes will zipper merge onto the bridge. I honestly have no
idea what this would look like any other way.

Zipper merges are obvious and natural if you set them up right - what it takes
is the knowledge to do it. Once people know that they should be yielding to
the mergers, the whole merge process speeds up considerably.

~~~
arecurrence
I see this as well whenever crossing the Lions Gate southbound. I suspect if
there weren't 4 lanes merging together it would be a different situation (I
don't see people doing this correctly in other parts of the peninsula that
merge).

------
adrr
I thought the zipper merge was the standard way to merge? You stay in your
lane till the merge section(end of your lane) and its every other car. Maybe
its a California thing.

~~~
kelnos
I've rarely seen people in (northern) California do proper zipper merges. CA
has some of the most clueless and inattentive driving I've ever seen.

~~~
Noted
I rarely have seen issues in California with zipper merge, when the lanes are
actually merging. Most of the time the issue I've seen is when people are
cutting over from a turn only lane to try and force their way to go straight.

~~~
joshwa
Turn-only lanes (using a turn-only lane to go straight) is where I see the
worst cheater/vigilante behavior. (It's always BMW's who do it, too... )

Those turn-only lanes are just wasted capacity that could be used to carry
more traffic into a zipper merge. I'm guessing that at some peak hour the turn
lane has utility, but at reverse-peak they should be able to switch to a
regular lane leading to a merge point.

~~~
dubfan
Zipper merging inside an intersection will almost certainly lead to gridlock
due to incomplete mergers before the light changes.

~~~
joshwa
Referring to exit-only lanes on highways, not signaled intersections.

------
kelnos
Since this is a solution that requires "everyone" to change their behavior, my
guess would be that it'd be more productive (and faster?) just to wait for
self-driving cars to be prevalent enough that they "set the tone" for what
constitutes normal driving in these situations.

------
Cthulhu_
I've recently sold my car (a crappy Opel) and replaced it with a motorcycle,
and my behavior in traffic has definitely changed re: merging. The other day
there was a mile-long queue in front of a highway exit, traffic was up on the
hard shoulder or whatever the term is. If I were still in my car, I would've
been polite and just queued up - would probably cost me 15 minutes to get to
the exit and further on.

Now though, I did full D-bag and just drove past most of the line. At the
exit, the queue started breaking up, leaving plenty of room for me to merge
into.

Actually if everyone took a motorcycle instead of their car, most of these
problems would be gone. But that's probably a silly argument.

------
buro9
This sounds like Italian driving.

If you haven't driven in Italy, expect zero braking during merges. I really do
mean zero.

Trucks will move over (at speed), cars will move over (at speed). The "zipper"
action is seamless and fluid, even when the vehicles are temporarily extremely
close to each other.

Just look down the road, see a merge may happen. If you are a truck move over,
if you are a car you may need to accelerate to move over.

The first time you experience this it looks and feels scary, especially as
people merge with only 50cm-1m between vehicles. But once you're used to it
you realise that you virtually never slow down and merges are really quick and
easy.

------
curtis
Late merging works fine in Seattle, and in my experience the lane that's
closed moves substantially faster than the open lane because Seattle drivers
will actually let you merge in. That's not how I recalled it working when I
lived in Texas though. In Texas if you got caught in the closed lane you were
pretty much stuck there for a while, while the guys in the open lane whizzed
by too fast for anybody in the slower (possibly stopped) closed lane to merge
safely.

~~~
arjie
If the person merging late had to stop, then it means they went too far
without getting a space (because they didn't take the chance they were given
or no one gave them space). This is the problem with zipper merging: if
everyone gets it right it's beautiful but the failure mode is near
catastrophic (effectively stopping one lane) and easy to get into. One or two
bad actors can ruin it.

------
aenean
Traffic management is a fascinating intersection of sociology, fluid dynamics,
behavior change, and urban planning.

If you're interested in this field, I can't recommend the work of Tom
Vanderbilt enough. His book "Traffic" brought urban planning to the masses in
the same manner "Freakonomics" made social and public policy accessible.

[http://tomvanderbilt.com/traffic/](http://tomvanderbilt.com/traffic/)

~~~
iLoch
I've always found it fascinating how a single bad driver can cause a massive
traffic jam ("ghost traffic jam"). I think this should be taught when you're
learning to drive as part of some sort of mandatory basic training - zipper
merges should be in there too.

------
blahedo
A lot of people and a lot of articles discuss resistance to this as a matter
of misguided "politeness", and a _LOT_ of the support for it carries a tone of
smugness---there is definitely a weirdly emotional component to this.

But here's the fairly objective thing I want to know: the people who have been
(very negatively!) described as "early merge vigilantes" generally operate by
staying in the lane that goes away but pacing the cars in the other lane,
blocking the people behind them from zooming ahead; and then quickly merging
just before the lane goes away (usually an enabler in the other lane will make
this work better so neither has to slow down or stop at this point). So here's
the question: isn't this _exactly_ what the zipper merge is supposed to
accomplish, with both lanes travelling the same speed? Why is this so-called
"vigilante" behaviour being described as bad? If a driver that's smug about
their late-merging behaviour being optimal is going noticeably faster in their
lane than the lane that merged, doesn't that mean that what they're doing is
exactly _not_ a zipper merge?

Perhaps the answer is that the ideal to aim for is not "late" merging, so much
as "speed matching" merging: when there is a merge ahead, if you're in the
faster of the two lanes (whichever one that is!), slow down a smidge _now_ and
then you won't have to screech to a braking halt at the merge point (and
you'll also make the flow better for everyone behind you). Zooming ahead
because there's a briefly clear section of road may be "late" merging in some
sense, but is not the same thing as "zipper" merging and is not improving
flow.

~~~
lamontcg
The point is also to fill both lanes, so your last suggestion doesn't work
very well.

And I've been known to be a "vigilante" before. I'd give it up in a second if
people would actually start filling the other lane.

There's a merge here in Seattle -- the southbound I-5 collector-distributor
with the onramp to 90 where it merges back into I-5 -- where people zipper
halfway reasonably well and I actually routinely stay in the less-filled lane
and late-merge.

Washingtonians are awful at late merging/zippering though. Even when people
are late merging you get tons of people merging early and then the line moves
forwards and it screws over the lane that is being merged into. People just
won't simply drive forwards to the merge spot.

Dividers might help in some cases, but when the road is empty and everyone is
doing 60+ mph the dividers are going to cause accidents. You could try to put
down double lines on the road to block merging, but nobody pays attention to
those here either.

Getting zippering into drivers ed and getting them early, spamming the TV with
ads, and putting signs up all over the place and carpet bombing the message
might work.

Happy to see them doing this.

Oh yeah, and there's definitely an emotional component to it. When I'm stuck
behind 50 cars and some asshat in a BMW goes speeding past to late merge the
world goes completely red. I would love to stop doing that. If everyone
zippers the asshat just has to pick a lane like everyone else, and there's no
way to "cheat".

And yes, "asshat" and "cheat" are all in my own brain. I find it extremely
difficult to stop thinking that way when I see it though.

------
dr_faustus
Well, this is (has always been) the standard in Germany and it works pretty
well. We even have one of those great German words for it:
Reißverschlussverfahren (= zipper procedure).

Concerning people not letting you in: In case of ending lanes (except ramps)
you are obliged to let people in. There is always the occasional douchebag
that doesnt but it almost never happend to me. At worst you have to wait for
one car to pass.

------
dubfan
I see the negative effects of early merging regularly. The freeway onramp
closest to my home leads to a frequently congested portion of the freeway.
People merging ASAP often end up having to stop on the onramp, blocking
traffic behind them which can then back up onto surface streets. They do this
despite the onramp merge lane continuing for quite some time after it first
connects to the freeway.

------
thirdstation
Perhaps instead of merging one lane into another, the animosity toward late
mergers can be alleviated by making all lanes move.

If no one feels like they are in the free lane, they'll be forced to
cooperate.

So, on a two-lane highway, make one center lane and have both lanes funnel
into it. then you can move that free-flowing lane wherever you need.

~~~
thirdstation
malandrew types faster than me. And has better ASCII art.

------
ch4s3
This is pretty brilliant, but how do you encourage this without a light or
years of including it in driver education?

~~~
dubfan
Even including it in driver's education isn't likely to help. Driver's
education teaches people to use blinkers, but from informal observation I'd
estimate 1/3 of drivers in my area don't use their blinkers at all.

------
emerod
In contrast to the states promoting zipper merging, Indiana recently
redesigned some interchanges to effectively eliminate the single merge point.
They added extra lanes so that one "preferred" lane (the one that formerly
backed up everyone for three miles) is no longer the sole access for any of
the off-ramps. Now, everyone has basically three miles in which to merge into,
out of, or across this lane, rather than piling into it all at once.

This picture doesn't show the full extent of the redesign, but the yellow
highlighted part is the former problem lane.

[http://www.in.gov/indot/files/MPOICI69_NBInterchange_2012.JP...](http://www.in.gov/indot/files/MPOICI69_NBInterchange_2012.JPG)

[http://www.in.gov/indot/3071.htm](http://www.in.gov/indot/3071.htm)

------
Jach
Alternatively... Since the government forces me to bring my vehicle to one of
their locations every other year for emissions testing, have them install a
speed control unit with a beacon to communicate with other cars. (Yes it will
be harder to install on some cars than others -- even just the beacon would be
valuable.) Over the course of five years, retrofit every vehicle with a beacon
and have it already installed on new cars, have severe penalties for vehicles
caught driving around not broadcasting their signal, and now everyone can have
a bit more automation in their automobiles since the systems will enforce safe
merge gaps and other nice things like computer-enforced speed limits. Plus it
prepares everyone for a fully automated experience that can come sometime in
the 2020s.

I can dream right?

------
colanderman
"Merge rudely."

It's only rude if no-one else is doing it (i.e. you're speeding ahead of
everyone merging early). If everyone stays in their lane until the merge
point, no-one's zooming ahead, so it stays fair.

------
walesmd
On most military bases, and therefore in military heavy towns like San
Antonio, the zipper merge is used to great effect. I've even seen it used at
T-intersections (where the perpendicular road must stop) - on almost every
military base, when traffic is backed up, you'll see drivers immediately
implement the zipper - one car from right of way, one from the intersecting
road.

------
IgorPartola
I really wish people would actually do this. I call this "driver karma". For
every person you let in, you get to go in front of another person. If everyone
followed this heuristic, we wouldn't have a problem. Oh, and if you let a bus
full of people in front of you, your score is increased by the number of
people on the bus :).

------
anishkothari
This 2008 article in Wired[1] changed the way I merge forever and it has paid
off when I drive in Chicago's endless construction and traffic.

[1][http://archive.wired.com/culture/culturereviews/magazine/16-...](http://archive.wired.com/culture/culturereviews/magazine/16-08/pl_print)

------
zobzu
Early merge feels more polite, late merge is safer and faster on the overall
traffic (and much faster if you're the only one doing it + you're seen as
impolite)

They want to make it more common. Pretty sure everywhere in EU everyone late
merge. In west USA at least, I only see early merges.

------
niix
Seems great in theory, but what if the other drive isn't willing to let you in
- or - vise versa?

------
mark-r
The nicest thing about zipper merging is that everyone can see the fairness of
it, when it works. It's the lack of fairness that most infuriates people with
the free-for-all system.

Minnesota still does a very poor job of letting people know where the expected
merge point is.

------
GFK_of_xmaspast
I grew up and learned to drive in Washington; I moved away 20 years ago but
come back regularly, and if there's one thing I know about Washington drivers
it's: they can't merge for shit.

------
Shivetya
With the low cost of portable lighting and signage why not traffic light both
lanes and alternate who goes through, just like we do with highway congestion
on ramp lights?

------
mchanson
I've never understood early merging. Why eliminate a lane of traffic before
necessary.

------
txlMan
In Germany we've been doing this for decades. Welcome to the future.

------
GreenPlastic
I'm the asshole who merges in at the last possible second. It's really
annoying that they're doing this as I routinely save 10 minutes off my commute
by jumping into lanes that will eventually merge in.

------
korzun
Want faster and safer traffic merging?

> Part of DMV road test should cover highway and emergency (road block)
> situations. > Utilize responsive testing (how fast person reacts to
> something). Could be an in-house application. > Older drivers should have
> extra testing once they hit certain age. > Re-test drivers every 10 years. >
> Driving and doing your make up? Reading a book/iPad? Eating chipotle?
> License suspension. Bye bye.

In general every situation where I had to steer out of the way was caused by
an older person who should NOT be driving.

Zipper merging on New York roads? Fuhgeddaboudit.

~~~
DanBC
> In general every situation where I had to steer out of the way was caused by
> an older person who should NOT be driving.

Do you have any statistics about driving accidents? Because all the stats I've
seen show that older drivers are safer better drivers than young people, and
this is especially true when comparing to young males under the age of 26.

~~~
korzun
Those statistics do not include cases where older person switches lanes into
your car and you luckily avoid it.

They also do not include cases where other people cause accidents and go on
their marry way while you wreck your vehicle avoiding them.

Like the other poster stated, it's young (novice drivers) and old drivers.

It's also a scientific fact that you reaction time decreases as you grow
older.

>Because all the stats I've seen show that older drivers are safer better
drivers than young people.

Sure.

[http://consumerreports.org/cro/magazine/2012/10/teenagers-
an...](http://consumerreports.org/cro/magazine/2012/10/teenagers-and-older-
people-are-the-riskiest-drivers/index.htm)

[http://www.cdc.gov/motorvehiclesafety/older_adult_drivers/ad...](http://www.cdc.gov/motorvehiclesafety/older_adult_drivers/adult-
drivers_factsheet.html)

> Age-related declines in vision and cognitive functioning (ability to reason
> and remember), as well as physical changes, may affect some older adults'
> driving abilities.5

> Per mile traveled, fatal crash rates increase starting at age 75 and
> increase notably after age 80. This is largely due to increased
> susceptibility to injury and medical complications among older drivers
> rather than an increased tendency to get into crashes

~~~
TheCoelacanth
> This is largely due to increased susceptibility to injury and medical
> complications among older drivers rather than an increased tendency to get
> into crashes

So it's not that they are more likely to get into crashes, it's that they are
more likely to die from the injuries that a crash causes while a younger
person would survive if they received the same injuries.

