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Zipper Merge News

Started by Mergingtraffic, September 04, 2016, 10:54:00 AM

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Mergingtraffic

I saw this article in the Danbury, CT News-Times:

Traffic jams are a daily headache on I-84 in Newtown and other places where the highway goes from three lanes to two. It can be frustrating seeing a stretch of that third lane sit empty as motorists move over to the other two and wait ... and really frustrating when the stray car zips by you using every last inch of the lane that's disappearing before moving over and cutting in front of everyone else.
The etiquette around when, exactly, you are supposed to move over, can be tricky. Connecticut is an "early merge"  state, meaning you are supposed to move over as soon as you can after seeing signs saying that the lane you are in is going away.
But other states, including Minnesota and Kansas, have implemented an alternative approach favored by many traffic engineers, and Connecticut is considering using it for construction zones.
It's called the "zipper merge,"  and calls for drivers to wait to merge until their lane is almost closed and then take turns with the car in the open lane when merging over.
Kevin Nursick, a spokesman for the Connecticut Department of Transportation, said that the state has favored the "early merge"  bo prevent drivers from getting stuck in a lane that is about to close or angering the drivers who poked along in the open lane.
But the state may ask drivers to use the zipper merge in construction zones when two lanes go down to one. This would allow drivers to use all lanes for longer, preventing congestion.
"If everyone is paying attention and takes their turn, then you can really keep the traffic moving,"  Nursick said.
John Ivan, a civil and environmental engineering professor from the University of Connecticut who studies road safety, said he supports the zipper merge. When drivers wait to merge, the majority of drivers in the designated lane wait a long time, while drivers who merge late cut the line, he said. If drivers use the zipper merge, the wait times are even and the line is not as long.
"Then, because that queue doesn't extend as long, it's a bit safer as far as drivers being surprised by sudden stopped traffic,"  Ivan said.
Still, the state is only considering the zipper for construction zones, Nursick said. In other merging situations, the DOT feels that traffic is moving too fast to safely pull off the zipper merge.
"You don't want to be waiting on someone's good nature and getting in at the last minute,"  Nursick said.
And the zipper merge only works if everyone knows to use it, he said.
"We've all seen it where folks will streak down that lane before it comes to end only to bypass more traffic,"  Nursick said. "And what does that result in? That results in traffic congestion for folks that are following the rules."

http://www.newstimes.com/local/article/Connecticut-considers-zipper-merge-to-ease-9200459.php

The article has me annoyed, so the CTDOT doesn't favor the zipper merge?!  So then, what's the point of giving notice of a closed lane if you're not supposed to use the available lane? Might as well just have one sign and close the lane then.  lol

I know CT DOT is behind the times or stuck in their ways, but c'mon.  The DOT comments kind of surprised me actually.
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vdeane

I have definitely noticed issues with people who streak down the lane and cut in when everyone else is doing an early merge.  It causes everyone else to have to wait even longer so one selfish person can cut ahead.

As far as I'm concerned, ranked from best to worst:
-zipper merge
-early merging
-early merging with some jerks trying to cut in line
Please note: All comments here represent my own personal opinion and do not reflect the official position of NYSDOT or its affiliates.

1995hoo

My problem with "early merging" is that if you have 50 drivers, you'll have 40 different opinions on where people should merge.
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Mergingtraffic

Quote from: 1995hoo on September 04, 2016, 05:03:06 PM
My problem with "early merging" is that if you have 50 drivers, you'll have 40 different opinions on where people should merge.

right and that's why I prefer zipper merging.  I just figured the DOT expected drivers to merge when the cones start to creep into the lane. 

But, unless there's a sign saying do a zipper merge, I don't see how it will ever be enforced.
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kalvado

There is a throughput limit of about 2000 vehicles per lane per hour. If there is more traffic than that, there will be a backup, zipper or early. If there is less traffic, there will be no backup, zipper or early. Even a short surge above 2k would create a backup.
Those who complain about "empty lane" and "inefficient use of space" are basically trying to kill a flock of birds with one stone. 

jeffandnicole

It's not a matter of strictly enforcing it...after all, people are still allowed to switch lanes if it's a passing zone. It's more important that people don't try to take matters in their own hands, such as trying to drive in both lanes, preventing one from pulling up in the lane to be closed.

Quote from: kalvado on September 04, 2016, 06:40:15 PM
There is a throughput limit of about 2000 vehicles per lane per hour. If there is more traffic than that, there will be a backup, zipper or early. If there is less traffic, there will be no backup, zipper or early. Even a short surge above 2k would create a backup.
Those who complain about "empty lane" and "inefficient use of space" are basically trying to kill a flock of birds with one stone. 

Also, such as what I came upon the other day...a stoppage in the work zone, due to moving equipment. Traffic didn't move for 10 minutes. Doesn't matter if you zipper early or not: traffic was completely stopped.

jakeroot

Quote from: Mergingtraffic on September 04, 2016, 10:54:00 AM
So then, what's the point of giving notice of a closed lane if you're not supposed to use the available lane? Might as well just have one sign and close the lane then.  lol

It's sort of a dilemma. On one hand, they're more or less required to give advanced warning of a lane-end scenario. But, they might have less early-merging if they didn't advertise the lane-ending at all. I think it's human nature to try and merge when you see the first "lane ends" sign, because you want to avoid A) being an asshole, or B) getting stuck later on because you passed on that gap 300 feet back. Thus, I'd prefer fewer lane ends sign. Two at most; one warning sign maybe 300 feet before the merge, and a final 'left' or 'right' black-on-yellow "merge" arrow where the lane physically starts merging. You certainly need to provide some warning, but some DOTs seem to go way overboard.

UCFKnights

Quote from: kalvado on September 04, 2016, 06:40:15 PM
There is a throughput limit of about 2000 vehicles per lane per hour. If there is more traffic than that, there will be a backup, zipper or early. If there is less traffic, there will be no backup, zipper or early. Even a short surge above 2k would create a backup.
Those who complain about "empty lane" and "inefficient use of space" are basically trying to kill a flock of birds with one stone.
Sure, thats true... if there are no exits or entrances anywhere in the congested zone. As soon as you add some exits in, when you are preventing people from exiting by congestion in front of them, then you are creating an additional delays and a further backup by the number of cars that want to exit before the merge but cannot. If you have an entrance, it could be causing it to back up off the ramp creating congestion on another road by not using the available space, in addition to another zipper merge area not getting used so additional space getting wasted and further pushing traffic back.

kalvado

Quote from: UCFKnights on September 04, 2016, 09:05:29 PM
Quote from: kalvado on September 04, 2016, 06:40:15 PM
There is a throughput limit of about 2000 vehicles per lane per hour. If there is more traffic than that, there will be a backup, zipper or early. If there is less traffic, there will be no backup, zipper or early. Even a short surge above 2k would create a backup.
Those who complain about "empty lane" and "inefficient use of space" are basically trying to kill a flock of birds with one stone.
Sure, thats true... if there are no exits or entrances anywhere in the congested zone. As soon as you add some exits in, when you are preventing people from exiting by congestion in front of them, then you are creating an additional delays and a further backup by the number of cars that want to exit before the merge but cannot. If you have an entrance, it could be causing it to back up off the ramp creating congestion on another road by not using the available space, in addition to another zipper merge area not getting used so additional space getting wasted and further pushing traffic back.

Which is true if traffic has to merge right. If merging left, it is exactly opposite to what you described.
Another undereducated-traffic-engineer style thought is that problems with entering-exiting traffic are more likely in dense urban areas with multiple alternatives. Pushing traffic away from commitment point is beneficial, since it encourages and enables traffic to use alternative roads, and eases  throughput-limited congestion.  :pan:

texaskdog

Zipper merging only works if you have two lanes merging into the middle, and then traffic moves where it needs to.  I hate the budgers so much, the ones who do it every day in non-construction zones

Jim

I've seen the zipper merges work very well when they're signed so everyone knows what you're supposed to do.  I can't remember which state or states did that well.  There were signs saying a lane is closed ahead, but to continue using both lanes to the merge point.  Signs indicated that lanes should alternate at the merge point.  Then there was also a big sign, right before the orange cones in one of the lanes, that indicated the merge point.
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Rothman

I could make an entire fleet out of the ships passing each other in the night in this thread.
Please note: All comments here represent my own personal opinion and do not reflect the official position(s) of NYSDOT.

jeffandnicole

I've said that NJ always seemed to be a late-merging state, keeping the travel lanes available as much as possible.  On a current construction project on 295 which closes lanes at night, the only advance warning of a lane closure is 1,000 feet ahead!  And by that point, you can see the flashing arrow anyway.  I've seen them use 1,500 foot warnings as the first warning quite often, but never just 1,000 feet ahead!

kphoger

Quote from: jakeroot on September 05, 2016, 04:50:42 PM
Quote from: texaskdog on September 05, 2016, 03:52:32 PM
No, it causes people to think this is an acceptable behavior even when it is not a construction zone.  In rush hour all the good people get over early, and the jerks wait til the last second and jam in.

If everyone merged when they saw an open merge zone, the backup would be enormous. The only reason a lane drop-backup doesn't start 20 miles back, is because of those good Samaritans merging where the lane ends.

If there is little volume on the roads, then merging doesn't matter -- merging is only an issue because of too many people trying to squeeze into one lane. If there isn't a lot of people, there isn't a lot of squeezing.

This.  If early merging were taken to its logical conclusion (at the risk of argumentum ad absurdum), then things would work even better if everyone moved over five miles upstream of the lane closure.  Or, better yet, ten miles upstream.  Or, better yet, close the whole lane for its entire length.

The reason that lane is there in the first place is because traffic volume warrants it.  The less of the lane that gets used, the more over capacity the road becomes.  The main pitfall of the zipper merge is the possibility of people coming to the end of the usable lane and then coming to a dead stop because no one will let them over.  When that happens, everyone has to step on the brakes when the driver eventually moves in at 4 mph.  If people actually did what they're supposed to, which is take turns at the merge point, then that wouldn't happen.  Minnesota, IMO, does the signage right on this one:  "TAKE TURNS AT MERGE". 

My biggest beef with early merging is the vigilantes who think they're doing a public service by riding the center stripe and blocking everyone else from going around them (truckers seem to be the worst about this).  This is not helping safety, as it encourages road rage and shoulder riding.
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kalvado

Quote from: kphoger on September 20, 2016, 03:32:30 PM

This.  If early merging were taken to its logical conclusion (at the risk of argumentum ad absurdum), then things would work even better if everyone moved over five miles upstream of the lane closure.  Or, better yet, ten miles upstream.  Or, better yet, close the whole lane for its entire length.
You are confusing road with parking lot. Parking lot capacity in measured by square feet. Road throughput is not.


Quote
The reason that lane is there in the first place is because traffic volume warrants it.  The less of the lane that gets used, the more over capacity the road becomes. 

Throughput of the road is limited by the spot of  least throughput.
did you ever hear words "weakest link"? This is exactly the case.

jakeroot

Quote from: kalvado on September 20, 2016, 07:09:30 PM
Throughput of the road is limited by the spot of  least throughput.
did you ever hear words "weakest link"? This is exactly the case.

No shit. That's our point. The consensus by the morons in this thread seems to be that if you merge the moment you see a gap, there won't be a backup at the merge point. The only way to guarantee this not to be an issue, by their standards at least, is to completely close off the lane that ends, such that there simply is no opportunity to be in the lane that ends, hence, no merge. The problem is, that's fucking stupid: more lanes equal higher volume, period. A single lane of travel does not have an infinite vehicle-per-hour throughput. Cars still have to leave a reasonable gap, and the road still has a speed limit.

For example, If a single lane has a VPH throughput of 600 cars, three lanes have a throughput of 1800 cars. Now, this should be obvious, but it's a concept that seems to be ignored by those who merge early. Merging early does not increase the maximum efficiency of a lane -- that is determined by the speed limit, and the following distance of the cars in said lane.

Now, does a merge lower the maximum theoretical throughput of a lane? Of course. But sometimes, lanes have to end. And sometimes, you need multiple lanes to handle demand. It's a god damn balancing act, and there's no perfect solution here.

kalvado

Quote from: jakeroot on September 20, 2016, 07:59:35 PM
Quote from: kalvado on September 20, 2016, 07:09:30 PM
Throughput of the road is limited by the spot of  least throughput.
did you ever hear words "weakest link"? This is exactly the case.

No shit. That's our point. The consensus by the morons in this thread seems to be that if you merge the moment you see a gap, there won't be a backup at the merge point. The only way to guarantee this not to be an issue, by their standards at least, is to completely close off the lane that ends, such that there simply is no opportunity to be in the lane that ends, hence, no merge. The problem is, that's fucking stupid: more lanes equal higher volume, period. A single lane of travel does not have an infinite vehicle-per-hour throughput. Cars still have to leave a reasonable gap, and the road still has a speed limit.

For example, If a single lane has a VPH throughput of 600 cars, three lanes have a throughput of 1800 cars. Now, this should be obvious, but it's a concept that seems to be ignored by those who merge early. Merging early does not increase the maximum efficiency of a lane -- that is determined by the speed limit, and the following distance of the cars in said lane.

Now, does a merge lower the maximum theoretical throughput of a lane? Of course. But sometimes, lanes have to end. And sometimes, you need multiple lanes to handle demand. It's a god damn balancing act, and there's no perfect solution here.

I thought most drivers know 2 second rule - that means lane throughput of 1800 VPH. That's OK, though, feel free to continue arguing. I hope that would help you to pass your license test.

jakeroot

Quote from: kalvado on September 20, 2016, 08:54:27 PM
I thought most drivers know 2 second rule - that means lane throughput of 1800 VPH.

Where did you come up with 1800? I pulled 600 VPH out of my ass, just as an example.

Quote from: kalvado on September 20, 2016, 08:54:27 PM
That's OK, though, feel free to continue arguing. I hope that would help you to pass your license test.

I don't how many times I've had to say this to you, but here I go again:

What?

kalvado

Quote from: jakeroot on September 20, 2016, 09:09:01 PM
Quote from: kalvado on September 20, 2016, 08:54:27 PM
I thought most drivers know 2 second rule - that means lane throughput of 1800 VPH.

Where did you come up with 1800? I pulled 600 VPH out of my ass, just as an example.

Oh, out of your ass... You need to stop giving us your shit...

1995hoo

Quote from: kalvado on September 20, 2016, 09:23:32 PM
Quote from: jakeroot on September 20, 2016, 09:09:01 PM
Quote from: kalvado on September 20, 2016, 08:54:27 PM
I thought most drivers know 2 second rule - that means lane throughput of 1800 VPH.

Where did you come up with 1800? I pulled 600 VPH out of my ass, just as an example.

Oh, out of your ass... You need to stop giving us your shit...

WTF are you even talking about?????
"You know, you never have a guaranteed spot until you have a spot guaranteed."
—Olaf Kolzig, as quoted in the Washington Times on March 28, 2003,
commenting on the Capitals clinching a playoff spot.

"That sounded stupid, didn't it?"
—Kolzig, to the same reporter a few seconds later.

kalvado

Quote from: 1995hoo on September 20, 2016, 09:33:36 PM
Quote from: kalvado on September 20, 2016, 09:23:32 PM
Quote from: jakeroot on September 20, 2016, 09:09:01 PM
Quote from: kalvado on September 20, 2016, 08:54:27 PM
I thought most drivers know 2 second rule - that means lane throughput of 1800 VPH.

Where did you come up with 1800? I pulled 600 VPH out of my ass, just as an example.

Oh, out of your ass... You need to stop giving us your shit...

WTF are you even talking about?????

Did you ever think about role of "ass" in humans? One of the things is that output of gastrointestinal tract is located there.
Food you consume travels through gastrointestinal tract, substances your body need are absorbed -  and leftovers are ejected in a form of feces, commonly known as "shit". It comes from "anus", locates between buttocks  - area commonly known as "ass".
So looks like there is only one type of substance that jakeroot could  pull out of his ass..

paulthemapguy

This thread is hilarious.  People can't even agree on the function of a human ass. 

On a broader note, a merge is never an ideal situation.  It's something that has to happen, like a necessary evil.  You aren't going to find a way to make merges function in an ideal way, other than to take the cars away.
I see jakeroot's point.  In order to maximize the serviceability of the road with the merge, you utilize as many lanes as possible for as long as possible--so with that considered, early mergers compromise efficiency in a way that's easily avoidable.  In areas with dense traffic, merging at the last possible moment is an inevitability--maximizing lane usage when all of it is needed.  I will readily admit, though, that I try to be an early merger whenever possible...but this is only when traffic isn't so dense (LOS A, B, maybe C).  If the traffic flow upstream of the merge exceeds the peak flow of the downstream segment with fewer lanes, merging creates a shock of slowness which resolves once the traffic recovers to the peak flow of those fewer lanes.  Early merging just shifts that shock of slowness to a slightly earlier time, or extends the period of that slowness.  Does this extension of the slowness also slightly reduce its intensity (if that makes any sense), so that the early merge is worth it?  I'm not sure how early mergers would cause a WORSE delay overall...though I understand that their lane in particular would move slower than the lane that ends.
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jeffandnicole

A lot of it comes down to the area that one lives in.  Here in NJ, late merging is almost necessary because of the traffic we have.  The other day, Rt. 55 approaching Rt. 42 was jammed for about 4 miles.  Do you have 2, 4 mile lanes of traffic, or one long 8 mile jam, including traversing thru 3 interchanges?  Around here, using all available lanes is not only common, but necessary.  In more rural areas where people aren't used to traffic jams, they probably want to get over a bit earlier.  And guaranteed, the ones using the open lane to the end are those used to more congested conditions!

kalvado

Quote from: jeffandnicole on September 21, 2016, 06:17:33 AM
A lot of it comes down to the area that one lives in.  Here in NJ, late merging is almost necessary because of the traffic we have.  The other day, Rt. 55 approaching Rt. 42 was jammed for about 4 miles.  Do you have 2, 4 mile lanes of traffic, or one long 8 mile jam, including traversing thru 3 interchanges?  Around here, using all available lanes is not only common, but necessary.  In more rural areas where people aren't used to traffic jams, they probably want to get over a bit earlier.  And guaranteed, the ones using the open lane to the end are those used to more congested conditions!
Quick estimate gives 40-60 minutes worth of traffic in such backup.. I would say this qualifies as a parking lot!
And I would think at that point some active control measures - such as setting up detours - should start.. or there is no detour space as well?

1995hoo

Quote from: kalvado on September 20, 2016, 09:46:10 PM
Quote from: 1995hoo on September 20, 2016, 09:33:36 PM
Quote from: kalvado on September 20, 2016, 09:23:32 PM
Quote from: jakeroot on September 20, 2016, 09:09:01 PM
Quote from: kalvado on September 20, 2016, 08:54:27 PM
I thought most drivers know 2 second rule - that means lane throughput of 1800 VPH.

Where did you come up with 1800? I pulled 600 VPH out of my ass, just as an example.

Oh, out of your ass... You need to stop giving us your shit...

WTF are you even talking about?????

Did you ever think about role of "ass" in humans? One of the things is that output of gastrointestinal tract is located there.
Food you consume travels through gastrointestinal tract, substances your body need are absorbed -  and leftovers are ejected in a form of feces, commonly known as "shit". It comes from "anus", locates between buttocks  - area commonly known as "ass".
So looks like there is only one type of substance that jakeroot could  pull out of his ass..

I was reacting to your commentary having had nothing to do with the topic at hand and turning into pointless rude ranting. The so-called "two-second rule" had nothing to do with anything. Time for you to learn some manners.
"You know, you never have a guaranteed spot until you have a spot guaranteed."
—Olaf Kolzig, as quoted in the Washington Times on March 28, 2003,
commenting on the Capitals clinching a playoff spot.

"That sounded stupid, didn't it?"
—Kolzig, to the same reporter a few seconds later.



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