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Bottleneck ramps

Started by ParrDa, September 25, 2017, 02:55:43 PM

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webny99

I alluded to this subject in "zipper merge news" but thought it might get more attention as a thread of its own.
For ramps that are choke points, how should traffic start merging?
Zipper doesn't really work because it slows thru traffic, but early merging doesnt either; it creates single-lane backups several miles long, an obvoius waste of capacity.
So, what are your thoughts on how to maintain flow in these cases?
This is not meant to be an exhaustive list, but if you can think of any major bottleneck ramps, do tell about your experiences driving through it.


jwolfer

Quote from: ParrDa on September 25, 2017, 02:55:43 PM
I alluded to this subject in "zipper merge news" but thought it might get more attention as a thread of its own.
For ramps that are choke points, how should traffic start merging?
Zipper doesn't really work because it slows thru traffic, but early merging doesnt either; it creates single-lane backups several miles long, an obvoius waste of capacity.
So, what are your thoughts on how to maintain flow in these cases?
This is not meant to be an exhaustive list, but if you can think of any major bottleneck ramps, do tell about your experiences driving through it.
Bottleneck ramps in Orlando area are i4 at the Florida Turnpike.. FTP at US17/92/441/SR 528.. both are old double trumpet toll road exits.. All electronic tolling will help

Z981


kalvado

Quote from: ParrDa on September 25, 2017, 02:55:43 PM
it creates single-lane backups several miles long, an obvoius waste of capacity.
Could you elaborate that phrase a little bit?

SO far it sounds more like a phrase BIllary or Dumpf would use; try to explain precisely where capacity is being wasted; why that capacity would otherwise be usable, speed up - or otherwise improve -traffic flow; and what is the metric for capacity you're using to begin with?

SectorZ

Is there any reason political based attacks on this forum are becoming more and more accepted?

kalvado

Quote from: ParrDa on September 25, 2017, 07:09:32 PM
Quote from: kalvado on September 25, 2017, 03:56:29 PM
Quote from: ParrDa on September 25, 2017, 02:55:43 PM
it creates single-lane backups several miles long, an obvoius waste of capacity.
Could you elaborate that phrase a little bit?

SO far it sounds more like a phrase BIllary or Dumpf would use; try to explain precisely where capacity is being wasted; why that capacity would otherwise be usable, speed up - or otherwise improve -traffic flow; and what is the metric for capacity you're using to begin with?
Well, I used the word "obvious" to infer that it didn't need to be explained. If one lane is stopped, and the others are moving with plenty of spare space, or "capacity", then capacity is being wasted. One does not need a "metric" per se to measure capacity.
As far as how to utilize that extra space, that's basically what I'm asking.
Obviously, you're not using proper metrics here!

kalvado

Quote from: ParrDa on September 25, 2017, 07:16:51 PM
Quote from: SectorZ on September 25, 2017, 06:57:28 PM
Is there any reason political based attacks on this forum are becoming more and more accepted?
I realize that was probably kalvado's intent, but chose to ignore it and skip to the content. IMO the recipient of the "attack" makes things infinitely worse by getting offended.
Actually message was more "don't behave as a politician, try to think!"
I believe "politician' these days is pretty insulting word - but doesn't go into profanity range yet.

kalvado

Quote from: ParrDa on September 25, 2017, 07:54:13 PM
Quote from: kalvado on September 25, 2017, 07:22:42 PM
Quote from: ParrDa on September 25, 2017, 07:16:51 PM
Quote from: SectorZ on September 25, 2017, 06:57:28 PM
Is there any reason political based attacks on this forum are becoming more and more accepted?
I realize that was probably kalvado's intent, but chose to ignore it and skip to the content. IMO the recipient of the "attack" makes things infinitely worse by getting offended.
Actually message was more "don't behave as a politician, try to think!"
I believe "politician' these days is pretty insulting word - but doesn't go into profanity range yet.
Either way. It was intended as an attack (for which profanity is not a pre-requisite).
Still waiting for your "thoughts" about a concept as simple as capacity, by the way.
I would measure road capacity as number of vehicles able to complete given trip per unit of time. 
And would you please provide your definition?

vdeane

Quote from: ParrDa on September 25, 2017, 02:55:43 PM
Zipper doesn't really work because it slows thru traffic, but early merging doesnt either; it creates single-lane backups several miles long, an obvoius waste of capacity.
Early merge causes backups on the through lanes too.  Most people tend not to want to drive at highway speeds near slow traffic, even if the cause of the slow traffic does not affect their lane.  Probably better to seek to minimize delay.
Please note: All comments here represent my own personal opinion and do not reflect the official position of NYSDOT or its affiliates.

kalvado

Quote from: vdeane on September 25, 2017, 08:06:03 PM
Quote from: ParrDa on September 25, 2017, 02:55:43 PM
Zipper doesn't really work because it slows thru traffic, but early merging doesnt either; it creates single-lane backups several miles long, an obvoius waste of capacity.
Early merge causes backups on the through lanes too.  Most people tend not to want to drive at highway speeds near slow traffic, even if the cause of the slow traffic does not affect their lane.  Probably better to seek to minimize delay.
And early merge doesn't increase delay.
Suppose vehicles A...Y are going to the ramp, and vehicle Z s going through.
For zipper, Z wouldn't get through until all of A..Y entered the ramp - with a total delay of 25x ramp entry interval
FOr early merge, Z has a chance to pass at least some of these alphabet soup, with the total delay greater than ideal zero - but less than 25x for zipper.

This assumes extra lanes - or other engineering adjustments  or traffic control measures - are not available (and they normally are not in short term)

kalvado

Quote from: ParrDa on September 25, 2017, 09:04:31 PM
Quote from: kalvado on September 25, 2017, 08:17:35 PM
Quote from: vdeane on September 25, 2017, 08:06:03 PM
Quote from: ParrDa on September 25, 2017, 02:55:43 PM
Zipper doesn't really work because it slows thru traffic, but early merging doesnt either; it creates single-lane backups several miles long, an obvoius waste of capacity.
Early merge causes backups on the through lanes too.  Most people tend not to want to drive at highway speeds near slow traffic, even if the cause of the slow traffic does not affect their lane.  Probably better to seek to minimize delay.
And early merge doesn't increase delay.
Suppose vehicles A...Y are going to the ramp, and vehicle Z s going through.
For zipper, Z wouldn't get through until all of A..Y entered the ramp - with a total delay of 25x ramp entry interval
FOr early merge, Z has a chance to pass at least some of these alphabet soup, with the total delay greater than ideal zero - but less than 25x for zipper.

This assumes extra lanes - or other engineering adjustments  or traffic control measures - are not available (and they normally are not in short term)
Right. If there are only 2 thru lanes, your argument stands unquestioned. But if there are 3+ then zippering from the right two should still increase throughput/capacity utilization  :D
Obviously that is not the case.

kalvado

Quote from: ParrDa on September 25, 2017, 08:54:48 PM
Quote from: kalvado on September 25, 2017, 08:05:46 PM
Quote from: ParrDa on September 25, 2017, 07:54:13 PM
Quote from: kalvado on September 25, 2017, 07:22:42 PM
Quote from: ParrDa on September 25, 2017, 07:16:51 PM
Quote from: SectorZ on September 25, 2017, 06:57:28 PM
Is there any reason political based attacks on this forum are becoming more and more accepted?
I realize that was probably kalvado's intent, but chose to ignore it and skip to the content. IMO the recipient of the "attack" makes things infinitely worse by getting offended.
Actually message was more "don't behave as a politician, try to think!"
I believe "politician' these days is pretty insulting word - but doesn't go into profanity range yet.
Either way. It was intended as an attack (for which profanity is not a pre-requisite).
Still waiting for your "thoughts" about a concept as simple as capacity, by the way.
I would measure road capacity as number of vehicles able to complete given trip per unit of time. 
And would you please provide your definition?
I'd say capacity is available space. The definition you gave is my definition of throughput.
Your definition is perfectly accurate. But that is capacity of a parking lot, not capacity of a highway. To illustrate the difference:
You state that construction of a parking lot connected to interstate and not accessible from outside streets increases highway capacity. While that is definitely a novel concept, I don't think you would find a lot of support (2 famous persons may buy it, though) 

kalvado

Quote from: ParrDa on September 25, 2017, 09:38:08 PM
Quote
Obviously that is not the case.
Never seen a post so loaded with evidence.
Well,
Quote from: ParrDa on September 25, 2017, 07:09:32 PM
I used the word "obvious" to infer that it didn't need to be explained.

kalvado

Quote from: ParrDa on September 25, 2017, 09:45:25 PM
QuoteYour definition is perfectly accurate. But that is capacity of a parking lot, not capacity of a highway. To illustrate the difference:
You state that construction of a parking lot connected to interstate and not accessible from outside streets increases highway capacity.
Let's say available lane space, then.
OK, so adding couple of loops to a previously straight highway increases capacity?
Good point, my friend, we can make billions on those contracts!

kalvado

Quote from: ParrDa on September 25, 2017, 09:53:03 PM
Quote from: kalvado on September 25, 2017, 09:41:04 PM
Quote from: ParrDa on September 25, 2017, 09:38:08 PM
Quote
Obviously that is not the case.
Never seen a post so loaded with evidence.
Well,
Quote from: ParrDa on September 25, 2017, 07:09:32 PM
I used the word "obvious" to infer that it didn't need to be explained.
You didn't use that word for that purpose. You used it to annoy me, while obviously proving that you have no evidence to provide.
Besides, denying an argument requires evidence. Defining a word doesn't.
You started the thread with the statement about
Quote from: ParrDa on September 25, 2017, 02:55:43 PM
an obvoius waste of capacity.
while you struggle even defining word "capacity". You see why did mention certain high profile celebrities here?

In my case, I definitely can both define "capacity" (and differentiate "capacity" from "throughput") and defend my statements. But I still want to see your consistent definition of "highway capacity" so that we can use at least some words in the same way (unlike said high profile folks).

kalvado

Quote from: ParrDa on September 25, 2017, 10:01:15 PM
Quote
OK, so adding couple of loops to a previously straight highway increases capacity?
It certainly does. Google "capacity".
Said action would not increase throughput.
Meriam-Webster dictionary has 5 definitions for the word "capacity", Oxford dictionary has 3 major definitions and 6 subdefinitions, while Google dictionary lists 2 definitions. Which definition do you rely on? Why would you choose that one, but not any other ?
In either case, if adding random loops increases "highway capacity" according to your definition - maybe creating - and using - that "capacity" is not a positive thing? Then  your original statement translates into "zipper merge leads to something bad". I totally buy the last statement, if that is the point you're trying to make. 

kalvado

Quote from: ParrDa on September 25, 2017, 11:24:07 PM
This is ridiculous. All talk; "I can do this, I can do that" and absolutely no substance. If you want to bicker about capacity, start a "capacity" thread and have at it.
I have no problem defining capacity; I did so twice, in replies 13 and 20. I also looked over all of the 14 definitions you mentioned and not one made reference to movement or time, two essentials in your definition.
So I'll give it a few weeks and, sometime when you're offline, start a new thread on this topic (which was a good one, BTW) without mentioning capacity.
<end thread>
Too bad you try to talk about something  you're unable to define. Good thing that you learned about existence of dictionaries. Next time I will explain you what "textbook" is.

formulanone

#16
Just to break up the banter...

Can an engineer explain where the best point to allow for one lane to merge to another? I understand there's a variety of reasons a a lane (or two) merges at what seems to be an incorrect place:

1) terrain
2) right-of-way not acquired
3) funds ran dry
4) mixture of new and existing highway infrastructure

How much distance is ideal for Highway A to join, and then merge with Highway B, while leaving enough room for the exit for Road C? I know it seems easy enough on paper, but what's the formula for how much distance and lane capacity to achieve an LOS that isn't E/F right off the bat?

Is it better to have traffic zipper merge before it joins up to the new thru route, or mix up with the flow of traffic? Some of this is curious to me, because I see some situations that are baffling (long gore points with an extremely tiny spot to merge with traffic and others which seem to be near-perfect for conditions (though, even with 4 miles of notice, somebody still doesn't figure out they're going to have to merge until the last second).

kalvado

Quote from: formulanone on September 26, 2017, 07:35:47 AM
Just to break up the banter...

Can an engineer explain where the best point to allow for one lane to merge to another? I understand there's a variety of reasons a a lane (or two) merges at what seems to be an incorrect place:

1) terrain
2) right-of-way not acquired
3) funds ran dry
4) mixture of new and existing highway infrastructure

How much distance is ideal for Highway A to join, and then merge with Highway B, while leaving enough room for the exit for Road C? I know it seems easy enough on paper, but what's the formula for how much distance and lane capacity to achieve an LOS that isn't E/F right off the bat?

Is it better to have traffic zipper merge before it joins up to the new thru route, or mix up with the flow of traffic? Some of this is curious to me, because I see some situations that are baffling (long gore points with an extremely tiny spot to merge with traffic and others which seem to be near-perfect for conditions (though, even with 4 miles of notice, somebody still doesn't figure out they're going to have to merge until the last second).
An opinion of a physicist, if that counts:
1. Lanes are counted as integers. You cannot have 2¾ marked lanes, and expect most of the time 3 cars to pass through that point at the same time. Having road that wide is only good if you're tapering lane in or out, not as sustained stretch - you mark either 2 or 3 lanes. This is somewhat meaningless, but important since:
2. there will always be a rate-limiting point - or bottleneck -  where choke would initiate at high flow. BTW, this statement is not specific to lane merge or traffic control. In case of lane variation, choke point usually occurs at the point where number of lanes is reduced. If pavement marks are visible enough, and motorists are somewhat compliant - number of marked lanes is a good metric. 
3. best strategy for traffic control is such that maximizes flow through the bottleneck - if there are no other specific objectives, e.g. minimizing accident rate at problematic spot.  Although once maximum achievable number is exceeded (and that number seems to be about 1800-2000 vehicles/hour per lane for car-mostly traffic), there is a backup .

Those are very generic statements, and bottleneck flow maximization strategy is the biggest question.  What fuels this discussion in misunderstanding of what "bottleneck" is, and assumption that some black magic can help to exceed maximums. There is some wiggle room, but not much, 10-15% at most.

Design parameters may vary, apparently. Most important parameters I can see are ability of traffic to accelerate/decelerate - car to truck ratio and grade slope. Speed, of course; lane width probably plays a role. I assume that numbers have to be somewhere in MUTCD. I assume those numbers are such that acceleration lane has to allow achieving flow speed for slowest vehicle, and maintaining that speed long enough for either passing 2-3 vehicles at 10% speed differential or coming to a full stop...


jemacedo9

#18
I'm very familiar with the I-490 W to NY/I-590 issue...and the problem is that there is no answer.  It's a classic weave issue, which normally means there isn't enough room between the on-ramp from Penfield Rd and the off-ramp to NY/I-590 for the weaving to happen at speed for the volume that is there.  Normally in weave situations, the answer is to lengthen the weave length, but there is no room.

The ONLY way to reduce backups on I-490 would be to permanently close the on-ramp from Penfield Rd.  That would cause the following:
- dump traffic either onto East Ave, which would cause a greater backup at N Winton Rd to get to 490W
- force traffic to take N Landing Rd to Blossom Rd (which is a bad intersection already) to get to NY 590 N or I-590 S (but not to 490)
- force traffic to track back to NY 441, and that on ramp to I-490 is also brutal in the afternoon and causes lesser backups in I-490 W, but those would increase.

Maybe all of those would ease the situation on 490...if that was your only priority. But it would make 441 worse, and the Blossom/Landing Rd situation worse.

ET21

The Hillside Strangler between I-294, I-290, and I-88. Outdated ramps cause daily backups during the rush hour periods.
The local weatherman, trust me I can be 99.9% right!
"Show where you're going, without forgetting where you're from"

Clinched:
IL: I-88, I-180, I-190, I-290, I-294, I-355, IL-390
IN: I-80, I-94
SD: I-190
WI: I-90, I-94
MI: I-94, I-196
MN: I-90

vdeane

#20
Quote from: ParrDa on September 26, 2017, 08:34:28 PM
Exactly. This case isn't just a merge, it's also a nasty weave, making it particularly challenging to get from Penfield Road to I-490 without getting rear ended; as you're forced to merge first, then accelerate.
Or you could start accelerating on the ramp before you get to the acceleration lane/weave, like you're supposed to.  People have an unfortunate tendency to want to merge in at slow speeds and then accelerate (at every ramp in the Capital District, not just loops or weaves).  Unless ramp length or curvature dictates otherwise, there is no reason why you should not be at freeway speeds by the time you get to the end of the ramp in the first place.  So much congestion could be reduced just by people learning to drive properly.

In any case, I don't think the backups there are caused by the weave (well, not that one anyways).  It's because a very large number of people (1/4 to 1/3 of the total traffic on the road) are heading onto a single lane ramp with a sharp curve ending in another weave.  So many people on I-490 west are going to NY 590 north that every time I go "home" these days I stay in the middle lane (unless traffic is unusually light) and move over into the void left by all the people moving into the exit only lane (since the ramp to I-590 south is an option lane).

Quote from: ParrDa on September 25, 2017, 09:00:59 PM
Early merge causes backup in a single through lane, sure. Several miles of it in some cases.
But on the 490, heading west every afternoon, the left and center lanes rarely slow below 40 mph, where the right lane slows to a crawl just past Exit 24 for the 590 North ramp.
No, it causes backups in ALL the lanes.  Go drive on the Northway in rush hour sometime.  Preferably NB during the evening peak the Thursday/Friday before Travers weekend.  I've been stopped in the left lane because of a merge on the right.  People see brake lights in one lane and instinctively slow down, even though the merge doesn't affect them.

Of course, it doesn't help that people in the Capital District don't give a crap if they cut your off so close that you have to slam the brakes so hard that your tires skid.  Lane changing maneuvers here are clearly influenced by close proximity to NYC and Boston, which is ironic because drivers here (with the exception of downtown Albany) are generally less agressive than western NY.
Please note: All comments here represent my own personal opinion and do not reflect the official position of NYSDOT or its affiliates.

vdeane

Quote from: ParrDa on September 28, 2017, 10:30:11 PM
I don't find WNY drivers that aggressive, care to expound?
I don't think I see too many people passing on the right here.  It certainly does happen, but not with the "rock in a stream" effect that seems to be common around Rochester.  Plus people take a long time to start from lights, and merging into the freeway below speed seems to be more common here.  Or maybe I'm just homesick.
Please note: All comments here represent my own personal opinion and do not reflect the official position of NYSDOT or its affiliates.

froggie

Quote from: ParrDaPassing on the right is definitely more commonplace than it should be around here. But I'd attribute that to too much left lane camping, not aggression.

New Yorkers in general are experts at "left lane camping"...they're one of the top three states I've observed over the years that do so.

Rothman

Ohio has to be one of the 2.  Ohioans are the worst.

In my experience, NYers are only really bad at left lane blocking on multi-lane arterials.
Please note: All comments here represent my own personal opinion and do not reflect the official position(s) of NYSDOT.

vdeane

Quote from: ParrDa on September 29, 2017, 09:24:10 PM
^ Passing on the right is definitely more commonplace than it should be around here. But I'd attribute that to too much left lane camping, not aggression.
One can only pass on the right if the car in front leaves space on their right. And we have way to many people doing so; it's not worth trying to get all of them to move over.
I guess we're lacking that "east coast" mentality of using the left lane as a means of getting ahead, and having it so easy with traffic, the general population just isn't as anxious to get ahead. This means those of use who have places to go come across as aggressive because we have to resort to passing on the right.
Middle lane camping is very common in both Rochester and the Capital District.  The difference is, people in the Capital District are likely to wait until they can pass on the left (or cut off someone in the left lane... the one bit of aggression that exists here outside of downtown Albany), whereas in Rochester you can be going 60 in the middle lane, have to cars approaching behind, one goes left, one goes right, both pass you like you're standing still (and then both immediately get back in the middle lane).

I think people in NY tend to view the right lane as the "exit" (and entrance) lane.
Please note: All comments here represent my own personal opinion and do not reflect the official position of NYSDOT or its affiliates.



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