Why can't people merge onto an interstate properly anymore?

[kalvado]

Last second merge when general traffic merges early generally makes things worse to much worse.

It sounds like you're still assuming there's one "ending" lane and one "continuing" lane.  Which means you still seem to misunderstand the concept of a zipper merge.



For what it's worth...





Oh, wait, that was some junky DOT writeup.

So, an excellent solution is in search of a matching problem. Or there is anything else to see? 
There is no discussion in these slides. They could write "moon is made of cheese" in the same font. Of course, you may believe in that text, and in the moon made of cheese -  and you're protected by the First amendment in your believes. But, really, is that the discussion level we would like to have? 

[jakeroot]

I thought you were studying urban design, not philosophy? Reducing an issue to a paradox was a fashionable thing in the ancient world, possibly even earning you a textbook mention of "Jakeroot's paradox". By now most of them are resolved by mathematical logic, though, so let's try doing that.

"Supply and demand" is a good answer. "momentary supply and demand" would be a great one. "momentary supply and demand in a situation of perishable supply and inelastic demand" for an extra credit.

So, why lane change affects "supply and demand" ratio?
PS: extra credit for considering supply and demand question in a context of  ">  like" traffic throughput curve

Trust me, this is well beyond either my undergrad or graduate degrees. I'm not trying to get overly technical with my suggestion that zipper merge is better, and I don't think I possess the mathematical skills to prove it beyond relatively crude suggestions such as 'more lanes = more capacity', or 'ending lanes early is no different than ending them later', or even 'merging is merging no matter where it is done'.

The issue, I think, with trying to use excessive levels of math to determine which is the higher capacity option is that the math only works if drivers practice the higher capacity option. I don't know what that higher/highest capacity option is, but I feel that normal drivers simply do not possess the basic level of math required to quickly determine that NOW is the best time to merge based on a serious of not-necessarily-obvious factors, assuming that is the best option at most times. Merging at the lane-drop, and not much, if at all, sooner, is a very simple concept that I think drivers can grasp relatively fast, and it's pretty effective in terms of maintaining whatever theoretical throughput may remain when lanes have to be dropped.

Last second merge when general traffic merges early generally makes things worse to much worse.

Here's a fun consideration: what about areas where general traffic zipper merges by default? There are several locations in Seattle with heavy and consistent merging during peak hours where zipper merging is the norm (here is a good example). How does merging early in these scenarios affect the overall flow of the merging situation? In these situations, is it beneficial to continue zipper merging with traffic, or try and change things up by merging early? As a side-note, that example will soon be replaced by a three-lane meter as evidenced by loop detectors; any drivers not zipper merging will now be forced to zipper, so to speak.

[kalvado]

I thought you were studying urban design, not philosophy? Reducing an issue to a paradox was a fashionable thing in the ancient world, possibly even earning you a textbook mention of "Jakeroot's paradox". By now most of them are resolved by mathematical logic, though, so let's try doing that.

"Supply and demand" is a good answer. "momentary supply and demand" would be a great one. "momentary supply and demand in a situation of perishable supply and inelastic demand" for an extra credit.

So, why lane change affects "supply and demand" ratio?
PS: extra credit for considering supply and demand question in a context of  ">  like" traffic throughput curve

Trust me, this is well beyond either my undergrad or graduate degrees. I'm not trying to get overly technical with my suggestion that zipper merge is better, and I don't think I possess the mathematical skills to prove it beyond relatively crude suggestions such as 'more lanes = more capacity', or 'ending lanes early is no different than ending them later', or even 'merging is merging no matter where it is done'.

The issue, I think, with trying to use excessive levels of math to determine which is the higher capacity option is that the math only works if drivers practice the higher capacity option. I don't know what that higher/highest capacity option is, but I feel that normal drivers simply do not possess the basic level of math required to quickly determine that NOW is the best time to merge based on a serious of not-necessarily-obvious factors, assuming that is the best option at most times. Merging at the lane-drop, and not much, if at all, sooner, is a very simple concept that I think drivers can grasp relatively fast, and it's pretty effective in terms of maintaining whatever theoretical throughput may remain when lanes have to be dropped.

Last second merge when general traffic merges early generally makes things worse to much worse.

Here's a fun consideration: what about areas where general traffic zipper merges by default? There are several locations in Seattle with heavy and consistent merging during peak hours where zipper merging is the norm (here is a good example). How does merging early in these scenarios affect the overall flow of the merging situation? In these situations, is it beneficial to continue zipper merging with traffic, or try and change things up by merging early? As a side-note, that example will soon be replaced by a three-lane meter as evidenced by loop detectors; any drivers not zipper merging will now be forced to zipper, so to speak.

This is really simple logic, not rocket science.
Answer I was looking for is that during the lane change - and for some time before and after change - car needs a spot in both lanes, so effective demand goes up with lots of changes, hence possibly causing supply-demand ratio to trip into deficiency mode and congestion to grow.  Aligning with the gap in the other lane also takes more space from the current lane "supply". Should be well within the scope, I would say!

[kphoger]

So, an excellent solution is in search of a matching problem. Or there is anything else to see? 
There is no discussion in these slides. They could write "moon is made of cheese" in the same font. Of course, you may believe in that text, and in the moon made of cheese -  and you're protected by the First amendment in your believes. But, really, is that the discussion level we would like to have? 

So which point on those slides do you disagree with?

– Merging early creates a longer tailback?  (I think you've already stated that you agree with this.)

– Rear-end crashes happen because people merge all over the place?  (I assume this means the folks who slow down to a near standstill in the "empty" lane, a half-mile before it ends, to try and merge in–while other drivers approach from behind at near-highway speeds.  Do you have a solution to this?)

– Drivers exhibit road rage and some straddle the line to try and "be the cop"?  (I'm sure we've all witnessed this, and sometimes it leads to driving on the shoulder or tailgating.)

– Zipper merge application is inconsistent?

– Road rage isn't necessarily eliminated by implementing a zipper merge, and most people still get irritated by early mergers?

– The zipper merge is still unfamiliar to many drivers?

[kalvado]

So, an excellent solution is in search of a matching problem. Or there is anything else to see? 
There is no discussion in these slides. They could write "moon is made of cheese" in the same font. Of course, you may believe in that text, and in the moon made of cheese -  and you're protected by the First amendment in your believes. But, really, is that the discussion level we would like to have? 

So which point on those slides do you disagree with?

(1) Merging early creates a longer tailback?  (I think you've already stated that you agree with this.)

(2) Rear-end crashes happen because people merge all over the place?  (I assume this means the folks who slow down to a near standstill in the "empty" lane, a half-mile before it ends, to try and merge in–while other drivers approach from behind at near-highway speeds.  Do you have a solution to this?)

(3) Drivers exhibit road rage and some straddle the line to try and "be the cop"?  (I'm sure we've all witnessed this, and sometimes it leads to driving on the shoulder or tailgating.)

(4) Zipper merge application is inconsistent?

(5) Road rage isn't necessarily eliminated by implementing a zipper merge, and most people still get irritated by early mergers?

(6) The zipper merge is still unfamiliar to many drivers?

(numbers added for the ease of reference)
1. Agreed
2. Rear end collisions may occur whenever traffic comes to a crawl from highway speed, early or late merge equally possible. So?
3. Solution: do not spread fake news about so-called "zipper" to discourage erratic behavior.
4. Solution: do not spread fake news about so-called "zipper" to encourage more consistent behavior.
5. road rage would be there whenever there is a congestion. What would cause road rage flare out is irrelevant - anything works. 
6. Solution: do not spread fake news about so-called "zipper"

[jakeroot]

This is really simple logic, not rocket science.
Answer I was looking for is that during the lane change - and for some time before and after change - car needs a spot in both lanes, so effective demand goes up with lots of changes, hence possibly causing supply-demand ratio to trip into deficiency mode and congestion to grow.  Aligning with the gap in the other lane also takes more space from the current lane "supply". Should be well within the scope, I would say!

Okay, how about this: next time I'm upstate, let's get some coffee and we can discuss this in-real-time. I'm definitely not stubborn but I would love to chat with you about this with, say, a pen and paper.

[kalvado]

This is really simple logic, not rocket science.
Answer I was looking for is that during the lane change - and for some time before and after change - car needs a spot in both lanes, so effective demand goes up with lots of changes, hence possibly causing supply-demand ratio to trip into deficiency mode and congestion to grow.  Aligning with the gap in the other lane also takes more space from the current lane "supply". Should be well within the scope, I would say!

Okay, how about this: next time I'm upstate, let's get some coffee and we can discuss this in-real-time. I'm definitely not stubborn but I would love to chat with you about this with, say, a pen and paper.

Sure, let me know.
Zoom is a plan B, though

[Avalanchez71]

I have seen some of the early mergers block up the right lane runners that late merge.  This behavior doesn't phase the right lane runner as they believe they can grab whatever spot to get going.  They seem not to grasp the concept of their behavior is the cause of the back-up.

Now in the case of I-65/SR 396 merge it would be nice if in advance many of the I-65 NB travelers could move over as safe as possible to the left lane allowing the merging traffic from SR 396 to move on in I would think there would be no back-up.

[kphoger]

(2) Rear-end crashes happen because people merge all over the place?  (I assume this means the folks who slow down to a near standstill in the "empty" lane, a half-mile before it ends, to try and merge in–while other drivers approach from behind at near-highway speeds.  Do you have a solution to this?)

2. Rear end collisions may occur whenever traffic comes to a crawl from highway speed, early or late merge equally possible. So?

So, if both lanes are being utilized equally until the merge point, then the situation I described is eliminated.  And, if the tailback is going to happen regardless, and rear-end collisions are prone to happen my mere fact of that tailback, then the two are not "equally possible".

[kphoger]

I have seen some of the early mergers block up the right lane runners that late merge.  This behavior doesn't phase the right lane runner as they believe they can grab whatever spot to get going.  They seem not to grasp the concept of their behavior is the cause of the back-up.

It isn't necessarily the cause of the backup.  The cause of the backup is all the traffic going through half the lane-space.

There have been plenty of times that I've driven to almost the end of the merge point, found a decent space to merge in, and caused zero congestion that wasn't already there.  No disadvantage compared to moving over at first sign of the tailback.

[kalvado]

(2) Rear-end crashes happen because people merge all over the place?  (I assume this means the folks who slow down to a near standstill in the "empty" lane, a half-mile before it ends, to try and merge in–while other drivers approach from behind at near-highway speeds.  Do you have a solution to this?)

2. Rear end collisions may occur whenever traffic comes to a crawl from highway speed, early or late merge equally possible. So?

So, if both lanes are being utilized equally until the merge point, then the situation I described is eliminated.  And, if the tailback is going to happen regardless, and rear-end collisions are prone to happen my mere fact of that tailback, then the two are not "equally possible".

So, what is the difference between "running into a car stopped in  want-to-merge spot" and "car stopped at the end of the queue"?
Idiots running full speed past a backup AND failing to realize there is a problem to watch out for AND rear-ending other cars after all that are totally at fault in such accidents, though.

[kphoger]

The difference is that a stopped car in an otherwise open lane is more unexpected than a stopped car at the end of a merging lane.

[hbelkins]

It seems we're talking about two different things here -- merging onto a freeway from an entrance ramp (the original subject of this thread) -- and merging at temporary lane closures due to construction.

In years past, I wanted to know which lane was closed and which was open well in advance of the closure. I would actually advocate for signs as far back as 5 or 10 miles if backups were common at the merge point. When I encountered this during a work zone on I-64 when I was commuting between Winchester and Frankfort, I moved into the open lane as soon as possible when I approached the lane closure, and got irked at the people who ran in the closing lane all the way up to the merge point and then bullied their way into the open lane. I got infuriated one day when they changed the closed lanes, I did not know, and got caught in the closing lane and had difficulty getting into the open lane.

In cases like these, especially where slowdowns or stoppages are common, a zipper merge makes sense. You avoid one lane being backed up and people flying along in the soon-to-be-closed lane and then shoving their way into line (or using their signal and hoping some nice motorist will let them in).

I'm pretty sure I have seen examples of places where, well in advance of a lane closure, signs pointed out that it was illegal to continue in that lane beyond a certain point.

All of this is different than a merge from an on-ramp, where generally the traffic already on the freeway has the ROW and the entering traffic has to yield if necessary.

Kentucky doesn't frequently use zipper merges. I've seen them promoted in a handful of projects, but haven't seen any applicable signage here.

[kphoger]

I'm pretty sure I have seen examples of places where, well in advance of a lane closure, signs pointed out that it was illegal to continue in that lane beyond a certain point.

Oklahoma likes to do that.  "STATE LAW / MERGE NOW".  My question is this:  if it's illegal not to merge, then why is the lane beyond that point even open?

All of this is different than a merge from an on-ramp, where generally the traffic already on the freeway has the ROW and the entering traffic has to yield if necessary.

I've pointed this out elsewhere, but that isn't necessarily the law.  In Illinois (location of the OP), to reiterate:

The law says, and I quote:

At an intersection where traffic lanes are provided for merging traffic the driver of each vehicle on the converging roadways is required to adjust his vehicular speed and lateral position so as to avoid a collision with another vehicle.

Correct.  Under Illinois state law, it is not only the responsibility of the driver entering the highway to adjust his speed.  It is also the responsibility of the driver already on the highway to adjust his speed too.

If there was a close call at a merge point, then both drivers were equally to blame.

Once again, |Crash_It| demonstrates that he doesn't understand what the law actually says, while showcasing his misguided road rage.

[jakeroot]

I'm pretty sure I have seen examples of places where, well in advance of a lane closure, signs pointed out that it was illegal to continue in that lane beyond a certain point.

Oklahoma likes to do that.  "STATE LAW / MERGE NOW".  My question is this:  if it's illegal not to merge, then why is the lane beyond that point even open?

I was writing my own reply when you posted yours. I have never heard of such a sign. So they're posted even when there is no clear reason to not merge later?

[CtrlAltDel]

I'm pretty sure I have seen examples of places where, well in advance of a lane closure, signs pointed out that it was illegal to continue in that lane beyond a certain point.

Oklahoma likes to do that.  "STATE LAW / MERGE NOW".  My question is this:  if it's illegal not to merge, then why is the lane beyond that point even open?

I was writing my own reply when you posted yours. I have never heard of such a sign. So they're posted even when there is no clear reason to not merge later?

Does anyone know what the law actually says?

ETA: The law seems to have been repealed in 2018.

ETA: Here it was:

D. The “Merge Now” traffic-control device that is used to warn and guide the public using the highway to merge, shall be located no greater than one (1) mile nor less than one thousand five hundred (1,500) feet in advance of the highway construction or maintenance area. Whenever any traffic-control device requires traffic to merge due to the closure of a section or lane of highway, the merge shall be completed:

1. As soon as practicable after passing the traffic-control device; and

2. Without passing any other traffic proceeding in the same direction.

[kalvado]

I'm pretty sure I have seen examples of places where, well in advance of a lane closure, signs pointed out that it was illegal to continue in that lane beyond a certain point.

Oklahoma likes to do that.  "STATE LAW / MERGE NOW".  My question is this:  if it's illegal not to merge, then why is the lane beyond that point even open?

All of this is different than a merge from an on-ramp, where generally the traffic already on the freeway has the ROW and the entering traffic has to yield if necessary.

I've pointed this out elsewhere, but that isn't necessarily the law.  In Illinois (location of the OP), to reiterate:

The law says, and I quote:

At an intersection where traffic lanes are provided for merging traffic the driver of each vehicle on the converging roadways is required to adjust his vehicular speed and lateral position so as to avoid a collision with another vehicle.

Correct.  Under Illinois state law, it is not only the responsibility of the driver entering the highway to adjust his speed.  It is also the responsibility of the driver already on the highway to adjust his speed too.

If there was a close call at a merge point, then both drivers were equally to blame.

Once again, |Crash_It| demonstrates that he doesn't understand what the law actually says, while showcasing his misguided road rage.

I don't think legal meaning of "lane ends" sign is universal across the states. Moreover, I looked into the issue a few years back, and NY has no legal definition of who has the right of way in such situation.  Possibly there is a precedent somewhere, possibly every judge would see it as they think it should be.
I know at least one situation (2 lanes exiting roundabout quickly becoming one) where town police lieutenant in charge of traffic enforcement definitely had an opinion which didn't match design assumptions.

THat is totally different path of discussion, though, as existing law may not be the optimal one from traffic perspective.

[mrsman]

It sounds like you're still assuming there's one "ending" lane and one "continuing" lane.  Which means you still seem to misunderstand the concept of a zipper merge.

The above is a perfect introduction to me contributing the following:
There's unique signage at some merges in Maryland that are specifically geared towards encouraging zipper merging and making it clear that neither lane is "ending" versus "continuing".

The most prominent example is the I-70 EB ramp to I-695 NB, which has to condense into one lane to squeeze thru the existing stack interchange. (Click ahead in the streetview link to see the signs at the actual "zipper" point - this ramp backs up at peak times and will continue to do so until the interchange is reconstructed, but drivers are generally good at following the signs and alternating at the actual merge point.)

Have any other states tried signage similar to this?

I drive through there frequently enough to know that it does work very well.  Where two lanes merge into one, and both lanes have equivalent importance as a lane, then the drivers should take turns.  But where you have an on-ramp or a neckdown on a multiple lane road (3 lanes to 2), then there is clearly more signage that indicates that a lane is ending and people in that lane need to merge into other traffic, yielding to the thru traffic in the adjacent lane.

For construction issues, it seems clear that similar logic should apply.  If construction dictates a 2 to 1 neckdown, then it is better for all involved to alternate the right of way.  But where it is 3 to 2, then the right lane simply ends and traffic is going to need to merge over and make use of all of the lanes available.

[kphoger]

ETA: The law seems to have been repealed in 2018.

Thank goodness!

Where two lanes merge into one, and both lanes have equivalent importance as a lane, then the drivers should take turns.  But where you have an on-ramp or a neckdown on a multiple lane road (3 lanes to 2), then there is clearly more signage that indicates that a lane is ending and people in that lane need to merge into other traffic, yielding to the thru traffic in the adjacent lane.

For construction issues, it seems clear that similar logic should apply.  If construction dictates a 2 to 1 neckdown, then it is better for all involved to alternate the right of way.  But where it is 3 to 2, then the right lane simply ends and traffic is going to need to merge over and make use of all of the lanes available.

This sounds reasonable.  I had never really considered the difference between 2-to-1 and 3-to-2, but it does seem there is an important distinction to be made.

[kalvado]

ETA: The law seems to have been repealed in 2018.

Thank goodness!

Where two lanes merge into one, and both lanes have equivalent importance as a lane, then the drivers should take turns.  But where you have an on-ramp or a neckdown on a multiple lane road (3 lanes to 2), then there is clearly more signage that indicates that a lane is ending and people in that lane need to merge into other traffic, yielding to the thru traffic in the adjacent lane.

For construction issues, it seems clear that similar logic should apply.  If construction dictates a 2 to 1 neckdown, then it is better for all involved to alternate the right of way.  But where it is 3 to 2, then the right lane simply ends and traffic is going to need to merge over and make use of all of the lanes available.

This sounds reasonable.  I had never really considered the difference between 2-to-1 and 3-to-2, but it does seem there is an important distinction to be made.

And for better or worse, MUTCD has only signs to specify a specific closed lane - left or right. One may assume that the closing lane should be at a disadvantage.
Sings are W4-2 and W9-1,2,3

[sprjus4]

https://goo.gl/maps/6L8yi92fXggpisFu6

Seems effective.

[kphoger]

And for better or worse, MUTCD has only signs to specify a specific closed lane - left or right. One may assume that the closing lane should be at a disadvantage.
Sings are W4-2 and W9-1,2,3

https://goo.gl/maps/6L8yi92fXggpisFu6

Seems effective.

Yes, there are plenty of ways to sign it.  But none of them are in the MUTCD, are they?  Unless you simply posted a W4-2 sign on the right and its mirror image on the left.  I don't think that would technically be a violation of the MUTCD.

[kalvado]

And for better or worse, MUTCD has only signs to specify a specific closed lane - left or right. One may assume that the closing lane should be at a disadvantage.
Sings are W4-2 and W9-1,2,3

https://goo.gl/maps/6L8yi92fXggpisFu6

Seems effective.

Yes, there are plenty of ways to sign it.  But none of them are in the MUTCD, are they?  Unless you simply posted a W4-2 sign on the right and its mirror image on the left.  I don't think that would technically be a violation of the MUTCD.

Just for reference, european version:
https://starttraffic.uk/image/catalog/product-photos/signs/post-mount/warning-signs/inline/road-narrows-both-sides-inline516.jpg

[Avalanchez71]

I carpooled with a right lane runner one day and she just didn't not understand the concept of right lane running.  I tried to tell her that she is slowing traffic down.  She said but this lane is faster.  She said I can't understand why there is a back-up. 

[kphoger]

Australia has almost-but-not-quite:

Road narrows


End divided road


One lane