It occurs to me that making entering cars on the CD lane yield to exiting loop traffic (roundabout rules) would reduce CD lane abuse, and improve overall smoothness by keeping the loops from having to slow down to yield. The cloverleaf can be built smaller since the merging speed of traffic exiting the loop wouldn't matter since they have right of way. The downside I guess is having to yield to the right, but that's the only downside I can think of.
I guess I'm a little clueless on this one, what is CD lane abuse?
While I can see your point as well, having different merging rules for entering a c/d lane and entering the freeway itself is a recipe for disaster.
Quote from: SectorZ on January 01, 2020, 03:56:39 PM
I guess I'm a little clueless on this one, what is CD lane abuse?
I'm just guessing, but is it when, in congested conditions, thru traffic uses the C/D lanes for thru travel to bypass a bit of the congestion?
Quote from: SectorZ on January 01, 2020, 03:56:39 PM
I guess I'm a little clueless on this one, what is CD lane abuse?
While I can see your point as well, having different merging rules for entering a c/d lane and entering the freeway itself is a recipe for disaster.
Indeed, C/D lanes (or "local" lanes) are sometimes designated as through freeway lanes, such as by "All Lanes Through" signs. Especially when the main lanes don't have quite enough capacity for all through traffic. Only difference from the main lanes is sometimes the C/D lanes have somewhat lower speed limits and travel speeds.
This idea might work better in a "priorité Ã droite" country where traffic entering from the right always has the right of way.
Quote from: yand on January 01, 2020, 12:16:32 PM
It occurs to me that making entering cars on the CD lane yield to exiting loop traffic (roundabout rules) would reduce CD lane abuse, and improve overall smoothness by keeping the loops from having to slow down to yield. The cloverleaf can be built smaller since the merging speed of traffic exiting the loop wouldn't matter since they have right of way. The downside I guess is having to yield to the right, but that's the only downside I can think of.
The huge downside is if there's a lot of traffic coming in from the loop, those entering the C/D lane would back up onto the mainline, causing congestion, which is why in hundreds of cases you never see this engineering design.
It will also be vastly ignored, just like those on the loop are ignoring the yield signs to begin with.
This has been tried at the cloverleaf interchange between Interstate 10 and Loop 1604 in San Antonio. It doesn't work very well - there are regular backups in the C/D lanes because of the volume of weaving traffic on and off the loop ramps, and the backups extend onto the main lanes of 1604.
Curiously, this arrangement was implemented to keep the backups from being worse! This TexasHighwayMan page (http://www.texashighwayman.com/101604yield.shtml) explains the history of this interchange and how the worse backups are mitigated by this yield arrangement.
Quote from: TheOneKEA on January 01, 2020, 06:55:03 PM
This has been tried at the cloverleaf interchange between Interstate 10 and Loop 1604 in San Antonio. It doesn't work very well - there are regular backups in the C/D lanes because of the volume of weaving traffic on and off the loop ramps, and the backups extend onto the main lanes of 1604.
Curiously, this arrangement was implemented to keep the backups from being worse! This TexasHighwayMan page (http://www.texashighwayman.com/101604yield.shtml) explains the history of this interchange and how the worse backups are mitigated by this yield arrangement.
Indeed...
https://www.google.com/maps/@29.5904476,-98.6004482,3a,49y,89.84h,91.55t/data=!3m6!1e1!3m4!1sbuJRW-9t60IZDGp6tS4NRQ!2e0!7i16384!8i8192!5m1!1e1
At least that bottleneck will be completely gone in a few years.
Quote from: jeffandnicole on January 01, 2020, 05:34:43 PM
The huge downside is if there's a lot of traffic coming in from the loop, those entering the C/D lane would back up onto the mainline, causing congestion, which is why in hundreds of cases you never see this engineering design.
Making the loop yield seems to work in many cases because of low traffic, but its flaws quickly become apparent in many of the nation's overstressed cloverleafs. Under current rules, if there's a lot of traffic coming from the CD lane then the mainline feeding the stopped loop would be backed up.
A cloverleaf is basically a roundabout with slightly longer distance between exits, and as we know from roundabouts, making the loop yield to entering traffic is generally a bad idea - as TheOneKEA's link demonstrates.
Ideally loop traffic would be leaving enough following distance for CD traffic to zipper merge, so both sides are continuously moving, regardless of the amount of input traffic. The CD yield accomplishes merging by requiring the CD lane to slow down, rather than requiring the geometrically-speed limited loop traffic to speed up.
Quote from: jeffandnicole on January 01, 2020, 05:34:43 PM
It will also be vastly ignored, just like those on the loop are ignoring the yield signs to begin with.
Legal liability
Traffic coming off the loop is already going at a relatively low speed when having to yield at the merge. Not so for traffic exiting into the C/D lane from the mainline. Requiring the latter to yield would result in numerous rear-end collisions.
Also, what about situations when the C/D lane is specifically designated as a thru lane, either permanently or when there's a split/merge configuration during road work? Making an exception for the loop ramp to yield in that situation would add to the confusion.
Quote from: wanderer2575 on January 01, 2020, 08:28:49 PM
Traffic coming off the loop is already going at a relatively low speed when having to yield at the merge. Not so for traffic exiting into the C/D lane from the mainline. Requiring the latter to yield would result in numerous rear-end collisions.
Firstly, rear end collisions can always be avoided by maintaining the correct following distance.
Secondly, it is best practice for safety to match speed with and maintain relative position to merging traffic ahead of a merge. This can be encouraged by giving the CD lane the same advisory speed as the loop's design speed, or even enforced by speed limit.
Thirdly, if you are approaching at high speed and the road is clear, you will likely arrive at the merge point first and chances are extremely slim that you will need to yield at all.
Quote from: wanderer2575 on January 01, 2020, 08:28:49 PM
Also, what about situations when the C/D lane is specifically designated as a thru lane, either permanently or when there's a split/merge configuration during road work? Making an exception for the loop ramp to yield in that situation would add to the confusion.
Thru traffic sometimes has right of way, but not always. A simple sign on the CD side: "Yield to loop traffic" clears up the confusion. Net efficiency is still greater when the loop is kept free flowing, thru lane or not.
Quote from: yand on January 01, 2020, 08:51:03 PM
Quote from: wanderer2575 on January 01, 2020, 08:28:49 PM
Traffic coming off the loop is already going at a relatively low speed when having to yield at the merge. Not so for traffic exiting into the C/D lane from the mainline. Requiring the latter to yield would result in numerous rear-end collisions.
Firstly, rear end collisions can always be avoided by maintaining the correct following distance.
Secondly, it is best practice for safety to match speed with and maintain relative position to merging traffic ahead of a merge. This can be encouraged by giving the CD lane the same advisory speed as the loop's design speed, or even enforced by speed limit.
Thirdly, if you are approaching at high speed and the road is clear, you will likely arrive at the merge point first and chances are extremely slim that you will need to yield at all.
Quote from: wanderer2575 on January 01, 2020, 08:28:49 PM
Also, what about situations when the C/D lane is specifically designated as a thru lane, either permanently or when there's a split/merge configuration during road work? Making an exception for the loop ramp to yield in that situation would add to the confusion.
Thru traffic sometimes has right of way, but not always. A simple sign on the CD side: "Yield to loop traffic" clears up the confusion. Net efficiency is still greater when the loop is kept free flowing, thru lane or not.
Every single one of your statements is assuming a perfect world. You're proposal is missing the factor of reality.
Quote from: sprjus4 on January 01, 2020, 08:53:06 PM
Every single one of your statements is assuming a perfect world. You're proposal is missing the factor of reality.
In a perfect world, CD yield is more efficient than loop yield.
In an imperfect world, the fudge factor applies to both CD yield and Loop yield, and CD yield is still more efficient
Roundabouts, DDIs etc, all designs proving themselves in the USA despite our imperfect reality
Quote from: yand on January 01, 2020, 08:51:03 PM
Secondly, it is best practice for safety to match speed with and maintain relative position to merging traffic ahead of a merge. This can be encouraged by giving the CD lane the same advisory speed as the loop's design speed, or even enforced by speed limit.
Slowing down the CD lane doesn't work if it's carrying lots of through traffic, and the resulting congestion backs up into the main lanes.
Quote
Quote from: wanderer2575 on January 01, 2020, 08:28:49 PM
Also, what about situations when the C/D lane is specifically designated as a thru lane, either permanently or when there's a split/merge configuration during road work? Making an exception for the loop ramp to yield in that situation would add to the confusion.
Thru traffic sometimes has right of way, but not always. A simple sign on the CD side: "Yield to loop traffic" clears up the confusion. Net efficiency is still greater when the loop is kept free flowing, thru lane or not.
That assumes drivers even notice that sign at speed, let alone comprehend the unusual driving rule it prescribes. You're being really, really optimistic that your signs will be powerful enough to overcome customary driver behavior.
Quote from: yand on January 01, 2020, 08:58:54 PM
Quote from: sprjus4 on January 01, 2020, 08:53:06 PM
Every single one of your statements is assuming a perfect world. You're proposal is missing the factor of reality.
In a perfect world, CD yield is more efficient than loop yield.
In an imperfect world, the fudge factor applies to both CD yield and Loop yield, and CD yield is still more efficient
Roundabouts, DDIs etc, all designs proving themselves in the USA despite our imperfect reality
Face it, cloverleafs are outdated, and the best adaptation to customary driver behavior is to not try so hard to save them. In an imperfect world, sometimes we're stuck with them, and entering/exiting traffic will have to continue adapting to cloverleaf deficiencies. Better, and an increasingly common practice, to reengineer those interchanges to get rid of closely-spaced and conflicting slow loop movements. Such as by converting/replacing them to parclos, or SPUIs, or DDIs, or diamond ramps with roundabouts, that get rid of some or all of the loops, and give exiting/entering traffic longer acceleration/deceleration lanes.
I think the keyword of the day is liability.
Part of what causes a change in behavior over time is who gets blamed in an accident. Lack of enforcement is not a reason to not have rules.
Quote from: oscar on January 01, 2020, 09:29:43 PM
That assumes drivers even notice that sign at speed, let alone comprehend the unusual driving rule it prescribes. You're being really, really optimistic that your signs will be powerful enough to overcome customary driver behavior.
People adapt to changes. Beginning deceleration a few hundred ft earlier is a very simple thing to do. Yielding to the right is not unusual at all, people deal with left entrances all the time. If necessary, a specially angled lane marking would make it obvious who has right of way
Quote from: oscar on January 01, 2020, 09:29:43 PM
Slowing down the CD lane doesn't work if it's carrying lots of through traffic, and the resulting congestion backs up into the main lanes.
Self correcting problem - if the right lane backs up then people will switch to the left lane
Quote from: oscar on January 01, 2020, 09:29:43 PM
Face it, cloverleafs are outdated, and the best adaptation to customary driver behavior is to not try so hard to save them. In an imperfect world, sometimes we're stuck with them, and entering/exiting traffic will have to continue adapting to cloverleaf deficiencies. Better, and an increasingly common practice, to reengineer those interchanges to get rid of closely-spaced and conflicting slow loop movements. Such as by converting/replacing them to parclos, or SPUIs, or DDIs, or diamond ramps with roundabouts, that get rid of some or all of the loops, and give exiting/entering traffic longer acceleration/deceleration lanes.
Putting up a few signs isn't "trying hard" at all. Cloverleafs still have their place as an extremely cost effective 4 way freeway-to-freeway interchange, greatly enhanced by CD lanes and a simple rule change.
I note this thread specifically refers to cloverleafs with C/D roads. Would you try to apply the same principle to cloverleafs that don't have C/D roads? I ask because I think that's a bad idea for two reasons. First, having traffic in a thru lane on the highway slowing to yield to entering traffic is a bad idea. Second, it would mean the priority rule would vary depending solely on whether there were a C/D road, and I don't think that's a good idea.
Quote from: yand on January 01, 2020, 07:57:43 PM
Quote from: jeffandnicole on January 01, 2020, 05:34:43 PM
The huge downside is if there's a lot of traffic coming in from the loop, those entering the C/D lane would back up onto the mainline, causing congestion, which is why in hundreds of cases you never see this engineering design.
A cloverleaf is basically a roundabout with slightly longer distance between exits, and as we know from roundabouts, making the loop yield to entering traffic is generally a bad idea - as TheOneKEA's link demonstrates.
A cloverleaf is nothing like a roundabout, other than the fact that it's round.
QuoteIdeally loop traffic would be leaving enough following distance for CD traffic to zipper merge, so both sides are continuously moving, regardless of the amount of input traffic.
Infinitely impossible. There are maximum traffic flows that, when exceeded, will cause any roadway to start to congest. This is historically been graded or decades from A (moving without restriction) to F (congested).
QuoteThe CD yield accomplishes merging by requiring the CD lane to slow down, rather than requiring the geometrically-speed limited loop traffic to speed up.
Uh....
Quote
Legal liability
What does that even mean? You may wanna take some law classes. Sticking a sign where you damn well please, ignorant of engineering rules and guidelines, isn't "legal liability". Can I stick a stop sign on the interstate and call it a day, sighting this made up 'legal liability'?
Quote from: yand on January 01, 2020, 08:51:03 PM
it is best practice for safety to match speed with and maintain relative position to merging traffic ahead of a merge. This can be encouraged by giving the CD lane the same advisory speed as the loop's design speed, or even enforced by speed limit.
You mean the same advisory speeds and speed limit speeds that are vastly ignored when understated?
QuoteThirdly, if you are approaching at high speed and the road is clear, you will likely arrive at the merge point first and chances are extremely slim that you will need to yield at all.
Wait...I thought you wanted an advisory speed. Now you don't.
Quote
Thru traffic sometimes has right of way, but not always. A simple sign on the CD side: "Yield to loop traffic" clears up the confusion. Net efficiency is still greater when the loop is kept free flowing, thru lane or not.
Yeah, that ain't gonna clear up confusion. If you think it does, then why doesn't the existing Yield signs on the loop cause traffic to yield to the C/D lane?
Quote from: yand on January 01, 2020, 09:59:20 PM
I think the keyword of the day is liability.
Part of what causes a change in behavior over time is who gets blamed in an accident. Lack of enforcement is not a reason to not have rules.
Cool. Then rear-end accidents are virtually unheard of. :rolleyes:
Quote
People adapt to changes. Beginning deceleration a few hundred ft earlier is a very simple thing to do.
No it's not.
QuoteYielding to the right is not unusual at all, people deal with left entrances all the time.
No they don't.
Quote
Self correcting problem - if the right lane backs up then people will switch to the left lane
No they don't. And when they do, they are probably going at a slower speed than what the left lane was going, and now you have what is your common, every day, every rush hour, traffic jam.
Face it - your grand vision of people simply doing what you believe they should automatically do is a dreamworld. You're basically contradicting decades of sound principle engineering practiced over the entire world. Unless there's a very good reason to have thru traffic give up the right-of-way, you never have thru traffic give up the right-of-way.
Quote from: oscar on January 01, 2020, 09:29:43 PM
Face it, cloverleafs are outdated, and the best adaptation to customary driver behavior is to not try so hard to save them.
When the alternative is installing several traffic signals where there were no traffic signals, they are definitely better.
People are really underestimating the power of technology to change driver knowledge and behavior. Thanks to viral content, now everyone on the internet lists KRETP as their "biggest driving pet peeve", or that its more efficient to drive to the end of an ending lane and then zipper merge.
Quote from: 1995hoo on January 01, 2020, 10:03:51 PM
I note this thread specifically refers to cloverleafs with C/D roads. Would you try to apply the same principle to cloverleafs that don't have C/D roads? I ask because I think that's a bad idea for two reasons. First, having traffic in a thru lane on the highway slowing to yield to entering traffic is a bad idea. Second, it would mean the priority rule would vary depending solely on whether there were a C/D road, and I don't think that's a good idea.
If an interchange is busy enough for the rule to yield an effect, then it deserves to have a CD lane. The main subject of this thread is CD roads specifically for an interchange, CD roads acting as local thru lanes are largely a separate subject. Zipper merging is absolutely a good idea for best efficiency and safety and is accomplished by both lanes working together - in the case of short acceleration lanes or drivers refusing/unable to speed up (but where ramp traffic isnt supposed to stop), mainline traffic should slow down to accomodate.
Drivers are taught and tested about yielding, not loops or CD roads. A CD road with a yield sign just looks like any other road with a yield sign.
Quote from: jeffandnicole on January 01, 2020, 10:52:17 PM
A cloverleaf is nothing like a roundabout, other than the fact that it's round.
And the fact that there's a shared loop for left movements
Quote from: jeffandnicole on January 01, 2020, 10:52:17 PM
Infinitely impossible. There are maximum traffic flows that, when exceeded, will cause any roadway to start to congest. This is historically been graded or decades from A (moving without restriction) to F (congested).
(https://i.imgur.com/9M9MPc8.png)
Barring any additional bottlenecks, smooth flow of traffic can be achieved regardless of input traffic. A following distance large enough to allow merging can be maintained at any speed.
Quote from: jeffandnicole on January 01, 2020, 10:52:17 PM
What does that even mean? You may wanna take some law classes. Sticking a sign where you damn well please, ignorant of engineering rules and guidelines, isn't "legal liability". Can I stick a stop sign on the interstate and call it a day, sighting this made up 'legal liability'?
Engineering rules merely discourage left yields - they are clearly allowed as evidenced by the hundreds of left exits and entrances on interstates. The purpose of legal liability is so that if there is a crash, the driver obeying the rules is not penalized.
Quote from: jeffandnicole on January 01, 2020, 10:52:17 PM
Quote from: yand on January 01, 2020, 08:51:03 PM
it is best practice for safety to match speed with and maintain relative position to merging traffic ahead of a merge. This can be encouraged by giving the CD lane the same advisory speed as the loop's design speed, or even enforced by speed limit.
You mean the same advisory speeds and speed limit speeds that are vastly ignored when understated?
Merge with slow traffic ahead
Advisory speed 35mph
The advisory speed is only "understated" when there is no reason for it to be that low. Geometry OR speed of crossing traffic are both reasons. People follow advisory speeds when they understand its purpose.
Quote
QuoteThirdly, if you are approaching at high speed and the road is clear, you will likely arrive at the merge point first and chances are extremely slim that you will need to yield at all.
Wait...I thought you wanted an advisory speed. Now you don't.
I'm just telling you what would happen if you ignore the advisory speed... nothing.
Quote
Quote
Thru traffic sometimes has right of way, but not always. A simple sign on the CD side: "Yield to loop traffic" clears up the confusion. Net efficiency is still greater when the loop is kept free flowing, thru lane or not.
Yeah, that ain't gonna clear up confusion. If you think it does, then why doesn't the existing Yield signs on the loop cause traffic to yield to the C/D lane?
You keep claiming this but it is based on zero data. I would estimate ~60% or a slight majority of drivers follow ramp yield signs - its not safe to pass ramp traffic because the chance they aren't yielding is still pretty high, but most people make an effort.
Quote
Quote from: yand on January 01, 2020, 09:59:20 PM
I think the keyword of the day is liability.
Part of what causes a change in behavior over time is who gets blamed in an accident. Lack of enforcement is not a reason to not have rules.
Cool. Then rear-end accidents are virtually unheard of. :rolleyes:
[/quote]
If the car behind had right of way, there would be a lot more rear endings.
Quote
Quote
Self correcting problem - if the right lane backs up then people will switch to the left lane
No they don't. And when they do, they are probably going at a slower speed than what the left lane was going, and now you have what is your common, every day, every rush hour, traffic jam.
That's just how option lanes work. In free-flowing traffic they provide flexibility. If there's exiting traffic backing up the option lane then thru traffic treats it as exit only.
Quote
QuoteYielding to the right is not unusual at all, people deal with left entrances all the time.
No they don't.
ok new jersey
Quote from: yand on January 02, 2020, 07:50:40 AM
People are really underestimating the power of technology to change driver knowledge and behavior. Thanks to viral content, now everyone on the internet lists KRETP as their "biggest driving pet peeve", or that its more efficient to drive to the end of an ending lane and then zipper merge.
Ha. While there's plenty of people that do list that as their biggest pet peeve, there's many people that don't. Hell, there's a number of people even on these forums that believe in Keep Center Except to Pass rather than Keep Right Except to Pass.
QuoteQuoteYeah, that ain't gonna clear up confusion. If you think it does, then why doesn't the existing Yield signs on the loop cause traffic to yield to the C/D lane?
You keep claiming this but it is based on zero data. I would estimate ~60% or a slight majority of drivers follow ramp yield signs - its not safe to pass ramp traffic because the chance they aren't yielding is still pretty high, but most people make an effort.
My comment is based on zero data? Then by all means, please show your data.
Quote from: TheOneKEA on January 01, 2020, 06:55:03 PM
This has been tried at the cloverleaf interchange between Interstate 10 and Loop 1604 in San Antonio. It doesn't work very well - there are regular backups in the C/D lanes because of the volume of weaving traffic on and off the loop ramps, and the backups extend onto the main lanes of 1604.
Curiously, this arrangement was implemented to keep the backups from being worse! This TexasHighwayMan page (http://www.texashighwayman.com/101604yield.shtml) explains the history of this interchange and how the worse backups are mitigated by this yield arrangement.
In all four directions, the loop ramp becomes an added accel/decel lane. Basically, the yield sign for the mainline C/D traffic is meaningless: there is no traffic to which one must merge. Indeed, other locations like
here (https://goo.gl/maps/cS5JxG8hJaCEQuMt6) or
here (https://goo.gl/maps/48juGUjbxkbUFARx5), with basically the exact same C/D arrangement, don't use any yield signs at all.
Quote from: MikeTheActuary on January 01, 2020, 04:07:54 PM
Quote from: SectorZ on January 01, 2020, 03:56:39 PM
I guess I'm a little clueless on this one, what is CD lane abuse?
I'm just guessing, but is it when, in congested conditions, thru traffic uses the C/D lanes for thru travel to bypass a bit of the congestion?
What's wrong with this? If more capacity exists on the C/D road, then why shouldn't people use it?
Quote from: yand on January 02, 2020, 07:50:40 AM
A CD road with a yield sign just looks like any other road with a yield sign.
No it doesn't. It looks like a wide-open highway with a little red triangle on a stick along one side.
Do you imagine that, at some random diamond interchange on-ramp, you could put a stop sign on the freeway mainline and simply expect everyone on the freeway to stop? Of course not! That's the because people are much more apt to choose their behavior based on what the highway itself really does look like than they are based on a piece of metal erected in the grass. And a C/D road looks like a freeway. And people aren't inclined to yield to entering traffic on freeways.
Quote from: kphoger on January 02, 2020, 03:09:51 PM
Quote from: MikeTheActuary on January 01, 2020, 04:07:54 PM
Quote from: SectorZ on January 01, 2020, 03:56:39 PM
I guess I'm a little clueless on this one, what is CD lane abuse?
I'm just guessing, but is it when, in congested conditions, thru traffic uses the C/D lanes for thru travel to bypass a bit of the congestion?
What's wrong with this? If more capacity exists on the C/D road, then why shouldn't people use it?
On a flat freeway that already has multiple lanes, a temporary additional lane provides little to no capacity increase, plus the hazard of merging back in. The purpose of the CD lane is to remove the impact of the low speed loop from thru traffic.
Quote from: kphoger on January 02, 2020, 03:09:51 PM
Quote from: yand on January 02, 2020, 07:50:40 AM
A CD road with a yield sign just looks like any other road with a yield sign.
No it doesn't. It looks like a wide-open highway with a little red triangle on a stick along one side.
Wrong. Seeing a yield sign after taking an exit is the most normal thing ever. What it looks like is "I turned right and then kept left and now am on a 1 lane road and now there's a yield sign and I'm supposed to shift right again".
Quote
Do you imagine that, at some random diamond interchange on-ramp, you could put a stop sign on the freeway mainline and simply expect everyone on the freeway to stop? Of course not!
False analogy. The primary purpose of the CD lane is to keep left turning traffic from interfering with mainline. 99% of cars in a cloverleaf CD lane are trying to exit. Its just left turning traffic giving way to other left turning traffic.
BTW, freeways and even interstates can have interruptions all the time. Right here on this forum are full of examples of freeway mainlines unceremoniously interrupted by the occasional at grade intersection. If people see multiple signs telling them "stop sign ahead/prepare to stop" and step-down speed limits, maybe a cruiser in the median, they absolutely will stop, even if they're on a wide 1 way 2 lane road with a breakdown lane. Only roadgeeks actually care about the precise norms of freeway mainlines or whatnot. Normal people regularly refer to highways with at grade intersections as freeways.
The fact that my suggestion is currently being used on an interstate shows that it is clearly allowed. If it even yields a slight improvement, it will be worth it.
Quote from: yand on January 02, 2020, 04:16:45 PM
Quote from: kphoger on January 02, 2020, 03:09:51 PM
Quote from: MikeTheActuary on January 01, 2020, 04:07:54 PM
Quote from: SectorZ on January 01, 2020, 03:56:39 PM
I guess I'm a little clueless on this one, what is CD lane abuse?
I'm just guessing, but is it when, in congested conditions, thru traffic uses the C/D lanes for thru travel to bypass a bit of the congestion?
What's wrong with this? If more capacity exists on the C/D road, then why shouldn't people use it?
On a flat freeway that already has multiple lanes, a temporary additional lane provides little to no capacity increase, plus the hazard of merging back in. The purpose of the CD lane is to remove the impact of the low speed loop from thru traffic.
meh. Tough cookies. If I can get to where I'm going faster by taking the C/D road, then I'm going to take the C/D road.
Quote from: yand on January 02, 2020, 04:16:45 PM
Quote from: kphoger on January 02, 2020, 03:09:51 PM
Quote from: yand on January 02, 2020, 07:50:40 AM
A CD road with a yield sign just looks like any other road with a yield sign.
No it doesn't. It looks like a wide-open highway with a little red triangle on a stick along one side.
Wrong. Seeing a yield sign after taking an exit is the most normal thing ever. What it looks like is "I turned right and then kept left and now am on a 1 lane road and now there's a yield sign and I'm supposed to shift right again".
When one road clearly keeps going in a straight trajectory and the other one is an slow-speed interchanging ramp from an entirely different road, seeing a yield sign is very much not normal.
Quote from: yand on January 02, 2020, 04:16:45 PM
Only roadgeeks actually care about the precise norms of freeway mainlines or whatnot. Normal people regularly refer to highways with at grade intersections as freeways.
Normal people don't expect to have to stop or yield while on an Interstate.
Quote from: yand on January 02, 2020, 04:16:45 PM
The fact that my suggestion is currently being used on an interstate shows that it is clearly allowed. If it even yields a slight improvement, it will be worth it.
Where is this being used -- I would like to see such an application.
Quote from: akotchi on January 02, 2020, 04:54:00 PM
Quote from: yand on January 02, 2020, 04:16:45 PM
The fact that my suggestion is currently being used on an interstate shows that it is clearly allowed. If it even yields a slight improvement, it will be worth it.
Where is this being used -- I would like to see such an application.
See below. Although, as I stated earlier, the yield signs are basically pointless there, as the on-ramp forms an added accel/decel lane.
Quote from: TheOneKEA on January 01, 2020, 06:55:03 PM
This has been tried at the cloverleaf interchange between Interstate 10 and Loop 1604 in San Antonio. It doesn't work very well - there are regular backups in the C/D lanes because of the volume of weaving traffic on and off the loop ramps, and the backups extend onto the main lanes of 1604.
Curiously, this arrangement was implemented to keep the backups from being worse! This TexasHighwayMan page (http://www.texashighwayman.com/101604yield.shtml) explains the history of this interchange and how the worse backups are mitigated by this yield arrangement.
Quote from: kphoger on January 02, 2020, 04:37:12 PM
Quote from: yand on January 02, 2020, 04:16:45 PM
Quote from: kphoger on January 02, 2020, 03:09:51 PM
Quote from: yand on January 02, 2020, 07:50:40 AM
A CD road with a yield sign just looks like any other road with a yield sign.
No it doesn't. It looks like a wide-open highway with a little red triangle on a stick along one side.
Wrong. Seeing a yield sign after taking an exit is the most normal thing ever. What it looks like is "I turned right and then kept left and now am on a 1 lane road and now there's a yield sign and I'm supposed to shift right again".
When one road clearly keeps going in a straight trajectory and the other one is an slow-speed interchanging ramp from an entirely different road, seeing a yield sign is very much not normal.
Easy fix, not that its necessary
(https://imgur.com/titjExJ.png)
Quote from: kphoger on January 02, 2020, 04:37:12 PM
Quote from: yand on January 02, 2020, 04:16:45 PM
Only roadgeeks actually care about the precise norms of freeway mainlines or whatnot. Normal people regularly refer to highways with at grade intersections as freeways.
Normal people don't expect to have to stop or yield while on an Interstate.
CD roads are clearly part of the interchange. Interchange ramps are not part of the interstate mainline and nobody expects the ramp to have same priority as the mainline.
Quote from: kphoger on January 02, 2020, 05:02:10 PM
Quote from: akotchi on January 02, 2020, 04:54:00 PM
Quote from: yand on January 02, 2020, 04:16:45 PM
The fact that my suggestion is currently being used on an interstate shows that it is clearly allowed. If it even yields a slight improvement, it will be worth it.
Where is this being used -- I would like to see such an application.
See below. Although, as I stated earlier, the yield signs are basically pointless there, as the on-ramp forms an added accel/decel lane.
I think drivers of top heavy and underpowered commercial vehicles would disagree. So do taxpayers who benefit from cost savings of cloverleafs built smaller.
Quote from: kphoger on January 02, 2020, 04:37:12 PM
Normal people don't expect to have to stop or yield while on an Interstate.
I've heard people refer to arterial roads that are 4-lane divided highways with spread out traffic signals, and even go through some towns that serve mainly long-distance traffic as interstates.
The term has been spread culturally to essentially any long-distance road, whether it has intersections, signals, or even passes thru towns as an "interstate".
I've even heard some people refer as a 2-lane long distance road as an "interstate".
Oklahoma DOT actually tried exactly this at the I-35/I-240 interchange in the late 90s. The C/D road traffic displayed a strong preference for crashing into cars from the ramps rather than yielding. No amount of orange flags on the yield and yield ahead signs corrected this behavior (and let me tell you the orange flag industry in Oklahoma had to have had a literal banner year while this was going on), so they had to change it back after everyone in central Oklahoma made fun of ODOT for not knowing how to set up proper traffic control on a cloverleaf.
Do c/d lanes without cloverleafs have to yield to ramp traffic? If so, you're making an inconsistent design for these ramps, and inconsistent experiences among the same types of ramp systems will lead to more consistent accidents.
How anyone can say with a straight face that these do
not look like a wide-open highway is beyond me.
(https://i.imgur.com/GTrQW8V.png)
(https://i.imgur.com/1nmOQqT.png)
Quote from: yand on January 02, 2020, 05:27:22 PM
CD roads are clearly part of the interchange. Interchange ramps are not part of the interstate mainline and nobody expects the ramp to have same priority as the mainline.
No, it isn't necessarily clear that C/D roads are part of the interchange. Especially at large system interchanges with C/D roads that might even serve more than one exit, the C/D road can function as a second part of the highway.
While you're correct in asserting that people don't expect the ramp to have the same priority as the mainline, that's an argument against yourself. Nobody expects traffic from the loop on-ramp to have as much priority as traffic that's on the C/D mainline, and yet think it won't be any problem at all to have the mainline yield to the ramp.
Quote from: yand on January 02, 2020, 05:27:22 PM
Quote from: kphoger on January 02, 2020, 04:37:12 PM
the yield signs are basically pointless there, as the on-ramp forms an added accel/decel lane.
I think drivers of top heavy and underpowered commercial vehicles would disagree. So do taxpayers who benefit from cost savings of cloverleafs built smaller.
Which part would they disagree with? The fact that the on-ramp forms an added accel/decal lane? How do these drivers feel about similar interchanges that don't use any yield signs at all, such as ones I've already posted?
Taxpayers benefit from interchanges that aren't cloverleaves.
Quote from: Scott5114 on January 02, 2020, 06:30:55 PM
Oklahoma DOT actually tried exactly this at the I-35/I-240 interchange in the late 90s. The C/D road traffic displayed a strong preference for crashing into cars from the ramps rather than yielding. No amount of orange flags on the yield and yield ahead signs corrected this behavior (and let me tell you the orange flag industry in Oklahoma had to have had a literal banner year while this was going on), so they had to change it back after everyone in central Oklahoma made fun of ODOT for not knowing how to set up proper traffic control on a cloverleaf.
Oh, you mean common sense happened?
Quote from: kphoger on January 02, 2020, 07:36:30 PM
Quote from: Scott5114 on January 02, 2020, 06:30:55 PM
Oklahoma DOT actually tried exactly this at the I-35/I-240 interchange in the late 90s. The C/D road traffic displayed a strong preference for crashing into cars from the ramps rather than yielding. No amount of orange flags on the yield and yield ahead signs corrected this behavior (and let me tell you the orange flag industry in Oklahoma had to have had a literal banner year while this was going on), so they had to change it back after everyone in central Oklahoma made fun of ODOT for not knowing how to set up proper traffic control on a cloverleaf.
Oh, you mean common sense happened?
Naturally. Point being that if your cool new road idea was once used as instance of an ODOT Special, maybe you need to reconsider whether it's really a cool idea or not...
Quote from: Scott5114 on January 02, 2020, 06:30:55 PM
Oklahoma DOT actually tried exactly this at the I-35/I-240 interchange in the late 90s. The C/D road traffic displayed a strong preference for crashing into cars from the ramps rather than yielding. No amount of orange flags on the yield and yield ahead signs corrected this behavior (and let me tell you the orange flag industry in Oklahoma had to have had a literal banner year while this was going on), so they had to change it back after everyone in central Oklahoma made fun of ODOT for not knowing how to set up proper traffic control on a cloverleaf.
The late 90s was a long time ago, many things are different now. I'm certainly interested in the data for how this arrangement has impacted the San Antonio Loop 1604/I-10 interchange. Maybe 20+ years has not changed a thing and the same epidemic of crashes are occurring in Texas at this very moment.
Quote from: kphoger on January 02, 2020, 07:36:30 PM
No, it isn't necessarily clear that C/D roads are part of the interchange. Especially at large system interchanges with C/D roads that might even serve more than one exit, the C/D road can function as a second part of the highway.
I already addressed this. Cloverleaf exclusive CD lanes and Local Lanes are both called CD lanes, but obviously not the same thing. One is a ramp built exclusively to facilitate left turning movements without disturbing the mainline, the other facilitates travelling between any combination of the express lane access points and numerous local exits/entrances.
Quote from: kphoger on January 02, 2020, 07:36:30 PM
While you're correct in asserting that people don't expect the ramp to have the same priority as the mainline, that's an argument against yourself. Nobody expects traffic from the loop on-ramp to have as much priority as traffic that's on the C/D mainline, and yet think it won't be any problem at all to have the mainline yield to the ramp.
Exiting traffic behaves differently from mainline traffic. Turns out if you intend to take the loop, you're much more open to slowing down and working with traffic already in the loop. Changing the yield sign just reinforces this behavior.
Quote from: kphoger on January 02, 2020, 07:36:30 PM
How anyone can say with a straight face that these do not look like a wide-open highway is beyond me.
Nah. This looks like a slightly enlarged 1 lane road with no breakdown lane, no passing lane, multiple incoming on ramps, and is about to end and merge onto the wide open highway next to it very soon.
Quote from: yand on January 02, 2020, 08:06:02 PM
The late 90s was a long time ago, many things are different now.
No it's not, and no they aren't.
Quote from: yand on January 02, 2020, 08:06:02 PM
Exiting traffic behaves differently from mainline traffic. Turns out if you intend to take the loop, you're much more open to slowing down and working with traffic already in the loop. Changing the yield sign just reinforces this behavior.
I can say first hand I don't slow -way- down far before the ramp to exit unless it's congested. I'll ride up at full speed, and decrease speed once on the deceleration ramp and begin taking the turn.
Quote from: yand on January 02, 2020, 08:06:02 PM
Nah. This looks like a slightly enlarged 1 lane road with no breakdown lane, no passing lane, multiple incoming on ramps, and is about to end and merge onto the wide open highway next to it very soon.
It looks like a wide-open highway. I'm not going to crawl 25 - 30 mph on that lane. In free-flowing conditions, I'd ride up at 55 - 65 mph until passing the merge if somebody was not already entering at slow speed, then decrease, enter the deceleration lane, then slow down before and on the loop.
Quote from: sprjus4 on January 02, 2020, 08:14:27 PM
Quote from: yand on January 02, 2020, 08:06:02 PM
Exiting traffic behaves differently from mainline traffic. Turns out if you intend to take the loop, you're much more open to slowing down and working with traffic already in the loop. Changing the yield sign just reinforces this behavior.
I can say first hand I don't slow -way- down far before the ramp to exit unless it's congested. I'll ride up at full speed, and decrease speed once on the deceleration ramp and begin taking the turn.
Quote from: yand on January 02, 2020, 08:06:02 PM
Nah. This looks like a slightly enlarged 1 lane road with no breakdown lane, no passing lane, multiple incoming on ramps, and is about to end and merge onto the wide open highway next to it very soon.
It looks like a wide-open highway. I'm not going to crawl 25 - 30 mph on that lane. In free-flowing conditions, I'd ride up at 55 - 65 mph until passing the merge if somebody was not already entering at slow speed, then decrease, enter the deceleration lane, then slow down before and on the loop.
The behavior you described is compatible with a yield sign and advisory speed on the CD lane.
Quote from: yand on January 02, 2020, 08:06:02 PM
I'm certainly interested in the data for how this arrangement has impacted the San Antonio Loop 1604/I-10 interchange.
My suspicion is that the placement of the yield sign hasn't had much effect on driver behavior at all, but I too am interested to know if anyone has more information. Here in Wichita, at the 54/135 turban interchange, where ramps converge to form one lane
such as here (https://goo.gl/maps/7rJGkKhmxC3UrBUH9), the placement of the yield sign has near-zero effect on how people merge: they simply take turns. In fact, more people tend to ignore the placement of the yield sign (instead simply assuming that traffic on the right should merge into traffic on the left) than heed it. FYI, this is a merge point that I use daily, so my personal anecdotal perspective on trending driver behavior there actually does mean something.
Quote from: yand on January 02, 2020, 08:06:02 PM
Changing the yield sign just reinforces this behavior.
As I've already stated, and as other members have already corroborated, changing the yield sign does little to change actual driver behavior. The geometry of the highway affects driver behavior much more.
Quote from: sprjus4 on January 02, 2020, 08:14:27 PM
It looks like a wide-open highway. I'm not going to crawl 25 - 30 mph on that lane. In free-flowing conditions, I'd ride up at 55 - 65 mph until passing the merge if somebody was not already entering at slow speed, then decrease, enter the deceleration lane, then slow down before and on the loop.
I'm rather fond of the tactic taken with the C/D lanes I've encountered in the Montréal area, where the C/D lane gets a discrete posted (but usually ignored) speed limit.
For example: https://www.google.com/maps/@45.3806692,-73.5185478,3a,75y,167.36h,103.76t/data=!3m6!1e1!3m4!1sSFqlX9SUJbLlxfhBX9sqgA!2e0!7i16384!8i8192
Personally, I cannot recall the last time I saw a yield sign at an on-ramp anywhere.
I will pray I am never on the same highway as the OP, and that if I am, they better have the best insurance.
Quote from: renegade on January 03, 2020, 01:32:56 PM
Personally, I cannot recall the last time I saw a yield sign at an on-ramp anywhere.
I will pray I am never on the same highway as the OP, and that if I am, they better have the best insurance.
Having yield signs at on-ramps or not is generally a state-by-state thing. The OP must be from a state where they're common.
Quote from: Scott5114 on January 02, 2020, 07:39:33 PM
Naturally. Point being that if your cool new road idea was once used as instance of an ODOT Special, maybe you need to reconsider whether it's really a cool idea or not...
This has got to be the quote of the month, and we're only 3 days into it. :clap:
Quote from: kphoger on January 03, 2020, 02:51:25 PM
Quote from: renegade on January 03, 2020, 01:32:56 PM
Personally, I cannot recall the last time I saw a yield sign at an on-ramp anywhere.
I will pray I am never on the same highway as the OP, and that if I am, they better have the best insurance.
Having yield signs at on-ramps or not is generally a state-by-state thing. The OP must be from a state where they're common.
They're not used much in Illinois, Indiana, Ohio, Wisconsin, or Michigan. Iowa used to use them, but I'm not so sure anymore.
Yeah, a lot of states don't even use them at all.
Quote from: kphoger on January 02, 2020, 07:36:30 PM
How anyone can say with a straight face that these do not look like a wide-open highway is beyond me.
I have no opinion on the loop-ramp-yielding question, but I have to say that neither of these pictures looks like a wide-open highway. They both look like ramps to me, mostly because there is only one lane and because there is a bigger highway right next to them.
(https://i.imgur.com/jwZRbbl.png)
(https://i.imgur.com/XONC3tH.png)
Offramp yielding happened naturally at the eastbound George Washington Parkway to northbound I-395 ramp (https://www.google.com/maps/@38.8728161,-77.0475659,17z/data=!5m1!1e1) just outside of Washington DC. This is a cloverleaf off a mainline, not a C/D, but I was following traffic to let SB I-395 to EB Geo Washington pass through until there was a big enough gap in front of me to accelerate and then decelerate into it. Worse, it was backed up because traffic was cutting the line straight to my ramp, and I needed to go to the bathroom, and every delay was several more seconds of pain.
Example of an anti-CD abuse sign. (https://goo.gl/maps/79rEAYYMD6wrNXk97)
Quote from: ErmineNotyours on January 05, 2020, 12:07:06 AM
Offramp yielding happened naturally at the eastbound George Washington Parkway to northbound I-395 ramp (https://www.google.com/maps/@38.8728161,-77.0475659,17z/data=!5m1!1e1) just outside of Washington DC. This is a cloverleaf off a mainline, not a C/D, but I was following traffic to let SB I-395 to EB Geo Washington pass through until there was a big enough gap in front of me to accelerate and then decelerate into it. Worse, it was backed up because traffic was cutting the line straight to my ramp, and I needed to go to the bathroom, and every delay was several more seconds of pain.
Funny you mention this: the last time I was in DC, I took a taxi from the city to DCA and passed through that exact same interchange. Despite the presence of a yield sign on the loop ramp from the northbound GW Parkway, the driver came to a full stop in the right lane of I-395 to let all the loop traffic in. We sat there for probably around 30 seconds, until he decided there was a big enough gap between cars to gun it into exit 10B.
Quote from: US 89 on January 05, 2020, 02:35:17 AM
Quote from: ErmineNotyours on January 05, 2020, 12:07:06 AM
Offramp yielding happened naturally at the eastbound George Washington Parkway to northbound I-395 ramp (https://www.google.com/maps/@38.8728161,-77.0475659,17z/data=!5m1!1e1) just outside of Washington DC. This is a cloverleaf off a mainline, not a C/D, but I was following traffic to let SB I-395 to EB Geo Washington pass through until there was a big enough gap in front of me to accelerate and then decelerate into it. Worse, it was backed up because traffic was cutting the line straight to my ramp, and I needed to go to the bathroom, and every delay was several more seconds of pain.
Funny you mention this: the last time I was in DC, I took a taxi from the city to DCA and passed through that exact same interchange. Despite the presence of a yield sign on the loop ramp from the northbound GW Parkway, the driver came to a full stop in the right lane of I-395 to let all the loop traffic in. We sat there for probably around 30 seconds, until he decided there was a big enough gap between cars to gun it into exit 10B.
When I'm in DC (and on the few occasions where I'm not on the metro), I usually pass right through this spot, although usually in the left lane so as to exit onto 14th. Merging in the DMV is a concept that they don't seem to fully grasp.
Quote from: sprjus4 on January 02, 2020, 05:33:46 PM
I've heard people refer to arterial roads that are 4-lane divided highways with spread out traffic signals, and even go through some towns that serve mainly long-distance traffic as interstates.
The term has been spread culturally to essentially any long-distance road, whether it has intersections, signals, or even passes thru towns as an "interstate".
I've even heard some people refer as a 2-lane long distance road as an "interstate".
This definitely varies by region. In Seattle, the term "interstate" is virtually unheard of. You're either very specific (e.g. "Interstate 5") or you just say "freeway". Non-freeway roads are usually referred to by their specific name; sometimes, "highway".