daily menu » rate the banner | guess the city | one on oneforums map | privacy policy | DMCA | news magazine | posting guidelines

Go Back   SkyscraperCity > Infrastructure and Mobility Forums > Highways & Autobahns

Highways & Autobahns All about automobility



Global Announcement

As a general reminder, please respect others and respect copyrights. Go here to familiarize yourself with our posting policy.


Reply

 
Thread Tools
Old November 27th, 2016, 12:40 AM   #1
Ryme Intrinseca
Registered User
 
Join Date: Aug 2016
Posts: 197
Likes (Received): 119

US interchanges

Following on from my EU interchanges thread, I've now compiled figures for the number of four-way full access freeflow interchanges in every US state. Here is a summary of results:



Some comments:

- Of 833 qualifying interchanges, 386 (46%) are cloverleafs. The next most common grouping is offside (18%), followed by stack (11%), 3 loop (9%) and cloverstack (6%). Compared to the EU, there are far more stacks but fewer cyclic.
- California 'wins' with 69 qualifying interchanges, followed by Texas (65), Virginia (60), Illinois (52) and New York (46). Southern California has 41, which would rank it sixth in the US were it a state.
- Florida is the third most populous state but has relatively few qualifying interchanges (23), while Alaska, Hawaii, Idaho, or Montana have none.
- In terms of state distribution of types, Texas has most stacks (38) and offside (10), California has most 1 loop (11) and cloverstacks (13), North Carolina has most 3 loop (9), while Virginia has most cloverleafs (47). Several states are tied for cyclic (2 each) and 2 loop (3 each).

This is how I classified qualifying interchanges:

- Stack includes classic four-level stacks, stackturbines, and stackmills.
- Cyclic includes turbines as well as windmill/octopus-type designs.
- 1 loop refers to single loop designs, including those in a stack-like arrangement, those in a turbine-like arrangement, and those in a windmill-type arrangement.
- Cloverstack refers to design with two loops in opposite corners, including 'cloverstack classic', 'clovercorner', partially-unrolled cloverleafs, cloverturbines, and clovermills.
- 2 loop refers to designs with two adjacent loops in either a stack, corner, turbine or windmill-like arrangement.
- 3 loop refers to triple loop designs in either a stack, corner, turbine, or windmill-type arrangement.
- Cloverleaf includes modified cloverleafs as well as classic cloverleafs.
- Other nearside refers to any design lacking offside entries or exits that does not fall into any of the above categories.
- Offside refers to any design with one or more offside entries and/or exits, which I define broadly to include junctions where one of the mainlines merges or diverges (e.g. this). The Offside category includes Offside stack, Offside 1 loop, Offside cloverstack, Offside 2 loop, Offside 3 loop, Divided (i.e., both mainlines split), Gothic (i.e. mainline(s) swap over), and Other offside.

Qual refers to the total number of interchanges in the Stack, Cyclic, 1 Loop, and Cloverstack groups. This is a good measure of the number of high quality interchanges, i.e. those lacking weaving areas and offside entries/exits. Qual % is the state's percentage of the total number of quality interchanges. Qualscore is the percentage of the state's interchanges that meet the quality criteria.

The table above sums the data for several subtypes. The second table provides the more detailed information by subtype:



I take the condition of 'freeflow' seriously, and disqualify interchanges with toll booths, pedestrian crossings, level crossings, traffic lights, at-grade long turns (i.e. left in a right hand traffic country), and four-way merges or diverges.
__________________

Bender, EasySeven, JohnFlint1985 liked this post

Last edited by Ryme Intrinseca; April 8th, 2017 at 09:33 PM.
Ryme Intrinseca no está en línea   Reply With Quote

Sponsored Links
Old November 28th, 2016, 02:43 PM   #2
Exethalion
Remember Me
 
Exethalion's Avatar
 
Join Date: Dec 2008
Location: Stuttgart
Posts: 845
Likes (Received): 645

Would this also exclude non signalized stackabouts like the one in Metairie?
Exethalion no está en línea   Reply With Quote
Old November 29th, 2016, 01:11 PM   #3
Ryme Intrinseca
Registered User
 
Join Date: Aug 2016
Posts: 197
Likes (Received): 119

Quote:
Originally Posted by Exethalion View Post
Would this also exclude non signalized stackabouts like the one in Metairie?
Yes, I exclude all interchanges that require a roundabout to complete movements under the 'no at-grade long turn' clause. Hence the UK only had 12 qualifying interchanges - it would have about four times that if you included stackabout-type designs!
Ryme Intrinseca no está en línea   Reply With Quote
Old November 29th, 2016, 02:22 PM   #4
Exethalion
Remember Me
 
Exethalion's Avatar
 
Join Date: Dec 2008
Location: Stuttgart
Posts: 845
Likes (Received): 645

I understand your reasoning, but the behaviour of a vehicle making a left turn at a stackabout, and for example a cloverleaf with weaving (an interchange that really pushed Germany way up the rankings!) is quite similar. On a stackabout, the car must make one yielding merge at the entrance to the roundabout, then continues relatively free flowing, albeit at-grade, until it exits. On a cloverleaf it is free flowing around the loop, then has to yield/mere with the mainline or collector lane, and actually has to undergo weaving twice, if anything I would regard this as more disruptive than a single lane stackabout. Please correct me if I have missed something with this analysis.

Of course the UK chose to signalize many of their stackabouts, which I rightly agree rules them out completely. I asked because the example in Metairie is in the minority as far as this interchange design is concerned.
__________________

Ryme Intrinseca liked this post
Exethalion no está en línea   Reply With Quote
Old November 29th, 2016, 03:41 PM   #5
Ryme Intrinseca
Registered User
 
Join Date: Aug 2016
Posts: 197
Likes (Received): 119

Quote:
Originally Posted by Exethalion View Post
I understand your reasoning, but the behaviour of a vehicle making a left turn at a stackabout, and for example a cloverleaf with weaving (an interchange that really pushed Germany way up the rankings!) is quite similar. On a stackabout, the car must make one yielding merge at the entrance to the roundabout, then continues relatively free flowing, albeit at-grade, until it exits. On a cloverleaf it is free flowing around the loop, then has to yield/mere with the mainline or collector lane, and actually has to undergo weaving twice, if anything I would regard this as more disruptive than a single lane stackabout. Please correct me if I have missed something with this analysis.
I agree with what you're saying, and had thought the same myself previously.

The problem is that if you're counting unsignalized stackabouts as freeflow, it seems like you should also count a simple at-grade roundabout with four arms as a four-way full access freeflow junction as well! Or if you add a 'grade separated' clause, you will still have to be including a basic two-bridge roundabout junction like this.

An alternative would be to discount any interchange with weaving spaces. But this would not only discount cloverleafs but three and two loop designs as well, like this for instance. These are the kind of major system interchanges that I was aiming to survey.

It's a tricky issue and I decided the best solution was just to say that roundabouts, as a type of at-grade junction, don't count.

But I do have a partial solution to the 'grade inflation' that countries like Germany get from all their cloverleafs. I now provide a 'quality' number, which is basically the total number of qualifying interchanges that lack weaving spaces or offside entries and exits (i.e. stacks, cyclic, 1 loop, and cloverstacks). Germany only has 13 interchanges of this sort, only one more than the UK.

It's not perfect but it's the best compromise I was able to find.
Ryme Intrinseca no está en línea   Reply With Quote
Old December 22nd, 2016, 06:01 PM   #6
Ryme Intrinseca
Registered User
 
Join Date: Aug 2016
Posts: 197
Likes (Received): 119

Data for the Midwest now added to OP
Ryme Intrinseca no está en línea   Reply With Quote
Old December 23rd, 2016, 04:38 AM   #7
Jschmuck
Registered User
 
Join Date: May 2008
Location: Green Bay
Posts: 825
Likes (Received): 250

Quote:
Originally Posted by Ryme Intrinseca View Post
I agree with what you're saying, and had thought the same myself previously.

The problem is that if you're counting unsignalized stackabouts as freeflow, it seems like you should also count a simple at-grade roundabout with four arms as a four-way full access freeflow junction as well! Or if you add a 'grade separated' clause, you will still have to be including a basic two-bridge roundabout junction like this.

An alternative would be to discount any interchange with weaving spaces. But this would not only discount cloverleafs but three and two loop designs as well, like this for instance. These are the kind of major system interchanges that I was aiming to survey.

It's a tricky issue and I decided the best solution was just to say that roundabouts, as a type of at-grade junction, don't count.

But I do have a partial solution to the 'grade inflation' that countries like Germany get from all their cloverleafs. I now provide a 'quality' number, which is basically the total number of qualifying interchanges that lack weaving spaces or offside entries and exits (i.e. stacks, cyclic, 1 loop, and cloverstacks). Germany only has 13 interchanges of this sort, only one more than the UK.

It's not perfect but it's the best compromise I was able to find.
Well I think what it can come down to is that roundabouts DO have posted yield signage for vehicles entering the roundabout(s), whereas MOST cloverleafs do not have posted yield signage.
__________________
MilRockee/Madtown/Green Bay
Jschmuck no está en línea   Reply With Quote
Old December 23rd, 2016, 02:22 PM   #8
Ryme Intrinseca
Registered User
 
Join Date: Aug 2016
Posts: 197
Likes (Received): 119

Quote:
Originally Posted by Jschmuck View Post
Well I think what it can come down to is that roundabouts DO have posted yield signage for vehicles entering the roundabout(s), whereas MOST cloverleafs do not have posted yield signage.
A high proportion of cloverleafs in the US have a yield or stop sign on at least one ramp.

Signage is also used differently between different countries, e.g. in many european countries roundabouts are not signed for a yield.

So I think using a sign-based criterion would have very undesirable effects.

Last edited by Ryme Intrinseca; December 23rd, 2016 at 02:41 PM.
Ryme Intrinseca no está en línea   Reply With Quote
Old December 24th, 2016, 02:23 AM   #9
Jschmuck
Registered User
 
Join Date: May 2008
Location: Green Bay
Posts: 825
Likes (Received): 250

Quote:
Originally Posted by Ryme Intrinseca View Post
A high proportion of cloverleafs in the US have a yield or stop sign on at least one ramp.

Signage is also used differently between different countries, e.g. in many european countries roundabouts are not signed for a yield.

So I think using a sign-based criterion would have very undesirable effects.
I should elaborate, I was probably referring to interstate to interstate cloverleafs, many of them do not have yield signs.
__________________
MilRockee/Madtown/Green Bay
Jschmuck no está en línea   Reply With Quote
Old February 11th, 2017, 11:05 PM   #10
Ryme Intrinseca
Registered User
 
Join Date: Aug 2016
Posts: 197
Likes (Received): 119

I've now completed the West region and added the results to the OP.

While the Northeast and Midwest were quite similar to each other in terms of distribution of interchanges types, with cloverleafs dominating (67% and 56% respectively), the West has a much more even distribution of types, with stacks (22%) edging out cloverstacks (19%) for the top spot.

As that comparison suggests, interchanges in the West tend to be of higher standard designs, with a QUALSCORE (percentage of qualifying interchanges with no weaving or left hand entries/exits) of 58%, versus 7% for the Northeast and 13% for the Midwest.

On the other hand, the West had fewer qualifying interchanges (107) than the Northeast (135) or Midwest (238), despite having a higher population than either.
Ryme Intrinseca no está en línea   Reply With Quote
Old February 12th, 2017, 06:04 PM   #11
Innsertnamehere
insertoronto
 
Innsertnamehere's Avatar
 
Join Date: Jun 2010
Location: Toronto
Posts: 3,960
Likes (Received): 680

The west has less dense of a highway network, which means less intersecting freeways. It is generally a newer freeway network though, which means it has higher design standards (less cloverleafs).
Innsertnamehere no está en línea   Reply With Quote
Old March 25th, 2017, 08:45 PM   #12
Ryme Intrinseca
Registered User
 
Join Date: Aug 2016
Posts: 197
Likes (Received): 119

I've now completed the final region (South), and therefore have data for the entire United States - see the OP.

I found 833 qualifying interchanges nationwide, with the cloverleaf unsurprisingly the most common interchange (386 or 46%), followed by offside (153), stack (94), 3 loop (73) and cloverstack (46). The state with most qualifying interchanges was California (69), followed by Texas (65), Virginia (60), Illinois (52) and New York (46).

The South had the highest regional share, with 42% of the total, a slight overperformance given it has 37% of the population. In terms of the balance of interchanges, it falls midway between the cloverleaf-dominated Midwest and Northeast and the cloverleaf-shy West. Texas has far more stacks than any other state (38), but this is counterbalanced by states like Virginia, which has the highest number of cloverleafs (47).

Last edited by Ryme Intrinseca; March 25th, 2017 at 09:27 PM.
Ryme Intrinseca no está en línea   Reply With Quote
Old March 27th, 2017, 12:21 AM   #13
Ryme Intrinseca
Registered User
 
Join Date: Aug 2016
Posts: 197
Likes (Received): 119

I've rearranged the data in the OP so it's presented for the whole US rather than by region, which is hopefully an improvement.
Ryme Intrinseca no está en línea   Reply With Quote
Old March 29th, 2017, 06:47 PM   #14
Ryme Intrinseca
Registered User
 
Join Date: Aug 2016
Posts: 197
Likes (Received): 119

For California and Texas I gathered regional data as follows:



Central California corresponds to the ten counties between Stanislaus and Tulare.

I defined East Texas and South Texas broadly, so they include Houston and San Antonio respectively, and West Texas as everything west of a line running roughly from Abilene to Del Rio.
__________________

EasySeven liked this post

Last edited by Ryme Intrinseca; March 30th, 2017 at 12:37 PM.
Ryme Intrinseca no está en línea   Reply With Quote


Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Related topics on SkyscraperCity


All times are GMT +2. The time now is 09:27 AM.


Powered by vBulletin® Version 3.8.11 Beta 4
Copyright ©2000 - 2018, vBulletin Solutions Inc.
Feedback Buttons provided by Advanced Post Thanks / Like (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.

SkyscraperCity ☆ In Urbanity We trust ☆ about us | privacy policy | DMCA policy

tech management by Sysprosium