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Author Topic: Louisiana Gets 1st Diverging Diamond Interchange (I-210 @ Cove Lane/Nelson Road)  (Read 7748 times)

Anthony_JK

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My state hasn't been too innovative regarding interchange types, but that may be changing.

The I-49 Connector project in Lafayette will introduce Louisiana to the SPUI, with 2 of them proposed at Second/Third Streets and Johnston Street.

And now, the reconstruction of I-210 in Lake Charles will introduce the state's first diverging diamond interchange (DDI), with the Nelson Road interchange rebuild. The original Nelson Road interchange was a traditional diamond which will be converted to a DDI. The other part of the project will include the addition of a second interchange (a more conventional tight diamond) with Cove Lane, which will be extended to a new roadway which will access the casinos on the north side of I-210. In addition, an auxiliary lane will be built on I-210 in both directions between Cove Lane and Nelson Road.

The LaDOTD has a page dedicated to this project, which includes a drawup of the proposed project, here:

http://wwwapps.dotd.la.gov/administration/public_info/projects/home.aspx?key=46

Perhaps we'll see more DDI's and SPUI's here in Louisiana??
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Henry

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If there ever were plans for new/rebuilt interchanges for the Shreveport, Baton Rouge and New Orleans areas, these would make great projects!
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jbnv

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My state hasn't been too innovative regarding interchange types, but that may be changing.
You forgot the continuous-flow intersections in Baton Rouge and Lafayette. ;)

The I-49 Connector project in Lafayette will introduce Louisiana to the SPUI [... at] Johnston Street.
Why?? They should get rid of that ugly turn that links Johnston St. to Louisiana Ave., and this is their one shot to do it. No reason why they can't do something like this:

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Anthony_JK

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My state hasn't been too innovative regarding interchange types, but that may be changing.
You forgot the continuous-flow intersections in Baton Rouge and Lafayette. ;)

CFI's are intersections, not interchanges....and the Johnston St./Camillia Blvd./Guilbeau Rd. intersection that was recently completed is technically not a CFI, but a "reduced phase intersection".

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The I-49 Connector project in Lafayette will introduce Louisiana to the SPUI [... at] Johnston Street.
Why?? They should get rid of that ugly turn that links Johnston St. to Louisiana Ave., and this is their one shot to do it. No reason why they can't do something like this:



Ahhh, HELL TO THE NO.

Louisiana Ave. is a major arterial connector linking downtown and ULL to northeast Lafayette. It's even important enough that LADOTD added an interchange with I-10 and plans to extend it north beyond there to Gloria Switch Road east of Carencro. The I-49 Connector is expensive enough as it is. Besides, that "hook" will get strengthed out a bit because a grade seperation of the BNSF/UP railine will be built along with the SPUI interchange at Johnston St.

Plus, your proposed directional ramps would be spaced way too close and with too tight curves for safety, let alone Interstate design standards; and it would interfere with the other proposed downtown SPUI at Second/Third Sts.

Why fix what isn't really broken when what is proposed does the job adequately?
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jbnv

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... it would interfere with the other proposed downtown SPUI at Second/Third Sts.

There is no SPUI at Second/Third Sts. in my proposal. I don't see any need for it whatsoever. An offramp before Mudd Ave. would give SB traffic access to downtown; those commuters would then take Evangeline Thruway to the street of their choice. A similar ramp into the NB provides the egress. Traffice from the south to downtown can exit at Johnston St.

Louisiana Ave. is a major arterial connector linking downtown and ULL to northeast Lafayette. It's even important enough that LADOTD added an interchange with I-10 and plans to extend it north beyond there to Gloria Switch Road east of Carencro. The I-49 Connector is expensive enough as it is. Besides, that "hook" will get strengthed out a bit because a grade seperation of the BNSF/UP railine will be built along with the SPUI interchange at Johnston St.

Louisiana Ave is a thru road and in some cases a more convenient route to I-10, but I would not call it a major artery. The fact that it goes to I-10 hasn't magically made it another Ambassador Caffery. I grew up on Webb St. and am very familiar with that part of Lafayette. Between Evangeline Thruway and Willow St., it hasn't changed much in the 23 years since I moved away. And I don't see it changing.

The funny jog won't cease to exist just by putting a SPUI over I-49. When I-49 is completed through Lafayette, only local traffic will make that jog. Most of the traffic will take I-49. It makes sense to have US 167 flow smoothly onto/off of I-49. It doesn't make sense to force the connection just for the sake of preserving the connection.

Plus, your proposed directional ramps would be spaced way too close and with too tight curves for safety, let alone Interstate design standards.

OK, take out Chestnut St. to make room for them. When I drew this, I compared it with I-49 through southern Alexandria. There's more room in this Lafayette corridor than there is in the Alexandria corridor, and they actually built I-49 in there. I'm not a traffic engineer but I wouldn't have drawn and kept it if I didn't feel that it was at least plausible.

Why fix what isn't really broken when what is proposed does the job adequately?

You think it's not broken. I cringe every time I have the misfortune of driving through it.
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NE2

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Is it ugly or just offensive to anal roadgeeks?
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jbnv

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Is it ugly or just offensive to anal roadgeeks?

Both.
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Anthony_JK

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The Second/Third couplet feeds directly to Congress St., which is a major arterial that serves the western portion of Lafayette, the former University Medical Center, the ULL athletic facilities (Cajun Field, Cajundome, and Tigue Moore Field), and Southwest Regional Medical Center. It is more than justified as a full interchange exit for I-49...especially since recently imposed rules do not allow for internim partial "slip ramp" exits.

Chestnut Street is already scheduled to be mostly removed under the proposed Connector anyway.

Your interchange design would still not work because 1) the proximity of the railline would necessitate either superelevated or depressed access roads with sharp turns violating design standards; and 2) there really is still no need to sever the connection between Johnston St. and Louisiana Avenue and essentially divide the city...and your removal of the 2nd/3rd interchange would simply make it that much worse.

BTW...the SPUI would actually be UNDER I-49 for both the 2nd/3rd and Johnston exits...and there are also plans to essentially consolidate the exit ramps off I-49 into one two-lane exit that would then split off to sere both interchanges.


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jbnv

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The Second/Third couplet ...

I lived in Lafayette as recently as 2012, and my mother and sister still live there. I know what the major roads serve.

The UL facilities and the hospital are all at or near the intersection of Congress and Bertrand. Traffic that needs to go north from there should take Bertrand Drive to get to I-10, not take Congress Street into downtown Lafayette to get to Evangeline Thruway. Upgrade Bertrand Drive to a freeway spur from I-10 (which I've never heard anyone propose) and this would be even more so.

The gateway to western Lafayette is Amb. Caffery and Bertrand Drive from I-10, not Congress/2nd/3rd from the Thruway.

... there really is still no need to sever the connection between Johnston St. and Louisiana Avenue and essentially divide the city...

The I-49 connector will do more to "divide" the city (which already has ample racial divide as it is) than preserving the Johnston/Louisiana connection. Most traffic coming north on Johnston St. will go onto I-49; it will not continue onto Louisiana Ave. This is reality. I prefer to design our roads to meet the needs of traffic flow, not cater to some racial fairy tale.

... and your removal of the 2nd/3rd interchange would simply make it that much worse.

You make it sound like I am intentionally designing I-49 to bypass north Lafayette. I'm working on another design that uses a SPUI. It still has only one SPUI. One of my ideas would actually increase access to the northside from NB I-49.

BTW...the SPUI would actually be UNDER I-49 for both the 2nd/3rd and Johnston exits...

Yes, let's throw away the opportunity we have to get Johnston St. over the railroad for... what reason exactly?

... and there are also plans to essentially consolidate the exit ramps off I-49 into one two-lane exit that would then split off to sere both interchanges.
*facepalm* We already have a local road to serve these streets. It's Evangeline Thruway. So instead of building this thing to actually improve traffic flow in and out of the corridor, we're going to build something that duplicates existing functionality.

This is the same sort of thinking that gave us a throttled Camellia Blvd instead of a direct connection between Johnston St. and Kaliste Saloom Rd. Doing things the way we've always done them.
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Anthony_JK

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 I have family who stay in Lafayette, and I live 20 miles north...so it's not as if I don't know what I'm saying.

You can make all the plans you want, but I'm going off the ROD that was approved by FHWA and the LADOTD....and simple common sense.

First, I didn't say that Congress St. was the "gateway" to western Lafayette; only that it was a major corridor from downtown to western Lafayette, and it uses the Second/Third couplet to connect to Evangeline Thruway. Severind entryg that connection would be far more divisive, and would also deny a second entry to downtown from the north.

Second....racial divide?? Really?? The Sterling Grove area is predominately White, and the proposed freeway is elevated and shifted away from the Sterling Grove Historical District (which borders the northbound Evangeline Thruway between Simcoe St. and Mudd Avenue.); and the freeway retains numerous crossing points at Simcoe, 2nd/3rd, Jefferson, Johnston, and 14th/Taft streets. Plus, it's curved away from the (mostly Black) neighborhoods fronting the Evangeline Thruway, running generally parallel to the BNSF railline. Or, would you rather I-49 go around the city via Teche Ridge through St. Martin Parish?? Lotsa luck there.

North Lafayette is already served by the Willow St. interchange. The 2nd/3rd interchange is there to access downtown.

The proposed SPUI at Johnston St. includes a grade seperation of the BNSF railline where Johnston would pass underneath the railline and I-49, just as Jefferson St. already does. The same design is also proposed at 2nd/3rd; which would be converted to a virtual boulevard passing underneath the railline before seperating back into individual streets at Cypress St. There's really no need to pass Johnston St. "over the railroad".

And once again, the proximity of Johnston St. and Louisiana Avenue and the BNSF line make your proposed directional ramps connecting Johnston St. prohibitively more expensive than the proposed and approved design. Not to mention, gross violation of grade design standards.

The real justification for the I-49 Connector is to provide direct freeway access to critical destinations, complete I-49 South through Lafayette in the most direct and convenient means possible, and add much needed capacity to the existing network. Evangeline Thruway is more than capable of handling local traffic, but without I-49 being built, it will get overwhelmed at the first hurricane evacuation from South Louisiana.

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jbnv

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... would you rather I-49 go around the city via Teche Ridge through St. Martin Parish??

No I do not.

You can make all the plans you want, but I'm going off the ROD that was approved by FHWA and the LADOTD....and simple common sense.

I see nothing sensical about this plan. And DOTD doesn't exactly have a great track record in planning a statewide highway system. FHWA can approve anything that they want; they don't need to know or care anything about the affected community, and they don't have to pay for it either.

First, I didn't say that Congress St. was the "gateway" to western Lafayette; only that it was a major corridor from downtown to western Lafayette, and it uses the Second/Third couplet to connect to Evangeline Thruway. Severind entryg that connection would be far more divisive, and would also deny a second entry to downtown from the north. ... The 2nd/3rd interchange is there to access downtown.

My concepts don't deny downtown anything. If anything, by using Evangeline Thruway as a local service route, I'm giving that part of town more traffic than the state does. Traffic going downtown can get there via Johnston St. or Evangeline Thruway.

The 2nd/3rd interchange is simply unnecessary. Few people are going to use it. Almost nobody will use it to come in from out of town and go to the Cajundome or the hospital.

The proposed SPUI at Johnston St. includes a grade seperation of the BNSF railline where Johnston would pass underneath the railline and I-49, just as Jefferson St. already does. The same design is also proposed at 2nd/3rd; which would be converted to a virtual boulevard passing underneath the railline before seperating back into individual streets at Cypress St. There's really no need to pass Johnston St. "over the railroad".

Why are they planning to do this? Are you really trying to argue that two graded routes under an existing railroad is a better solution than one overpass over it? Are they going to have to rebuild the railroad? Also, we know that the Jefferson St. underpass floods when it rains--do these plans include a drainage system? Have the environment people given this idea a stamp of approval?

And once again, the proximity of Johnston St. and Louisiana Avenue and the BNSF line make your proposed directional ramps connecting Johnston St. prohibitively more expensive than the proposed and approved design. Not to mention, gross violation of grade design standards.

Fine. I'll offer you and the state an even simpler proposal: A southbound split to Evangeline Thruway at Mudd Ave. and a northbound split at Pinhook Road. At Johnston Street, just three ramps: one from I-49 southbound to Johnston St., and one from Johnston St. to I-49 northbound and southbound. With this design, local traffic uses Evangeline Thruway to get to any part of central Lafayette. Express traffic flows through on I-49, bypassing the nonexistent exits that it wasn't going to use with no concern whatsoever.

I know you're not going to like this idea, but here are the facts: This plan provides the same access to downtown and northern Lafayette that the state's plan does. But it requires less cement, less money and less time to complete. And it does not involve digging two new underpasses or rebuilding an existing rail line.
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Anthony_JK

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Since this is getting away from the original purpose of the thread, which was to talk about the I-210/Cove Lane DDI, I'll soon create a new thread for this debate.

But suffice it to say, I don't agree with the notion that jbnv knows more about what should be done for I-49 through Lafayette than the MPO, the LADOTD, and the FHWA which approved the current proposal. He has every right to propose his alternative, of course...and I have as much a right to say it won't work and that the current proposal of LADOTD is more than adequate.
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jbnv

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But suffice it to say, I don't agree with the notion that jbnv knows more about what should be done for I-49 through Lafayette than the MPO, the LADOTD, and the FHWA which approved the current proposal.

Unlike the FHWA and most employees of DOTD, I actually lived in Lafayette over the course of several decades and have much personal familiarity with the area in question. But hey, DOTD doesn't solicit my opinion and their work speaks for itself.

and I have as much a right to say it won't work and that the current proposal of LADOTD is more than adequate.

Yay free speech.

Since this is getting away from the original purpose of the thread, which was to talk about the I-210/Cove Lane DDI, I'll soon create a new thread for this debate.

Do we have a thread for the I-49 connector through Lafayette? It belongs there.
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Anthony_JK

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I will be starting that thread shortly...but for perspective, here is a pic of the proposed routing of the I-49 Connector through Lafayette as approved in the 2003 ROD.



Feel free to compare that to jbnv's proposal and judge for yourself.

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