Flyovers at Diamond Interchanges

[intelati49]

This is kind of a general question, but related to a Central states topic.  To use MO 171 and MO 249 as I-49 the interchange at 171 and US 71 in Carthage will have to be upgraded.  In a minutes Document I found a MoDot employee said that the interchange would get $10 million. Would adding a flyover ramp to the diamond interchange work as a interchange? Or is this a disaster waiting to happen?

BTW, How do I post an image?

[Scott5114]

To post an image, upload it to another website (if you don't have your own, http://imgur.com is a nice simple one) and then enclose the URL for it in tags.

I assume that simply adding a flyover to a diamond interchange wouldn't work because there would still be two at-grade intersections that would have to be dealt with. Of course I'm not too certain if I understand the proposed configuration here, so maybe the image you're thinking of posting will help.

[rickmastfan67]

The tags Scott is talking about are:

Code Select Expand

[img][/img]

[Scott5114]

Of course the software would try and interpret my blank example tags as the real thing, even helpfully inserting a http:// for me :roll:

[Revive 755]

This is kind of a general question, but related to a Central states topic.  To use MO 171 and MO 249 as I-49 the interchange at 171 and US 71 in Carthage will have to be upgraded.  In a minutes Document I found a MoDot employee said that the interchange would get $10 million. Would adding a flyover ramp to the diamond interchange work as a interchange? Or is this a disaster waiting to happen?

As an interchange, it should work.  MoDOT is apparently going to try adding a flyover to the I-44/MO 141 interchange in Valley Park, which has the complications of one-way outer roads.  As for being an interstate quality interchange, MoDOT may not get approval for switching I-49 to the MO 171/MO 249 route unless the current SB US 71 exit is redesigned into a more sweeping ramp

It has kind of been done elsewhere, such I-40 at TN 155 on the west side of Nashville:
http://maps.google.com/maps?hl=en&ie=UTF8&ll=36.155791,-86.8504&spn=0.014293,0.041199&z=16

It also appears to have been tried on I-15 in Las Vegas:
http://maps.google.com/maps?hl=en&ie=UTF8&ll=36.101553,-115.177424&spn=0.007152,0.020599&t=k&z=17

and on I-215 in Salt Lake City:
http://maps.google.com/maps?hl=en&ie=UTF8&ll=40.632796,-111.84715&spn=0.013434,0.041199&t=k&z=16

[TheStranger]

It has kind of been done elsewhere, such I-40 at TN 155 on the west side of Nashville:
http://maps.google.com/maps?hl=en&ie=UTF8&ll=36.155791,-86.8504&spn=0.014293,0.041199&z=16

It also appears to have been tried on I-15 in Las Vegas:
http://maps.google.com/maps?hl=en&ie=UTF8&ll=36.101553,-115.177424&spn=0.007152,0.020599&t=k&z=17

and on I-215 in Salt Lake City:
http://maps.google.com/maps?hl=en&ie=UTF8&ll=40.632796,-111.84715&spn=0.013434,0.041199&t=k&z=16

The closest example near me (surface street/freeway interchange with added flyover) is US 50 at Prairie City Road in Folsom:
http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=Prairie+City+Road,+Folsom,+CA&aq=&sll=40.632649,-111.836486&sspn=0.011399,0.015707&ie=UTF8&hq=&hnear=Prairie+City+Rd,+Folsom,+Sacramento,+California+95630&ll=38.642517,-121.156411&spn=0.011732,0.015707&z=16

[intelati49]

To post an image, upload it to another website (if you don't have your own, http://imgur.com is a nice simple one) and then enclose the URL for it in tags.

Thanks.



Green is new roadway.
Black is ROW.
Red is bridges.
Orange is existing roadway to be removed.

[JREwing78]

EBD to NBD would probably be a smoother curve than what's shown here. The WBD to NBD ramp will also probably be realigned so that it doesn't have to go under the EBD to NBD ramp. That would be one less bridge that would have to be built.

There's a similar concept being floated in Madison, WI for the US-12/18 and US-51 interchange, but there's a parallel road (the old Madison Beltline highway) that has to be worked around (likely shifted north of its existing location). Plans are here: http://www.dot.wisconsin.gov/projects/us51-stoughtonrd/alts.htm

[US71]

I'm not sure that would, er, fly. I've heard rumors of 249/Future 49 being extended further north from 171 to include a more direct exit to Carterville. Would it be cheaper to upgrade 171 or build a new roadway?