I-49 should be signed as such immediately.

[Grzrd]

I-49 is legislated by Congress, per FHWA.

High Priority Corridor 72's statutory language provides a Congessional designation of I-49 from Kansas City to Shreveport, as per FHWA's interpretation of the language:

72.The North-South corridor, along Interstate Route 49 North, from Kansas City, Missouri, to Shreveport, Louisiana.

However, in regard to the US 90 corridor from Lafayette to New Orleans, Congress has apparently left the numbering discretion up to LaDOTD, as reflected by the statutory language of High Priority Corridor 74:

74.The portion of United States Route 90 from Interstate Route 49 in Lafayette, Louisiana, to Interstate Route 10 in New Orleans, Louisiana.

Hmmmmm ..... Maybe there is a covert I-6 Congressional Caucus within the Louisiana delegation? 

edit

Interestingly, FHWA notes that High Priority Corridor 37 ("37.United States Route 90 from I-49 in Lafayette, Louisiana, to I-10 in New Orleans.") is officially designated as a Future Interstate.  Is there any substantial difference between the language of HPC 37 and HPC 74? ........ unless I-10 goes near a New Orleans outside of Louisiana. 

[Grzrd]

Big difference, I-49 must go by rules presented by FHWA and AASHTO. I-69 is a congress mandated highway. Thus, signs and approvals are on two different time tables. The first must be complete, the second, is eh, good enough for now. The whole East, Central, 369, I-2, and Houston area don't even touch the rest of I-69.

MAP-21 changed the rules, not only for I-69 (and I-11), but also for the "other" interstates. This post discusses MAP-21's impact on the "other" interstates, whether Congress mandated a number or not.  Also, the post following the linked post provides some historical context for the origin of this thread.

[US71]

Looks like AHTD now has permission from AASHTO to post I-49. Now if the Federal Highway Administration will sign off on it, we could start seeing signs.

http://www.shreveporttimes.com/viewart/20131028/NEWS/131028008/Arkansas-gets-initial-OK-Interstate-49-name-

[M86]

Looks like AHTD now has permission from AASHTO to post I-49. Now if the Federal Highway Administration will sign off on it, we could start seeing signs.

http://www.shreveporttimes.com/viewart/20131028/NEWS/131028008/Arkansas-gets-initial-OK-Interstate-49-name-

This makes me happy.  Assuming this passes, MoDOT and AHTD need to post some "Future I-49 Corridor" signage.

I know a lot of the people here in NW Arkansas refer to current I-540 as "the bypass".  It drives me insane... Because now we need a bypass of "the bypass".

[bugo]

It was once US 71, US 62, now it's I-540 and it will soon be I-49.  Is there any wonder why they call it "the bypass"?

[US71]

It was once US 71, US 62, now it's I-540 and it will soon be I-49.  Is there any wonder why they call it "the bypass"?

It was originally called the "71 Bypass" when it first opened, as was the extension to Bella Vista. No one (except maybe a few people at AHTD) gave any thought to to I-540 or I-49 when the "bypasses" were built.