Interstate 12

[apjung]

It's almost the same as I-57 bypassing St. Louis to Chicago and the I-55 (being a major N/S Interstate) going to St. Louis.

[achilles765]

Frankly, I have always kinda thought it would make more sense for IH 12 to be IH10, have IH 55 continue from its current ending into New Orleans.  The stretch from Baton Rouge to IH 55 in Laplace could be IH 410 or 610 or 255, current IH 610 could be an IH 455 or 655, and IH 59 could continue to meet IH 55 near downtown.  Sure it would be weird, but it'd work.  Or have IH 59 use current IH 510 down to end at the River, and IH 55 could end where IH 59 meets it, at the current IH10/IH 510 interchange.  Or even better, have the new IH 49 south be numbered IH 10, and have IH 12 (or 410) use the IH 10/IH 12 route all the way to Slidell, and the stretch from Baton Rouge to new Orleans can be IH x10 or IH x55. All weird, but really what solution to this puzzle isn't weird in some way?

[lamsalfl]

Frankly, I have always kinda thought it would make more sense for IH 12 to be IH10, have IH 55 continue from its current ending into New Orleans.  The stretch from Baton Rouge to IH 55 in Laplace could be IH 410 or 610 or 255, current IH 610 could be an IH 455 or 655, and IH 59 could continue to meet IH 55 near downtown.  Sure it would be weird, but it'd work.  Or have IH 59 use current IH 510 down to end at the River, and IH 55 could end where IH 59 meets it, at the current IH10/IH 510 interchange.  Or even better, have the new IH 49 south be numbered IH 10, and have IH 12 (or 410) use the IH 10/IH 12 route all the way to Slidell, and the stretch from Baton Rouge to new Orleans can be IH x10 or IH x55. ]All weird, but really what solution to this puzzle isn't weird in some way?

There's no problem that needs a solution.  The current setup is the simplest setup, least confusing, and uses far less route numbers than your are suggesting.  Don't fix something that isn't broken, esp. if it makes it worse!

[vdeane]

I would say the fact that through traffic has to go I-10 -> I-12 -> I-10.  I-10 is a 2di, which means that it's supposed to cater to through traffic, yet it acts as a 3di in the New Orleans area.  I-12 is also pretty short for a 2di (IMO a 2di shouldn't be allowed if it would be shorter than 100 miles).

[Anthony_JK]

I would respond to that with:
,
1) NOLA is probably the most important metro area between Houston and Mobile, It shouldn't be bypassed with a 3di.
2) I-12 serves its purpose nicely as a major NOLA bypass and as an intercontinential route, even if it is short.

[vdeane]

New Orleans is pretty far out of the way.  And there are plenty of other cities that are bypassed by 2dis and get all service by 3dis.  Look at Pittsburgh with I-70, I-76, and I-79.  San Francisco is even more important than New Orleans (according to Google Maps), yet the only reason it has a 2di is because it was the most convenient place for I-80 to peter out.  East-west traffic to Sacremento has to access the city through a BUSINESS ROUTE because I-80 bypasses it! (though this is not true with north-south traffic on I-5).  As a lesser example, look at Rochester, NY.  While 2dis going through cities is the norm, it's not a rule.

As an aside, I've never been fond of bypassing part of a route with another route.  A route should be the shortest road between any two points on the route except for minor deviations as required to maintain equitable travel standards for through (NOT local) traffic.

[Urban Prairie Schooner]

Via its current route, I-10 connects all of south Louisiana's major cities, including directly connecting the state's largest (and most prominent) city and metro area with the state capital and second largest metro area. 10 and 12 receive about the same amount of traffic, though 12 is more heavily used by freight trucks.

The route numbers have been established for decades and fit into the overall interstate numbering system.  If it ain't broke, don't fix it.

[lamsalfl]

Well it's a good thing we're not wasting time debating something that was decided on nearly 60 years ago.

[froggie]

While 2dis going through cities is the norm, it's not a rule.

It depends on how you define the "rule".  FHWA, in this article, states The major route numbers generally traverse urban areas on the path of the major traffic stream..  By this definition, it's proper to have I-10 through New Orleans as that's the major traffic stream.

Something else to keep in mind:  in the original Interstate planning, I-12 would not have remet I-10 in Slidell because I-10 was not originally intended to go through Slidell....it was originally to follow US 90 more directly into Mississippi.  In this original planning, I-12 would have met I-59 in Slidell, while I-59 would have met I-10 somewhere in East New Orleans.

[vdeane]

The numbering makes a lot more sense in that case.  I can understand why they didn't do it though - that area doesn't strike me as needing two east-west interstates so close to each other.

[brownpelican]

The numbering makes a lot more sense in that case.  I can understand why they didn't do it though - that area doesn't strike me as needing two east-west interstates so close to each other.

Exactly. Had I-10 been built as originally planned, it would have been one long bridge/viaduct that Katrina would have wiped out. We know how much replacing the Twin Spans cost. Imagine replacing the original I-10 at double or twice the cost of that.

[jwolfer]

Really, I-12 should be I-10 and I-10 should be the auxiliary.

Sort of like Tampa/St Pete getting I-275 and I-75 being the bypass... Originally I-75 ended in Tampa with I-4 crossing the bay into St Pete.  I would guess 75 was put on the bypass because the Sunshine State Skyway was only 2 lanes back then or because of the toll.  I don't really know

[mwb1848]

I-12 carries the transcontinental traffic.  Good enough reason for me to give it a 2di.

I think this gets to the heart of when rigorously following policy doesn't exactly serve the traveling public.

I know several non-highway folks who have blindly followed I-10 thru New Orleans rather than taking I-12 on trips across Louisiana.  Also, the control cities are kinda obscure... Though Hammond and Slidell make sense from a policy standpoint, they probably don't offer a ton of help to cross-country travelers.

f I-12 was signed at I-10 (with BR and Mobile as control cities) and I-10 signed as something else, they'd be able to cruise along, follow the route they expect to follow, and get where they're going faster.

[UptownRoadGeek]

I hope these blind trips through N.O. occured before mapping services,  i.e: Google, Mapquest, were widely available. It's actually easier to continue onto I-12 by mistake than to stay on the I-10 as the interchanges give I-12 traffic priority. Plus, the control cities are roughly the same. Baton Rouge <- Hammond -> Slidell for I-12 and Baton Rouge <- New Orleans -> Business District -> Slidell for I-10.  Although I can see where putting a secondary sign saying something like "MS Gulf Coast traffic keep left or follow I-12", being helpful I just don't see a reason why large scale signage needs to be changed. At this point, people choosing to stay on I-10 either want to go to N.O. or have only a general idea of where they were headed in the first place as there really is no conflicting signage. Mobile doesn't appear until you're halfway across Mississippi and those control cities will have already changed 2 or 3 times between that point and the LA/MS border. I honestly think that it would be even more confusing.

[mwb1848]

Again, these are non-highway folks. I don't think it's uncommon for "civilians" to expect to just get on a road and go. Especially, when their origin and their destination are on the same highway.

To your point about control cities, It's fascinating that Alabama and Louisiana still retain the pre-1980's control cities of Bay St. Louis and Pascagoula... neither of which are immediately served by I-10 but were directly served when I-10 traffic had to exited onto US 90 at the state line. Mississippi consistently uses cities of interstate importance -- New Orleans and Mobile -- as primary control cities on I-10. (Which is surprising given their deep commitment to McComb and Grenada on I-55.)

If I'm far from home neither Hammond, Slidell, Pascagoula, Bay St. Louis, McComb, nor Grenada help me figure out where on earth I'm going.

[Urban Prairie Schooner]

I-12 carries the transcontinental traffic.  Good enough reason for me to give it a 2di.

I think this gets to the heart of when rigorously following policy doesn't exactly serve the traveling public.

I know several non-highway folks who have blindly followed I-10 thru New Orleans rather than taking I-12 on trips across Louisiana.  Also, the control cities are kinda obscure... Though Hammond and Slidell make sense from a policy standpoint, they probably don't offer a ton of help to cross-country travelers.

f I-12 was signed at I-10 (with BR and Mobile as control cities) and I-10 signed as something else, they'd be able to cruise along, follow the route they expect to follow, and get where they're going faster.

I would not be opposed to signing I-12 with additional control cities in order to clarify its role as a New Orleans bypass. "Hammond - Gulfport", "Slidell - Gulfport" (or Mobile), and "Hammond - Baton Rouge" would be more appropriate anyway. (I-12 is already signed for Baton Rouge from I-10 on its east end.) Most through travelers don't care much about Hammond or Slidell, nor are they major destinations for most out-of-state traffic. Hammond and Slidell are control points primarily because they are locations of junctions with other major interstates. Also, Hammond is a regional center and university town.

Additionally, there could be advance signage on I-10 (and I-59) stating to the effect "Exit (159/267B) use I-12 (east/west) for New Orleans bypass" at either junction.

[bassoon1986]

Or even sign Hammond/ Mississippi from the 10/12 split in BR.

As far as the I-12 as a 2di or 3di, I doubt seriously most people would blindly follow I-10 or accidentally not follow 12 as a shorter route. 5 seconds of looking at a map and 99% of GPS' will tell you 10-12-10 is the obvious way to go.

[pctech]

A sign at the approach of the 10/12 split would be sufficient.  aka. To Miss Gulf Coast,bypass New Orleans use I-12. I don't think that many people are getting lost these days though...

[UptownRoadGeek]

A sign at the approach of the 10/12 split would be sufficient.  aka. To Miss Gulf Coast,bypass New Orleans use I-12. I don't think that many people are getting lost these days though...

Exactly. Most "non-highway" people, these days, are simply going wherever Google or their Garmin/TomTom is telling them to go.

[pctech]

When the Interstate system was originally routed  in Louisiana, I wonder if they considered having the I-10/12 split at Lafayette? I-10 would have followed US 90 to NOLA and through like it does now. I-12 would have crossed the basin to Baton Rouge and continued to meet up with I-10/59 as it does now. That would leave a gap from Baton Rouge to New Orleans though.

[NE2]

When the Interstate system was originally routed  in Louisiana, I wonder if they considered having the I-10/12 split at Lafayette? I-10 would have followed US 90 to NOLA and through like it does now. I-12 would have crossed the basin to Baton Rouge and continued to meet up with I-10/59 as it does now. That would leave a gap from Baton Rouge to New Orleans though.

I-12 was not part of the system at all until 1957. Going back almost to the earliest plans, what became I-10 was routed through Baton Rouge (the ca. 1943 interregional plan appears to send it via Orange-Deweyville-Dequincy-Opelousas-Baton Rouge; the 1939 plan did in fact use US 90, with no route through Baton Rouge).

And then there was the proposed Acadian Thruway (1950s), from Lafayette to Lutcher. I guess this would have been in addition to I-10.

[apjung]

Close call on I-12 in Livingston Parish caught on dashcam
http://www.wwltv.com/story/news/2015/02/18/dashboard-camera-captures-near-accident-on-i-12/23606853/

[roadman65]

A sign at the approach of the 10/12 split would be sufficient.  aka. To Miss Gulf Coast,bypass New Orleans use I-12. I don't think that many people are getting lost these days though...

At the other end in Slidell, there is a "Baton Rouge" sign in addition to "Hammond" that directs through I-10 motorists that they can bypass NOLA.

[BamaZeus]

Close call on I-12 in Livingston Parish caught on dashcam
http://www.wwltv.com/story/news/2015/02/18/dashboard-camera-captures-near-accident-on-i-12/23606853/

Perfect "bootlegger 180" by the driver of the black car.   I am duly impressed that he didn't even nick the other car.

[Anthony_JK]

When the Interstate system was originally routed  in Louisiana, I wonder if they considered having the I-10/12 split at Lafayette? I-10 would have followed US 90 to NOLA and through like it does now. I-12 would have crossed the basin to Baton Rouge and continued to meet up with I-10/59 as it does now. That would leave a gap from Baton Rouge to New Orleans though.

I-12 was not part of the system at all until 1957. Going back almost to the earliest plans, what became I-10 was routed through Baton Rouge (the ca. 1943 interregional plan appears to send it via Orange-Deweyville-Dequincy-Opelousas-Baton Rouge; the 1939 plan did in fact use US 90, with no route through Baton Rouge).

And then there was the proposed Acadian Thruway (1950s), from Lafayette to Lutcher. I guess this would have been in addition to I-10.

I always wondered if what is now US 190/LA 12 was originally proposed to be I-12 and the proposed Acadian Thruway (via the Sunshine Bridge) would have become I-10 to NOLA. Also, the original plans for what became I-110 would have extended along US 61 south to fill that gap?