This is my idea for a more modern, upgrade interchange at the I-10/I-12/I-59 junction in Slidell, LA.  While the existing interchange functions fairly well, it is beginning to show its age and there are also occasional slowdowns with the ramps to/from I-12.  The existing interchange also has two left-exits as well as two tight loop ramps.

My goal was to determine an improved interchange configuration while remaining within the existing interchange footprint as much as possible.  A secondary goal was to include a design for a new service interchange on I-10 at LA 1090/Military Rd, to serve eastern portions of Slidell.

In the comments below, Military Rd is also known as LA 1090, and Gause Blvd is also known as US 190.

The background imagery is 2007 aerial imagery from NAIP.  Click on the image for a larger graphic (warning, larger graphic is 1.5MB).

Some features of my proposal:

• The I-10 mainline generally maintains its existing configuration, although design speed on the curve is somewhat reduced in order to provide for new right-side exits and retain the existing ponds just southeast of the interchange.  A design speed of at least 60 MPH should still be possible.
• The I-12 mainline generally maintains its existing configuration, with a slight change in the eastbound connection to eastbound I-10.
• The southbound I-59 mainline remains unchanged.
• The northbound I-59 split from I-10 is changed from a left-side split to a right-side split.
• The flyover ramp from northbound I-59 to westbound I-12 is changed from a left-side exit to a right-side exit.  A slight reduction in the design speed of this ramp to 40 MPH may be needed to fit within the footprint.
• A new flyover ramp from eastbound I-12 to northbound I-59 replaces the busy and very-tight 20 MPH loop ramp.  A design speed of at least 40 MPH should be possible.
• A new service interchange is added on I-10 at Military Rd.  The eastbound ramps would be a diamond configuration, with a long eastbound off-ramp from both I-10 and I-12.  The westbound ramps would be a folded-diamond configuration, with the westbound on-ramp being a loop.
• A westbound collector-distributor (C/D) road is included between the Welcome Center and the ramps to/from Military Rd.
• Crawford Landing Dr would be realigned to fit in the westbound C/D road and westbound ramps to/from Military Rd.

The premise behind the interchange at Military Rd is to improve access to eastern Slidell and to reduce congestion on Gause Blvd and the I-10/Gause Blvd interchange.  Presently, access to eastern Slidell to/from the east is very limited, requiring one to either travel a roundabout way via US 190 and US 90 (and MS 604/MS 607 if going to Stennis Space Center), or to head a few miles out of the way to the west along Gause Blvd to access I-10.  This both adds time/distance to eastern Slidell travel and also increases traffic on Gause Blvd and at the I-10/Gause Blvd interchange, which is already congested for several hours a day.  By adding a new interchange at I-10/Military Rd and improving Military Rd between the new interchange and Gause Blvd, traffic on Gause Blvd and at the I-10/Gause Blvd interchange will be reduced.  Traffic may also be reduced along Brown Switch Rd between Military Rd and US 11, reducing the need for improvements along that route.

Three weaving areas would be introduced under my proposal:

• Westbound I-10 between the Rest Area/Welcome Center and Military Rd.  As this weave would be located on a C/D road and not on the mainline, no additional mitigation would be needed.
• Westbound I-10 between the Military Rd/Welcome Center on-ramps and the westbound I-10/I-12 split.  At just over 1/2 mile, this one is not technically a weave but does present some operational problems with traffic from Military Rd and the Welcome Center wanting to continue on westbound I-10.  To mitigate this, a new loop ramp with a 30 MPH design speed is included from westbound I-12 to southbound I-59, which then accesses westbound I-10.  Traffic on the westbound on-ramps from Military Rd and the Welcome Center would be prohibited from crossing over to westbound I-10 directly and would use this new loop ramp instead.  An additional mitigation measure would be to begin the westbound I-10/I-12 split at or before the Military Rd overpass.
• Southbound I-59 between the loop ramps at I-12.  This weaving area is easily mitigated with a collector-distributor lane that's partially separated from the mainline lanes.

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Page last modified 19 August, 2008