I-55/I-69 and MS 302/Goodman Rd. Parclo (Why the Left Turns?)

[Ned Weasel]

I noticed this during some semi-random Google Maps browsing--

I searched and searched the forum for a post about this, and I couldn't find anything.  Can someone explain why there are left turns from MS 302/Goodman Rd. to I-55/I-69?  I realize that redundant left turns can sometimes be justified, but what's the reasoning behind these?  (Also notice the pavement marking for the straight-through movement from the northbound exit ramp to the northbound entrance ramp.)

https://maps.google.com/?ll=34.962728,-89.999458&spn=0.003233,0.005284&t=k&z=18

[lordsutch]

I noticed this during some semi-random Google Maps browsing--

I searched and searched the forum for a post about this, and I couldn't find anything.  Can someone explain why there are left turns from MS 302/Goodman Rd. to I-55/I-69?  I realize that redundant left turns can sometimes be justified, but what's the reasoning behind these?  (Also notice the pavement marking for the straight-through movement from the northbound exit ramp to the northbound entrance ramp.)

https://maps.google.com/?ll=34.962728,-89.999458&spn=0.003233,0.005284&t=k&z=18

I'd imagine they were included mostly to make it easier for traffic from the shopping centers adjacent to the interchange to make those movements, rather than crossing several lanes of traffic. They may have also made construction staging easier.

[Brian556]

Here's one in Lewisville, TX where traffic heading NE can turn right or left to reach NB I-35E. The sign, however, says to turn left.
https://maps.google.com/?ll=33.007453,-96.970975&spn=0.003005,0.00626&t=k&z=18

[Anthony_JK]

Perhaps the left turn movements are designed for trucks and heavy trailers who might not be able to negotiate the tight 25 mph loops?? And, the allowing of through movements are for people who are lame enough to miss their exit but want to get back onto the freeway??

[Ned Weasel]

Here's one in Lewisville, TX where traffic heading NE can turn right or left to reach NB I-35E. The sign, however, says to turn left.
https://maps.google.com/?ll=33.007453,-96.970975&spn=0.003005,0.00626&t=k&z=18

The right turn also serves commercial development, so it isn't exactly the same thing.  While the left turn in your example isn't necessary to provide the movement from eastbound Round Grove Road to northbound I-35E, it probably provides a less congested path.

[Ned Weasel]

I'd imagine they were included mostly to make it easier for traffic from the shopping centers adjacent to the interchange to make those movements, rather than crossing several lanes of traffic. They may have also made construction staging easier.

There are triple left turn lanes from northbound Southcrest Parkway to westbound MS 302/Goodman Road, so if you take the right-most left turn lane, you're already in the lane that puts you on the loop ramp to southbound I-55/I-69.  And there are double left turn lanes from southbound Interstate Drive to eastbound MS 302/Goodman Road, so only one lane change is required in order to take the loop ramp to northbound I-55/I-69 (two lane changes if you wait too long).

I can see why those left turns would be there while the interchange was under construction, but I'm not sure why they wouldn't be removed upon completing it as a parclo.

[UptownRoadGeek]

There are multiple examples of the same set up in the Jackson area along I-55 and I-20. Shrug

[lordsutch]

There are triple left turn lanes from northbound Southcrest Parkway to westbound MS 302/Goodman Road, so if you take the right-most left turn lane, you're already in the lane that puts you on the loop ramp to southbound I-55/I-69.  And there are double left turn lanes from southbound Interstate Drive to eastbound MS 302/Goodman Road, so only one lane change is required in order to take the loop ramp to northbound I-55/I-69 (two lane changes if you wait too long).

I can see why those left turns would be there while the interchange was under construction, but I'm not sure why they wouldn't be removed upon completing it as a parclo.

The lane layouts at both of those lights have been radically revamped since the I-55 interchange was originally rebuilt.  If anything, having multiple turn lanes makes it more useful to be able to get on I-55 from the left or the right, particularly for non-locals who'd be likely to be going to the restaurants etc in Horn Lake & Southaven.

As UptownRoadGeek points out, it's not an atypical MDOT design pattern of that era.  For example, you can turn left or right off westbound County Line Road in Jackson to get on I-55 south.

[Ned Weasel]

There are multiple examples of the same set up in the Jackson area along I-55 and I-20. Shrug

Oh.  I see some of those now.

[UptownRoadGeek]

I-55/Goodman Rd
I-55/MS 22
I-55/Sowell Rd
I-55/County Line Rd
I-55/Siwell Rd
I-20/Springridge Rd
I-20/Raymond-Clinton Rd

Are a few examples that I can think of. I'm sure that there are more. Whatever the reason, it's safe to say that they have been doing this since the late 80's up until the early 2000's which would be when the current Memphis area exits were built. They have them in Tennessee also.

[berberry]

At the full cloverleaf US-49 and I-59 in Hattiesburg, a left turn is allowed from sb 59 to sb 49 even though there's a loop ramp and no need for super lane changes to use it.  I think it's done for more convenient access to a truckstop, but I've never really slowed down enough there to take a close look.

[bassoon1986]

Here's one in Lewisville, TX where traffic heading NE can turn right or left to reach NB I-35E. The sign, however, says to turn left.
https://maps.google.com/?ll=33.007453,-96.970975&spn=0.003005,0.00626&t=k&z=18

The right turn also serves commercial development, so it isn't exactly the same thing.  While the left turn in your example isn't necessary to provide the movement from eastbound Round Grove Road to northbound I-35E, it probably provides a less congested path.

When I lived near there, I took the right turn because the merge onto the service road on the left turn was an immediate crossing of lanes to enter I-35E. The right turn reduced time waiting on the left green arrow, too.

[Ned Weasel]

At the full cloverleaf US-49 and I-59 in Hattiesburg, a left turn is allowed from sb 59 to sb 49 even though there's a loop ramp and no need for super lane changes to use it.  I think it's done for more convenient access to a truckstop, but I've never really slowed down enough there to take a close look.

This one seemed truly baffling at first, but, after looking at Street View, I think I can see why it's like that--

https://maps.google.com/?ll=31.358517,-89.347015&spn=0.001191,0.002642&t=k&z=19&layer=c&cbll=31.358517,-89.347015&panoid=GjzJ_6jeDrF-qeDuozarDg&cbp=12,238.51,,0,0

There's a barrier that blocks off what would otherwise be an allowed left turn.  Notice, however, that the sign assembly shows a hard right arrow for Classic Drive but an upward diagonal right arrow for NB US 49/WB MS 42.  (In my opinion, this sign for Classic Drive should read "TO Classic Drive" with an advance right turn arrow.)  This seems to have been done to allow motorists to turn into the left lanes (it's usually illegal to turn directly into the left lane, but people do that routinely when it's possible), in order to make the left turn onto Classic Drive, rather than channeling everyone into the number 3 through lane on NB US 49.