The new DDI in Joplin

[brianreynolds]

Wednesday morning, while en route from Houston to Hastings MI via the scenic route, I was northbound on I-49 and about to turn eastbound on I-44.  Instead, I backtracked a few miles on I-44 to visit the new DDI at Range Line Road.

This was my first personal experience with a DDI.  I passed through on Range Line Road in both directions twice, then entered I-44 eastbound from the north. 

I know that one goal is a compact interchange that uses a minimum of real estate.  However, my early impression is that this is a bit too compact.  The traffic movements seemed not very smooth.  Maybe the tight turns are intended to slow the traffic, but I felt it would be better if it was stretched about 20% in a north-south aspect, maybe a bit east-west too.

Having read about the DDI design concept several times over the recent few years, it did not seem exotic to me.  But I'd guess that it seems plenty weird to those who are completely unfamiliar.

[apeman33]

It kinda had to be compact. There's not a lot of space in that general area, especially on the north side of I-44. I'm still not sure I like the design. My only other experience with a DDI is in Branson. It seemed that it was better to drive through.

[M86]

It kinda had to be compact. There's not a lot of space in that general area, especially on the north side of I-44. I'm still not sure I like the design. My only other experience with a DDI is in Branson. It seemed that it was better to drive through.

Well, the DDI did replace a cloverleaf, so there's room.   
I didn't see any issues driving through it, and I've driven through the I-44/MO 13 and the US 60/National Avenue DDIs in Springfield, and the one at US 65/MO 248 in Branson.

My question is:  Can you turn left on red at a DDI?  I don't remember seeing any signage at the 3 DDIs I've driven through.  The one at I-44/MO 13 has a yield sign for left turning traffic exiting, but the one is Branson has a traffic signal.

[NE2]

My question is:  Can you turn left on red at a DDI?  I don't remember seeing any signage at the 3 DDIs I've driven through.  The one at I-44/MO 13 has a yield sign for left turning traffic exiting, but the one is Branson has a traffic signal.

Depends if you can turn left on red in the state.
http://www.driversedguru.com/driving-articles/drivers-ed-extras/can-you-make-a-left-turn-on-red/

According to a 2003 pamphlet issued by AAA, the following locations prohibit a left turn on red: Connecticut Missouri North Carolina Rhode Island Vermont New York City

(that page is wrong about arrows - you can turn on a red arrow in some states - so you should probably check the laws to be sure)

MODOT did post no turn on red signs at one DDI near St. Louis.

[M86]

MODOT did post no turn on red signs at one DDI near St. Louis.

Interesting.  It's a dual left too.

I just looked on Streetview, and the DDI in Branson does have a Left Turn Signal sign posted, so I assume no left on red.

[NE2]

I just looked on Streetview, and the DDI in Branson does have a Left Turn Signal sign posted, so I assume no right on red.

If you mean no left on red, that would be true whether or not it's marked as a left turn signal. (You certainly can't go straight on red...)

[M86]

If you mean no left on red, that would be true whether or not it's marked as a left turn signal. (You certainly can't go straight on red...)

With the Left Turn Signal signage at the DDI in Branson, I assume no left turn on red.  If I remember right, MODOT used a red arrow/left arrow/green arrow assembly.

[NE2]

My point is that it doesn't matter what type of signal it is. There's no left on red in Missouri, period.

[M86]

My point is that it doesn't matter what type of signal it is. There's no left on red in Missouri, period.

Eh, ok?  So, out-of-town motorists are supposed to know about that? That's my point. 

With a DDI, there should be increased signage, because it is a new traffic pattern, that is foreign to 99.9% of drivers.
I love MODOT, but they need that additional signage.

[NE2]

My point is that it doesn't matter what type of signal it is. There's no left on red in Missouri, period.

Eh, ok?  So, out-of-town motorists are supposed to know about that? That's my point. 

Out-of-state motorists are supposed to know the laws of the state they're driving in. Ideally they'll be warned and educated on a first offense, but it's up to the driver to know the laws.

[M86]

Out-of-state motorists are supposed to know the laws of the state they're driving in. Ideally they'll be warned and educated on a first offense, but it's up to the driver to know the laws.

Ridiculous... How is a driver supposed to know every law, especially at a Diverging Diamond interchage?  We're talking about a "No Left Turn on Red" signage at DDIs in Missouri.

Good grief.

[NE2]

No, we're talking about whether you can turn left on red from a one-way to a one-way PERIOD. This includes a large number of intersections in St. Louis and Kansas City.

[Alps]

My question is:  Can you turn left on red at a DDI?  I don't remember seeing any signage at the 3 DDIs I've driven through.  The one at I-44/MO 13 has a yield sign for left turning traffic exiting, but the one is Branson has a traffic signal.

Depends if you can turn left on red in the state.
http://www.driversedguru.com/driving-articles/drivers-ed-extras/can-you-make-a-left-turn-on-red/

According to a 2003 pamphlet issued by AAA, the following locations prohibit a left turn on red: Connecticut Missouri North Carolina Rhode Island Vermont New York City

(that page is wrong about arrows - you can turn on a red arrow in some states - so you should probably check the laws to be sure)

(that page is wrong about New Jersey - no left turn on red there either)

[1995hoo]

No left on red in DC either.

Frankly, I think extremely few drivers know left on red is legal in states where it is allowed. It may be mentioned in the driver's manual, but very few people notice it.

It's the type of thing that if you're a non-local driver, a cop might use discretion and just give you a lecture. My brother knows it's illegal to turn on red (left or right) in New York City unless there's a sign, but I was riding with him when he did it simply out of habit when a cop was right behind him. Cop pulled him over immediately but didn't give him a ticket, just a talking-to. No doubt my brother being polite and admitting that he simply forgot the rule didn't hurt.

[M86]

I emailed MoDOT, just to see what they say.  I was confused (even though I probably shouldn't have been) because I had driven through the DDI at I-44/MO 13 in Springfield, and that had a yield sign.  Then, about a year later, I drive through the DDI in Branson that had a traffic signal for left-turning traffic exiting.  I just think a No Turn On Red sign should be warranted, considering DDIs are very new and rare.  Just my 2 cents!

[kphoger]

No, we're talking about whether you can turn left on red from a one-way to a one-way PERIOD. This includes a large number of intersections in St. Louis and Kansas City.

OK, there are two issues at play here.  Generally, turning left on red from a one-way street onto a two-way street is prohibited.  I'm not aware of any places that's legal at all; if there are places, then they are few.  If that's as far as you take the question, then the answer would be an obvious NO, you can't turn left on red at a DDI.

BUT, the prohibition against left on red is, presumably, based on the fact that left-turning traffic must deal with both directions of traffic on the crossroad–where as turning right on red (or left in the case of two one-way streets) means you only have to deal with one direction of traffic.  At a DDI–unlike in typical intersection layouts–turning left on red from the exit ramp does not require you to deal with both directions of traffic on the crossroad, and is functionally the same as turning left from a one-way street onto another one-way street–a movement which is legal in many places.  So it's still a fair question to ask if it has been written into law that left on red at a DDI is legal, just as it had once been written into law that left on red at an intersection of two one-ways is legal.

So, to paraphrase what I quoted from NE2:
If a state allows left turns on red from a one-way street onto a one-way street (which Missouri apparently does not, although I didn't know that until now), how does that state treat the same movement at a DDI?  As a one-to-two-way movement, or as a one-to-one-way movement?

[M86]

A MoDOT representative emailed me back:

Thanks for your email.  Yes, you can make a left on red at the Diverging Diamond interchanges.  You must stop on red, but are free to go if the oncoming direction is clear.

After looking at the DDI on Streetview, again, at US 65/MO 248 in Branson, the right turning traffic at the off-ramp (I'm going by northbound US 65) has signage that states "Right On Red After Stop".

Turning left, the only signage is "Left Turn Signal".  The left turn signal has a full red circle, but a green arrow.

[NE2]

WTF? I guess MODOT doesn't know their own state's laws.

[M86]

WTF? I guess MODOT doesn't know their own state's laws.

The email was from a "Senior Customer Relations Specialist", so I assume they asked an engineer or someone at MoDOT who knows stuff about a DDI... Maybe?

[kphoger]

Engineers don't usually know the exact wording of traffic laws.  Heck, cops don't always know it.

[jeffandnicole]

Out-of-state motorists are supposed to know the laws of the state they're driving in. Ideally they'll be warned and educated on a first offense, but it's up to the driver to know the laws.

Ridiculous... How is a driver supposed to know every law, especially at a Diverging Diamond interchage?  We're talking about a "No Left Turn on Red" signage at DDIs in Missouri.

Good grief.

Most drivers don't know every traffic law in their own state.  There's more to laws than the speed limit and stop signs.

[M86]

I received a reply from MODOT, after I inquired about the No Left on Red Law in Missouri.  Um, fail.

If there is a traffic signal. you must wait for the green light to proceed.  If there is a yield sign, then you may proceed if the oncoming traffic is clear.   

Some of the Diverging Diamond interchanges have traffic signals and the others have yield signs.

Anyone have a contact for a MODOT engineer, or someone higher up?  These "customer service" peeps fail.

[kphoger]

Personally, I've found you're better off looking up the laws yourself online.  If you can't find an exception to the general rule written into law, then you should assume the general rule applies to DDIs as well.

[Big John]

Engineers don't usually know the exact wording of traffic laws.  Heck, cops don't always know it.

At least the traffic engineers should.  A traffic analysis and traffic signal timing program needed to be performed at these intersections and part of the program input is whether turns on red are permitted.  If they didn't know, then they should take the conservative approach and assume they aren't and see if the intersection still has an acceptable level of service under this harder constraint.

[Revive 755]

Engineers don't usually know the exact wording of traffic laws.  Heck, cops don't always know it.

A good transportation agency ought to have a book of traffic related laws floating around the office though.