PHOENIX (3 TV / CBS 5) Valley drivers will encounter a new kind of traffic interchange in the next few months. Two new diverging diamond interchanges will be opening along the new South Mountain portion of the Loop 202.

“As a driver, I know it’s going to be a little bit concerning,” said ADOT spokesman Tom Herrmann.

That’s because these interchanges have you driving on the left.

[WATCH: What drivers should know about interchange for new Loop 202]

As drivers approach the interchange, they go through a controlled intersection with a light. One direction of traffic moves at a time, shifting traffic over to the left side for vehicles entering the Loop 202, and shifting traffic back over the right side for vehicles exiting the Loop 202.

The interchange makes the shape of a diamond, hence the name.

“Because you’re never turning left across traffic there’s no need for a left turn arrow. So traffic moves a little more smoothly with a diverging diamond,” Herrmann said.

The two diverging diamond interchanges will go in at Desert Foothills Parkway and 17th Avenue. They’ll be a first for the state.

Technically, both will be half diverging diamond interchanges because local traffic is unable to go south onto the Gila River Indian Reservation.

There are two others planned elsewhere in Arizona.

One will go in at I-17 and Happy Valley road sometime next year, and another is planned in the Tucson area in the next few years.

And if these interchanges perform well, ADOT could be installing more.

“There’s no reason to believe these won’t go well,” Herrmann said.

[SPECIAL SECTION: Phoenix Traffic]


Copyright 2019 KPHO/KTVK (KPHO Broadcasting Corporation). All rights reserved.



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(27) comments


Wrong-way drivers are only going to be further facilitated by wrong-way intersections.

Jess Itsme

Our Government hard at work... Just trying to "THIN THE HERD" that's all! [lol]


Not to worry. Phoenix drivers are well known as highly intelligent, highly adaptable, and patient motorists... I'm sure they'll handle this traffic change with aplomb, courtesy, and caution...


"One will go in at I-17 and Happy Valley road sometime next year,"

morons. they are putting it in right now


A U.S. Department of Transportation study at five diverging-diamond interchanges in 2014 observed 156 wrong-way traffic maneuvers during a 6-month period. The report stated that these wrong-way turns were "much more likely to take place during night time and off-peak times of day."

Should be interesting to see how this plays out with wrong way drivers here in Phoenix.


I'm all for it but we still have idiots that can't drive on the correct side of the freeway. I just wonder how bad they will negotiate these things ??


Arizona is way behind - lots of states already have these. They are not confusing.

Wyoming redneck

They installed one of these diamond intersections in Cheyenne where there was heavy truck traffic and it really made traffic flow better.


Tom Herrmann you are and idiot, and that is a complement. You design roads that have squeeze lanes just past an exit ramp (202 & Dobson) that should be exit only lanes so that hot shots in F250, etc get in the right lane and push the accelerator to the floor to get by 3 or 4 cars ahead of them then crowd over to the left. In fact you killed a young man doing that on northbound Higley at Main within the last year leaving a 3 year old without her daddy. Another thing you design roundabouts that are far too small for large vehicles to negotiate (Brown & the 202) in fact it is hard for a regular car. I have driven Canadian roundabouts with no problems, but they are twice the size of your mini killers.. And now this. We have a bad enough time with drunks driving the wrong way on interstates and this will compound the problem. You just like to play games with peoples lives apparently.


we are angry.


when the state designs roads to CAUSE wrecks and kill people you bet.


Think about who you are talking about, though. NOTHING is going to stop a drunk driver. These diverging diamonds, navigated even by a half-wit, don't pose a threat. And the DO help a TON. Anyone who has been around Happy Valley and 17 at rush hour is BEGGING for this thing to be finished.


I got transferred to Salt Lake City last year for a couple months and they have these intersections. I was really apprehensive at first, but once you go through one, you can see the genius in these things. And they make it impossible for a wrong way driver to get on the freeway. These are way better than round abouts


“There’s no reason to believe these won’t go well,” Herrmann said." Famous last words of someone attempting to reinvent the wheel!

Arizona Hospitality

It does look like it would deter wrong way drivers. Unfortunately, they cannot do that at every existing interchange without major reconstruction.


Just more business for the funeral homes, body shops, and something for the local media to chew on. [scared]


These work VERY well all over the US and the World... lets hope Arizona's are too stupid to figure them out.

Show Me Data

As I recall, when ADOT put in the then single-lane roundabouts on Happy Valley Road in 2001, their representative said "if these interchanges perform well, ADOT could be installing more. There’s no reason to believe these won’t go well.” It's déjà vu all over again.


and the area around happy valley and 17 was freaking desert back then LOL.

18 years and and about 300,000 homes later......


and for traffic patterns at the time, they worked great. look at the roundabouts on the way out town enrt to vegas. those work perfect...because the traffic pattern is low.


Brilliant idea with all of the wrong way drivers here. Complete morons


This design makes it impossible to go the wrong way on a freeway. You would crash and disable your car before you got to the ramp.


Arizona DPW really likes to experiment. I am sure this won't cause any confusion. /s


I have driven these before. Only complete ret@rds will have trouble


Hmmm. We already have too many wrong way drivers in Arizona, wonder if this is a wise idea?


This may confuse our wrong way drivers



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