ajGoes, thats not what i mean, but i guess i cant explain it

i mean thinking outside the box about how lights can be used

I'm pretty sure the inventors of the diverging diamond interchange were thinking outside the box.

I think traffic engineering is fascinating. I'd like to learn more about it.

moved

Most newer systems are the 'activated' type, where traffic flow determines cycle lengths. Los Angeles has one of the best traffic light systems in the US with constant monitoring of more than 4000 of its traffic signals. I can get into more detail on the different types of traffic signals, but it's a big can of worms that I don't want to open.

To the OP - there are two main advantages to these interchanges:
1. Protected turns (less crashes)
2. More throughput capacity due to less cycles required on the traffic signal.

As for the 'newness' of a concept - when you change road markings or install something minor - 2 weeks is usually what you need for >90% of the drivers to adjust.

When you introduce a new concept - it's a few years. In places where people know how to drive it takes a year or two. In places where they don't, like the US [where you don't need to know how to drive to get a license, you just need to know how to press two pedals - hopefully not both at the same time - turn the steering wheel and follow signs] - it takes longer.

BTW. There's a variation of this concept called the SPUI which is also better at handling traffic than the conventional interchange, but doesn't require overlapping traffic lanes.

ive never seen traffic light with extremely short green lights, in multiple directions, to prevent backups in multiple directions

it would be (technically) possible to have traffic lights acting almost more like stop signs with 'exceptions' (to stopping)

Where I can see the hangup for some is that, if you're not getting onto the freeway and just going "straight", the likelihood of your running into a red light seems increased to a near certainty.

With traditional overpasses, there's a fair chance you pass over the freeway without having to stop.

These are new to me also.

Where it seems there would be a problem is with the traffic crossing over the highway merging in opposite directions. Looking at the orange lanes, the cars coming off NB 85 heading west will all be merging from the 2 left lanes into the two right lanes; simultaneously, westbound traffic on the secondary road wanting to get onto SB 85 will be merging from the right lanes into the left ones. All this over a pretty short stretch of road, about the width of the interstate.

Roads I've seen with this type of cross-merge always feel pretty dangerous to me.

The off ramp from the highway is normally signaled as part of the crossing. When traffic westbound is stopped and traffic eastbound is cleared by the signal, the off ramp from the highway to the westbound direction is cleared.

I went through my first one a few months ago (forget where it was... Utah, maybe?), and I'm pretty sure some sort of word that started with the letter "F" came out of my mouth

When they built one in Brighton, NY at an intersection that backed up in every direction people screamed how awful, unsafe, etc. Over a year later despite more traffic the intersection barely backs up at peak times and the accident rate is also down.

Wouldn't two roundabouts achieve the same result without the need for lights?

I share your impression and your question. The first time I encountered this in St. Louis it was nightime with fog and it was truly disorienting.

Couldn't the same thing be addressed (asking, not asserting) with better traffic light timing?

I noticed the same, especially at night.

Concur.

Also concur

Oh, that would be much worse from my perspective. I detest traffic circles.

Okay, I was wrong - I actually HAVE driven one of these recently. A half version was built at MD 295 @ Arundel Mills Blvd, replacing a two roundabout setup that had only been in place for a few years. I never realized it until I looked at an aerial view just now in response to Norri's question below. I just didn't realize it, because I always take the free right onto MD 295 NB, which bypasses the DDI, and was a free right even when the roundabouts were in place.

Apparently, yes, a two roundabout system does the same thing. For some reason, though, the two roundabouts were removed from the MD 295 @ Arundel Mills Blvd interchange when the Maryland Live casino was built a couple of years ago. I don't know whether the DDI handles traffic better or with fewer accidents or what, but apparently the MD State Highway Administration thinks it does.

https://goo.gl/maps/QSMSxbDKzmn

Yup, dumbbell or teardrop junctions would work:

https://goo.gl/maps/ubJzB9XFvsy
https://goo.gl/maps/D8T1vzwWQCN2

although the latter isn't so good for HGVs. But at least you don't end up with utter disasters of junctions like this:

https://goo.gl/maps/rjfVX8fg6CE2

Just... Why? One of the roundabouts and one of the grade junctions are signal controlled as well, too, just to make sure the A421 gets nice and backed up.

Never seen one of these. On first observation, I don't get what it is improving. You still have two lighted intersections, only now they are crossing each other and involve corners. You also have a bad crossing traffic - traffic exiting the highway not only has to merge with traffic, but the traffic entering the highway has to cross that merging traffic. And pedestrians have 4 major intersection crosses now.

I guess I am still not getting what it supposedly improves.