DDI Diverging Diamond Interchange
 

Have any of you guys used/driven through this kind of traffic control configuration? Safer and faster; for all vehicles, bikes and pedestrians. https://www.youtube.com/watch?v=UasNoY58cEY

Make the crossings split level, then you would not need traffic lights at all. Just a couple of bridges or tunnels to aid cyclists and pedestrians crossing the access roads.

Then, maybe the bridge itself could be split level. Double decked, it would be twice as narrow and maybe even cheaper to build. And again no traffic lights would be needed.

More tunnels and overpasses add a lot of cost and need to be built big enough for oversized and superheavy transport trucks.

Removing pedestrians and cyclists completely helps a lot.

I've never driven one of these in a rush hour situation. They handle normal traffic well, though.

Helps what, exactly, a lot? Certainly not the pedestrians and cyclists.

It looks reasonable. I've never driven one.

Safer and faster than squeezing your hand in a vise, perhaps. But preferable?

I absolutely hate airlock type traffic lights- where they're placed in pairs and the first light can do anything it wants, but you can't do anything until the farther light allows the gap between them to empty. Given traffic lag, you could sit through an entire green and be looking at another red before there's even room on the other side of your intersection to allow you to cross.

What's worse than airlock lights? Combined ramps, where accelerating traffic moving to the left gets to mix with decelerating traffic moving to the right. As an added bonus, this interchange also mixes in crossing traffic that doesn't want to get on the main highway at all.

A regular Diamond interchange has two lights on the secondary road, and traffic in both directions on the secondary road can be completely unimpeded by reds. The Diverging Diamond can't ever allow traffic in both directions at the same time on the secondary road.

We've already got one bridge here. A cloverleaf has a bridge and zero stoplights. None.

I haven't, but I'd like to. It seems to be a very interesting interchange. If you're interested in stuff like that, you may want to check out skyscrapercity.com. They frequently get into discussions about roadway intersections.

Ontario uses ****loads of Parclo A4 interchanges. All turns are right turns.
https://en.wikipedia.org/wiki/Partia...af_interchange

I have driven across a DDI interchange many times, I was confused as to why they didn't just make it an A4. (I used to drive on it before they turned it into a DDI.)

You know, this all makes me feel SO much better about having to occasionally stop to let a herd of wild horses cross the road :-)

These are used extensively here in Utah. Most new interchanges are done this way and many older ones are being rebuilt to the new configuration. They can get quite complex when dealing with frontage roads, but they still work better than the original.

Cloverleafs use a lot of space.

They also like the Displaced Left-Turn Intersection here for busy surface streets.

Can't speak for every community, but around here cyclists have little regard for and road rules. I have no problem with them having their own paths to cause chaos and keep them out of traffic.

DDI intersections are large and traffic doesn't follow normal patterns meaning slow and jay walking pedestrians get caught in traffic.

Giving them their own overpass or route saves everyone a headache.

Same effect, no stop lights.

http://www.carmel.in.gov/modules/sho...px?imageid=720
http://www.carmel.in.gov/modules/sho...px?imageid=720

Traffic circles are great in light traffic, but heavy traffic becomes a nightmare.

We have a couple of these Split Diamond Interchanges now near me. I agree with Charlie with having to potentially sit and wait at red lights for a while though.

NCDOT: I-485 Charlotte Outer Loop

Define heavy? You don't take a main thoroughfare through a roundabout, just the traffic that is merging on/off. You use traditional exits that go into traffic circles instead of stop lights.

Those traffic circles are in one of the most highly traveled area of indiana.

I checked out the youtube of the simulation. In heavy traffic, the roundabout will be full and approaching traffic will back up, waiting for an opening. In this case, with two lanes in the roundabout, it doesn't matter which lane has a vehicle in it, the approaching vehicles must assume any vehicle in the roundabout will veer to the right and therefore must wait until it passes.

Again, in light traffic, roundabouts work great., but in heavy traffic you get gridlock.

Cars already in the circle are only part 1. Cars stopped in the left lane waiting to enter the circle have to watch over their right shoulders at the same time for jerks sailing down the right lane and popping into the circle at the last moment, just as the lead car in the left lane tries to enter.

Driving a tiny, underpowered car, I'm almost as big a mark as truckers. But I've got a manual transmission and an attitude, and those jerks need a hell of a speed advantage to keep me from putting them in the grass. It happens a lot more than it should- I've had two in the last month. 10% of the time is pathetic. One came to a dead stop to avoid being put on the grass and the other got stopped by the state trooper who was watching the area, whose attention I got by laying on the horn as I launched.

Any interchange where I live is a major thoroughfare. Interchanges are too expensive to waste on lightly traveled roads.

As to what constitutes heavy traffic, I suppose it is relative. I live in a highly built up area of about 2 million people. While Salt Lake and the Wasatch Front are similar in population to the Indianapolis metropolitan area, we are squeezed by mountains, the Great Salt Lake and Utah Lake, into a narrow corridor. Add in an almost pathological disregard for planning and that leaves us with horrendous rush hours.

UDOT has been very aggressive in testing innovative solutions to traffic flow. The Detroit left turn is probably the worst and it has only been used in a couple of spots that I have found so far. They tried the Displaced Left-Turn Intersection (also called the Mexican left turn because it was first used in Mexico City.) about 15 years ago and have become quite fond of it.

It takes some getting used to and it is very frustrating when you forget to get in the turn lane. They time the lights well so there is no wait after the first light turns green, unless you floor it.

Roundabouts are found in slower, lightly used secondary roads and they usually work quite well.

There is a roundabout in my wife's city, Guayaquil, Ecuador. It is at a bottleneck and was a major nightmare, and that was before the traffic got really bad after they dropped the heavy tariff on automobiles back in the 90's. They have since built around it, though I don't know how the improvements have fared through the earthquakes the past couple of months.

Wish you could explain that to the Nevada DOT :-(