this post was submitted on 10 Oct 2024
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I think a diverging diamond interchange is actually a pretty elegant solution. That being said, I'd rather have public transport than better traffic infrastructure.
my city is literally prohibited from using public funds for any type of train because of some GOP devil magic thing -- so all we have is busses, which suck because you're still beholden to traffic jams and lights and speed limits and roads. pointless and not even a sense of whimsy or transcendence
I think the diverging diamond interchange is terrible. Because of the crossover, traffic can only cross the interchange in one direction at a time, so most of the traffic in the interchange is not moving most of the time.
A pair of roundabouts connected to on ramps eliminates the danger of left turns without stopping the majority of traffic most of the time.
A massive overbuilt interchange that cannot function without traffic lights is the opposite of elegant.
I'm not so sure about that. The appropriate use of a diverging diamond is when there is a lot of traffic entering and exiting from the ramps, and some of that traffic can go at the same time as the traffic crossing the interchange in one direction.
I don't live in the USA but don't these mostly replace intersections that already have traffic lights?
Also there is a proposed variant without traffic light called DCMI but I don't think there has been any build due to patents or something.
I've read descriptions of how they work numerous times and cannot wrap my head around how having traffic going opposite directions cross paths does anything helpful.
Great, you're now on the appropriate side to make the turn at the far side of the interchange, so the people making the turn don't have to cross traffic to do so, at the cost of every car that crosses the interchange now having to cross traffic twice.
What?
More people are turning than crossing.
Oh. I think I get it. You put the diverging diamond on the route with less traffic where most is expected to be exiting onto the main highway or whatever. You wouldn't put one at a place where two equally busy highways intersected.
That makes more sense.
The Well There's Your Problem podcast has an excellent episode about traffic engineering where they go into diverging diamonds a bit.
I think this is also the episode where they lay out essentially the mission statement of the show, that engineering decisions reflect the politics of those who mandate them, and how the hard sciencey disciplines we think of as "objective" are anything but.
It's a shame they haven't put it on their main channel, which is here: https://youtube.com/@welltheresyourproblempodca1465
We have ine and it's eay better than what we had to deal with before. It solved the traffic.