0
$\begingroup$

Thinking it might be possible to incorporate the diverging aspect of DDIs into a 4-way roundabout, I came up with this free-flow (highway-to-highway) interchange, which only requires 4 relatively small flyovers/underpasses (compared to similar structures).

Diverging Roundabout (Here is a mirror image if you happen to drive on the other side.)

I couldn't find it on the wikis. Is this a thing? Since I'm not an expert, I wonder if there are use cases, what are the pros and cons and whether something like this exists in the real world?

Navigation is pretty straightforward. Here's how it works:

  • To turn right, use the right lane.
  • To turn left, use the left lane and merge left.
  • To go strait, use the left lane and stay on that lane.

(In practice you would just have to follow the big road signs overhead, just as with any other large highway interchange.)

Notes: U-turns are also possible, using the left lane and merging to the right twice. Weaving is probably not much of an issue as merging to the right only happens in the rare cases of U-turns and sub-optimal routings.

Improve this question
$\endgroup$
7
  • 2
    $\begingroup$ This is neater: en.wikipedia.org/wiki/Magic_Roundabout_(Swindon) $\endgroup$
    – Solar Mike
    Commented Jan 26 at 20:07
  • $\begingroup$ @SolarMike: It's not the same category. (Btw, I never understood what problem, if any, the Magic Roundabout aims to solve). The one I show is a free-flow interchange for things like highways where you never stop. It's comparable in terms of functionality to the various Stack Interchanges, although possibly on a smaller scale. $\endgroup$
    – Stéphane Gimenez
    Commented Jan 26 at 21:10
  • $\begingroup$ Here's the Interchange page that lists other things it can be compared with. $\endgroup$
    – Stéphane Gimenez
    Commented Jan 26 at 21:29
  • $\begingroup$ @Stéphane - the magic roundabout seems to allow traffic can flow both clockwise and counterclockwise around the large circle? (I don't have a stake in this discussion nor anything specific to contribute, just seems like that is the novelty) $\endgroup$
    – Pete W
    Commented Jan 26 at 21:37
  • $\begingroup$ @Pete: Yes, but you have to yield everywhere on the way, often requiring you to stop the vehicle. It's a city intersection. High capacity interchanges only use splitting and merging lanes. $\endgroup$
    – Stéphane Gimenez
    Commented Jan 26 at 21:42

1 Answer 1

Reset to default
0
$\begingroup$

What is the goal? The scale of the interchange is rather large, and larger diameters enable higher speeds, which contribute to more crashes and more severe crashes. In a roundabout all drivers in the circular roadway travel in the same direction and safety is achieved with the slower speeds of the small diameter.

Diverge-abouts I-49 @ 155th Street, Belton, MO: https://goo.gl/maps/gF3xKf8e6vbb8E3m6 Video: https://www.youtube.com/watch?v=JVGymEOgHv8&list=PLV9GK4DC6CemY6I0E0nM-BnvH1FK7BChi (12 crashes on the east side of the interchange for 2017-2020) US-50 @ MO-291S, Lee’s Summit, MO: https://goo.gl/maps/oJweVEDnfxJ2G6Qw9 Video: https://www.youtube.com/watch?v=3Qs_NNS8Bvs&list=PLV9GK4DC6CenBzUbogCAy-nHIeA1yiB0J&index=6 (The most recent year-long analysis of crash records (prior to Covid) showed 35 total crashes. 32 of those were fender benders and 21 were northbound drivers failing to yield. For 2020, the database reports 23 crashes for the north side of the interchange.)

Improve this answer
$\endgroup$
1
  • $\begingroup$ I will edit the question to make it clearer. I'm describing a highway to highway interchange. There are no "yields". The only conflicts are lane merges. The radius of the ring would be much, much larger (comparable to the size of the "diamond" you can observe if you zoom out from those locations). What you show are the slow parts of interchanges used to enter/exit the highway. BTW, they look like unusual variations on the Diverging Diamond Interchange that use a roundabout on one side (conventional, with yields, and slow speed for safety) as one of the crossovers. Extremely unusual i believe. $\endgroup$
    – Stéphane Gimenez
    Commented Jan 29 at 20:57

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.