just looking at flow and intersections i am thinking would a single lane off ramp from the upper roundabout to the short ground level off shot under the on ramp be good to stop the congestion at the on ramp on the upper roundabout just a thought

Glad you liked the guide! The way CSL zones on curves has always annoyed me, so I pretty much always use grids for RICO, and wanted to find a good one :)

I look forward to seeing your take on Ys. I mostly use my Double Triangle interchange -- https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=2056199123 -- which I think has a certain elegance to it, but it isn't particularly exciting or pretty.

Thanks me22ca dude, much appreciated.
You're right about pretty much everything. With a roundabout interchange it's essential to use TMPE,and even then you're going to be limited because there's only so many vehicles you can get on and off the roundabout. I do have a few more interchanges in my pipeline, based more on the Y branching idea, that was my last roundabout-based one... I think.

One more thing, I just read your Optimal Square Grid guide (https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=2035626231) . I'm a big fan of city grids and that was just an excellent read

Very pretty work once again, Rich!

(Not that I'd personally use it, since I don't think there's ever a good reason to have 6 highways run join like this, and even with TMPE I don't find roundabout-based interchanges have good enough throughput to be used for system interchanges. I think for this I'd just put a Y in the middle, then a Y on each branch of it, with a bit of merging space, rather than fight with the merging on the roundabout.)