There's a configuration for bike safety that's basically a mini roundabout superimposed on a normal intersection. It doesn't significantly increase the size of the intersection, but the geometry works out in a way where bikes can go at near full speed, but it's impossible for a right turning car and straight going bike to get into a collision without seeing each other first (assuming both are looking forward while driving).

Is there a picture/diagram you could link to that would show this configuration in more detail?

Pretty small: a mini roundabout isn't really any bigger than just the intersection: https://en.wikipedia.org/wiki/Roundabout#Mini-roundabouts

Mini roundabouts are very likely to be confusing horrors, outside of low-speed residential zones, parking lots and the like.

See the city of Nantes in France (roundabout’s paradise), navigating the intersections is horrible. In a few parts of town they even have double mini roundabouts. The only reasonable explanation I found is “security by confusion” : if you have no idea how to drive through the intersection, you’re more likely to slow down. Well it doesn’t make the intersection really safer.

I've seen some in Vancouver that are little more than an oversize planter with a scrub in it stuck in the middle of the intersection. As long as it deflects traffic to the side a bit, a slowdown is achieved and the main purpose fulfilled.

Yea there are a bunch of those in Seattle neighborhoods, they work well.

In my experience with the ones in Seattle, people who are turning left use the wrong side of the mini roundabout to save 3 seconds of driving time.

The UK historically has lots of roundabouts, the design guidelines are here : https://www.google.com/url?q=https://trl.co.uk/uploads/trl/d...

Basically they recommend 28m diameter if you are going to have a central island, otherwise it should be a mini-roundabout (capable of being driven over)

I’ll add that in my family’s home town (farming town in Perthshire) in Scotland, there are mini roundabouts that are just a spot of white paint in the middle of the intersection. It works fine.