Here's video of a shared-space treatment applied to a major street in Köniz, a suburb near Bern, Switzerland. It was designed by Fritz Kobi, then-chief traffic engineer for the Bern, with the assistance of Ben Hamilton-Baillie.
The article where I found this video says that the street has an AADT of 22,000 vehicles per day, though I'm not sure where that's being measured or even if it's an accurate count. If it is, it's pretty impressive
I like the idea of shared space a lot, but this seems to be at the upper limit of what's possible—at least for car throughput. Ideally, shared space increases overall throughput by encouraging more people to walk or cycle through the area.