My favorite five-way intersection that should be a roundabout was on flashing red yesterday, and I concluded that was a time for me to monitor this natural experiment. At 4:30 on May 12 I video of the intersection for 4 minutes. I counted 100 cars and 11 pedestrians and bikes in just over 4 minutes. Simply multiplying 111*15 gives a capacity of 1665 units per hour. This is somewhat off my estimates from a signalized intersection. On the other hand, delays were rather short, and while there were short queues at some of the approaches (which helps ensure the intersection is fully utilized), they were not getting longer over time.
The video is below:
A map of the location.