https://safety.fhwa.dot.gov/intersec...s/fhwasa10006/
Table 2: Common Inscribed Circle Diameter Ranges
Multilane Roundabout (2 lanes) WB-50 (WB-15) 150 to 220 ft (46 to 67 m)
Multilane Roundabout (2 lanes) WB-67 (WB-20) 165 to 220 ft (50 to 67 m):
I would guess that the roundabout at Buena Vista and El Camino Real to be about 120 feet in diameter, not sure. but no where near the 220 ft in the chart.
I think our roundabouts are too small.