This document discusses capacity analysis of rotary intersections. It defines a rotary intersection as a special form of at-grade intersection where traffic circulates around a central island in a clockwise direction. The document outlines the key design elements of rotaries including entry/exit radii, island radius, weaving sections. It presents a formula from Transportation Road Research Lab to calculate a rotary's capacity based on the weaving section with the highest proportion of weaving traffic. An example calculation is provided to illustrate applying the formula. The conclusion emphasizes that rotaries reduce traffic complexity through weaving but capacity depends on analyzing the critical weaving section.