Relationship between Entry and Circulating Flow at Roundabouts

Abstract

The capacity of roundabouts can be predicted using relationships between the entry and the circulating flow. Use the relationship derived by the Transport and Road Research Laboratory to calculate the reserve capacity of the intersection whose geometric features are:

• inscribed circle diameter, D, 40 m

• entry width, e, 8m

• approach half width, v, 7.3 m

• circulation width, u, 8 m

• effective length over which flare is developed, ℓ¹, 20 m

• entry radius, r, 25 m

• entry angle, Ø, 30°.