





Intersection - Roundabout
Minimal delays at lower traffic volumes. Little maintenance required. Crash severity is usually lower than at cross intersections.
Roundabouts should be circular in shape with the axis of branches traversing the centre of the circle. The approach should be on a straight line wherever practicable. The entry path radius and deflection must be such that vehicles are not able to enter and pass through the roundabout without first slowing to a safe speed. Unless there is strong justification on ground of capacity, it is not advisable to increase the number of lanes at the entry of a roundabout. Solid structures should not be located on the central island. Vulnerable zones for roadside safety also include the outside of the circulatory carriageway and splitter islands Painted kerbs around the island can reduce the risk of it being run into. Poor visibility on the approach to roundabouts, or high entry speeds, can lead to crashes. A high standard of signing is needed to inform drivers in advance and to guide them through a roundabout Facilities to help pedestrians cross the arms of the intersection should be provided in most urban locations. Roundabouts can be difficult for large vehicles, particularly buses, to use. Designers should be conscious of the risk that roundabouts can be present for cyclists and other slow vehicles, such as animal drawn vehicles. Roundabouts should be avoided along and at the bottom of steep gradient. Enhanced road safety treatments are needed if a roundabout is located at the end of a free-flow highway. Roundabouts with three or more lanes on the approach and along the circulatory carriageway are not advisable due to increased potential conflicts.
Treatment Summary
Case Studies
Related Images
Large multi-lane roundabout. Image credit: iStock Mini roundabout in Singapore. Image credit: Alina Burlacu Roundabout with pedestrian crossing facility in China. Image credit: RIOH Yellow bar marking provided as speed calming measure on roundabout approach, A27 Chichester, UK. Image from Google street view







