Where Should Roundabouts be Considered?

Further Reading: When should roundabouts replace traffic circles?

Roundabouts are a feasible and practical alternative to other types of control where:

• Traffic flows do not exceed about
  • 2,000 vehicles per hour for one-lane roundabouts; and,
  • 4,000 vehicles per hour for two-lane roundabouts; and,
  • 6,000 vehicles per hour for three-lane roundabouts; and,
  • 8,000 vehicles per hour for four-lane roundabouts.
• Locations experience high rates of angle, rear-end or loss-of-control collisions.
• Stop signs are creating unacceptable delays for side street motorists, but where a traffic signal is not warranted, or where a traffic signal would result in greater delays than a roundabout.
• There is a high proportion of left turning traffic, or where the major traffic route is not straight through the intersection.
• Intersections have unusual geometry or more than four legs.

• It is important to emphasize the transition between urban and rural environments (i.e. gateways).

Roundabouts are not always practical or feasible where:

• Land availability is limited.
• Sight distance of the entry points is limited, such as on abrupt crest vertical curves on the intersection approaches.
• Traffic signal progression is critical, as in some cases roundabouts can disrupt traffic platooning.