Where Should Roundabouts Be Considered?

 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.
  • Adjacent to railways, where space to queue traffic is limited and premption equipment for traffic signal poses an operational challenge for the operating authority.

Good Locations for Roundabouts:


 Further Reading: When should roundabouts replace traffic circles?


What about snow removal at roundabouts?

A number of communities in snowy areas have installed roundabouts. There were some initial changes at first for snowplow crews, but once the snow started falling there were generally no major issues with snow removal. A truck generally starts on the truck apron and plows around the roundabout to the outside then plows each entry and exit pushing to snow to the outside. Roundabouts also make it easier for a snowplow to turn.

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