Roundabouts are routinely implemented at interchange ramp terminals as a pair of roundabouts, or a single-circle roundabout, and can be installed at interchanges with frontage roads as a means of collecting and distributing traffic within this type of context. Within urban areas, the existing or forecasted traffic volume at an interchange may likely exceed the capacity of a two-lane roundabout. Special consideration must be given to high-volume roundabout interchange studies and schematics to confirm the feasibility and reasonability of a roundabout interchange.

A major advantage roundabout interchanges provide is a reduced bridge width over the freeway due to the omission of auxiliary turn lanes that are often required at signalized interchanges. shows the relative width of bridge needed to accommodate one lane in each direction across the interchange.

The reduction in bridge width can lead to environmental, construction duration, and cost benefits. Another advantage is the prevention of wrong-way maneuvers. As drivers circulate within the roundabout the entry lanes are angled in such a way that discourages drivers from making a right-turn and exiting the roundabout in the wrong direction.

When roundabout interchanges are installed where capacity is not exceeded during the peak period, the resulting level of service will typically far exceed that of other methods of interchange control due to off-peak periods operating at or near free-flow conditions. Minimal delay is achieved for 22+ hours of the day in this scenario.

Refer to and RDM for additional roundabout information.