Appropriate locations for Roundabouts include
locations where there is insufficient room for adequate
queue storage, such as at interchanges or at entrances
to bridges and tunnels. Other potential candidates
include intersections with high accident rates,
particularly accidents involving cross street through
and/or left-turn movements. Poor candidates include
intersections of roads with highly imbalanced approach
volumes, which give a disproportionate advantage
to the low-volume approaches.
Problems encountered at existing Roundabout locations
that should be evaluated in new Roundabout design
processes have included increased maintenance costs
for the central island (additional or difficult
snow removal, additional sign costs, and the need
to do maintenance at night), lack of signalized
pedestrian crossings, larger vehicles running over
central islands, and how to locate driveways near
Roundabout entrances.
Though a thorough investigation of design and
construction costs has not been undertaken, a sampling
of dual-lane Roundabouts on state highways has shown
a cost range of $350,000 to $500,000 per installation
(excluding right-of-way), varying with size, drainage
and landscaping costs.