Section 2: Benefits of Mini-Roundabouts
Mini-roundabouts are emerging in the United States as a potential intersection type. They may be an optimal solution for a safety or operational issue at an existing stop-controlled or signalized intersection where there is insufficient right-of-way for a standard roundabout installation. Of course, mini-roundabouts are not always feasible or optimal solutions for every problem. The benefits of mini-roundabouts, and some constraining factors (derived largely from international experience, particularly in the U.K., where mini-roundabouts were invented), are described below [4].
Compact size – A mini-roundabout can often be developed to fit within existing right-of-way constraints. Note that mini-roundabouts are generally not recommended for intersections with more than four legs. However, in some cases there may be adequate spacing between legs to allow for two closely-spaced mini-roundabouts
Operational Efficiency – A mini-roundabout may provide less delay for a critical movement or for an overall intersection in comparison to other intersection alternatives. However, as with all roundabout types, mini-roundabouts do not provide explicit priority to specific users such as trains, transit, or emergency vehicles.
Traffic Safety – Mini-roundabouts have been used successfully in the U.K. to improve safety at intersections with known crash problems, with reported crash rate reductions of approximately 30 percent as compared to signalized intersections [5].
Traffic Calming – Designed properly, a mini-roundabout reduces speeds and can be implemented as part of a broader traffic calming scheme. The low-speed environment also enhances the intersection for nonmotorized users. However, mini-roundabouts cannot provide the same level of speed reduction as their larger counterparts and thus are less suited for roadways with speeds exceeding 30 to 35 mph (50 to 55 km/h).
Access Management – A mini-roundabout can be used to provide efficient access to a new or existing development. However, in the cases of large trucks and other large vehicles, the diameter may be too small to accommodate U-turn maneuvers that would be readily accommodated at a larger roundabout.
Aesthetics – In comparison to full-size roundabouts, mini-roundabouts do not allow opportunities for landscaping in the central island. As with comparably sized traditional intersections, landscaping opportunities are limited to the periphery of the intersection.
Environmental Benefits – A mini-roundabout may offer an environmental benefit compared to conventional intersections through reduced delay, fuel consumption, and vehicle emissions.
