Mini roundabouts and neighborhood traffic circles

Small-scale circular islands that act as a kind of intersection, offering yield-controlled entries and counterclockwise circulation in order to improve safety and reduce delays.g S-shaped curves that essentially narrow the roadway width and create an environment that slows down drivers.

Features

Raised circular islands constructed in the center of residential street intersections, mini roundabouts and neighborhood traffic circles can reduce speed by directing drivers to maneuver around them. Sometimes used instead of stop signs, they are unsignalized measures designed to support low speeds.

Mini roundabouts have traversable islands and yield control on all approaches, so they function like other roundabouts. Neighborhood traffic circles are typically built at the intersections of local streets to provide traffic calming or aesthetic benefits. They operate as two-way or all-way stop-controlled intersections, typically without raised channelization to guide approaching traffic into the circulatory roadway.

Example photos

Costs & considerations

Feature	Estimated cost	Percent speed reduction
Landscaped traffic mini-circle	Asphalt street: $6,000 Concrete street: $8,000-$15,000	12-42%

*Note: Estimates are based on past projects and commonly used materials, and may vary depending on roadway condition, location, time, and other factors. Estimates assume work can be accomplished within the roadway; costs will increase substantially if work requires ROW takings or curb displacement. The speed reduction percentages were sourced from FHWA's Engineering Speed Management Countermeasures Table linked in the resources below.

Potential speed benefits

Mini roundabouts and neighborhood traffic circles have been found to effectively reduce the speed most people drive on a road. In one analysis, mini traffic circles were found to reduce the 85^th percentile speed by 11 percent on urban roads. (FHWA Speed Management Toolkit: Table 4)

Visit the FHWA table on potential speed reduction for more information. While this data is all collected under differing circumstances and in different environments (volume of vehicles, rural vs. urban areas, etc.), it is still a helpful gauge for what each countermeasure can do.

Learn more about mini roundabouts

When considering mini roundabouts and neighborhood traffic circles, it’s important to keep in mind the MassDOT Project Development Guidelines (Chapter 16). These are very specific design policies and standards you’ll need to adhere to, so that any changes you make meet federal and state guidelines

For example:

• Neighborhood traffic circle islands are usually 12-16 feet in diameter.
• The inscribed circles of mini-roundabouts are 45-90 feet with a design vehicle of an SU-30.
• Circulatory signage should direct through traffic to proceed to the right of the circle.
• The design vehicle for neighborhood traffic circles is a single truck with a 45-foot turning radius.
• Vegetation should be designed to capture stormwater, if possible. (NYC Street Design Manual) 

Many of these details are included in Chapter 16 of our guide.

You can find more information about Mini-roundabouts and neighborhood traffic circles in these resources:

• ITE Fact Sheet
• FHWA Traffic Calming ePrimer
• NACTO Urban Street Design Guide
• FHWA PedBikeSafe
• Engineering Countermeasures for Reducing Speeds - Safety | Federal Highway Administration