FHWA-SA-10-007

Technical Summary

Mini-Roundabouts
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assumes no liability for the use of the information contained in this document.

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Foreword

This technical summary is designed as a reference for State and local transportation officials, Federal Highway 

Administration (FHWA) Division Safety Engineers, and other professionals who may be involved in the design, 

selection, and implementation of mini-roundabout intersections. Because experience with mini-roundabouts 

is limited in the United States, the information presented here draws primarily upon guidance and experience 

from other countries with reference to American guidance as appropriate. This technical summary explores the 

unique characteristics of mini-roundabouts while reinforcing the need to apply the principles-based approach 

common to all roundabout design. It provides readers with an overview of the key considerations for planning, 

analysis, and design of single-lane mini-roundabouts. 

Section 1 of this document summarizes the characteristics of mini-roundabouts. Section 2 presents benefits of 

mini-roundabout intersections compared to alternative intersection solutions. Sections 3-6 provide an overview 

of user, location, operational and design considerations respectively.

The information presented herein is a summary of principles outlined in the FHWA document Roundabouts: An 

Informational Guide [1] and the forthcoming 2nd Edition [2] (hereafter referred to as the Roundabout Guide), 

which is in progress at the time of this writing and due to be published in 2010. Specific considerations for 

single-lane and multilane roundabouts are summarized in a separate FHWA document titled Roundabout 

Technical Summary [3]. Figures are from the Roundabout Guide unless otherwise noted.

This publication does not supersede any publication; and is a Final version.
FHWA | Mini-Roundabouts iii

Contents

Introduction 1

Section 1: Characteristics of Mini-Roundabouts 3

Section 2: Benefits of Mini-Roundabouts . . . . . . . . . . . . . . . . .4

Section 3: User Considerations 4

3.1 Motorists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3.2 Pedestrians . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3.3 Bicycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3.4 Emergency Vehicles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Section 4: Location Considerations 5

4.1 Common Site Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4.2 Site Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Section 5: Operational Analysis . . . . . . . . . . . . . . . . . . . . . . .6

Section 6: Design Considerations 7

6.1 Horizontal Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

6.2 Pedestrian Design Treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

6.3 Bicycle Design Treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

6.4 Sight Distance and Visibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

6.5 Vertical Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
iv FHWA | Mini-Roundabouts

6.6 Pavement Markings and Signs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

6.7 Lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

6.8 Landscaping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

6.9 Other Design Details and Applications . . . . . . . . . . . . . . . . . . . . . . . . . .12

Section 7: Costs 13

Section 8: References . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
FHWA | Mini-Roundabouts 1

Introduction

Mini-roundabouts are a type of roundabout characterized by a small diameter and traversable 

islands (central island and splitter islands). Mini-roundabouts offer most of the benefits of regular 

roundabouts with the added benefit of a smaller footprint. As with roundabouts, mini-roundabouts 

are a type of intersection rather than merely a traffic calming measure, although they may produce 

some traffic calming effects. They are best suited to environments where speeds are already low 

and environmental constraints would preclude the use of a larger roundabout with a raised central 

island. Mini-roundabouts are common in the United Kingdom (U.K.) and France and are emerging in 

the United States (including states such as Maryland and Michigan), Germany, and other countries.

This technical summary focuses on single-lane 

mini-roundabouts. Because experience with miniroundabouts is limited in the United States, the 

information presented here draws primarily upon 

guidance and experience from other countries with 

reference to American guidance as appropriate. This 

technical summary explores the unique characteristics 

of mini-roundabouts while reinforcing the need to 

apply the principles-based approach common to all 

roundabout design. It provides readers with an overview 

of the key considerations for planning, analysis, and 

design of mini-roundabouts.

The information presented herein is a summary of 

principles outlined in the FHWA document Roundabouts: 

An Informational Guide [1] and the forthcoming 2nd 

Edition [2] (hereafter referred to as the Roundabout 

Guide), which is in progress at the time of this writing 

and due to be published in 2010. Specific considerations 

for single-lane and multilane roundabouts are 

summarized in a separate FHWA document titled 

Roundabout Technical Summary [3]. Figures are from the 

Roundabout Guide unless otherwise noted.

Adapted from Photo by Lee Rodegerdts (used with permission)
2 FHWA | Mini-Roundabouts
FHWA | Mini-Roundabouts 3

Section 1: Characteristics of Mini-Roundabouts

A mini-roundabout is a type of intersection that can be used at physically-constrained locations in 

place of stop-controlled or signalized intersections to help improve safety problems and reduce excessive delays at minor approaches [1]. Figure 1 illustrates the design features of a mini-roundabout; 

these features are described further later in this summary. Mini-roundabouts generally have an 

inscribed circle that is small enough to stay within the existing right-of-way (or within the existing 

curb lines if adequate space is available). Mini-roundabouts operate in the same manner as larger 

roundabouts, with yield control on all entries and counterclockwise circulation around a mountable 

(traversable) central island. 

Mini-roundabouts are distinguished from neighborhood 

traffic circles primarily by their traversable islands and 

yield control on all approaches, which allows them to 

function as other roundabouts do. Neighborhood traffic 

circles are typically built at the intersections of local 

streets for reasons of traffic calming and/or aesthetics. 

They typically are operated as two-way or all-way stopcontrolled intersections and frequently do not include 

raised channelization to guide approaching traffic 

into the circulatory roadway. At some neighborhood 

traffic circles, left-turning vehicles must turn in front 

of the central island, potentially conflicting with other 

circulating traffic. 

To help promote safe operations, the design of miniroundabouts generally aligns passenger cars on the 

approach in such a way as to naturally follow the 

circulatory roadway and minimize running over the 

central island to the extent possible. Due to the small 

footprint, large vehicles are typically required to over-run 

the fully traversable central island (as shown in Figure 1). 

Figure 1: Design Features of a Mini-Roundabout
4 FHWA | Mini-Roundabouts

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].

3.1 Motorists 

As with other types of roundabouts, mini-roundabouts 

can enhance the safety for drivers, including older 

drivers, by:

•	 Allowing more time to make decisions, act, and react; 

•	 Reducing the number of directions in which a driver needs 

to watch for conflicting traffic; and

•	 Reducing the need to judge gaps in fast traffic accurately. 

Attention should be paid to the placement of signs and 

pavement markings to make them clear, visible, and 

•	 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 miniroundabouts.

•	 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, miniroundabouts 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.

Section 3: User Considerations

The various user types of a mini-roundabout have unique characteristics that should be considered 

in the planning and design process. Some of the characteristics of four user groups—motorists, pedestrians, bicyclists, and emergency vehicles—are discussed here; a more complete discussion can 

be found in the Roundabout Guide.
FHWA | Mini-Roundabouts 5

Section 4: Location Considerations

As noted previously, mini-roundabouts are an intersection form that may have some traffic calming properties. Because of their design characteristics, mini-roundabouts are most effective in lower 

speed environments in which all approaching roadways have posted speed of 30 mph or less and 

an 85th-percentile speed of less than 35 mph (55 km/h) near the proposed yield and/or entrance 

line [6]. For any location with an 85th-percentile speed above 35 mph (55 km/h), the mini-roundabout can be included as part of a broader system of traffic calming measures to achieve an appropriate speed environment.

There are a number of locations where miniroundabouts are commonly found to be advantageous 

and a number of situations that may adversely affect 

their feasibility. As with any decision regarding 

intersection treatments, care should be taken to 

understand the particular benefits and trade-offs for 

each project site. 

4.1 Common Site Applications

Mini-roundabouts can be used at existing intersections 

to replace two-way stop control, all-way stop control, 

or a traffic signal. Mini-roundabouts can improve 

the operation of an intersection by reducing the 

dominance of the traffic flow from one direction over 

others, facilitating access and reducing delay to minor 

street movements, and improving overall intersection 

capacity [4]. 

Mini-roundabouts generally have a narrower range 

of applications than other types of roundabouts. The 

following applications represent some of the situations at 

which mini-roundabouts may be advantageous (further 

discussion can be found in the Roundabout Guide): 

•	 Space-constrained locations with reasonable 

approach speeds (30 mph [50 km/h] or less) 

– Because mini-roundabouts require less space than 

larger roundabouts, they may be a solution where a 

larger roundabout will not fit, provided that speeds are 

reasonable. 

•	 Residential environments – Mini-roundabouts offer 

a low-speed, low-noise intersection option that requires 

little ongoing maintenance.

unambiguous to all users, including older drivers. Trucks 

and other large vehicles can be accommodated at a 

mini-roundabout by using mountable islands. Further 

details on design vehicles are provided later in this 

technical summary.

3.2 Pedestrians

Pedestrians are accommodated at pedestrian crosswalks 

around the perimeter of the mini-roundabout. The 

splitter islands at mini-roundabouts typically do not 

provide the same degree of refuge as those at other 

roundabouts, thus typically requiring pedestrians to 

cross the street in one stage (as with many conventional 

intersections).

The Americans with Disabilities Act requires that all new 

and modified intersections, including roundabouts, be 

accessible to and usable by people with disabilities. The 

accessibility of mini-roundabouts to pedestrians with 

vision disabilities has not been specifically researched 

but is not expected to require treatments beyond those 

provided for similar single-lane roundabouts. Further 

discussion can be found in the Roundabout Guide.

3.3 Bicycles

Mini-roundabouts are generally located in environments 

where bicyclists are comfortable negotiating the 

roundabout as a motor vehicle. In the event a bicyclist 

desires to navigate the intersection as a pedestrian, 

sidewalks and crosswalks are provided.

3.4 Emergency Vehicles

Because of the traversable design of the central island 

and splitter islands, emergency vehicles are unlikely to 

have significant difficulty negotiating a mini-roundabout. 
6 FHWA | Mini-Roundabouts

•	 Intersections with high delay – A roundabout can 

be an ideal application to reduce delay at stop-controlled 

intersections that do not meet signal warrants.

4.2 Site Constraints

Due to their smaller proportions, mini-roundabouts are 

not suitable for all locations. Certain site-related factors 

may significantly influence the design, requiring that a 

more detailed investigation of some aspects of the site 

be carried out. A number of these factors (many of which 

are valid for any intersection type) are listed below:

•	 High volumes of trucks will significantly reduce the 

capacity of a mini-roundabout, as trucks will occupy most 

of the intersection when turning [1]. Additionally, high 

volumes of trucks overrunning the central island may lead 

to rapid wear of the roadway markings.

•	 Mini-roundabouts are not recommended in locations 

in which U-turn truck traffic is expected, such as at the 

ends of street segments with medians or other access 

restrictions. However, in the expectation that U-turns are 

likely to occur, the design of a mini-roundabout should 

accommodate U-turns for passenger cars. Due to the 

small inscribed circle diameter, larger vehicles may not be 

capable of making a U-turn movement.

•	 Locations with light volumes of minor street traffic may not 

provide a suitable location for a mini-roundabout. Major 

street vehicles may become conditioned over time to 

ignore the intersection control due to a lack of minor street 

vehicles presence, which requires major street drivers to 

slow and proceed cautiously through the intersection. One 

rule of thumb used in the U.K. is to have at least 10 percent 

of the total intersection volume generated from the minor 

street [7]. Another measure used in the U.K. is that miniroundabouts should not be considered at intersections 

with volumes below 500 daily vehicles on the minor street 

[6].

•	 Challenges for other types of roundabouts, including 

physical complications, proximity to significant generators 

of traffic, and proximity to other traffic control devices 

(e.g., signalized intersections, at-grade rail crossings) or 

bottlenecks, etc., may make it politically or economically 

infeasible to construct a mini-roundabout. These and other 

conditions are discussed further in the Roundabout Guide 

and in the Technical Summary on Roundabouts.

The existence of one or more of these conditions does 

not necessarily preclude the installation of a miniroundabout. Experience in the United States is limited to 

date, but there may be comparable conditions in other 

countries where mini-roundabouts have successfully 

overcome one or more of the conditions listed above. 

To address these conditions, additional analysis, design 

work, and coordination with affected parties may be 

needed to resolve conflicts and help in the decisionmaking process. In some cases, the conditions identified 

above cannot be overcome, and another intersection 

type may be more suitable.

Section 5: Operational Analysis

Mini-roundabouts are generally recommended for intersections in which the total entering daily traffic volume is no more than approximately 15,000 vehicles. While a mini-roundabout may perform 

acceptably at higher volume locations, there has been limited experience for such sites in the United 

States. Multilane mini-roundabouts have been used in the U.K. but are rare elsewhere. 

Operational performance models for mini-roundabouts 

have not been developed for U.S. conditions as of this 

writing. The calibration to U.S. drivers of international 

models, such as those from the U.K., has not been 

determined as of this writing. 
FHWA | Mini-Roundabouts 7

Mini-roundabout design applies many of the same 

principles used for other types of roundabouts, 

including:

•	 Provide slow entry speeds and consistent speeds through 

the roundabout by using deflection;

•	 Provide smooth channelization that is intuitive to drivers;

•	 Provide adequate accommodation for the design vehicles; 

•	 Design to meet the needs of pedestrians and bicyclists; 

and

•	 Provide appropriate sight distance and visibility.

The Roundabout Guide and/or the Technical Summary 

on Roundabouts provide more detailed design 

guidelines [2, 3]. The remainder of this document 

focuses on the design aspects and considerations that 

are unique to mini-roundabouts.

6.1 Horizontal Design

Mini-roundabout design applies many of the 

same principles and details of the design of larger 

roundabouts but with different emphasis areas. 

Given that the central island of a mini-roundabout is 

fully traversable, the overall design should provide 

channelization that naturally guides drivers to the 

intended path. Sub-optimal designs may result in drivers 

turning left in front of the central island (or driving over 

the top of it), improperly yielding, or traveling at excess 

speeds through the intersection. The following key 

horizontal design areas for considerations are highlighted 

below: size, design vehicle, design speed, central island, 

entrance line placement, and splitter islands.

6.1.1 Size

A mini-roundabout is often considered as an alternative 

to a larger, single-lane roundabout due to a desire to 

minimize impacts outside of the existing intersection 

footprint. Therefore, the existing intersection curb line 

is a typical starting point for establishing the miniroundabout inscribed circle diameter. Mini-roundabouts 

should be made as large as possible within the 

intersection constraints. However, a mini-roundabout 

inscribed circle diameter generally should not exceed 

90 ft (30 m). Above 90 ft (30 m), the inscribed circle 

diameter is typically large enough to accommodate the 

design vehicles navigating around a raised central island. 

A raised central island provides physical channelization 

to control vehicle speeds; therefore, a single-lane 

roundabout design is preferred where a diameter greater 

than 90 ft (30 m) can be provided. 

6.1.2 Design Vehicle

The location and size of a mini-roundabout central 

island (and the corresponding width of the circulatory 

roadway) is dictated primarily by passenger car swept 

path requirements. The island location should be at the 

center of the left-turning inner swept paths which will be 

near, but not necessarily on, the center of the inscribed 

circle. The off-tracking of a large design vehicle should 

be accommodated by the footprint of the central island; 

meanwhile, passenger cars should be able to navigate 

through the intersection without being required to overrun the central island. 

As with single and multilane roundabouts, it is desirable 

to also accommodate buses within the circulatory 

roadway to avoid jostling passengers by over-running 

Section 6: Design Considerations

The geometric design of a mini-roundabout, as with other types of roundabouts, requires the 

balancing of competing design objectives. Roundabouts operate most safely when their geometry 

forces traffic to enter and circulate at slow speeds. Poor roundabout geometry has been found to 

negatively impact roundabout operations by affecting driver lane choice and behavior through the 

roundabout. Many of the geometric parameters are governed by the maneuvering requirements of 

the design vehicle and the accommodation of nonmotorized users. Thus, designing a roundabout is 

a process of determining the optimal balance between safety provisions, operational performance, 

and accommodation of design users. For these reasons, roundabout design techniques are difficult 

to standardize, and there is rarely only one “right” way to design a roundabout.
8 FHWA | Mini-Roundabouts

the central island. However, for very small inscribed 

circle diameters, the bus turning radius is typically too 

large to navigate around the central island while staying 

within the circulatory roadway, thus requiring buses to 

travel over the central island. The potential trade-off to 

designing for a bus instead of a passenger car is that the 

design may result in a wider circulatory roadway and 

smaller central island.

6.1.3 Design Speed

The location of the central island should allow for all 

movements to be accommodated at the intersection 

with counterclockwise circulation. Designing the central 

island size and location to provide deflection through 

the roundabout will encourage proper circulation and 

reduced speeds through the intersection.

6.1.4 Central Island

The central island is typically fully traversable and may 

either be domed or raised with a mountable curb and 

flat top for larger islands. Although painted central 

islands are commonly used in the U.K., flush central 

islands are discouraged in other countries to maximize 

driver compliance. Composed of asphalt concrete, 

Portland cement concrete, or other paving material, the 

central island should be domed using 5 to 6 percent 

cross slope, with a maximum height of 5 

in (12 cm). Although fully mountable and 

relatively small, it is essential that the central 

island be clear and conspicuous. Islands 

with a mountable curb should be designed 

in a similar manner to truck aprons on 

normal roundabouts. 

6.1.5 Placement of Entrance Line

The entrance line is integral to the 

geometric design of a mini-roundabout, 

and incorrect placement can introduce 

undesirable driver behavior. Figure 2 

illustrates one particular situation where the 

design allows passenger cars to turn left in 

front of the central island. In this case, the 

combination of the intersection skew angle, 

small size of the central island, small size of 

the splitter islands, and large width of the 

circulatory roadway makes it comfortable 

for a driver to turn left in front of the central 

island instead of navigating around it 

introducing the risk of drivers taking this 

undesirable action. 

Two possible design improvements are illustrated in 

Figure 3: (a) advancing the entrance line forward, or (b) 

simultaneously enlarging the central island and reducing 

the circulatory roadway width, with the entrance line 

coincident with the inscribed circle of the roundabout. 

For the option of advancing the entrance line forward, 

the outer swept path of passenger cars and the largest 

vehicle likely to use the intersection are identified for all 

turning movements, and the advanced entrance line is 

placed at least 2 ft (0.6 m) outside of the vehicle paths. 

Skewed approaches are one particular situation where 

advancing the yield line may be beneficial to discourage 

vehicles from making a left-turn in front of the central 

island. However, this may result in a reduction of 

capacity, as advancing the yield line may affect yielding 

behavior at the entry. 

6.1.6 Splitter Islands

As with larger roundabouts, splitter islands are generally 

used at mini-roundabouts to align vehicles, to encourage 

deflection and proper circulation, and to provide 

pedestrian refuge. Splitter islands are raised, mountable, 

or flush depending upon the size of the island and 

whether trucks will need to track over the top of the 

splitter island to navigate the intersection. In general, 

Figure 2: Undesirable Design that Allows Left Turns in Front of Central Island
FHWA | Mini-Roundabouts 9

raised islands are preferred over flush islands. The 

following are general guidelines for the types of splitter 

islands under various site conditions:

•	 Consider a raised (nontraversable) island if one or more of 

the following conditions exist:

- All design vehicles can navigate the roundabout without 

tracking over the splitter island area; 

- Sufficient space is available to provide an island with a 

minimum area of 50 ft2

 (4.6 m2); and

- Pedestrians are present at the intersection with regular 

frequency.

•	 Consider a mountable (traversable) island if:

- Some design vehicles must travel over the splitter 

island area and truck volumes are minor; and

- Sufficient space is available to provide an island 

with a minimum area of 50 ft2

 (4.6 m2).

•	 Consider a flush (painted) island if:

- Vehicles are expected to travel over the splitter 

island area with relative frequency to navigate the 

intersection; 

- An island with a minimum area of 50 ft2

 (4.6 m2) 

can not be achieved; and

- The approach has low vehicle speeds (preferably 

no more than 25 mph [40 km/h]).

Figure 4 displays recommended longitudinal dimensions 

for splitter islands at mini-roundabouts. In some cases it 

may not be feasible to achieve the dimensions in Figure 

4 due to narrow approach widths. Where necessary, the 

islands may only extend between the entrance line and 

the crosswalk. More details related to the design of the 

pedestrian refuge area are discussed in the next section 

on Pedestrian Design Treatments.

In some cases, sufficient space may be available to 

provide a raised island within the pedestrian refuge 

area, but does not extend fully to the entrance line. An 

example of a raised island being terminated prior to 

the entrance line to accommodate the design vehicle 

Figure 3: Possible Design Improvements

(a) Move entrance line forward (b) Enlarge central island

Figure 4: Recommended Splitter Island Dimensions

Figure 4: Recommended Longitudinal Dimensions for Splitter Islands at Mini-Roundabouts
10 FHWA | Mini-Roundabouts

is illustrated in Figure 5. If raised islands are 

used, care should be taken to ensure that 

they are visible to approaching motorists. 

6.2 Pedestrian Design 

Treatments

At conventional intersections, pedestrian 

ramps and pedestrian crossings are typically 

located near the curb returns at the corners 

of the intersection. When converting to a 

mini-roundabout, these corner pedestrian 

crossing locations will likely require 

relocation. The pedestrian crossing is 

recommended to be located 20 to 25 ft (6.1 

to 7.6 m) upstream of the entrance line to accommodate 

one vehicle queue ahead of the crossing.

Where a mountable or raised splitter island is used, the 

walkway through the splitter island should be “cutthrough” instead of ramped. This is less cumbersome for 

wheelchair users and allows the cut-through walkway 

to be aligned with the crosswalks, providing guidance 

for all pedestrians, but particularly for those who are 

visually-impaired. The cut-through walkway should be 

approximately the same width as the crosswalk, ideally a 

minimum width of 10 ft (3 m).

Sidewalk ramps are provided to connect to the sidewalks 

at each end of the crosswalk. Wherever sidewalks 

are separated from the roadway by a planting strip, 

ramps do not need flares and instead can have curbed 

edges aligned with the crosswalk, which provide 

alignment cues for pedestrians with visual impairments. 

A detectable warning surface consisting of raised 

truncated domes, as required by the Americans with 

Disabilities Act, should be applied to each ramp.

Where a minimum splitter island width of 6 ft (1.8 m) is 

available on the approach, a pedestrian refuge can be 

provided within the splitter island. In some cases, the 

available roadway width may not be sufficient to provide 

an adequate refuge area, in which case pedestrians 

will need to cross in one stage. Where a pedestrian 

refuge is provided, the refuge area must be defined with 

detectable warning surfaces that begin at the curb line 

and extend into the cut-through area a distance of 2 ft 

(0.6 m). This results in at least 2 ft (0.6 m) of clear space 

between detectable warning surfaces on a splitter island. 

Detailed standards for detectable warning surfaces can 

be found in the ADA Accessibility Guidelines (ADAAG) 

and through the U.S. Access Board [8].

6.3 Bicycle Design Treatments

Since typical on-road bicycle travel speeds are 

approximately 12 to 20 mph (20 to 30 km/h), the speeds 

of vehicles approaching and traveling through miniroundabouts are similar to those of bicyclists. Bicyclists 

are encouraged to navigate through a mini-roundabout 

as if they were a vehicle. Where bicycle lanes are 

provided on the approaches to a mini-roundabout, they 

should be terminated to alert drivers and bicyclists of the 

need for bicyclists to merge into traffic. One suggested 

practice is to terminate the bike lane at least 100 ft (30 

m) upstream of the entrance line, provide a 50-ft (15-m) 

taper ending prior to the crosswalk at the roundabout 

entry, and use a dotted bike lane stripe for the last 50 to 

200 ft (15 to 60 m) prior to the beginning of the taper [1]. 

For a more detailed description of bicycle design 

techniques, refer to the Roundabout Guide.

6.4 Sight Distance and Visibility

The principles of sight distance and visibility at miniroundabouts are consistent with other roundabouts and 

other intersections. Detailed guidelines for evaluating 

sight distance and visibility are provided in the 

Roundabout Guide [2] and the Technical Summary on 

Roundabouts [3]. 

6.5 Vertical Design

Mini-roundabouts should generally be designed to 

be outward draining to place the central island at the 

highest point of the intersection for maximum visibility. 

This technique of sloping outward is recommended 

primarily because it:

•	 Promotes safety by raising the height of the central island 

and improving its visibility;

Figure 5: Raised Splitter Island Terminated in Advance of the Entrance Line

Photo: Lee Rodegerdts (used with permission)
FHWA | Mini-Roundabouts 11

•	 Promotes lower circulating speeds; 

•	 Minimizes breaks in the cross slopes of the entrance and 

exit lanes; and 

•	 Drains surface water to the outside of the roundabout. 

This is consistent with most standard intersection 

grading, where the high-point is located near the 

center of the intersection and slopes towards the outer 

curbs. Therefore, in most retrofit situations, installation 

of a mini-roundabout would not necessarily require 

significant grade modifications to the intersection. 

6.6 Pavement Markings and Signs

At mini-roundabouts, pavement markings and signs 

work together to create a comprehensive system to 

guide and regulate road users. Pavement markings and 

signs are simpler at mini-roundabouts than at other 

types of roundabouts. 

The Federal Highway Administration has published the 

2009 Edition of the Manual on Uniform Traffic Control 

Devices, which includes major revisions and additions 

related to signage and markings at roundabouts. For 

more detailed guidelines, designers 

should refer to the 2009 MUTCD and the 

Roundabout Guide [2, 9]. 

6.6.1 Pavement Markings

Pavement markings for mini-roundabouts 

are largely similar to those for other 

roundabouts. However, because the 

islands may be either flush or mountable, 

additional pavement markings can be used 

to improve the visibility of key features, 

including the direction of circulation and 

splitter islands. A sample pavement marking 

plan for a mini-roundabout is given in

Figure 6. A wide white dotted line is used to 

designate the entrance location, similar to 

other roundabouts. Some optional features 

include the following (not necessarily 

shown on Figure 6):

•	 Pavement marking arrows in the circulatory 

roadway in front of each entry to indicate 

the direction of circulation;

•	 Yield lines and/or legends; 

•	 For flush splitter islands, an appropriate hatching pattern 

(e.g., a diagonal hatch similar to those used for marking 

obstructions, such as those shown in Figure 3B-15 of the 

2009 MUTCD [9]) within the splitter island envelope to 

further emphasize the splitter island location; 

•	 Rumble strips or raised pavement markers within the 

envelope of a flush splitter island to discourage light 

passenger vehicles from driving over top of the islands; and 

•	 Yellow color over the entire central island.

If the entire center island is colored yellow, an anti-skid 

surface is recommended to increase surface friction 

and avoid slick surfaces, particularly for bicycles and 

motorcycles. A textured surface that provides a visible 

differentiation from the circulatory roadway and is 

accompanied by a solid yellow line may also be used. 

Note that vehicles overrunning a textured surface may 

create additional noise, which may be perceived as a 

problem in residential areas.

6.6.2Signing

The principal difference in signing at mini-roundabouts 

compared to other roundabouts is that no signs can 

Figure 6: Sample Pavement Marking Plan for a Mini-Roundabout
12 FHWA | Mini-Roundabouts

be located within the fully mountable central island. As 

a result, the Circular Intersection (W2-6) warning sign 

is typically used on each approach in advance of the 

YIELD sign. YIELD signs are typically placed as close as 

practical to the entrance line and can be supplemented 

with a Roundabout Circulation plaque (R6-5P). Advance 

directional guide signs and exit guide signs are typically 

unnecessary given the size of the mini-roundabout and 

the nature of the approach roadways (generally lowspeed local streets). However, standard street name 

signs should be used and are typically mounted on the 

same posts as the yield signs (similar to conventional 

intersections). Figure 7 gives a sample signing plan for a 

mini-roundabout. 

For splitter islands that are either painted or are fully 

mountable, KEEP RIGHT signs cannot be used. KEEP 

RIGHT signs may be provided for raised non-mountable 

islands, particularly where a pedestrian refuge is 

provided; however, care should be taken to ensure the 

sign does not obscure the view of the central island 

approaching the mini-roundabout. Some agencies 

are experimenting with illuminated bollards to mark 

splitter islands. 

6.7 Lighting

It is important that mini-roundabouts, including their 

pedestrian crossing areas, be visible to 

approaching drivers. Consideration needs 

to be given to ensuring the intersection 

is conspicuous at night, which may mean 

providing additional street lighting. The 

Design Guide for Roundabout Lighting [10], 

published by the Illuminating Engineering 

Society, is the primary resource that should 

be consulted in completing a lighting plan 

for all roundabout types including miniroundabouts. The Roundabout Guide also 

provides a summary of lighting principles, 

and the same principles for lighting 

traditional intersections apply to miniroundabouts.

6.8 Landscaping

Landscaping of mini-roundabouts is 

minimal due to the traversable nature 

of the central island and (often) splitter 

islands. However, it is possible to provide 

landscaping around the perimeter of the intersection. 

Any landscaping that is provided should be designed 

to minimize roadside hazards and to maintain adequate 

stopping and intersection sight distance throughout the 

roundabout.

6.9 Other Design Details and Applications

More design details and applications of miniroundabouts exist than are covered in this technical 

summary; however, some of the more notable 

considerations are described below:

•	 Right-turn bypass lanes – Roundabouts and miniroundabouts can employ right-turn bypass lanes similar 

to those used at conventional intersections. Bypass lanes 

are designed either to yield to exiting traffic or to form 

an additional lane next to exiting traffic (which may then 

merge into the exiting traffic).

•	 Access management – Driveways in the vicinity of 

roundabouts and mini-roundabouts may experience 

restrictions in access similar to those in the vicinity of 

signalized intersections. Mini-roundabouts may offer the 

opportunity to include driveways as a curb cut or a fully 

developed approach with splitter islands depending on the 

volume characteristics and other factors.

Figure 7: Sample Signing Plan for a Mini-Roundabout
FHWA | Mini-Roundabouts 13

•	 At-grade rail crossings – At-grade rail crossings 

through or near a mini-roundabout introduce challenges 

related to the control of the rail crossing itself, queue 

clearance on the tracks, and the associated effects on the 

mini-roundabout. Mini-roundabouts have been installed 

near at-grade rail crossings in the U.K.

•	 Evacuation routes – Mini-roundabouts can be located 

on evacuation routes by using similar manual control 

treatments (e.g., flagging, police control) that are used at 

other types of intersections. Vehicles are allowed to travel 

over the central island, if necessary.

•	 Bus stops – Bus stops can be provided on either the 

entry or exit side of a mini-roundabout. Bus stops should 

not be provided within the circulatory roadway. Pedestrian 

access to and from the bus stop, including the location of 

the bus stop relative to the nearest crosswalk, should be 

carefully considered.

Refer to the Roundabout Guide for additional 

information on these and other topics. 

Section 7: Costs

Construction costs for mini-roundabouts vary widely depending upon the extent of sidewalk modifications or other geometric improvements and the types of materials used. In most cases, miniroundabouts have been installed with little or no pavement widening and with only minor changes 

to curbs and sidewalks as shown in the example in Figure 8. Construction costs have ranged from 

about $50,000 for an installation consisting entirely of pavement markings and signage to $250,000 

or more for mini-roundabouts that include raised islands and pedestrian improvements. 

A benefit-cost analysis may be useful for programming 

purposes, as it is recognizes that not all of the benefits 

and costs can be quantified by pure construction costs. 

The safety, operational, and environmental benefits 

of mini-roundabouts can be quantified 

and compared to the initial construction 

and ongoing maintenance cost over the 

life cycle of the roundabout. Although 

research is needed on the service lives of 

mini-roundabouts in the United States, 

they are likely to be comparable to the 

intersections they replace, depending on 

construction materials, weather conditions, 

traffic conditions, and other factors. When 

compared to signalized intersections, miniroundabouts are likely to have longer service 

lives due to less maintenance. More detail 

can be found in the Roundabout Guide. 

Figure 8: Example Mini-Roundabout

Photo: Maryland State Highway Administration 

(used with permission)
14 FHWA | Mini-Roundabouts

Section 8: References

1. Robinson, B. W., L. Rodegerdts, W. Scarbrough, W. Kittelson, R. Troutbeck, W. Brilon, L. Bondzio, K. Courage, M. 

Kyte, J. Mason, A. Flannery, E. Myers, J. Bunker, and G. Jacquemart. Roundabouts: An Informational Guide. Report 

FHWA-RD-00-067. FHWA, U.S. Department of Transportation, June 2000.

2. Rodegerdts, L. A., et al. Roundabouts: An Informational Guide, 2nd Edition. National Cooperative Highway Research 

Program Project 03-65A. Transportation Research Board, National Academy of Sciences, Washington, D.C., Work in 

progress, estimated publication 2010.

3. Rodegerdts, L. A., W. E. Scarbrough, and J. A. Bansen. Roundabout Technical Summary. FHWA, Washington, 

D.C., 2010.

4. Department for Transport and the County Surveyors Society. Mini Roundabouts, Good Practice Guidance. 

Department for Transport, United Kingdom, November 27, 2006. http://www.dft.gov.uk/pgr/roads/tss/gpg/

miniroundaboutsgoodpractice.pdf, accessed July 23, 2009.

5. Bodé, Christian, and Faber Maunsell. “Mini-Roundabouts: Enabling Good Practice.” Proceedings, European 

Transport Conference, Strasbourg, France, September 18-20, 2006.

6. Department for Transport. “TD 54/07, Design of Mini-Roundabouts.” Design Manual for Roads and Bridges, Volume 

6, Road Geometry; Section 2, Junctions, Part 2. Department for Transport, United Kingdom, August 2007.

7. Sawers, C. Mini-Roundabouts: A Definitive Guide for Small and Mini-Roundabouts (Right Hand Drive Version). Moor 

Value Ltd. (U.K.), 2007.

8. United States Access Board. Americans with Disabilities Act Accessibility and Architectural Barriers Act 

Accessibility Guidelines, July 2004.

9. Federal Highway Administration (FHWA). Manual on Uniform Traffic Control Devices. FHWA, Washington, D.C., 2009.

10. Illuminating Engineering Society. Design Guide for Roundabout Lighting. Publication IES DG-19-08. Illuminating 

Engineering Society of North America, New York, February 2008.

For More Information

Ed Rice

Intersection Safety Team Leader, 

FHWA Office of Safety

202.366.9064

ed.rice@dot.gov

Visit FHWA’s intersection safety web site to download this and 

other case studies highlighting proven intersection safety 

treatments from across the country:

http://safety.fhwa.dot.gov/intersection

FHWA-SA-10-007 February 2010