Research, Development, and Technology Turner-Fairbank Highway Research Center 300 Georgetown Pike, McLean, VA 22101-2296

www.tfhrc.gov

An Evaluation of Signing for Three-Lane 

Roundabouts

SUMMARY REPORT

Introduction

Since the introduction of the modern roundabout 

to North America nearly two decades ago, roundabout acceptance has continued to grow. As of 

2007, there are more than 1,000 roundabouts in 

North America, and that number is growing rapidly.(1) This acceptance is attributed to the superior 

operational and safety performance of roundabouts 

relative to conventional signalized intersections 

in appropriate conditions.(2–4) Although multilane 

roundabouts have been found to be safer than 

conventional alternatives, especially with 

respect to injury and 

fatal crashes, they 

are not without safety 

challenges. One of 

these challenges is 

getting motorists to 

select and stay in their 

proper lanes as they 

navigate the roundabout. Some motorists take the fastest 

path through roundabouts by entering in 

the right lane, crossing to the center 

lane midway through 

the circular roadway, 

and then crossing 

back into the right 

lane at the exit.(5,6) This behavior creates a risk of 

sideswipe crashes. Another challenge for both 

safety and operational efficiency is that motorists 

sometimes have difficulty interpreting lane-control 

arrows in the roundabout context.(7,8) Even with 

these unresolved issues, the safety and operational 

advantages of one- and two-lane roundabouts are 

so substantial that engineers have begun to introduce three-lane roundabouts where traffic cannot 

be accommodated in one or two lanes.(9) Figure 1 

shows a three-lane roundabout in Michigan.

FHWA Publication No.: FHWA-HRT-10-030

FHWA Contact: Joe Bared, HRDS-05, (202) 493-3314, joe.bared@dot.gov

Figure 1. Michigan three-lane roundabout. 

 Source: Michigan Department of Transportation Photography Unit
2

The use of three-lane roundabouts raises the 

concern that low comprehension and compliance could be a bigger problem than at two-lane 

roundabouts for the following reasons: (1) the 

larger radii of three-lane roundabouts enable 

higher speeds, (2) angles of impact in three-lane 

roundabouts may be more severe when errant 

vehicles stray across multiple lanes from their 

assigned lane, and (3) traffic volumes will be 

higher, and thus, more vehicles will be affected 

by incidents. The present study is intended to 

address this concern of low comprehension 

and compliance.

Objectives

The objectives of this study are to identify 

signing and marking strategies that result in 

higher levels of comprehension and compliance in lane selection on the approach to roundabouts and to examine the effects of these 

strategies on lane use after an approach lane 

has been selected.

Approach

Participants first drove three times through a 

series of six different simulated three-lane 

roundabouts while their lane use was recorded. 

Following the driving simulation, participants 

watched videos of approaches to roundabouts 

and indicated which lanes they could use to reach 

a particular destination and which lanes they were 

restricted from using. These two measures indicated to researchers the extent to which participants understood roundabout lane restrictions. 

Probing for understanding was important because 

drivers tend to use the right lane for right turns 

and the left lane for left turns, and these selections 

would nearly always be appropriate. However, a 

three-lane roundabout might be marked such that 

particular turning movements could be legal from 

two or three lanes. If drivers do not use all allowed 

lanes, the roundabout might not operate at the 

capacity for which it was designed.

The context for the evaluation was simulated 

roundabouts with four legs and three entry lanes. 

Exit leg geometry and marking configurations 

varied to conform to the lane restrictions. Fishhook 

lane restriction signs and markings, as described 

in the proposed revisions to the Manual on 

Uniform Traffic Control Devices (MUTCD), were 

used on all roundabout approaches except where 

the experimental design called for alternative 

navigation signage.(10) 

Compliance was assessed by observing which 

lanes drivers used on the approaches to and within 

the roundabouts and by assessing the extent to 

which drivers stayed in their initially selected lane 

as they navigated each roundabout. Comprehension was assessed by asking drivers to indicate 

which lanes they were permitted to use and which 

lanes they were restricted from using.

Strategies employed to improve comprehension 

and compliance included the following:

•	 The use of overhead signs.

•	 The redundancy in signs and markings.

•	 The use of both navigation and lane control 

signs to communicate lane restrictions.

Method

The following three lane restriction signing conditions were tested:

•	 Roadside regulatory: Consisted of groundmounted fishhook lane-control markings 

and signs.

•	 Overhead regulatory: Consisted of overhead 

fishhook lane restriction signs with fishhook 

markings.

•	 Overhead navigation: Consisted of overhead green navigation signs with lane-use 

indications with upward pointed arrows.

The experimental treatments were located 400 ft 

(122 m) from the roundabout entrance. Downstream from that location, signs and markings 

did not differ between signing conditions.

In all three signing conditions, a diagrammatic 

navigation sign was located 800 ft (244 m) upstream of the entrance to the circular roadway 
3

(see figure 2). The sign was used to inform participants of the location of their destination, 

(i.e., the intended roundabout exit leg). Participants 

were instructed to drive to McLean. The exit to 

McLean varied from trial to trial. For each of six 

roundabout lane restrictions and layout combinations, the exit for McLean was to the right once, 

straight ahead once, and to the left once. The 

combination of six turn restrictions and three 

turning movements resulted in 18 unique trials.

A roundabout ahead warning sign (W2-6) was 

located 600 ft (183 m) upstream of each roundabout entrance. The experimental manipulation 

consisted of different signs 400 ft (122 m) upstream of the entrance. Figure 3 through figure 5 

provide a view from the driver’s perspective of 

the three sign conditions that include the roadside regulatory condition, the overhead regulatory condition, and the overhead navigation sign 

condition. Fishhook markings that matched the 

lane restrictions on the signs were placed in 

each lane 400 ft (122 m) upstream of the entrance.

In all conditions, fishhook regulatory signs and 

markings were placed on both sides of the road 

40 ft (12 m) upstream of the yield line. Fishhooks 

were not used on the overhead navigation signs 

due to space constraints and because conventional arrows were deemed sufficient for this 

application.

All other signs and markings were consistent with 

the proposed amendments to the MUTCD.(10,11)

Figure 2. Guide sign located upstream of the circular 

roadway. 

Figure 3. Roadside regulatory condition.

Figure 4. Overhead regulatory condition. Figure 5. Overhead navigation condition.
4

Table 1 shows the six lane restrictions that were 

used. The geometry and markings of the circulatory roadway and roundabout exits were modified 

to correspond with the lane restrictions. An example 

of the lane restriction markings is shown in figure 6. 

Each of 18 simulated roundabouts was preceded 

by a one-lane roadway segment, which was 165 ft 

(50 m) long and widened to three lanes over a 

distance of 120 ft (37 m). Three lanes were available 100 ft (31 m) upstream of the diagrammatic 

sign for the next roundabout, which ensured 

that all participants started in the same lane (the 

center lane) at the beginning of each roundabout 

approach. The roadway and roundabout environment consisted of simulated grassy fields with a 

tree line visible in the distance. The only structure 

in the simulation scenario was a warehouse-like 

building that was to the right on the approach to 

all 18 roundabouts.

The Driving Simulator

Components of the Federal Highway Administration (FHWA) Highway Driving Simulator (HDS) 

included a 1998 Saturn SL1 chassis, five projectors 

each with a resolution of 2,048 by 1,536 pixels, 

and a 240-degree cylindrical projector screen 

situated 9 ft (2.7 m) from the driver’s design 

eye point. The vehicle chassis was mounted on 

a 3 degree-of-freedom (roll, pitch, and heave) 

motion system. The vehicle dynamics model was 

calibrated to approximate the characteristics of a 

small passenger sedan. Data capture was synchronized to the frame rate of the graphics cards 

(mean @ 100 frames per second). Data recorded 

from the vehicle dynamics model included speed, 

vehicle position, and heading. Engine, wind, tire, 

and other environmental sounds were provided.

Participants

Participants from the Washington, DC, metropolitan 

area who responded to newspaper advertisements 

and internet postings or who heard of the study 

through word-of-mouth were recruited. Participants 

included individuals who had participated in 

previous FHWA studies as well as newly recruited 

people. Individuals who participated in the earlier 

roundabout signing and marking studies or had 

previously experienced simulator sickness were 

not recruited for this study. A total of 96 licensed 

drivers completed the study. Drivers were paid 

for their participation. Seven other participants 

dropped out before completing the study because 

of simulator sickness symptoms. 

Procedures

Participants were randomly assigned to the 3 sign 

conditions, with 32 participants in each condition 

with equal numbers of males (24 under 65 years old 

Table 1. Six-lane restriction combinations used in the 

experiment.

Restriction 

Conditions

Left 

Lane

Center 

Lane

Right 

Lane

1 L LTR R

2 LT T TR

3 L LT TR

4 LT TR R

5 L T R

6 L TR R

L = Left turn only.

R = Right turn only.

T = Through movement only.

LT = Shared by left-turn and through movements.

TR = Shared by right-turn and through movements.

LTR = Shared by all movements.

Figure 6. Geometry and markings for LT, T, and TR lane 

restrictions.
5

and 24 at or over 65 years old) and females 

(24 under 65 years old and 24 at or over 

65 years old). Upon arriving at the FHWA laboratory, participants were asked to read and sign 

an acknowledgment of informed consent. Their 

vision was then tested to ensure a minimum 

20/40 acuity in at least one eye. Next, a brief 

health screening questionnaire was administered 

to ensure that they had no acute health impairments. Finally, participants were administered 

a Simulator Sickness Questionnaire (SSQ) and a 

postural stability test to establish a baseline for 

later administration of those same tests.(12,13)

Simulator Drives

Before beginning the main driving simulation, 

participants completed two drives that lasted 

about 5 minutes each to accustom themselves to 

the HDS. The first of these drives was on a wide 

roadway that was free of traffic or obstructions. 

On the roadway, participants were asked to accelerate, brake, and change lanes until they felt comfortable with the simulated vehicle handling. The 

second accustomization drive was intended to 

ensure that participants were exposed to simple 

single-lane roundabouts. Participants were 

instructed to drive towards McLean, which was 

the same instruction as in the experimental drive 

that followed. The specified destination was 

presented at least once in three directions: to the 

right, straight ahead, and to the left at successive 

single-lane roundabouts.

The final drive in the simulator was the experimental drive. A series of 18 roundabouts were 

presented in a different random order to each 

participant. The roundabouts consisted of each of 

the six roundabout geometries coupled with 

the destination, McLean, which occurred once 

in each of three directions: to the right, straight 

ahead, or to the left. Participants were instructed 

to drive as they normally would and to obey all 

traffic laws.

Each of the three drives was followed by an administration of the SSQ and postural stability tests to 

assess the extent of possible simulator sickness 

symptoms.

Questionnaire

The HDS was intended to allow the testers the 

opportunity to observe how participants drove 

given one of three sign conditions. It was assumed 

that lane choice varied in relation to how well the 

participants understood the signs and markings. 

However, the driving simulation could not unambiguously assess the extent to which participants 

fully understood the signs and markings. For 

instance, drivers might prefer to use the right 

lane when turning right and not use the center 

lane even when that use was permitted for right 

turns. Therefore, the driving simulation was 

followed by a questionnaire intended to more 

completely assess the participants’ understanding 

of the lane restriction signs and markings.

The questionnaire was administered on a touch 

screen video monitor. On an adjacent monitor, 

participants were asked to view the same 

18 roundabout approaches that they had just 

driven through. The sign condition on those 

roundabouts was the same as that in the simulator, but the roundabouts were presented in a 

different random order. The video displayed the 

approach from before the diagrammatic sign up to 

the yield line, at which point, the video froze and 

a question appeared on the touch screen monitor. 

The lane-restriction markings were not visible in 

the frozen image. 

Above a picture of three lanes, the touch screen 

displayed the question “Which lanes can be used 

if you are going to McLean?” The participants were 

instructed to touch those lanes that could be used 

legally to proceed to McLean. When touched, a 

black ball appeared in the lane. A second touch 

in the same lane would remove the ball. When 

satisfied with the choice(s), the participants 

touched a box below the picture labeled “OK.” 

The touch screen monitor then displayed “Which 

lanes could result in a traffic ticket if you used 

them to go to McLean?” above a picture of three 

lanes. Participants were instructed to touch the 

lanes that were not allowed. An orange ball 

appeared in the selected lanes. When the participant pressed “OK,” a “Next Roundabout” button 

became available. Pressing that button grayed out 

the questionnaire screen, and a new roundabout 
6

approach was displayed on the adjacent monitor. 

After completing the questionnaire, participants 

were debriefed and compensated.

Research Design

The research design was a factorial design in which 

sign condition was a between-groups factor with 

three levels (roadside regulatory, overhead regulatory, and overhead guide sign). It was crossed with 

the within groups turning movement factor which 

also had three levels (left turn, through movement, 

and right turn). There were 32 participants in each 

sign condition. 

The dependent measures were all binary. The 

dependent measures for the HDS were lane use 

(correct/incorrect) and lane change within the 

roundabout (yes/no). The dependent measures 

for the questionnaire were lanes allowed (correct/ 

incorrect) and lanes not allowed (correct/incorrect). 

Results

The findings from the driving simulation are presented first, describing the lane choice and lanechanging results. The questionnaire findings are 

presented after the driving simulation findings.

Driving Simulation Findings

The lane choice and lane change findings were 

analyzed using a generalized linear estimation 

model that was suitable for binary dependent 

measures and categorical independent variables 

with repeated measures.(14) Lane choice and lane 

changing were analyzed separately because, in 

many instances, more than one lane might have 

been an appropriate choice so that drivers could 

have changed lanes and still have been in an 

appropriate lane. However, lane changes within a 

roundabout were not appropriate. Therefore, once 

participants reached 40 ft (12.2 m) upstream 

of the yield line, changing lanes was not appropriate whether or not the new lane was appropriate for the assigned turning movement.

Lane Choice

Lane choices were recorded at 11 locations at 

each of the 18 roundabouts. These locations, 10 

of which are illustrated in figure 7, were as follows:

•	 Location 1: At 800 ft (244 m) upstream of 

the yield line.

•	 Location 2: At 600 ft (183 m) upstream of 

the yield line.

•	 Location 3: At 400 ft (122 m) upstream of 

the yield line.

•	 Location 4: At 40 ft (12.2 m) upstream of 

the yield line.

Figure 7. Lane selection measurement locations.
7

•	 Location 5: At the edge of the yield line 

entrance.

•	 Location 6: At the right turn exit.

•	 Location 7: In the circular roadway adjacent 

to the first splitter island beyond the entry.

•	 Location 8: At the exit for the through 

movement.

•	 Location 9: In the circular roadway adjacent 

to the second splitter island beyond the entry.

•	 Location 10: At the exit for the left turn 

movement.

•	 Location 11: In the circular roadway adjacent 

to the third splitter island beyond the entry.

At each of these locations, the lane occupied was 

classified as correct or incorrect. To be classified 

as correct, the vehicle had to be either wholly 

within an allowed lane or to have less than half 

of the vehicle’s width outside of the allowed 

lane. Table 2 shows the percentage of drivers 

who were in inappropriate lanes 400 ft (122 m) 

upstream of the roundabout to exit the roundabout for the left-turning movement. At 400 ft 

(122 m), it is technically incorrect to label 

any lane as inappropriate; however, because there 

was no conflicting traffic in the simulation, there 

was also no reason at that point for drivers not 

to have moved to an appropriate lane for the 

upcoming maneuver. The 40-ft (12.2-m) location 

was where the lane demarcations became solid 

Table 2. Percentage of drivers in an inappropriate lane 400 ft (122 m) upstream as a function of turning movement. 

Location Sign Condition Left (Percent)

Right 

(Percent)

Through 

(Percent) Wald c2 Probability 

of Error

Location 3

Roadside Regulatory 27 8 26

Overhead Regulatory 20 5 21 5.09 0.08

Overhead Navigation 13 7 18

Location 4

Roadside Regulatory 24 4 18

Overhead Regulatory 18 3 17 7.56 0.02

Overhead Navigation 11 2 9

Location 5

Roadside Regulatory 23 4 18

Overhead Regulatory 18 3 18 7.35 0.03

Overhead Navigation 11 2 8

Location 6

Roadside Regulatory 6

Overhead Regulatory 5 3.24 0.20

Overhead Navigation 2

Location 7

Roadside Regulatory 12 12

Overhead Regulatory 6 14 3.74 0.15

Overhead Navigation 6 8

Location 8

Roadside Regulatory 3

Overhead Regulatory 5 2.76 0.25

Overhead Navigation 2

Location 9

Roadside Regulatory 14

Overhead Regulatory 7 4.22 0.12

Overhead Navigation 10

Location 10

Roadside Regulatory 18

Overhead Regulatory 20 0.90 0.64

Overhead Navigation 15

Note: Blank spaces indicate movements that do not exist, and the statistical measures are for one location at a time. Bold indicates 

that the probability is less than 0.05, and the condition is statistically significant.
8

so that lane changes beyond that point were 

inappropriate. On the right side of table 2, the 

Wald chi-square statistic for sign condition test 

is shown, and the exact probability for that chisquare value is provided. The Wald chi-square 

value was evaluated with 2 degrees of freedom.

At each measurement location, from 400 ft (122 m) 

upstream until the appropriate exit for the assigned 

turning movement, a generalized linear model 

was fit to the data, in which direction (three 

categories) was treated as a repeated measure, 

and sign condition was treated as a between 

subjects categorical variable. The effects of sign 

condition, turn direction, and the interaction of 

turn direction with sign condition were tested 

using a generalized estimating equations model 

that used a binomial distribution and a logit link.(15)

At location 3 (see figure 7), which was 400 ft 

(122 m) upstream of the yield line, the difference 

between signing conditions was not statistically 

significant, c2(2) = 5.1, p = 0.08. The effect of turn 

direction was significant, c2(2) = 45.0, p < 0.001, as 

more drivers that were intending to make left or 

through movements were out of position than drivers intending to turn right. The interaction of turn 

direction and signing condition was not statistically significant for this or any subsequent analysis.

At location 4, which was 40 ft (12.2 m) upstream 

of the yield line, the overhead navigation sign 

condition was superior to either of the regulatory 

sign conditions. The main effect of sign condition 

was significant, c2

(2) = 7.6, p < 0.05. Again, the 

errors were primarily associated with left and 

through movements averaged across sign condition as 97 percent of drivers preparing to turn 

right used an appropriate lane. The turning movement effect was significant, c2

(2) = 39.7, p < 0.001.

At location 5, which was where drivers crossed 

the yield line and entered the circulatory 

roadway, the findings were similar to those 

at the preceding measurement location. Sign 

condition was significant, c2

(2) = 7.35, p < 0.05, as 

was the effect of turning movement, c2

(2) = 38.2, 

p < 0.001.

At location 6, which showed the exit for the 

right-turning movement, there were no significant 

differences between sign conditions, and 96 percent 

of drivers were in a correct lane.

In the circular roadway at location 7, which was 

between the center island and the first splitter 

island, sign condition did not have a significant 

influence on appropriate lane use. The direction of 

the movement had a significant effect on correct 

lane choice, c2

(1) = 5.2, p < 0.05. At this location, 

when averaged across sign condition, drivers 

going left were in an appropriate lane 93 percent of 

the time, whereas drivers going straight were in 

the correct lane 89 percent of the time.

At location 8, which was the exit for the through 

movement, there was no significant sign condition 

effect on appropriate lane use, and drivers were 

in appropriate lanes 97 percent of the time.

At location 9, which was in the circular roadway 

between the center island and the second splitter island, sign condition also had no significant 

influence on appropriate lane use. Drivers were 

in appropriate lanes 90 percent of the time. 

At location 10, which was at the exit for the leftturn movement, drivers used appropriate lanes 

only 83 percent of time, and sign condition had 

no significant effect on appropriate lane use. 

Thus, with respect to appropriate lane use, the 

overhead navigation sign had a positive effect 

before drivers entered the circular roadway and 

had no significant influence after they entered 

the circular roadway. 

Inappropriate Lane Changes

Once in an appropriate lane, it was desirable that 

drivers did not change lanes. The occurrence of a 

lane change was treated as a binary variable (yes/

no). As with lane choice, the data were analyzed 

using a generalized linear equations model with 

roundabout and turn direction as repeated measures. Independent variables included in the test 

were signing condition and turn direction when 

appropriate. Table 3 shows the percent of drivers 
9

who changed lanes within the circulatory roadway and the results of tests of the effect of sign 

condition on lane change frequency. The percentages shown in table 3 were not conditioned on 

whether drivers began in an allowed lane or 

changed to an allowed lane—all lane changes made 

by vehicles that used assigned roundabout exit 

were included.

Drivers in the overhead navigation sign condition were less likely than drivers in the other two 

signing conditions to change lanes during the 

right-turn movement. Between the entrance and 

the exit for the through movement, drivers in the 

overhead navigation condition were almost half 

as likely to change lanes as drivers in the other 

signing conditions. However, once drivers were 

past the first splitter island, the lane changing of 

drivers making the left-turn movement was not 

significantly influenced by signing condition.

Questionnaire Findings

Two response variables (dependent measures) 

were derived from responses to the questionnaire: 

(1) whether the identification of lanes that were 

allowed for a particular turning movement was 

correct or incorrect and (2) whether the identification of the lanes which could be ticketed if used 

of a particular turning movement was correct 

Table 3. Percent of drivers changing lanes within the circular roadway and tests of the significance of signing 

condition on lane changing.

Roundabout Location

Roadside 

Regulatory 

(Percent)

Overhead 

Regulatory

(Percent)

Overhead 

Navigation 

(Percent) Wald c2 (2) Probability Significance

Between entrance 

and right-turn exit 

(locations 5 and 6) 7 10 1 8.20 0.02 Significant*

Between entrance 

and first splitter 

(locations 5 and 7) 21 26 13 8.26 0.02 Significant*

Between first splitter 

and through exit 

(locations 7 and 8) 16 20 11 8.39 0.02 Significant*

Between first and 

second splitter 

(locations 7 and 9) 6 6 7 0.16 0.92

Not 

significant

Between second 

splitter and left exit 

(locations 9 and 10) 5 18 11 5.38 0.07

Not 

significant

* If the probability is less than or equal to 0.05, the condition is statistically significant.

Table 4. Percentage of incorrect responses in identifying allowable and prohibited lanes for turning movements. 

Roundabout Location

Roadside 

Regulatory 

(Percent)

Overhead 

Regulatory

(Percent)

Overhead 

Navigation 

(Percent) Wald c2 (2) Probability Significance

Lanes allowed 21 14 11 4.6 0.10

Not 

significant

Lanes ticketed 21 17 13 2.7 0.26

Not 

significant
10

or incorrect (see table 4). A generalized linear 

equation model was used to test for the 

significance of the sign condition. A binary distribution with logit links was used.

As can be seen in table 4, the sign condition effect 

was not statistically significant for either the lanes 

allowed question or the lanes ticketed question. 

However, the percentages of incorrect responses 

roughly matched the percentages of inappropriate lane use in the driving simulation. Also, for 

responses to the question “Which lanes are 

you allowed to use?” the two overhead signing 

conditions combined produced marginally better 

comprehension than the roadside signage, c2(1) = 

4.0, p < 0.05. 

Discussion

The simulation and questionnaire results suggest 

the following: (1) overhead navigation signing in 

advance of multilane roundabouts yielded better 

compliance with lane restrictions than regulatory 

signing alone, and (2) a substantial percentage of 

drivers, perhaps up to 20 percent, did not understand lane restrictions in the context of roundabouts. Although overhead advance navigations 

signs can increase comprehension to about 

90 percent, that benefit applies primarily to roundabout approaches. Drivers changed lanes within 

the roundabouts at rates of 10 to 25 percent.

It should be noted that no other vehicles were 

present in the driving simulation. Informal field 

observations suggest that drivers are more likely 

to stay in their lane when other vehicles are present. However, drivers are not always aware of other 

vehicles, so a high likelihood of improper lane 

changes, as observed in this study, is likely to be 

associated with higher crash rates.

Previous FHWA studies have reported the widespread misunderstanding of lane restriction signs 

and pavement markings in the context of roundabouts. Those studies were criticized for not including full context or redundant signs and markings. 

The present study included all of the signs and 

markings—both required and optional—that are 

included in the most recent proposed revisions to 

the MUTCD.(10) Nevertheless, the rates of misunderstanding are similar to those reported previously.

The overhead advance navigation signage in the 

navigation sign condition considerably improved 

driver compliance and comprehension. However, 

at multilane roundabouts, getting drivers to navigate to the appropriate lanes and stay in them 

remains a challenge. 

Conclusions and Recommendations

Overhead advance navigation signage is more 

favorable for roundabouts with three entering 

lanes. The proposed amendments to the MUTCD 

include a requirement, “Where the number of 

lanes available to through traffic on an approach is 

three or more, Mandatory Movement Lane Control 

(R3-5 and R3-5a) symbol signs, if used, shall be 

mounted overhead...”(16) The present findings 

support that requirement and further suggest that 

navigation signs at least supplement any other 

overhead lane-restriction signing.

At the time this summary report was prepared, four 

three-lane roundabouts were operating in Michigan. 

One of those, at MI-53 and Van Dyke Avenue in 

Sterling Heights, MI, has been operating since 

2003. Initially, the approach signing consisted of 

ground-mounted regulatory symbol signs. When 

the inappropriate lane changes resulted in a 

higher than expected crash rate, the Michigan 

Department of Transportation installed a series of 

ground-mounted diagrammatic guide signs that 

designated lanes to be used for particular destinations. Although it is too soon to say whether 

the navigation signs have reduced the crash 

rate, this example confirms the importance of 

providing guidance for drivers to choose and 

stay in lanes appropriate for their destination.

It appears that additional treatments beyond the 

overhead signs tested in this study are needed to 

keep drivers from changing lanes within roundabouts. One possible way to keep drivers in their 

lanes is to use a turbo roundabout, which has been 

adapted in several continental European countries.(17)

The turbo roundabout uses raised mountable 
11

curbs between lanes to discourage lane changes. 

This design also encourages drivers to move 

into the appropriate lanes before entering the 

roundabout. Another possibility for keeping 

drivers from changing lanes once they are guided 

to appropriate lanes includes installing enhanced 

lane markings and other forms of channeling 

such as rumble strips. Lane-marking enhancements might include wider lines between lanes. 

Research is needed to explore the effectiveness of turbo roundabouts or other novel treatments to improve driver comprehension of and 

compliance with lane restrictions at multilane 

roundabouts.

References

1. Rodegerdts, L.A. (2008). Roundabouts in North 

America, National Roundabouts Conference, 

Kansas City, KS.

2. Flannery, A., Kharofeh, J.P., Gautam, N., and 

Elefteriadou, L. (2000). Estimating Delay at 

Roundabouts, 23, Institute of Transportation 

Engineers, Nashville, TN.

3. Persaud, B., Retting, R., Garder, P., and Lord, D. 

(2001). “Safety Effect of Roundabout Conversions in the United States: Empirical Bayes 

Observational Before-After Study,” Transportation Research Record 1751, 1–8, Transportation Research Board, Washington, DC.

4. Thieken, S.L. (2008). “Implementing Multi-Lane 

Roundabouts in Urban Areas,” Transportation 

Land Use, Planning, and Air Quality, American 

Society of Civil Engineers, Orlando, FL.

5. Inman, V.W., Shafer, T., and Katz, B.J. (2003). 

Field Observations of Path and Speed of 

Motorists at Double-Lane Roundabouts, 2nd 

Urban Street Symposium: Uptown, Downtown, 

or Small Town: Designing Urban Streets 

That Work, Anaheim, CA.

6. Robinson, B.W., et. al. (2000). Roundabouts: 

An Informational Guide, Report No. FHWA-RD00-067, Federal Highway Administration, 

Washington, DC. 

7. Inman, V.W., Katz, B.J., and Hanscom, F.R. 

(2006). “Navigation Signing for Roundabouts,” 

Transportation Research Record 1973, 18–26, 

Transportation Research Board, Washington, DC.

8. Molino, J.A., Inman, V.W., and Katz, B.J. 

(2007). Lane Restriction Marking and Signing 

for Double-Lane Roundabouts: Results of 

an FHWA Simulator Experiment, ITE Spring 

Conference and Exhibit, San Diego, CA.

9. Kalousdian, A. (2004). “Michigan’s First ThreeLane Roundabout,” Michigan Contractor and 

Builder, Associated Construction Publications, 

LLC, Indianapolis, IN.

10. National Committee on Uniform Traffic Control 

Devices. (2007). 2007 Notice of Proposed 

Amendments for the Manual on Uniform 

Traffic Control Devices: MUTCD Figures, 

Federal Highway Administration, Washington, 

DC. Obtained from: http://mutcd.fhwa.dot.gov/

resources/proposed_amend/npa_figures.pdf. 

Site last accessed June 1, 2009.

11. Federal Highway Administration. (2003). 

Manual on Uniform Traffic Control Devices 

(MUTCD), Washington, DC.

12. Cobb, S.V. and Nichols, S.C. (1998). “Static 

Posture Tests for the Assessment of Postural 

Instability after Virtual Environment Use,” Brain 

Research Bulletin, 47, 459–464.

13. Kennedy, R.S., Lane, N.E., Berbaum, K.S., 

and Lilienthal, M.G. (1993). “Simulator Sickness Questionnaire: An Enhanced Method 

for Quantifying Simulator Sickness,” The 

International Journal of Aviation Psychology, 

3, 203–220.

14. Vittinghoff, E., Glidden, D.V., Shiboski, S.C., 

and McCulloch, C.E. (2007). Statistics for 

Biology and Health: Regression Methods 

in Biostatistics: Linear, Logistic, Survival, 

and Repeated Measures Models, Springer, 

New York, NY.

15. Stokes, M.E. Recent Advances in Categorical 

Data Analysis, SAS® Institute, Inc., Cary, NC. 
12

Researchers—Vaughan Inman authored this report and was the Principal Investigator. Bryan Katz 

and Kevin Sylvester of the FHWA provided valuable guidance on the sign design and markings. 

Pascal Beuse, Erin Dagnall, and Megan Hermosill recruited participants and guided them through 

the experiment. Mike Baumgartner, Ryan Cartwright, Peter Chou, and Jason Williams developed the 

driving simulation and questionnaire and operated and maintained the HDS. Wes Butch provided 

information on the roundabout at MI-53 and Van Dyke Avenue. The peer reviewers for this report 

were Scott Wainwright and Ed Rice of the FHWA. For information about this research contact, 

Joe Bared, FHWA Task Manager, HRDS-05, (202) 493-3314, joe.bared@dot.gov.

Distribution—This Summary Report is being distributed according to a standard distribution. 

Direct distribution is being made to the Divisions and Resource Center.

Availability—The report can be obtained from the FHWA Product Distribution Center by e-mail to 

report.center@dot.gov, by fax to (814) 239-2156, or by phone to (814) 239-1160. 

Key Words—Multilane roundabout, Driving simulation, Intersection safety, Lane restriction sign, 

Lane restriction, Signs, Markings, and Lane choice.

Notice—This Summary Report is disseminated under the sponsorship of the U.S. Department of 

Transportation in the interest of information exchange. The U.S. Government assumes no liability for 

the use of the information contained in this document. The U.S. Government does not endorse 

products or manufacturers. Trademarks or manufacturers’ names appear in this report only because 

they are considered essential to the objective of the document.

Quality Assurance Statement—The Federal Highway Administration (FHWA) provides highquality information to serve Government, industry, and the public in a manner that promotes 

public understanding. Standards and policies are used to ensure and maximize the quality, 

objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and 

adjusts its programs and processes to ensure continuous quality improvement.

march 2010 FHWA-HRT-10-030

HRDS-05/03-10(1.5M)E

Obtained from: http://www.ats.ucla.edu/stat/

sas/library/categorical.pdf. Site last accessed 

May 19, 2009.

16. Federal Highway Administration. (2008). “23 

CFR Parts 634 and 655: National Standards for Traffic Control Devices, Manual on 

Uniform Traffic Control Devices for 

Streets and Highways,” Federal Register, 277, 

Washington, DC. Obtained from: http://

frwebgate.access.gpo.gov/cgi-bin/getdoc.

cgi?dbname=2008_register&docid=fr02ja08-27.

pdf. Site last accessedOctober 20, 2009.

17. Fortuijn, L.G.H. (2009). Turbo Roundabouts: 

Design Principles and Safety Performance, 

Transportation Research Board 88th Annual 

Meeting, Washington, DC.