Research, Development, and Technology

Turner-Fairbank Highway Research Center

6300 Georgetown Pike

McLean, VA 22101-2296

Pedestrian Access to Roundabouts: 

Assessment of Motorists’ 

Yielding to Visually Impaired 

Pedestrians and Potential Treatments 

To Improve Access

PUBLICATION NO. FHWA-HRT-05-080 MAY 2006
 

FOREWORD 

The FHWA’S Intersection Safety Research Program is focused on improving highway 

safety through increasing knowledge and understanding of the effects of intersection 

design on safety and operational efficiency. Roundabout intersections have been shown 

to have both safety and operational benefits compared to alternative stop-controlled and 

signalized intersections; however, these benefits do not necessarily extend to all users. In 

particular, pedestrians who have visual impairments have reported difficulty using the 

pedestrian facilities at some roundabouts. The present studies were intended to document 

some of the difficulties pedestrians with visual impairments face and test potential 

treatments to improve roundabout accessibility for all users. 

Michael Trentacoste 

Director, Office of Safety 

 Research and Development 

NOTICE 

This document 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 its contents or use thereof. This report does not constitute a standard, 

specification, or regulation. 

The U.S. Government does not endorse products or manufacturers. Trade and 

manufacturers’ names appear in this report only because they are considered essential to 

the object of the document. 

QUALITY ASSURANCE STATEMENT 

The Federal Highway Administration (FHWA) provides high-quality 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. 
 

Technical Report Documentation Page 

1. Report No. 

FHWA–HRT–05–080 

2. Government Accession No. 3. Recipient’s Catalog No. 

5. Report Date 

May 2006 

4. Title and Subtitle 

Pedestrian Access to Roundabouts: Assessment of Motorists’ Yielding to 

Visually Impaired Pedestrians and Potential Treatments To Improve Access 

6. Performing Organization Code 

7. Author(s) 

Vaughan W. Inman, Gregory W. Davis, and Dona Sauerburger 

8. Performing Organization Report No. 

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) 

SAIC 

1710 SAIC Dr 

M/S T1-12-3 

McLean, VA 22102 

11. Contract or Grant No. 

DTFH61–02–C–00064 

13. Type of Report and Period Covered 

Final Report 

Oct 2003–Jan 2005 

12. Sponsoring Agency Name and Address 

Office of Safety Research and Development 

Federal Highway Administration 

6300 Georgetown Pike 

McLean, VA 22101 

14. Sponsoring Agency Code 

15. Supplementary Notes 

Prepared for: Joseph G. Bared, Ph.D., Office of Safety Research and Development, HRDS-05 

16. Abstract 

This report describes two related studies intended to address double-lane roundabout accessibility issues for visually 

impaired pedestrians. The first study was conducted on a closed course to evaluate the feasibility of a pavement treatment to 

alert blind pedestrians when vehicles have yielded to them. The second study examined drivers’ yielding behavior at a twolane roundabout and the effectiveness of the same roadway treatment in an operational environment. 

In the first study, there were two experimental conditions: a control condition and a treatment condition in which rumble 

strip-like devices were placed on the roadway surface. Seven individuals who have severe visual impairments participated. 

Participants stood at a crosswalk and used hand signals to indicate when they detected vehicles stopping or departing after a 

stop. Compared to the control condition, the sound strips treatment increased the probability of detecting stopped vehicles, 

and decreased by more than a second the amount of time needed to make a detection; however, the treatment did not reduce 

the number of false detections. False detections could result in the pedestrian crossing when moving vehicles are 

approaching the crosswalk. 

The second study was an experiment conducted at an operating roundabout. In that environment the rumble strip-like 

treatment was not effective, probably because the majority of vehicles stopped in the circular roadway before crossing over 

the rumble strips. A Yield to Pedestrians, State Law sign that was placed in the roundabout exit between the two travel lanes 

resulted in an increase in drivers’ yielding from 11 percent of vehicles in the control condition to 16 percent in the 

experimental condition. 

It was concluded that the treatments explored in these studies do not appear promising for double-lane roundabouts, but 

should be explored further to see if they might work at single-lane crossings.

17. Key Words 

VISUAL IMPAIRMENT, PEDESTRIAN, 

ROUNDABOUT, ACCESSIBILITY, YIELDING, 

CROSSWALK 

18. Distribution Statement 

No restrictions. This document is available to the public 

through the National Technical Information Service, 

Springfield, VA 22161. 

19. Security Classif. (of this report) 

Unclassified 

20. Security Classif. (of this page) 

Unclassified 

21. No. of 

Pages 

42 

22. Price 

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized
ii 

SI* (MODERN METRIC) CONVERSION FACTORS 

APPROXIMATE CONVERSIONS TO SI UNITS

Symbol When You Know Multiply By To Find Symbol 

LENGTH 

in inches 25.4 millimeters mm 

ft feet 0.305 meters m 

yd yards 0.914 meters m 

mi miles 1.61 kilometers km 

AREA 

in2 square inches 645.2 square millimeters mm2

ft2 square feet 0.093 square meters m2

yd2 square yard 0.836 square meters m2

ac acres 0.405 hectares ha

mi2 square miles 2.59 square kilometers km2

VOLUME 

fl oz fluid ounces 29.57 milliliters mL 

gal gallons 3.785 liters L 

ft3 cubic feet 0.028 cubic meters m3 

yd3 cubic yards 0.765 cubic meters m3 

NOTE: volumes greater than 1000 L shall be shown in m3

MASS 

oz ounces 28.35 grams g

lb pounds 0.454 kilograms kg

T short tons (2000 lb) 0.907 megagrams (or "metric ton") Mg (or "t") 

TEMPERATURE (exact degrees) o

F Fahrenheit 5 (F-32)/9 Celsius oC 

or (F-32)/1.8 

ILLUMINATION 

fc foot-candles 10.76 lux lx

fl foot-Lamberts 3.426 candela/m2 cd/m2

FORCE and PRESSURE or STRESS 

lbf poundforce 4.45 newtons N 

lbf/in2 poundforce per square inch 6.89 kilopascals kPa 

APPROXIMATE CONVERSIONS FROM SI UNITS 

Symbol When You Know Multiply By To Find Symbol 

LENGTH

mm millimeters 0.039 inches in 

m meters 3.28 feet ft 

m meters 1.09 yards yd 

km kilometers 0.621 miles mi 

AREA mm2

 square millimeters 0.0016 square inches in2 

m2 square meters 10.764 square feet ft2 

m2 square meters 1.195 square yards yd2 

ha hectares 2.47 acres ac

km2 square kilometers 0.386 square miles mi2 

VOLUME 

mL milliliters 0.034 fluid ounces fl oz 

L liters 0.264 gallons gal 

m3 cubic meters 35.314 cubic feet ft3 

m3 cubic meters 1.307 cubic yards yd3 

MASS 

g grams 0.035 ounces oz

kg kilograms 2.202 pounds lb

Mg (or "t") megagrams (or "metric ton") 1.103 short tons (2000 lb) T 

TEMPERATURE (exact degrees) o

C Celsius 1.8C+32 Fahrenheit oF 

ILLUMINATION 

lx lux 0.0929 foot-candles fc 

cd/m2 candela/m2 0.2919 foot-Lamberts fl

FORCE and PRESSURE or STRESS 

N newtons 0.225 poundforce lbf 

kPa kilopascals 0.145 poundforce per square inch lbf/in2

*SI is the symbol for th International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E e 380. 

(Revised March 2003)
iii 

TABLE OF CONTENTS 

CHAPTER 1. INTRODUCTION ....................................................................................................1 

BACKGROUND .......................................................................................................................1 

The Prevalence of Visual Impairment ................................................................................ 1 

Roundabout Overview ........................................................................................................ 1 

Motorists’ Yielding Behavior ............................................................................................. 3 

Street Crossing by Visually Impaired Pedestrians.............................................................. 3 

RESEARCH GOALS ................................................................................................................4 

Study 1 ................................................................................................................................ 4 

Study 2 ................................................................................................................................ 5 

CHAPTER 2. STUDY 1: CLOSED-COURSE EVALUATION ....................................................7 

METHOD ..................................................................................................................................7 

Test Facility ........................................................................................................................ 7 

Participants.......................................................................................................................... 9 

Procedures........................................................................................................................... 9 

QUANTITATIVE RESULTS .................................................................................................11 

Detection of Vehicles Blocking Both Lanes..................................................................... 12 

Detection of Individual Stopped Vehicles ........................................................................ 13 

Debriefing Results ............................................................................................................ 15 

Participant 1 ......................................................................................................... 15

Participant 2 ......................................................................................................... 16

Participant 3 ......................................................................................................... 16

Participant 4 ......................................................................................................... 16

Participant 5 ......................................................................................................... 17

Participant 6 ......................................................................................................... 17

Participant 7 ......................................................................................................... 17

DISCUSSION..........................................................................................................................18 

CHAPTER 3. STUDY 2: FIELD EVALUATION........................................................................19 

METHOD ................................................................................................................................19 

Roundabout Treatment...................................................................................................... 19 

Study 2 Procedures ........................................................................................................... 21 

RESULTS ................................................................................................................................22 

DISCUSSION..........................................................................................................................31 

CHAPTER 4. CONCLUSIONS AND RECOMMENDATIONS.................................................33 

REFERENCES ..............................................................................................................................35 
iv 

LIST OF FIGURES 

Figure 1. Illustration of single-lane roundabout with crosswalks....................................................2 

Figure 2. MUTCD R1–6..................................................................................................................6 

Figure 3. MUTCD R1–5..................................................................................................................6 

Figure 4. Layout of closed-course test facility.................................................................................8 

Figure 5. Example of driver’s script. .............................................................................................11 

Figure 6. Proportions of correct identifications of stopped vehicles shown by test condition, 

the lane in which the first vehicle to yield stopped, and the lane identified. .....................14 

Figure 7. Roundabout exit in baseline configuration.....................................................................20 

Figure 8. Sound-strip installation and mount for the street sign....................................................20 

Figure 9. Distance from crosswalk of vehicles stopping in the near lane......................................23 

Figure 10. Two vehicles that stopped for the pedestrians..............................................................24 

Figure 11. Distance between the crosswalk and a vehicle stopped in the far lane is shown as a 

function of treatment condition..........................................................................................25 

Figure 12. Pedestrians crossing after a correct detection of both lanes blocked. ..........................28 

Figure 13. Frequencies of delays between the time both lanes were blocked and when 

participants indicated both lanes were blocked. ................................................................29 

Figure 14. Amount of time drivers waited before moving on. ......................................................30 

LIST OF TABLES 

Table 1. Percentage of detection accuracy for vehicles blocking each lane..................................12 

Table 2. Correct detection of pairs of vehicles yielding side-by-side at the same time. ...............13 

Table 3. Drivers’ responses to the presence of visually impaired pedestrians in the 

crosswalk............................................................................................................................22 

Table 4. Lateral position of vehicles that stopped for pedestrians.................................................22 

Table 5. Trial outcomes. ................................................................................................................26 

Table 6. Average wait time before the first double yield. .............................................................30 

1 

CHAPTER 1. INTRODUCTION 

This report describes two related studies intended to address double-lane roundabout 

accessibility issues for visually impaired pedestrians. The first study was conducted on a closed 

course to evaluate the feasibility of a pavement treatment to alert visually impaired pedestrians 

when vehicles have yielded to them. The second study examined drivers’ yielding behavior at a 

two-lane roundabout and the effectiveness of the same roadway treatment in an operational 

environment. 

BACKGROUND 

People who are visually impaired may experience difficulty using roundabout crosswalks.(1,2)

Recent research has documented this difficulty, at least for cases where traffic volumes are 

high.(3) The problem, as summarized by the U.S. Access Board, consists of three parts:(1) 

1. Motorists do not yield to pedestrians where the crossing is not signal controlled. 

2. At roundabouts, noise from circulating traffic may make aural detection of gaps difficult. 

3. Gaps large enough to be aurally detected may be infrequent. 

The Americans with Disabilities Act (ADA) requires equal access to transportation facilities. 

The U.S. Access Board, which is responsible for developing guidelines for implementing the 

ADA, currently is considering guidelines for providing access at roundabouts.(4) The studies 

reported here are intended to contribute to an empirical basis for those guidelines. 

The Prevalence of Visual Impairment 

According to statistics compiled by the National Center for Health Statistics of the U.S. Centers 

for Disease Control and Prevention, as summarized by the American Foundation for the BlindTM, 

in 1996, there were approximately 1.3 million legally blind people in the United States.(5) Of 

these, approximately 109,000 people use long white canes, and another 7,000 use guide dogs. 

Approximately two-thirds of the people who use a long white cane or a guide dog are less than 

65 years old, and about half are employed full time. Although statistics are not available on the 

number of visually impaired individuals who travel independently on streets and sidewalks, the 

statistics on long cane and guide dog users suggest that this number is around 100,000. As the 

number of roundabout intersections grows, so will the importance of accessibility. Furthermore, 

treatments to improve access at roundabouts might also apply to other types of uncontrolled 

crosswalks, such as midblock crossings and right-turn slip lanes. With improvements to access at 

uncontrolled crossings, the number of visually impaired individuals who travel independently 

might increase. 

Roundabout Overview 

Roundabouts are circular intersections with specific traffic control and design features. These 

features include yield control at entry, channelized approaches, and geometric approach 

curvature (deflection) to induce entering traffic to slow to the design speed of the circular 

pathway. The typical location for crosswalks at roundabouts is illustrated in figure 1. Note that 

one end of each crosswalk terminates on a splitter island (a median) so that the pedestrian crosses 
2 

only one direction of traffic at a time. Because the crosswalks are set back from the intersection, 

conflicts with turning vehicles are minimized. Also, because all traffic is forced to travel on a 

curved path, vehicle speed is minimized, typically to between 32 kilometers per hour (km/h) (20 

miles per hour (mi/h)) and 44 km/h (30 mi/h). Additional information on the design of 

roundabouts may be found in the Federal Highway Administration (FHWA) publication 

Roundabouts: An Informational Guide.

(6) 

Figure 1. Illustration of single-lane roundabout with crosswalks. 

Roundabouts are appearing with increasing frequency in the United States, primarily because of 

their benefits to traffic operations and safety. Roundabouts usually result in less traffic delay than 

a signalized intersection, and they may have operational benefits as alternatives to intersections 

that are not signalized.(6) Numerous studies have shown that roundabouts have fewer injuryrelated crashes when compared to conventional intersections, and most studies also show that the 

overall crash rate is reduced when conventional intersections are replaced with roundabouts.(6,7)

Furthermore, pedestrian death and serious injury rates are lower at roundabouts than at 

conventional signalized and nonsignalized intersections.(6) 

Entrance Exit 

Splitter Island Crosswalk 

Circular Roadway 
3 

Motorists’ Yielding Behavior 

It has been widely observed that motorists frequently fail to yield to pedestrians in crosswalks, 

even though most motorists are aware of this legal requirement.(8,9) For instance, at five 

uncontrolled crossings in Madison, WI, the percentage of vehicles yielding to pedestrians who 

were starting to cross ranged from 0 to 10.6 percent.(10) Huang et al. reported greater variation in 

the percentage of pedestrians to whom approaching motorists yielded.(11) Their results, from 11 

different uncontrolled crossings in 4 States, ranged from 0 to 87 percent, with a mean of 50 

percent. Huang and Cynecki also reported on the percentage of pedestrians yielded to by 

approaching motorists.(12) Their study included data from eight uncontrolled crossings in seven 

States. Yield rates ranged from 0 to 58 percent and averaged 19 percent. 

Street Crossing by Visually Impaired Pedestrians 

The U.S. Access Board Web site provides a detailed description of the process a visually 

impaired person would typically engage in to prepare for and make a street crossing.(1) Although 

this process has many implications for roundabout accessibility, the present study addresses only 

one of these implications: the need to provide detectible gaps in traffic. A gap is any pause in 

traffic flow during which a pedestrian can cross a roadway without encountering vehicle 

conflicts. At signalized crossings, visually impaired pedestrians rely on the signals to create gaps, 

and may use surges in traffic flow to detect the signal phase. At uncontrolled crossings, such as 

at roundabouts, the visually impaired cannot predict gaps, and they must rely on other 

environmental cues to detect gaps. For a visually impaired pedestrian to make a safe crossing at a 

roundabout, a gap in traffic must occur; the pedestrian must be able to recognize when gaps are 

present; and the pedestrian must be able to recognize when gaps are not present. 

Gaps may occur in two ways: 

1. No vehicles arrive for the length of time necessary for the pedestrian to cross. 

2. Vehicles stop for the pedestrian. 

For gaps to be usable by pedestrians, the gap must be of sufficient length, and the pedestrian 

must be able to detect them. Sighted pedestrians detect gaps by looking in the direction of traffic. 

Visually impaired pedestrians detect gaps by listening. The visual and auditory information of 

approaching traffic can be blocked for either sighted or visually impaired pedestrians by 

obstructions such as landscaping, hills or bends in the road, and buildings. Although in certain 

circumstances the approaching traffic can be heard before it is seen, more often the sighted 

pedestrian can detect the approaching traffic long before the traffic can be heard, even under 

ideal listening conditions, because of features that affect the acoustics such as road surfaces and 

reflecting surfaces. Although visual information for sighted pedestrians can sometimes be 

obscured by fog or glare, the sounds upon which visually impaired pedestrians rely are much 

more easily masked by other sounds. Masking sounds often include the noise of receding 

vehicles or traffic at nearby intersections, but they can also come from many other environmental 

sources.(13,14,15)

Thus, there are many situations in which sighted pedestrians can easily determine gaps, but 

visually impaired pedestrians are unable to reliably identify the same gaps. Whereas sighted 

pedestrians may be able to see gaps behind approaching vehicles, the visually impaired cannot 
4 

hear such gaps. Furthermore, because the sound of receding vehicles masks gaps, the visually 

impaired may not recognize gaps for several seconds after they begin.(3) At a double-lane 

roundabout with 3.7-meter (m) (12-foot (ft)) lanes, a sighted person who walks at 1.2 meters per 

second (m/s) (4 feet per second (ft/s)) might accept a gap of little more than 6 s; however, the 

gap required by a visually impaired pedestrian must be larger. Vehicles passing the crosswalk 

create noise that can mask the silence of gaps behind them, and Guth et al. observed that it 

frequently takes 3 s or more before the noise of vehicles that have passed is diminished enough 

to allow detection of a following gap.(3) Thus, a visually impaired person may require a gap of 9 s 

or more. Furthermore, although the splitter island may represent a protected location for a 

sighted person to cross by looking in one direction at a time, the sound of traffic approaching and 

receding on the other side of the island is not masked by the island. Thus, the visually impaired 

pedestrian may require a 9 s gap in both directions before beginning to cross. After reaching the 

splitter island, visually impaired pedestrians may again require 9 s gaps in both directions 

because the sounds of traffic behind them will mask gaps in the entrance lanes. 

Given that simultaneous gaps of 9 s or more at both entry and exit lanes may be required for 

detection of naturally occurring gaps in moving traffic, and that gaps such as these may be rare 

during peak traffic at double-lane roundabouts, it may be necessary to stop traffic to provide 

access to visually impaired pedestrians. The U.S. Access Board recognized this when it drafted a 

proposal to signalize roundabouts.(4) Signals might not be necessary if drivers would stop for 

pedestrians with long white canes or guide dogs, and if those pedestrians could detect the 

resulting gaps in stopped traffic. The purpose of the present study was to examine treatments that 

might make this latter approach feasible. 

RESEARCH GOALS 

The goals of the present studies were to: (1) evaluate a method of aurally indicating when 

vehicles have yielded in both lanes of a double-lane roundabout exit (2) evaluate a method for 

increasing motorists’ yielding to visually impaired pedestrians, and (3) quantify motorists’-

yielding behavior at double-lane roundabouts. 

Study 1 

Study 1 addressed only the first of the three goals: to evaluate a method of aurally indicating 

when vehicles have yielded in both lanes of a double-lane roundabout. Not all visually impaired 

pedestrians will cross in front of idling vehicles; without the benefit of eye contact with the 

driver, it is difficult to determine a driver’s intent or the reason that the driver stopped in the first 

place. To cross a single lane, the visually impaired pedestrian listens for the idling engines of 

stopped vehicles. Some visually impaired pedestrians will cross in front of stopped vehicles. 

Crossing two lanes is more problematic than crossing one lane, because the pedestrian will 

normally want to determine that drivers have stopped in both lanes. However, the sound of one 

idling vehicle may mask the sound of another approaching vehicle, and the driver of that vehicle 

may not be looking for (or be able to see) a pedestrian stepping out from in front of a previously 

stopped vehicle. Unfortunately, as the results of this study show, the sound of one idling vehicle 

may also mask the sound of a second idling vehicle, especially when the first vehicle is in the 

lane closest to the pedestrian. 
5 

In the treatment condition of this study, strips were placed on the pavement to generate a sound 

that could be heard over the sound of idling vehicles and other traffic. The strips were needed to: 

(1) alert the pedestrian when vehicles approached in each of two lanes; (2) indicate when a 

vehicle passed the crosswalk (i.e., departed); and, most important, (3) indicate when an 

approaching vehicle did not pass and, by implication, was stopped. To ensure that all of the 

conditions of interest could be tested effectively, this study was conducted on a closed course 

where drivers yielded, failed to yield, and departed according to a script. 

Study 2 

Study 2 addressed all three goals (listed above). The study was conducted at a double-lane 

roundabout in Maryland. As with study 1, the effectiveness of sound-generating strips was 

evaluated. In addition, two traffic control signs were deployed to evaluate their effect on 

motorists’ yielding behavior. 

One of these signs was placed at the upstream edge (from a vehicle perspective) of the crosswalk 

on the demarcation between the travel lanes. This sign, designated R1-6 in the Manual on 

Uniform Traffic Control Devices (MUTCD), was 90 centimeters (cm) (36 inches) high by 30.5 

cm (12 inches) wide, with the sign bottom mounted 61 cm (23 inches) above the pavement on a 

breakaway post.(16) The sign, depicted in figure 2, shows a red triangular yield icon above the 

word “TO,” which is above a pedestrian icon, all on a white (i.e., regulatory) background. The 

white background is surrounded by yellow with the words “STATE LAW” above and the words 

“WITHIN CROSSWALK” below. Combining the words and icons in English, the sign reads, 

“State law, yield to pedestrian within crosswalk.” 

The second sign was placed below an existing crosswalk warning sign located to the right of the 

crosswalk. This white sign, designated R1-5 in the MUTCD (depicted in figure 3), had an arrow 

that pointed, roughly, to the upstream crosswalk demarcation line, a yield symbol, the words 

“HERE” and “TO,” and a pedestrian icon. By combining the words and icons, the sign reads, 

“Yield here to pedestrian.” The sign was 61 cm (24 inches) square. The purpose of adding this 

sign was to encourage drivers to stop at the crosswalk rather than at a distance away from the 

crosswalk, which might prevent the pedestrian from hearing idling engines. 
6 

Figure 2. MUTCD R1–6. 

Figure 3. MUTCD R1–5. 
7 

CHAPTER 2. STUDY 1: CLOSED-COURSE EVALUATION 

There were two experimental conditions in this study: a control condition and a treatment 

condition. In the treatment condition, rumble strip-like devices were placed on the pavement 

surface. Seven severely visually impaired individuals participated. These individuals regularly 

take pedestrian trips without sighted companions and at least occasionally make such trips to 

locations that they have not visited before. 

METHOD 

The basic requirements for a sound cue were: (1) vehicles approaching the crosswalk would 

trigger it, (2) the treatment would be relatively inexpensive to implement, and (3) the sound cue 

would provide distinctly audible cues in a roundabout environment. Initially, commercially 

available rumble strips, traffic counter tubes, and garden hoses were considered. The first 

challenge encountered was that cars about to yield at a crosswalk might be traveling at very low 

speeds. The rumble strips, tubes, and hoses that were evaluated failed to make sufficient noise 

when passed over at 3 to 11 km/h (2 to 7 mi/h). A treatment was eventually derived that 

appeared promising for testing, but it would need additional development to serve as a 

permanent engineering solution. That solution was to cut 3.8 cm (1.5 inch)-diameter 

polyvinylchloride (PVC) pipe lengthwise into thirds, then secure the pipe, concave side down, to 

the roadway with asphalt tape. Asphalt tape is normally used to secure traffic counting tubes. To 

prevent heavy vehicles from crushing the pipe, pieces of dowel cut lengthwise were placed 

between the PVC pipe and the roadway to provide additional support. Even when the 

approaching vehicle was driven at 3 km/h (2 mi/h), the PVC pipe device produced a clacking 

sound that could be heard over ambient traffic noise from a distance of about 20 m (66 ft). 

To provide a meaningful sound pattern that visually impaired pedestrians potentially could use, 

three rows of sound strips were laid transversely across the roadway. One row was placed on the 

upstream edge of the crosswalk, a second row was placed 6 m (20 ft) upstream of the first row, 

and a third row was placed 7.3 m (24 ft) upstream of the first row. A two-axle passenger car that 

passes over the strips generates a rapid “clack, clack, clack, clack” sound as the two axles pass 

over the two upstream rows, and then, after a brief delay, another “clack, clack” as the vehicle 

enters the crosswalk and departs. If the first four clacks are produced, but not the latter two, a 

stopped vehicle is signified. A pair of clacks that are not preceded by four closely spaced clacks 

indicates that a previously stopped vehicle has departed. 

Test Facility 

The test was conducted on a rounded, rectangular roadway at FHWA’s Turner-Fairbank 

Highway Research Center in McLean, VA. A scale drawing of the course is provided in figure 4. 

Although the circuit was somewhat larger than that of a double-lane roundabout, and the 2.9-m 

(9.5-ft) lanes were somewhat narrow, the course provided a method for approximating traffic 

movement at a double-lane roundabout. Because the sound-strip treatment could not be easily 

put down and removed, with- and without-strips test conditions were located at different points 

on the course, separated by approximately 50 m (165 ft). Platforms were placed 61 cm (2 ft) 

back from the outer edge of the roadway, adjacent to the two simulated crosswalks. These 

platforms, intended to simulate a curb, were 20 cm (8 inches) high. 
8 

Because only four cars were available to simulate traffic, it was believed that the ambient noise 

level on the closed course did not adequately represent the noise level at actual roundabouts. 

Therefore, during testing two loudspeakers were used to broadcast recorded traffic sounds. These 

loudspeakers were placed approximately 3 m (10 ft) from opposing sides of the pedestrian 

platforms, such that the A-weighted sound level was 68 decibels at the site where participants 

stood. This sound level approximated that measured during peak traffic at the roundabout used in 

study 2. 

20'

Noise

Strips

20'

Noise

Strips

Direction of

Travel

20'

Noise

Strips

20'

Noise

Strips

Participant

COMS

Experimenter

Control (without

strips) Test

Experimenter Location

100'

Experimental (with strips)

Test Location

Participant COMS

DRAWING SCALE: 1.5":40'

D

B

C A

Direction of

Travel

Direction

of Travel

Direction of

Travel

1 inch = 25.4 millimeters (mm), 1 ft = 0.305 m. 

Figure 4. Layout of closed-course test facility. 
9 

Participants 

Seven individuals with severe visual impairments were recruited (four reported having no vision, 

one reported minimal central vision only, one reported minimal peripheral vision only, and one 

had some perception of light). Although none of the participants who reported having some 

residual vision reported using visual cues when traveling, the participant with residual central 

vision said that he could sometimes detect crosswalk edges if there is high contrast between the 

pavement and the painted line. All participants who reported having some vision wore a 

blindfold during the tests. All participants received a hearing screening. All had hearing within 

the normal range except for one older male (participant 2), who had a low frequency hearing loss 

in his right ear. Further participant demographic information is provided with the individual 

debriefing results. Participants were paid $35 per hour, and they completed participation in about 

3 hours. 

Procedures 

Before data collection began, the participants were briefed and provided an opportunity to 

explore the mock intersection. The briefing did not include mention of the sound strips, and no 

participant asked about them during the test session. An orientation and mobility specialist was 

always present during the pretest, test, and debriefings. 

A series of 36 test trials followed 4 practice trials. Scripts governed the behavior of the four 

vehicles in each trial. The top speed was 24 km/h (15 mi/h), and the speed on turns was lower. 

The scripts comprised 18 trials that were repeated at each of the 2 crosswalks. Three participants 

(numbers 2, 4, and 7) were tested in the control condition first, followed by the treatment 

condition. The remaining four participants were tested in the treatment condition first. The 

drivers, who were paid for their participation, provided the four vehicles. The same four vehicles 

were used for all trials of individual participants; each participant performed the control and 

treatment trials with the same four vehicles; however, different participants worked with 

different sets of four vehicles. Most of the vehicles were late-model midsize or compact cars. 

One full-size sport utility vehicle and two full-size pickup trucks were also used; however, not 

more than one of these was used with any particular participant. 

Of the 18 trials, 8 trials called for a vehicle in the near (right) lane to yield first, 6 called for a 

vehicle in the far (left) lane to yield first, and 4 trials called for vehicles in each lane to yield at 

the same time. 

Throughout the remainder of this document, the near and far lanes are referred to rather than 

right and left lanes respectively because our focus is from the viewpoint of the pedestrian. For 

this study, the relationship of the vehicles to the pedestrian is more important than the nominal 

lane designations from a driver’s perspective. In both studies, the pedestrian stood on the 

sidewalk side of an exit lane. That is, as the pedestrian faced the road while standing on the 

sidewalk, a vehicle approached from the participant’s left side. If the participants had stood on 

the splitter island side of the exit lane (so that the left lane was the near lane), it is assumed that 

the near-far relationship would hold with respect to the participant’s performance; however, in 

that case, the vehicles would have approached the crosswalk from the participant’s right side. 
10 

The scripts roughly balanced the lanes that each of the four vehicles used, and the order in which 

each vehicle passed the crosswalk. In any given trial, a specific vehicle made between zero and 

four complete laps. In some trials, one or two of the vehicles did not move. The scripts were 

designed to obscure the number of vehicles, the amount of time between the start of a trial and its 

completion, and the time between the first vehicle yield and the second yield. In two trials, the 

first vehicle to yield pulled away after 10 s, so that in those two trials, both crosswalk approach 

lanes were never blocked at the same time. The scripts also directed vehicle speed (normal or 

slow) as vehicles passed the crosswalk. A different randomized order of trials was used for each 

participant and at each crosswalk. 

Figure 5 is an example of the script of one driver for one trial. In the example, vehicle 3 was 

assigned to the near (right) lane and yielded the first time it arrived at the crosswalk. Vehicle 1, 

which began at station ‘A’ upstream (behind) vehicle 3, stopped behind vehicle 3. (The station 

letters in figure 5 designate the locations where the vehicles waited for trials to begin. These 

letters correspond to the locations marked by those letters in figure 4.) Vehicle 4 started at station 

D, which was the closest starting location to the crosswalk, and passed the crosswalk twice (the 

second time slowly). Vehicle 2 passed the crosswalk once, and then yielded on its second 

approach to the crosswalk. After the trial was over, the vehicles returned to different stations, so 

that from trial to trial, a given vehicle would travel in different lanes and a different order with 

respect to the other vehicles. Each vehicle remained in the same lane throughout a trial and did 

not pass other vehicles, except when those vehicles stopped at the crosswalk and the trailing 

vehicle was to continue on another lap. 
11 

Figure 5. Example of driver’s script. 

During each trial, a participant stood on the platform and used hand signals to indicate when he 

or she detected vehicles stopping or departing after a stop. The participant’s signals and the 

vehicle movements were video-recorded for later scoring. 

QUANTITATIVE RESULTS 

The primary observed variables were accuracy in detecting blocked lanes (stopped vehicles) and 

wait time to detect stopped vehicles. Accuracy in detecting when stopped vehicles departed 

while the other lane remained unblocked was also recorded. Accuracy measures included: 

• Percentage of correct detections of stopped vehicles. 

• Percentage of misses (i.e., failure to detect stopped vehicle within 10 s). 

• Percentage of false alarms (i.e., incorrect detection of stopped vehicle). 

• Number of correctly detected departures of stopped vehicles. 
12 

Participants were instructed to use hand signals each time a vehicle stopped at the crosswalk and 

indicate which lane it occupied. To signal detection of vehicles stopped in the far lane, 

participants were to point at the vehicle. To signal detection of vehicles stopped in the near lane, 

participants were to point to their own right. To indicate that two vehicles were stopped side-byside (i.e., the crossing was blocked), they were to hold a hand over their head. The primary 

measure of effectiveness for this experiment was accuracy in the detection of both lanes being 

blocked. This measure was chosen because it was assumed that, with both lanes blocked by 

stopped vehicles, it might be judged appropriate for a visually impaired pedestrian to make a 

crossing. With only one lane blocked, a crossing would be less appropriate, because the presence 

of one idling vehicle creates noise that can mask the approach of other vehicles that might not 

stop. In the experiment, the participants did not actually make a crossing. The trials ended when 

the participant indicated that two vehicles were stopped (regardless of whether that indication 

was correct), or when the participant failed to indicate two stopped vehicles within 10 s of both 

lanes being blocked. In two trials, the first vehicle to yield waited for 10 s and then drove away 

before a second vehicle yielded in the other lane. Those trials ended when the participant 

indicated the second vehicle had stopped, or when the participant failed to indicate that vehicle 

was stopped within 10 s. 

Detection of Vehicles Blocking Both Lanes 

Table 1 shows the results for the detection of double yields (i.e., vehicles blocking each of the 

lanes). A hit was scored if the participant indicated that both lanes were blocked within 10 s of 

the second of two vehicles’ stopping. A false alarm was scored if at any time before both lanes 

were blocked, the participant indicated that both lanes were blocked and did not retract that 

decision within 1 s. A miss was scored if the participant did not detect that both lanes were 

blocked within 10 s. 

Table 1. Percentage of detection accuracy for vehicles blocking each lane.

Participant Hits 

Without Hits With

False 

Alarms 

Without

False 

Alarms 

With 

Misses 

Without 

Misses 

With 

1 47 87 7 7 47 7 

2 19 69 13 13 69 25 

3 50 50 13 13 38 38 

4 19 38 6 13 75 50 

5 44 63 0 13 56 25 

6 63 56 31 13 6 31 

7 13 38 0 19 88 44 

Mean 36 57 10 13 54 31 

As can be seen in table 1, five of the seven participants had superior hit rates with the sound 

strips in place compared to the results without the strips. This difference approaches statistical 

significance (z = –2.0, p < 0.05 by the Wilcoxon signed ranks test).(17) However, every 

participant had at least one false alarm in the treatment condition. False alarms are cause for 

concern because they imply that the individual might make a crossing in the belief that both 

lanes are blocked by stopped vehicles when, in fact, they are vulnerable to vehicles approaching 
13 

at speed. False alarm rates with and without the sound strips were roughly the same. The slightly 

superior hit performance in the treatment condition came from a corresponding reduction in 

misses. In the two trials in which both lanes were never blocked because one of the yielding 

vehicles departed after 10 s, all departures were detected except one. That one failure was in the 

treatment condition. 

In the treatment condition, participants also detected that both lanes were blocked more quickly 

than in the control condition (F (1, 6) = 26.4, p < 0.01). The mean time to report that both lanes 

were blocked was 3.5 s in the control condition and 2.3 s in the treatment condition. The standard 

deviation in both the control and treatment conditions was 1 s. The sound-strip condition 

accounted for 81 percent of the within-subjects variance. 

Unexpectedly, participants did not appear to have more trouble detecting two vehicles stopping 

at the same time than they did detecting two vehicles stopping with an intervening delay. Table 2 

shows the number of correct detections of both lanes being blocked by stopped vehicles when 

those vehicles arrived at approximately the same time. The control and treatment rates of 

simultaneous yield detection, 27.5 percent and 53.5 percent, respectively, are similar to the 

overall hit rates shown in table 1. As with the overall rates, the detection of simultaneous yields 

was significantly better in the treatment condition compared to the control condition (t (6) = 2.3, 

p < 0.05). 

Table 2. Correct detection of pairs of vehicles yielding side-by-side at the same time.

Participant Without With 

1 3 3 

2 0 3 

3 1 1 

4 0 2 

5 2 3 

6 2 3 

7 0 0 

Detection of Individual Stopped Vehicles 

To this point, results have been provided for the detection of two vehicles stopped side-by-side at 

the crosswalk or stop bar. These data were emphasized because the focus was on the accessibility 

of double-lane roundabouts, and it was assumed that crossing when only one vehicle has stopped 

at a two-lane crossing increased the risk of not hearing the approach of a second vehicle. 

However, participants indicated when they detected a vehicle stopping and in which lane. A hit 

was scored whenever the participant correctly identified, within 10 s, the presence and lane 

position of a stopped vehicle. 

A miss was scored if a stopped vehicle was not identified as stopped in the specified lane within 

10 s. A false alarm was scored when a vehicle was identified as stopped in a particular lane when 

it was not. If participants indicated that a response was incorrect within 1 s of making that 

response, then the first response was ignored whether or not it was correct. When a stopped 

vehicle was associated with the wrong lane, a miss was scored for one lane and a false detection 
14 

was scored for the other. This was the case with approximately 19 percent of the misses in the 

control condition and 13 percent of the misses in the treatment condition. 

Some participants incorrectly reported stops in a particular lane more than once within a trial 

(i.e., multiple false alarms). Multiple false alarms were possible in the single-lane case because 

participants could recognize that a vehicle was not stopped in that lane and could then falsely 

identify a subsequent stop. This was not the case in scoring for detection of both lanes blocked 

because in that scoring, a trial ended as soon as the participant indicated that both lanes were 

blocked. Because of the complexity of false alarm interpretation in the single-vehicle case, only 

hit rates are reported, and these should be interpreted with caution. 

Figure 6 shows the proportion of correct identifications of stopped vehicles by condition, lane, 

and the lane in which the first yield occurred. Overall, performance was better in the treatment 

condition than in the control (F (1, 6) = 15.4, p < 0.01). 

Figure 6. Proportions of correct identifications of stopped vehicles shown by test condition, 

the lane in which the first vehicle to yield stopped, and the lane identified. 

Identification tended to be more accurate when the first yield was in the far lane (F (1, 6) = 12.3, 

p < 0.05). The first vehicle to yield creates noise as it idles at the crosswalk. When it idles in the 

near lane, that noise can mask the later arrival of a second vehicle in the far lane. Participants 

were able to detect only 30 percent of the vehicles that stopped in the far lane when there was a 

vehicle already idling in the near lane. When the first vehicle to yield is in the far lane, its idling 

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Far Near Far Near

Proportion Correct Identifications

Far Lane Near Lane

With Strips Without Strips

Lane that Yields First:
15 

is somewhat attenuated by its greater distance from the participant, and the participant can 

usually detect the arrival of a second vehicle that comes between the participant and the vehicle 

in the far lane. When a vehicle yielded in the near lane, detection of which lane the vehicle was 

in was better if there was already a vehicle stopped in the far lane. 

Overall, performance in the detection of stops was better for vehicles in the lane nearest the 

participant (F (1, 6) = 8.2, p < 0.05); however, these effects were not additive, since the threeway interaction of condition, lane to yield first, and lane was significant (F (1, 6) = 10.4, p < 

0.05). In the control condition, detection performance for near-lane yields was affected very little 

by the presence of a stopped vehicle in the other lane. Conversely, in the control condition, 

detection performance for far lane yields was very sensitive to whether there was a vehicle 

already stopped in the near lane. The worst performance was for detection of vehicles stopping in 

the far lane when there was a vehicle idling in the near lane. 

In the treatment condition, there were no interactions. Detection of stopped vehicles in the near 

lane was consistently better than detection of stopped vehicles in the far lane. When a vehicle 

was already stopped in the far lane, detection of a vehicle stopping in the near lane was nearly 

perfect (only one participant missed one yield in this case). The sound cue treatment appears to 

have had two beneficial effects: (1) the detection of the presence of vehicles improved, and (2) 

given detection, lane identification accuracy was improved. The near perfect detection of near 

lane yields when a vehicle was already stopped in the far lane is primarily attributable to the first 

benefit. The improvement in detection of far-lane stops when the far lane vehicle was first to 

stop is primarily attributable to increased accuracy in locating those stops as being in the far lane. 

Debriefing Results 

After completing the test procedure, participants were debriefed. The debriefing sought 

impressions of the differences in the two crossing conditions as well as additional information on 

the participants’ experiences in making street crossings. The information obtained in these 

debriefings may be of interest to scientists and engineers who are concerned with accessibility. 

Participant 1 

Participant 1 is a middle-aged male. He takes walking trips outside his home or office every day. 

He travels alone during most of these trips. Many of these trips, almost every day, are to places 

he has not visited previously. He has some residual peripheral vision, but he relies primarily on 

hearing for street crossings. 

Despite his superior performance in the sound-strip trials, he reported that the “seams in the 

pavement” made it more difficult to hear the car engines for which he has been trained to listen. 

He said that he consciously tried to ignore the noise from the seams. When he was told that his 

only false alarm occurred when a second vehicle drove over a strip when pulling up behind a 

vehicle that had already yielded, he appeared to be surprised. He said that he thought that he had 

entirely ignored the seams, but that perhaps he had not done so. 

One issue in the accessibility of roundabouts is the amount of delay they impose on visually 

impaired pedestrians before these pedestrians identify an acceptable gap. In considering 

signalization versus other treatments, it may be worthwhile to consider the delay imposed by 
16 

traffic signals. Participant 1 estimates that at signalized intersections, even those with which he is 

familiar, he is delayed by at least 4 minutes. This is because he always waits through at least one 

signal cycle to be sure he knows what is happening. 

At some intersections where pedestrian call buttons are installed, he does not use them. His 

reason is that by the time he travels from the button to the crosswalk threshold and aligns himself 

with the crosswalk, the pedestrian phase has expired. At other crossings, he is unable to tell 

which crossing the accessible signal is indicating. In particular, he provided an example of an 

intersection he frequents where crossings are allowed only on one side of the intersection, but the 

accessible signal can be heard from both sides. 

Participant 2 

Participant 2 is an older (more than 65 years of age) male. He travels alone outside of his home 

or office every day. He estimates that about once a month he takes a pedestrian trip to a location 

that he has not been to before. 

He indicated that he noticed the sound strips, but did not realize that they were intended to help 

detect yielding vehicles. He said that he tried to use the information these strips provided. He 

indicated that he did not know the number or location of the strips, but that such knowledge 

would have helped. 

This participant said he sometimes crosses at uncontrolled crosswalks that have more than two 

lanes, even when only one lane is blocked. For instance, if it is otherwise quiet, he will walk in 

front of a vehicle that has yielded in the near lane so that he can better hear traffic in the far lane. 

Participant 3 

Participant 3 is a young adult female. She takes 6 to 12 pedestrian trips outside of her home or 

office every week. About half of these trips are with a sighted companion. She estimated that 

about once a month she takes a pedestrian trip to an unfamiliar location. 

She indicated that she learned a lot during the test. For instance, she says that she learned that it 

is easier to detect vehicles in the near lane. She volunteered that the “bumps” made it harder to 

hear the car engines. She said that at uncontrolled crossings, if a car yields for her, she normally 

waves it on. Initially she said that she would never cross in front of a yielding vehicle if there 

were more than one lane. Later, she amended this by saying that if she could tell that there were 

no other cars, she would cross in front of a single yielding vehicle, but added that her experience 

with the test indicates that she could probably never tell if there were no other vehicles. 

Participant 4 

Participant 4 was a middle-aged female who said that she takes about 15 pedestrian trips outside 

of her home or office during an average week. Most of those trips are without a companion. She 

said that she travels to unfamiliar locations almost every week. She said she does not use visual 

cues when traveling, but that she can perceive some light, which is mainly useful at night. 
17 

She indicated that the test was difficult because she could not tell from which direction the cars 

were coming. She noticed the sound of the strips and said they were useful, especially when two 

vehicles arrived at the same time. When asked what she does when vehicles yield for her at 

uncontrolled crossings, she said she just waits until they leave and it becomes quiet. She does not 

signal drivers to move on, because she is unsure how they will react and cannot see them to 

adjust to their reactions. She avoids crossing at intersections without signals. She hates stopcontrolled intersections because she never knows what cars are going to do. That is, she does not 

know whether they have stopped for her or whether they will remain stopped if she decides to 

cross. She avoids streets with more than two lanes if they do not have signals. At signalized 

intersections, she always waits through at least one cycle so that she is certain about what is 

occurring. She prefers crossing midblock to crossing at nonsignalized intersections. When 

roundabouts were described to her, she remarked that the crosswalks were too close to the 

intersection; it would be better if the crosswalk were midblock and away from the noise of the 

intersection. 

Participant 5 

Participant 5 is a middle-aged male. He estimated that he takes about 10 pedestrian trips per 

week outside of his home or office, all without a sighted companion. Of these trips, perhaps two 

per month would be to locations that he had not visited previously. He indicated that he uses his 

residual vision to locate the white lines that demarcate crosswalks, and also to follow sidewalks. 

Participant 6 

Participant 6 is a middle-aged female. She reported taking about three pedestrian trips per week 

without companions, and walking to a location she has not visited previously about once per 

month. 

She referred to the noise that the sound strips made as a “bubble wrap sound,” because they 

reminded her of the sound generated when her children pop the chambers in bubble wrap 

packing material. She stated that she preferred having the strips to not having them because they 

were helpful in detecting when cars had stopped. She also indicated that she sometimes does 

cross the two-lane street in front of her place of employment if vehicles stop for her. 

Participant 7 

Participant 7 is a middle-aged female who estimated that she makes one or two walking trips per 

week not near her house or office, usually with a sighted companion. She estimated that she 

takes walking trips alone to unfamiliar locations about six times per year. 

She indicated that detecting the vehicles was easier with the sound strips than without them. She 

said that she would cross at crosswalks when she could hear car engines idling in both lanes. 

Although she was the only participant in this study who acknowledged having previously 

crossed at an actual roundabout, she said that she would not do that again on her own. 
18 

DISCUSSION 

Study 1 indicated that a sound-strip installation could help some visually impaired pedestrians to 

detect yielding vehicles. The sound strips not only increased the probability of detecting stopped 

vehicles, but also decreased by more than a second the amount of time needed to make the 

detection. 

However, in planning this study, a very low false alarm rate was set as a goal (i.e., a low rate of 

indications that a vehicle was blocking a lane when it was not). This goal was set to avoid a 

situation where the existence of sound cues would create a false sense of security. The false 

alarm rate in the control (without strips) condition was 10 percent. With the strips, the false 

alarm rate was 13 percent (essentially unchanged). This level of false alarms would not be 

acceptable for a deployable system. 

Participants in this study were not trained to use the sound cues provided by the pavement 

treatment, nor were they informed of the treatment before the debriefing. It is conceivable that 

with training, detection performance with the sound strips would have been better, and false 

alarms might have been reduced. It is also possible that training would have no effect on 

performance, so the hypothesis that training would improve performance would need to be 

empirically verified. 

Training was not included in the study because adopting a treatment that requires training would 

require an ambitious and expensive outreach. The most desirable treatment would be one that is 

self-explanatory, and this study’s goal was to test whether the present treatment would work 

without training. 

The finding that the detection of individual stopped vehicles was greatly improved with the 

presence of the sound strips suggests that the strips are effective in alerting participants to the 

presence of individual stopped vehicles. If only one lane of traffic had to be monitored, 

performance with the strips might approach that for right-lane detection in this study (80 to 

90 percent correct detection). A sound-strip pavement treatment may be effective in single-lane 

roundabouts or right-turn slip lanes, even though the present results are not encouraging for the 

double-lane condition. The treatment has not been shown to work in the single-lane condition. 

The present results suggest that single-lane tests may be fruitful if some of the challenges 

identified in study 2 can be overcome. 
19 

CHAPTER 3. STUDY 2: FIELD EVALUATION 

In study 1, the drivers followed a script and were instructed to stop at the crosswalk, which they 

did. To ensure that there would be crossing opportunities; both lanes were blocked at some point 

in 16 of the 18 trials. In study 2, the drivers were untrained and presumably unaware that they 

were participating in a research study. The pedestrian participants were five of the seven 

participants from study 1. Thus, the pedestrians had been exposed previously to the sound strips, 

were aware of their purpose, and had been briefed on the layout of the strips from the previous 

study. 

Because a thorough evaluation of the sound strips required that vehicles yield, and because the 

literature suggested that yielding might be rare, a yield sign was placed in the street between the 

lanes at the edge of the cross walk. In exploratory visits to the roundabout, it was observed that 

vehicles yielded well upstream of the crosswalk; therefore, the yield sign was supplemented with 

a sign that indicated where to yield (see figure 3). 

METHOD 

The research design included one control and one experimental condition. All control 

observations were made before the experimental observations. Data collection took place in fall 

2004. Control observations were made between 5 p.m. and 6:30 p.m. in the 2 weeks that 

preceded the end of daylight savings time. Treatment observations were made between 3:30 p.m. 

and 5 p.m. during the 2 weeks that followed the switch to standard time. Traffic counts taken in 

spring 2004 showed that the traffic volume at the exit peaked at 5 p.m. at a rate of about 800 

vehicles per hour, and that the volume was symmetrically distributed about the peak. Because of 

the switch from daylight savings time to standard time, lighting conditions were approximately 

the same for the baseline and treatment conditions. Because all data were collected at the same 

roundabout, and since an adjacent commuter rail station generated traffic, it was likely that most 

of the drivers traversed the same exit daily at approximately the same time. By shifting the data 

collection time between the control and treatment conditions, an attempt was made to maximize 

the probability of observing different drivers from the same population. Because there were 10 

days of testing (5 in each condition), some drivers were observed more than once. The trials 

averaged 1.5 minutes in length, and there was an average of 15 trials per day. Thus, over the 90-

minute test interval, the participant and the mobility specialist were only at the crossing for about 

23 minutes. It is estimated that on any given test day, a daily roundabout user had about a one-infour chance of participating. 

Roundabout Treatment 

The roundabout exit in the control condition is shown in figure 7. Figure 8 shows the exit after 

the installation of the sound strips and the mount for the street sign. As in study 1, one sound 

strip was placed at the upstream edge of the crosswalk and extended across the road 

approximately 10.7 m (35 ft). The second and third strips were placed parallel to the first, 6.1 m 

(20 ft) and 7.3 m (24 ft) upstream, respectively. The street sign was bolted to the pavement on 

the lane marking at the upstream edge of the crosswalk. The sign mount can be seen in figure 8 

as the opening in the pavement where the center white line meets the crosswalk.
20 

Figure 7. Roundabout exit in baseline configuration. 

Figure 8. Sound-strip installation and mount for the street sign. 
21 

Study 2 Procedures 

Three video cameras were mounted atop an 8.5-m (28-ft) mast. The mast was located on a knoll 

on the side of the street opposite the exit of interest and about 15 m (49 ft) downstream from the 

exit crosswalk. One camera was used to videotape the participants, the certified orientation and 

mobility specialist, the crosswalk, and the vehicles approaching the exit. This camera was the 

only one used to capture the data reported here. A second camera was used to videotape traffic in 

the circular roadway, and a third camera filmed traffic that approached the roundabout entry 

adjacent to the exit. 

Before data collection began, the certified orientation and mobility specialist crossed with the 

participants several times so that the participants could familiarize themselves with the 

roundabout layout and traffic sounds. Although she was not visually impaired, the certified 

orientation and mobility specialist carried a long white cane and wore sunglasses. Every 

participant had either a long white cane or a guide dog. Before each trial, the participant and 

certified orientation and mobility specialist waited on the sidewalk approach to the exit 

crosswalk. When no vehicles were within about 15 m (49 ft), they stepped to the edge of the 

crosswalk ramp, and the certified orientation and mobility specialist began tapping her long 

white cane in the street at a rate of one tap per second. The red-tipped end of the cane traveled 

about 1 m (3.3 ft) vertically with each tap. The certified orientation and mobility specialist stood 

with one foot over the curb edge, in the gutter, so that she was technically in the crosswalk. The 

participant stood completely on the sidewalk to the left and upstream of the certified orientation 

and mobility specialist. 

The tapping of the cane signaled the beginning of a trial. A trial ended when one of the following 

events occurred: 

• The participant indicated that both lanes were blocked by stopped vehicles. 

• One of the lanes was blocked for 10 s or more and traffic was backing up. 

• Both lanes were blocked and the participant failed to indicate this occurrence within 10 s. 

• A pedestrian or motorist stopped to help the participant and certified orientation and 

mobility specialist cross. 

• Three minutes elapsed. 

In most cases, the certified orientation and mobility specialist and the participant made a crossing 

at the end of a trial. Although a crossing was not required for data collection, a crossing was 

performed to avoid confusing drivers who had clearly yielded or to reward those who had 

stopped to help. In a few cases, the certified orientation and mobility specialist and the 

participant stepped away from the crossing and waved on any drivers who might have stopped or 

slowed. Rest periods between trials varied from several seconds to several minutes; however, 

new trials were never started until all drivers who might have seen the end of the preceding trial 

had departed. This precaution was important because vehicles making a right turn into the exit 

sometimes formed long queues at the adjacent exit and were in a position to see the end of the 

preceding trial, albeit from some distance. 

Participants carried a wireless microphone so that their verbal responses could be recorded on the 

video recorder. Participants were instructed to indicate verbally when vehicles were stopped and 

when both lanes were blocked. Unlike the previous experiment, they were not asked to indicate 
22 

the lane in which vehicles stopped. However, participants were instructed to indicate when 

stopped vehicles departed. 

RESULTS 

Across all participants, 151 trials were observed (65 in the control condition and 86 in the 

treatment condition). As shown in table 3, during these trials, 1,944 vehicles approached the 

observed crosswalk. Most of those vehicles (1,671) passed the crosswalk without stopping. Only 

273 vehicles (14 percent) stopped, even if only momentarily, before passing the crosswalk. In the 

control condition, 11.5 percent of the vehicles stopped. In the treatment condition, 16.7 percent 

of the vehicles stopped. The results were consistent with the hypothesis that the “YIELD TO 

PEDESTRIAN” sign that was placed between the lanes induced a greater proportion of the 

drivers to stop (Χ2 

= 24.4, p < 0.0001). 

Table 3. Drivers’ responses to the presence of visually impaired pedestrians in the 

crosswalk. 

Driver Behavior Control Treatment Total 

Stopped 115 158 273 

Continued without stopping 881 790 1,671 

Total 996 948 1,944 

Table 4 shows in which lanes vehicles were stopped. The far lane category includes some 

vehicles that may have been straddling the two lanes. As reported elsewhere, drivers who are 

traveling straight through a roundabout tend to take the shortest path, which results in drivers 

who enter and exit in the near lane shifting to the far lane as they travel through the circular part 

of the roadway.(18) Some of the drivers in this study stopped within the circular roadway. Thus, 

some of the drivers who were classified as having stopping in the far lane may have been on a 

path that would have placed them in the near lane when they eventually reached the crosswalk. 

Table 4. Lateral position of vehicles that stopped for pedestrians.

Lane Control Treatment Total 

Near 77 117 194 

Far 38 41 79 

Total 115 158 273 

Although the sign placed between the lanes resulted in a small but statistically reliable increase 

in yield compliance, the nature of the compliance was less than optimal for the effectiveness of 

the pavement sound-strip treatment. Figure 9 shows the longitudinal distance from the crosswalk 

to the front of vehicles that stopped in the near lane. Dotted lines in the figure represent the 

distance of the sound strips from the crosswalk. It can be seen that the majority of the vehicles in 

the near lane did not fully traverse the strips. Figure 10 shows a video capture of two vehicles 

that stopped well upstream of the crosswalk and, thus, did not cross the sound strips. Vehicles 

that stopped 6 m (19.7 ft) from the crosswalk would have crossed the farthest upstream strip with 

their front axle. Their rear axle would not have crossed either of the upstream sound strips. Only 
23 

drivers that stopped within 3 m (9.8 ft) of the crosswalk likely would have triggered sounds from 

both upstream strips with both their front and rear axles. Thus, only 24 of the 194 vehicles that 

stopped in the near lane were likely to have generated the desired sound pattern. 

 1 m = 3.28 ft 

Figure 9. Distance from crosswalk of vehicles stopping in the near lane. 

0

5

10

15

20

25

30

35

40

45

1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5

Distance from Crosswalk (m) 

Frequency
24 

Figure 10. Two vehicles that stopped for the pedestrians. 

In the near lane, the stopping distance from the crosswalk did not vary significantly with 

treatment (p > 0.10). However, the vehicles that stopped in the far lane stopped farther from the 

crosswalk in the treatment condition than in the control condition (t (77) = 3.4, p < 0.01). 

Figure 11 shows the distribution of stopping distances for the far lane in the control and 

treatment conditions. 

The in-street and roadside signs appear to have induced more motorists to stop, but these signs 

were not effective in inducing motorists to stop closer to the crosswalk. Given that the majority 

of the yielding vehicles did not cross over the upstream strips before stopping, and that very few 

vehicles passed over the pair of strips with both axles, the effectiveness of the sound strips in 

cuing the visually impaired pedestrians to the presence of yielding vehicles clearly was 

compromised. 
25 

0

2

4

6

8

10

12

1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5

Distance from Crosswalk (m)

Frequenc

y

Control Treatment

 Note: 1 m = 3.28 ft. 

Figure 11. Distance between the crosswalk and a vehicle stopped in the far lane is shown as 

a function of treatment condition. 

Table 5 shows the outcome of the 151 trials. Five of the seven participants in study 1 returned to 

take part in study 2. Individuals retained the same participant number assigned from study 1. 
26

Table 5. Trial outcomes. 

Participant 

Control 

Hits 

(%) 

Treatment 

Hits 

(%) 

Control 

False 

Alarm 

(%) 

Treatment 

False 

Alarm 

(%) 

Control 

Time 

Out 

(%) 

Treatment 

Time Out 

(%) 

Control 

Miss 

(%) 

Treatment 

Miss 

(%) 

Control 

Good Sam

(%) 

Treatment 

Good Sam

(%) 

2 19 20 19 7 13 7 19 27 31 40 3 43 14 36 14 14 43 0 24 7 5 4 8 6 17 0 8 50 33 25 33 19 5 15 6 0 0 38 56 0 13 46 25 7 10 11 0 6 50 28 0 39 40 17 

Mean 19 12 14 5 25 37 32 21 10 25 
27 

Table 5 includes an outcome not anticipated in the research plan—many trials ended when a 

passing pedestrian or motorist stopped to assist the pedestrians in crossing (act of a Good 

Samaritan). These were labeled “Good Sam Crossings.” A crossing was given this designation 

when: (1) a pedestrian stopped to provide assistance, (2) a driver got out of his/her car to provide 

assistance, (3) a driver engaged in some overt behavior to influence other drivers to stop, or (4) a 

driver interacted with the pedestrians in a way that disrupted their ability to listen for other 

traffic. Each day during the study, at least one passing pedestrian stopped to offer assistance. In 

some cases, they were told that an experiment was being conducted and assistance was not 

needed. In other cases, it was not practical to explain the situation; such was the case when a 

pedestrian stepped into the street and flagged down traffic. Drivers, too, often stopped to offer 

crossing assistance. Other drivers maneuvered their vehicles across the traffic lanes to form a 

barricade, as did several transit bus drivers. Still other drivers rolled down their windows and 

shouted that it was safe to cross. 

The “Time Out” category included two different outcomes: (1) 3 minutes passed without two 

vehicles blocking the lanes, or (2) the certified orientation and mobility specialist determined that 

individual vehicles or traffic were excessively delayed. The latter occurred when a vehicle or 

series of vehicles yielded in the near lane, but no vehicles would yield in the far lane. 

The remaining categories are similar to those used in study 1. A correct identification was scored 

when vehicles blocked each of the lanes and the participant indicated that this was the case. 

Unlike the closed-course study, it was rare for two vehicles to stop side-by-side in the 

roundabout exit. In most cases, both lanes were considered blocked if vehicles stopped in such a 

way that it would be difficult for subsequent vehicles to maneuver into the roundabout exit. 

Figure 12 shows a video image of a treatment-condition crossing in which the participant 

correctly identified that both lanes were blocked. In this image, the vehicle blocking the left lane 

stopped about 12 m (39.4 ft) upstream of the crosswalk. 
28 

 

Figure 12. Pedestrians crossing after a correct detection of both lanes blocked. 

A false alarm was scored when the participant indicated that both lanes were blocked when, in 

fact, only one lane was blocked. A miss was scored when both lanes were blocked for 10 s, but 

the participant failed to indicate that both lanes were blocked. The proportion of the trials in each 

category differed significantly between the control and treatment conditions (Χ2

 (4) = 34.3, p < 

0.0001). However, it is unlikely that these differences are because of the treatment, since most 

yielding vehicles were not producing the desired sound cues by running over the sound strips. 

Practice, or a shift in response criteria, is a more likely cause to explain the performance 

differences. In any case, the observed changes were not in the predicted direction. 

Although 16.7 percent of the vehicles in the treatment condition stopped for the pedestrians, 

most of these stops were not useful and did not result in a detected crossing opportunity. There 

are several possible reasons for this. One is that the pedestrians did not immediately respond 

when the drivers stopped. Figure 13 shows the distribution of the delays between the time both 

lanes were blocked by fully stopped vehicles and the time when participants indicated that the 

lanes were blocked. One unexpected finding was that in three cases, participants identified the 

blocked lanes 2 s before both vehicles came to a complete stop. This apparent anomaly may have 

been attributed to participants shifting from the strategy that they normally use to detect stopped 

vehicles (idling engines) to listening for silence after detecting approaching vehicles. This 

strategy worked when there was no traffic approaching the opposing entrance and when all 

traffic in the circle stopped. Note that in figures 10 and 12, both of which show correct 

detections, there were no vehicles entering the roundabout from the opposing direction. 

Detection times in study 2 were comparable to the detection times found in study 1. 
29 

0

1

2

3

4

5

6

-2 -1 0 1 2 3 4 5 6 7 8 9

Time (s) to Detect Both Lanes Blocked

Frequenc

y

Figure 13. Frequencies of delays between the time both lanes were blocked and when 

participants indicated both lanes were blocked. 

When pedestrians did not begin to cross immediately, drivers sometimes moved on. To estimate 

how long drivers may wait, the amount of time that stopped drivers waited was tabulated. If the 

pedestrians crossed or stepped away from the curb, then the amount of time drivers waited was 

not included. This procedure yielded delay times for 28 drivers in the control condition and 56 

drivers in the treatment condition. A histogram of the wait times is provided in figure 14. In the 

control condition, drivers waited an average of 10.8 s. In the treatment condition, drivers waited 

an average of 4.7 s. In the control condition, wait times varied between 1 and 25 s. In the 

treatment condition, wait times varied between 1 and 20 s. The difference in wait times, not 

assuming equal variances between groups, was statistically reliable (t (39) = 5.1, p < 0.01). The 

difference in willingness to wait may have been because drivers who were induced to stop by the 

yield sign were not as committed to waiting as were drivers who stopped without the added 

inducement. If this hypothesis is correct, then the benefit for visually impaired pedestrians of 

yield signs is diminished. The bulk of the drivers who are influenced by the sign appear to be 

willing to wait only 3 to 6 s. Thus, these drivers may be pulling away just as the pedestrian with 

visual impairment begins to cross. 
30 

0

5

10

15

20

25

3 6 9 12 15 18 21 24 27

Wait Duration (s)

Frequency

Control Treatment

Figure 14. Amount of time drivers waited before moving on. 

The goal of the sound-strip treatment was to improve the detection of stopped vehicles. One 

question that could be asked is: If detection were immediate and perfect, how long would the 

visually impaired pedestrian have to wait? To provide an estimate of the amount of delay before 

both lanes were blocked, 74 trials were identified that did not end in a time out before the first 

double yield occurred or a Good Samaritan intervened. It can be seen in table 6 that the mean 

time before both lanes were blocked was 63 s. The longest wait observed was 245 s. The 15th 

percentile wait was 16 s, and the 85th percentile wait was 125 s. Thus, even with the low 

yielding rates of 11 to 16 percent that were observed in this study, wait times for a double yield 

are comparable to wait times at signalized intersections. 

Table 6. Average wait time before the first double yield. 

 Time (min:sec) Number of 

Passing Vehicles 

Maximum 4:05 47.0 

Minimum 0:00 0.0 

Average 1:03 8.9 

15th percentile 0:16 0.0 

85th percentile 2:05 19.1 

Number of trials 74 
31 

DISCUSSION 

One purpose of study 2 was to evaluate the effectiveness of an audible pavement treatment to 

assist pedestrians with visual impairment in detecting the presence of stopped vehicles at a 

double-lane roundabout exit. The treatment applied in the current study did not appear to be 

effective. The majority of the vehicles that stopped for the pedestrians stopped before crossing 

the treated area, and thus did not produce the intended sound cue. The same pavement treatment 

was used in study 1. In that study, performance was markedly improved by the treatment, even if 

it was not completely satisfactory. That study assumed that drivers would stop close to the 

crosswalk; however, in the field that assumption proved to be wrong. Drivers not only saw 

pedestrians long before they reached the roundabout crosswalk, they also frequently stopped 

before they entered the exit. This finding should be encouraging to those who are concerned 

about pedestrian conspicuity at roundabout exits. If drivers stop in the circular roadway (as was 

frequently observed in this study), then roundabout operations will be compromised both for 

motorists and visually impaired pedestrians. Moving crosswalks two car lengths away from the 

inscribed circle instead of the one car length, as seen at this particular roundabout, may improve 

vehicle operations. It is unclear that this would help visually impaired pedestrians detect yielding 

vehicles if drivers continue to stop one to three car lengths back from the crosswalk. For a 

pavement cuing system to work, vehicle behavior must be more consistent than it was in this 

study. The “YIELD HERE” sign used in this study did not appear to be effective in increasing 

consistency. 

Although fewer than 15 percent of the drivers came to a complete stop for the pedestrians, it 

should not be assumed that the remaining 85 percent of the drivers did not see or respond to the 

pedestrians. There were several indications that most drivers were aware of the pedestrians—

many drivers slowed, but did not come to a complete stop. The number of drivers who slowed is 

difficult to quantify because it would require knowing how fast they would have traveled if the 

pedestrians were not present. It appeared that most drivers attempted to engage in a nonverbal 

exchange with the pedestrians. In that attempted exchange, drivers signaled that they would yield 

if the pedestrians moved forward in response to their slowing. Apparently, the drivers did not 

perceive that people carrying long white canes or using guide dogs might not have access to this 

type of nonverbal exchange. Other drivers appeared to be unwilling to stop. Some honked as 

they accelerated past the crosswalk. Other drivers visibly altered their path to move farther away 

from the pedestrians. This last behavior was not unique to drivers who did not stop. A few 

drivers who stopped in the near lane proceeded to move on by merging into the far lane. In the 

treatment condition, this lane change required sharp maneuvers to avoid striking the yield sign. 

Another purpose of study 2 was to evaluate the effectiveness of an in-street “YIELD TO 

PEDESTRIAN” sign. Although a statistically significant increase in stopping was obtained, the 

increase was probably too small to have practical significance. Furthermore, it appears that 

drivers induced to stop by the sign are less patient than those who would stop regardless of the 

sign. Because visually impaired pedestrians take more time to leave the curb than sighted 

pedestrians, they are not likely to benefit from a small increase in brief stops. The size of the 

increase in yielding in this study was similar to those obtained in previous studies.(10,11) Those 

studies also show that motorist response varies from site to site, both in overall yielding rates and 

in response to the in-street sign; therefore, the reader is cautioned against overgeneralizing from 

the current findings. 
32 

The final objective of this study was to quantify motorists’ yielding behavior. In the absence of a 

treatment, 11 percent of the vehicles came to a full stop for two visually impaired pedestrians at 

the crosswalk threshold. Many more motorists slowed, and perhaps were willing to stop if the 

pedestrians had moved toward their path or taken more aggressive measures to take control of 

the crosswalk. Even with the low rate of yields, wait time for a double yield (see table 6) 

averaged only a minute. Thus, if a reliable sound cue were available so that visually impaired 

pedestrians could act immediately when two vehicles yield, then delay imposed by roundabout 

crosswalks would compare well with the delay imposed by traffic signals. 

An unexpected finding was the proportion of trials in which pedestrians or motorists intervened 

to assist the visually impaired pedestrians. Although this level of altruism is encouraging, it 

would be better if the assistance were more effective. Some of the assistance greatly increased 

the risk to both the pedestrians and the motorists. For instance, some of the drivers who stopped 

to shout out that it was okay to cross did not monitor other traffic and did not warn the 

pedestrians that cars were continuing to go through the exit. When a transit bus attempted to 

blockade the exit, two vehicles accelerated around the bus and drove briskly through the 

crosswalk even though the bus obstructed these drivers’ sight line to the pedestrians. Some 

pedestrians who stood in the crosswalk and signaled vehicles to yield watched the visually 

impaired pedestrians cross and turned their back to oncoming vehicles. Thus, we cannot 

recommend reliance on passersby to resolve accessibility challenges to the visually impaired. 
33 

CHAPTER 4. CONCLUSIONS AND RECOMMENDATIONS 

Study 1 showed that a pavement treatment can increase the proportion of double-lane yields that 

are detected and decrease the amount of time required to detect the yields. False detections of 

yields were not reduced by the treatment, and this problem would still need to be addressed. 

Study 2 showed that motorists might stop long before they reach either the crosswalk or the 

roundabout exit, thus rendering pavement treatments in the exit ineffective. Before sound 

treatments similar to the one evaluated in these studies can be made to work, the frequency of 

motorists’ yielding would need to increase, the location of the yields would need to be 

consistently closer to the crossing, motorists who yield would need to show more consistent 

patience, and the problem of false yield detection would need to be solved. 

A reliable yield detection system that did not rely on where motorists stop might be effective 

without changes in motorist behavior because wait times for double yields were relatively short. 

It is possible that a pavement treatment similar to that used in these studies would be effective at 

single-lane roundabouts. Study 1 showed that the second vehicle to yield is difficult to detect 

when it stops in the far lane, but is quite easy to detect when it stops in the near lane. Single-lane 

roundabouts do not present these challenges and might allow higher detection rates than were 

observed in study 1; however, single-lane operations were not observed in these studies, and the 

hypothesis that pavement treatments would be effective in the single-lane case requires empirical 

testing. 

The finding that motorists tend to stop well upstream of the crosswalk may suggest that 

roundabout crosswalks should be moved two or more vehicle lengths from the inscribed circle. 

Such a design would reduce the likelihood that vehicles yielding to pedestrians would obstruct 

the circular roadway. It might also increase the likelihood that an effective pavement treatment to 

cue visually impaired pedestrians can be devised. This hypothesis, too, requires empirical testing. 

Moving the crosswalks farther from the circular roadway may change driver behavior in several 

ways. For instance, it might decrease driver willingness to yield. Moving the crosswalks farther 

from the circular roadway would increase pedestrian travel distance; therefore, the effects of 

situating the crosswalks at a great distance from the circular roadway would need to be carefully 

studied to ensure any benefits that might result are not offset by a loss in benefits.

 35 

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