Research, Development, and Technology

Turner-Fairbank Highway Research Center

6300 Georgetown Pike

McLean, VA 22101-2296

The Effects of Commercial Electronic

Variable Message Signs (CEVMS) on 

Driver Attention and Distraction: 

An Update

Publication No. FHWA-HRT-09-018 February 2009
FOREWORD 

The Highway Beautification Act of 1965 outlined control of outdoor advertising, including 

removal of certain types of advertising signs, along the Interstate Highway System and the 

existing Federal-aid primary roadway system. Since that time, most States have evolved a body 

of legislation and/or regulations to control off-premise outdoor advertising (billboards), and 

many local governments have developed similar rules. 

The advent of new electronic billboard technologies, in particular the digital Light-Emitting 

Diode (LED) billboard, has necessitated a reevaluation of current legislation and regulation for 

controlling outdoor advertising. In this case, one of the concerns is possible driver distraction. 

In the context of the present report, outdoor advertising signs employing this new advertising 

technology are referred to as Commercial Electronic Variable Message Signs (CEVMS). They 

are also commonly referred to as Digital Billboards (DBB) and Electronic Billboards (EBB). 

The present report reviews research concerning the possible effects of CEVMS used for outdoor 

advertising on driver safety, including possible attention and distraction effects. The report 

consists of an update of earlier published work, an investigation of applicable research methods 

and techniques, recommendations for future research, and an extensive bibliography. The report 

should be of interest to highway engineers, traffic engineers, highway safety specialists, the 

outdoor advertising industry, environmental advocates, Federal policy makers, and State and 

local regulators of outdoor advertising. 

Michael F. Trentacoste Gerald Solomon 

Director, Office of Safety Director, Office of Real Estate 

 Research and Development Services 

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 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 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-09-018 

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

5. Report Date 

February 2009 

4. Title and Subtitle 

The Effects of Commercial Electronic Variable Message 

Signs (CEVMS) on Driver Attention and Distraction: An 

Update 6. Performing Organization Code: 

7. Author(s) John A. Molino, Jerry Wachtel, John E. Farbry, 

Megan B. Hermosillo, Thomas M. Granda 

8. Performing Organization Report No. 

9. Performing Organization Name and Address 10. Work Unit No. 

Human Centered Systems Team 

Office of Safety Research and Development 

Federal Highway Administration 

6300 Georgetown Pike 

McLean, VA 22101-2296 

11. Contract or Grant No. 

13. Type of Report and Period Covered 

Final Report, Phase I 

January 2008–October 2008 

12. Sponsoring Agency Name and Address 

Office of Real Estate Services 

Federal Highway Administration 

1200 New Jersey Avenue, SE 

Washington, DC 20590 14. Sponsoring Agency Code 

15. Supplementary Notes 

FHWA Contracting Officer’s Technical Representative (COTR): Thomas M. Granda, Safety Research and 

Development, FHWA 

16. Abstract 

The present report reviews research concerning the possible effects of Commercial Electronic Variable Message 

Signs (CEVMS) used for outdoor advertising on driver safety. Such CEVMS displays are alternatively known as 

Electronic Billboards (EBB) and Digital Billboards (DBB). The report consists of an update of earlier published 

work, a review of applicable research methods and techniques, recommendations for future research, and an 

extensive bibliography. The literature review update covers recent post-hoc crash studies, field investigations, 

laboratory investigations, previous literature reviews, and reviews of practice. 

The present report also examines the key factors or independent variables that might affect a driver’s response to 

CEVMS, as well as the key measures or dependent variables which may serve as indicators of driver safety, 

especially those that might reflect attention or distraction. These key factors and measures were selected, 

combined, and integrated into a set of alternative research strategies. Based on these strategies, as well as on the 

review of the literature, a proposed three stage program of research has been developed to address the problem. 

The present report also addresses CEVMS programmatic and research study approaches. In terms of an initial 

research study, three candidate methodologies are discussed and compared. These are: (1) an on-road 

instrumented vehicle study, (2) a naturalistic driving study, and (3) an unobtrusive observation study. An analysis 

of the relative advantages and disadvantages of each study approach indicated that the on-road instrumented 

vehicle approach was the best choice for answering the research question at the first stage. 

17. Key Words 

Commercial Electronic Variable Message Signs, 

CEVMS, Digital Billboards, DBB, Electronic 

Billboards, EBB, Driver Attention, Driver 

Distraction, Driver Safety, Outdoor Advertising 

18. Distribution Statement 

No restrictions. This document is available 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 

94 

22. Price 

N/A 

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 

1.0 INTRODUCTION................................................................................................................... 1

1.1 BASIC RESEARCH QUESTION................................................................................... 1

1.2 SCOPE ............................................................................................................................... 2

2.0 LITERATURE REVIEW UPDATE..................................................................................... 5

2.1 BACKGROUND ............................................................................................................... 5

2.2 POST-HOC CRASH STUDIES ...................................................................................... 5

2.3 FIELD INVESTIGATIONS ............................................................................................ 6

2.4 LABORATORY INVESTIGATIONS............................................................................ 9

2.5 PREVIOUS LITERATURE REVIEWS....................................................................... 11

2.6 REVIEWS OF PRACTICE ........................................................................................... 13

2.7 CONCLUSIONS FROM LITERATURE REVIEW................................................... 14

2.7.1 Basic Research Question.......................................................................................... 14 

2.7.2 Methodological Implications ................................................................................... 16 

3.0 KEY FACTORS AND MEASURES................................................................................... 19

3.1 KEY FACTORS (INDEPENDENT VARIABLES)..................................................... 19

3.2 KEY MEASURES (DEPENDENT VARIABLES)...................................................... 22

4.0 RESEARCH STRATEGIES................................................................................................ 25

5.0 FUTURE RESEARCH PROGRAM................................................................................... 29

5.1 STAGES........................................................................................................................... 29

5.2 APPROACH.................................................................................................................... 30

5.3 STRUCTURE.................................................................................................................. 31

5.3.1 Stage 1—Determination of Distraction ................................................................... 31 

5.3.2 Stage 2—Basis for Regulation................................................................................. 31 

5.3.3 Stage 3—Relationship to Crashes............................................................................ 32 

6.0 RECOMMENDED FIRST STAGE STUDY ..................................................................... 35

6.1 SUMMARY OF STUDY APPROACHES.................................................................... 35

6.1.1 On-Road Instrumented Vehicle ............................................................................... 35 

6.1.2 Naturalistic Driving ................................................................................................. 36 

6.1.3 Unobtrusive Observation ......................................................................................... 36 

6.2 COMPARISON OF STUDY ALTERNATIVES ......................................................... 37
iv 

7.0 CONCLUSIONS ................................................................................................................... 39

APPENDIX A—EXPANDED TABLES................................................................................... 41

A.1 KEY FACTORS (INDEPENDENT VARIABLES).................................................... 41

A.2 KEY MEASURES (DEPENDENT VARIABLES) ..................................................... 47

A.3 KEY RESEARCH STRATEGIES ............................................................................... 53

APPENDIX B—DETAILED DESCRIPTION OF STUDIES................................................ 61

B.1 ON-ROAD INSTRUMENTED VEHICLE APPROACH.......................................... 61

B.1.1 Method .................................................................................................................... 61 

B.1.2 Factors and Measures.............................................................................................. 61 

B.1.3 Advantages/Disadvantages...................................................................................... 62 

B.1.4 Budgetary Cost........................................................................................................ 63 

B.2 NATURALISTIC DRIVING APPROACH................................................................. 63

B.2.1 Method .................................................................................................................... 63 

B.2.2 Factors and Measures.............................................................................................. 64 

B.2.3 Advantages/Disadvantages...................................................................................... 65 

B.2.4 Budgetary Cost........................................................................................................ 65 

B.3 UNOBTRUSIVE OBSERVATION APPROACH ...................................................... 66

B.3.1 Method .................................................................................................................... 66 

B.3.2 Factors and Measures.............................................................................................. 66 

B.3.3 Advantages/Disadvantages...................................................................................... 67 

B.3.4 Budgetary Cost........................................................................................................ 67 

ACKNOWLEDGEMENTS ....................................................................................................... 69

REFERENCES............................................................................................................................ 71

BIBLIOGRAPHY....................................................................................................................... 75
v 

LIST OF TABLES 

Table 1. Expanded key factors (independent variables). .............................................................. 41 

Table 2. Expanded key measures (dependent variables). ............................................................. 47 

Table 3. Expanded key research strategies. .................................................................................. 53 

1

1.0 INTRODUCTION 

The present report reviews research concerning the possible effects of Commercial Electronic 

Variable Message Signs (CEVMS) used for outdoor advertising on driving safety. The report 

consists of an update of earlier published work by Farbry et al., which consists of an investigation 

of applicable research methods and techniques, recommendations for future research, and an 

extensive bibliography.(1) The Federal Highway Administration (FHWA) has evaluated possible 

safety effects of CEVMS in two previous studies. The first study was completed in 1980 and the 

second in 2001.(1,2) Since then, CEVMS technology has evolved, in particular the expanded use 

of digital Light Emitting Diode (LED) arrays, as well as the implementation of new 

programmable formats and messages. The present report concentrates on identifying potential 

factors that may contribute to determining whether there are any significant safety concerns or 

distraction effects with regards to CEVMS used for outdoor advertising. Throughout the present 

report, the acronym CEVMS will be employed to refer to both the singular and plural case. 

1.1 BASIC RESEARCH QUESTION 

The basic research question being addressed in this report is whether the presence of CEVMS 

along the roadway is associated with a reduction in driving safety for the public. Increases in 

vehicle crashes along a certain portion of the roadway are generally regarded as an indication of 

a possible safety concern. Thus, the measurement of crash rates in the vicinity of CEVMS in 

comparison with crash rates at matched control locations without CEVMS is one possible way to 

determine possible safety impacts. But, the crashes are rare multicausal events which are difficult 

to measure. Therefore, measurements of driving behavior in near-crash situations are sometimes 

taken as a substitute for crashes. These safety surrogate measures may then be generalized to 

other driving behaviors that represent possible precursors of crashes—like sudden braking, sharp 

swerving, or traffic conflicts—even though no crash occurs. Usually, because these safety 

surrogate measures are more frequent and easier to measure, they are often employed instead of 

or in addition to crashes. Thus, determining the frequency of occurrence of certain relevant 

safety surrogate driving behaviors in the vicinity of CEVMS in comparison with the frequency of 

occurrence of such behaviors at matched control locations without CEVMS is another possible 

way to determine possible safety impacts. The validity of using such safety surrogate measures 

rests on the assumption that they are related to actual vehicle crashes, which seems intuitively 

reasonable but has not been conclusively demonstrated. 

There is another approach to determining the possible safety impact of CEVMS. This approach 

is based upon the abstract psychological constructs of driver attention and distraction. A driver 

must devote a certain amount of attention to the driving task at hand, and sufficient distraction 

from that driving task could be associated with the higher risk of a crash. The measurement of 

driver eye glance behavior is often taken as an indirect indicator of attention. Thus, the driver’s 

eye glances should be concentrated in the region of the roadway ahead, and any frequent or long 

eye glances away from this region toward other objects, including CEVMS, could be regarded as 

an indication of possible driver distraction. If the eye glances toward a certain object and away 

from the roadway ahead are sufficiently frequent or sufficiently long to exceed criteria 

established for safe driving, this outcome can be taken as an indication of a possible safety 

impact. The validity of using eye glance behavior measures in this manner rests on two 
2

assumptions: that eye glances are related to attention and/or distraction and that there are 

generally accepted safety criteria for excessive eye glances away from the roadway ahead. These 

assumptions are not universally accepted. 

In summary, the basic research question is whether the presence of CEVMS along the roadway is 

associated with a reduction in driving safety for the public. The three fundamental methods for 

answering this question include if there is an increase in crash rates in the vicinity of CEVMS, if 

there is an increase in near-crashes or safety surrogate measures in the vicinity of CEVMS, and if 

there are excessive eye glances away from the roadway ahead in the vicinity of CEVMS. 

1.2 SCOPE 

In this report, a CEVMS will be defined as a self-luminous advertising sign which depicts any 

kind of light, color, or message change which ranges from static images to image sequences to 

full motion video. The CEVMS may also be referred to as an Electronic Billboard (EBB) or a 

Digital Billboard (DBB). The present report concentrates on the possible effects of CEVMS on 

driver attention, driver distraction, and roadway safety. The report is divided into 10 sections: 

Introduction, Literature Review Update, Key Factors and Measures, Research Strategies, Future 

Research Program, Recommended First Stage Study, Conclusions, References, Bibliography, 

and Appendices. 

Investigating the possible safety effects of CEVMS is sufficiently complex so that no single 

experiment will answer all of the relevant scientific and engineering questions. The present 

report outlines a top-level broad program of potential future research, and it defines in greater 

detail three possible studies, any one of which could serve as a possible first step. After these 

discussions, a course of action is recommended. Although off-premise advertising signs 

constitute the main focus of FHWA attention, the influence of on-premise advertising signs will 

also be considered to create a more comprehensive and consistent research approach. 

In parallel with the present project, a related study is being performed under National 

Cooperative Highway Research Program (NCHRP) Project 20-7 (256), titled “Safety Impacts of 

the Emerging Digital Display Technology for Outdoor Advertising Signs.” Both the present 

project and the NCHRP study begin with the understanding that, despite years of research, there 

have been no definitive conclusions about the presence or strength of adverse safety impacts 

from CEVMS. The two projects differ in three significant ways. First, the NCHRP study is 

undertaking a broad, critical review of the research literature in this field. The present project is 

more focused on literature update oriented toward the identification of suitable independent and 

dependent variables for future research. Second, the NCHRP study is reviewing current 

regulations and guidelines for the control of roadside advertising that may exist in foreign 

countries to assess their applicability to U.S. highways and streets. Aside from mention in the 

literature review update portion, the present report does not directly address regulations and 

guidelines. Third, the NCHRP study will synthesize current research results and current 

regulations and guidance to recommend how State and local governments might enact reasonable 

temporary guidance for the control of CEVMS within their own jurisdictions. Such guidance 

may be applicable on an interim basis pending the outcome of future, more conclusive research 

outlined in the present project. As a result, such interim guidance may need to change as new 
3

technical information is developed. The present report does not provide guidance to States on the 

control of CEVMS. 

5

2.0 LITERATURE REVIEW UPDATE 

2.1 BACKGROUND 

The research that addresses the possible safety and distraction effects of outdoor advertising 

billboards has been extensive and long standing. Dating back to the 1930s, this research reached 

a peak in the 1950s and 1960s. Research continued at low ebb through the 1980s, and then all but 

ceased. With the advent of newer billboard technologies (e.g., lamp matrix, rotating disc, trivision, and, most recently, LED) and with the corresponding questions raised by regulators, 

safety researchers, and the public, research has increased again since the turn of the century. 

These newer billboard technologies, especially the LED technology, ushered in the increasing 

use of CEVMS for on-premise and off-premise advertising. The current research focuses on 

information that has become available since the publication of the most recent FHWA report, but 

it also includes earlier relevant studies not previously identified.(1) The present review is 

organized into five major categories according to the research context for the study: post-hoc 

crash studies, field investigations, laboratory investigations, previous literature reviews, and 

reviews of practice. The categories that contain empirical data have a brief discussion of 

potential methodological problems inherent in the types of studies characteristic of that category. 

2.2 POST-HOC CRASH STUDIES 

Post-hoc crash studies review police traffic collision reports or statistical summaries of such 

reports to understand the causes of crashes that have taken place in the vicinity of some change 

to the roadside environment. In the present case, the change of concern is the introduction of 

CEVMS to the roadside or the replacement of conventional billboards with CEVMS. 

A number of studies have been conducted over the years using the crash methodology. Three 

such studies were not reviewed in prior FHWA studies. In a study similar to that conducted in 

the 1970s in Massachusetts, the Freeway Operations Unit of the Wisconsin Department of 

Transportation (WisDOT) analyzed bidirectional crashes on I-94 near an electronic billboard 

with a 5.0 s message dwell time.(3,4) Crash rate data were collected for 3 years prior to and 

3 years after sign operation began. For eastbound traffic, total crashes increased 36 percent over 

the 3 year post operational period compared to the baseline preoperational condition. In addition, 

side-swipe crashes increased 8 percent, and rear-end crashes increased 21 percent. For 

westbound traffic, total crashes increased 21 percent, sideswipe crashes increased 35 percent, 

and rear-end crashes increased 35 percent. The authors of the WisDOT study concluded that, “it 

is obvious that the variable message sign has had an effect on traffic, most notably in the increase 

of the side-swipe rate” (p. 3).(4) 

Stutts et al. conducted an analysis of several crash data reporting systems to identify major 

sources of driver distraction and the relative importance of different types of distraction as 

contributing factors in motor vehicle crashes.(5) Distraction was described as one form of 

inattention, and it has been implicated as a factor in more than half of the police reported 

inattention crashes identified by the National Highway Transportation Safety Administration.(6)

In this study, 8.3 percent of drivers involved in police-reported crashes were identified as 

distracted, but 35.9 percent of these crashes were coded as “unknown.” For this and other 
6

reasons, it is believed that the reported percentage of distraction-related crashes substantially 

under-represents the true statistics.(5) Among the types of distractions coded in the database, the 

largest contributor (29.4 percent) was “outside person, object, or event,” and the second largest 

(25.6 percent) was “other.” 

Smiley et al. studied the relationship between video advertising signs and motor vehicle crashes 

at downtown intersections and on the freeway.(7) Crash data were analyzed from three 

intersections before and after the introduction of video advertising signs. When the three 

intersections were evaluated individually, two demonstrated increases in both total and rear-end 

crashes; the third showed no significant increase in such crashes. The authors believe that the 

lack of statistical significance may be due to the small number of crashes identified. For the 

freeway environment, crash data on the video approach was compared to crash data for three 

non-video approaches, one of which was deemed the most comparable (control) segment. For 

this comparison, the authors report a negligible increase in injury collision crash frequencies on 

the video approach. 

Following the design of their earlier study on conventional billboards, Tantala and Tantala

analyzed police accident reports in the vicinity of seven digital billboards on interstate highways 

near Cleveland, OH.(8) Both their current and earlier studies were sponsored by the outdoor 

advertising industry. Reported crashes were analyzed for a period of 18 months prior to and after 

the conversion of these billboards from conventional to digital. They found essentially no 

statistically significant differences in crash rates before and after the conversion. 

Unfortunately, all post-hoc crash studies are subject to certain weaknesses, most of which are 

difficult to overcome. For example, the vast majority—more than 80 percent in one study—of 

accidents are never reported to police; thus, such studies are likely to underreport crashes. Also, 

when crashes are caused by factors such as driver distraction or inattention, the involved driver 

may be unwilling or unable to report these factors to a police investigator. Another weakness is 

that police, under time pressure, are rarely able to investigate the true root causes of crashes 

unless they involve serious injury, death, or extensive property damage. Furthermore, to have 

confidence in the results, researchers need to collect comparable data in such studies before and 

after the change and in the after phase at equivalent but unaffected roadway sections. Last, since 

crashes are infrequent events, data collection needs to span extended periods of time, both before 

and after introduction of the change. Few studies are able to obtain such extensive data. For a 

more specific analysis of some possible design and methodological concerns with the study by 

Tantala and Tantala, see Wachtel.(8,9) 

2.3 FIELD INVESTIGATIONS 

The spectrum of field investigations related to roadway safety is broad. It includes unobtrusive 

observation, naturalistic driving studies, on-road instrumented vehicle investigations, test track 

experiments, driver interviews, surveys, and questionnaires. Klauer et al., in one of several 

papers to emerge from a National Highway Traffic Safety Administration (NHTSA) project 

known as the “100-Car Naturalistic Driving Study,” provides preliminary information about the 

role of driver inattention in crashes and near-crashes.(10) Although the study did not specifically 

address CEVMS, it represents an important methodology for investigating driver distraction. 

Their results show that 78 percent of crashes and 65 percent of near-crashes included driver 
7

inattention and/or distraction as a contributing factor. This contribution from inattention and 

distraction is larger, by a factor of three, than previous research has indicated. The authors 

believe that the “100-Car Naturalistic Driving Study” provides the first direct link (i.e., without 

reliance on crash surrogate measures) showing distraction/inattention as a contributing factor to 

motor vehicle crashes. In another variant of the “100-Car Naturalistic Driving Study,” Klauer et 

al. identifies four specific unsafe behaviors that contributed to crashes and near-crashes.(11) One 

of these, inattention and/or distraction, is of direct relevance to the present project. This term is 

operationally defined by Klauer et al. as a driver looking away from the forward roadway for 

greater than 2.0 s. Under these conditions, the odds of a crash or near-crash are nearly twice 

those than when the driver attends to the forward roadway. The study stresses the importance of 

including near-crashes in the database for two reasons. First, the kinematics of crashes and nearcrashes are similar, meaning they involved comparable levels of driver emergency actions, such 

as swerving and hard braking. Second, 83 percent of the crashes in this study were not reported 

to the police. Thus, the study indicates that relying on crash statistics alone will substantially 

underreport crashes due to inattention and/or distraction. 

Lee, McElheny, and Gibbons undertook an on-road instrumented vehicle study on interstate and 

local roads near Cleveland, OH.(12) The project, conducted on behalf of the outdoor advertising 

industry, looked at driver eye glance behavior toward digital billboards, conventional billboards, 

comparison sites (sites with buildings and other signs, including digital signs), and control sites 

(those without similar signage). Performance measures, such as speed maintenance and lane 

keeping, were also recorded. Although the major data collection was done in daylight, a small 

pilot study was conducted at night. One of the key questions that the study sought to answer was 

whether longer glances consisting of over 1.6 s were associated more with any of the event 

types.(12) This question is based on findings from various studies, including the “100-Car 

Naturalistic Driving Study,” which indicates that longer glances away from the road are 

associated with higher crash rates.(13) In discussing their results, the authors state, “...the 

distributions of glance duration were similar across all event types, and there was no obvious 

pattern of longer glances being associated with any of the event types” (p. 59).(13) The findings 

from the nighttime pilot study led to, “the overall conclusion, supported by both the eye glance 

results and the questionnaire results, that the digital billboards seem to attract more attention than 

the conventional billboards and baseline sites (as shown by a greater number of spontaneous 

comments regarding the digital billboards and by longer glances in the direction of these 

billboards” (p. 10).(13) However, in view of the small number of participants, these data were not 

analyzed. The authors suggest that at least some of these findings, “would show statistical 

significance” if a larger study were to be conducted (p. 64).(13)

Beijer, Smiley, and Eizenman, working on behalf of the Government of Toronto, Canada, 

evaluated driver eye glances toward four different types of roadside advertising signs on roads in 

the Toronto, Canada area.(14) The study employed an on-road instrumented vehicle approach with 

a head-mounted eye-tracking device. Active signs—all but traditional billboards—consistently 

received longer glances and more total glances than fixed signs. The study found that 22 percent 

of all glances were defined as long or greater than 0.75 s. Since 22 of the 25 subjects made at 

least one long glance at an advertising sign, the authors conclude that, “distraction...was not just 

an isolated incidence” (p. 101).(14) The authors suggest that active signs may result in greater 

distraction than past studies of the effects of commercial signing might indicate. 
8

After a previous study raised concerns about the number and duration of glances made to video 

advertising signs along an expressway in Toronto, Canada, Smiley et al. conducted another study 

at the request of the city government.(7,15) Five different measures were taken, including eye 

movements, traffic conflicts, traffic speed and headway, crash data, and public surveys. The 

crash data results were described earlier. The results from the other measures were mixed. All of 

the video signs attracted attention; the probability of a driver’s looking at such a sign upon 

approach was nearly 50 percent. The average glance duration was 0.5 s, similar to those for 

official traffic signs. However, one-fifth of the video sign glances lasted longer than 0.75 s, and 

some lasted as long as 1.47 s, which were considered unsafe amounts of time. About 38 percent 

of glances at the video billboards were made when headways were 1.0 s or less, and 

25 percent of the glances took place when the signs were more than 20 o off the line-of-sight. 

These glances were also considered to be unsafe. According to the study, glances at static 

billboards and bus shelter ads were made at even greater angles and shorter headways. 

It is noteworthy that the earlier study that led to this research, also evaluating a video billboard 

on an expressway in Toronto, Canada, produced dramatically different results. This study found 

five times the number of glances per subject and three times the glance duration than did the later 

2004 study.(15) Smiley et al. attribute these differences to the longer sight distance available for 

the sign in the earlier study, the uninterrupted view, and the location of this sign on a curve.(7) 

Smiley et al. also employed safety surrogate measures of conditions which might be precursors 

of a possible crash.(7) The study measured these safety surrogate indicators by means of the 

unobtrusive observation method. The drivers of the vehicles were not aware that they were being 

observed. In this context, the study measured traffic conflicts, vehicle speed, and vehicle 

headway. When comparing video and non-video approaches at the same intersection, at one 

intersection the authors found no differences in traffic conflicts; however, at the other, they 

found a significant increase in drivers who applied their brakes without cause on the video 

approach. Given the comparability of sites, they concluded, “the only reason that could be found 

for increased braking...was the presence of the video sign” (p. 108).(7) The speed and headway 

data were inconclusive. 

In addition, Smiley et al. employed a “public” survey method to determine whether video 

advertising might be considered to have “a negative effect on traffic safety” (p. 110).(7)

Participants in the survey were approached at three intersection sites which had video 

advertising. Of the 152 persons surveyed at the 3 locations, 65 percent felt that video advertising 

signs had a negative effect on the ability of a driver to attend to pedestrians and cyclists. 

Furthermore, 59 percent of the people said that as drivers, their attention was drawn to such 

signs, while 49 percent of those felt that such signs had a negative effect on traffic safety. A 

surprisingly large number of people—9 out of 152—stated that they personally had experienced 

near-crashes, and 2 had experienced actual rear-end crashes that they associated with video 

advertising signs. In addition, 86 percent of the respondents suggested that restrictions should be 

placed on those types of signs, such as their locations and brightness. 

Three of the field investigations of CEVMS effects mentioned earlier employ indirect measures 

of driver attention (eye glances) in the context of an on-road instrumented vehicle experimental 

approach. Although CEVMS stimuli are real, the experimental approach suffers from a degree of 

artificiality in its implementation. The research participants usually drive in an experimental 
9

vehicle along a route which is contrived for experimental purposes, and the route does not serve 

a useful purpose in their daily lives. The research participants sometimes drive with an 

experimenter present in the instrumented vehicle, and they sometimes wear a head-mounted eyetracking device. Two of the three studies cited used a somewhat intrusive but more accurate 

head-mounted eye-tracking device. One study used a less obtrusive but also less accurate 

vehicle-mounted eye-tracking device, where cameras were mounted in the vehicle cab. Although 

the research participants were not told the purpose of the investigation, the participants were 

definitely aware that they were participating in a driving experiment of some kind, and they may 

not have exhibited entirely natural behaviors as a result. Furthermore, eye glance behavior is 

difficult to measure, and it is not easy to relate directly to attention and distraction. For a more 

specific analysis of some further design and methodological concerns with the Lee et al. study 

cited above, see Wachtel.(12,9) 

The unobtrusive observation method employed in the field by Smiley et al. to collect safety 

surrogate measures of potential crashes (e.g., sudden braking, inadequate headway, etc.) does not 

create an artificial environment for the driver.(7) Usually, the sensing devices (loop detectors, 

remote cameras, or posted human observers) are hidden in the environment, and they are not 

noticed by the drivers. There is no problem of artificiality; the drivers in the study are not even 

aware that they are part of a study. However, the safety surrogate variables being measured are 

usually infrequent, often multicausal, comparatively subtle, and difficult to measure. For 

CEVMS, these variables can also occur over great distances, adding to the difficulty in 

accurately and reliably capturing data relating to these variables. 

Finally, the public survey method employed by Smiley et al. collected the opinions, attitudes, 

and feelings of passersby at intersections with video advertising signs.(7) The results, while 

interesting as a measure of public sentiment, are difficult to relate to the basic research question 

of determining whether there are any significant distraction effects or concrete safety concerns 

with regards to CEVMS used for outdoor advertising. 

2.4 LABORATORY INVESTIGATIONS 

Laboratory investigations related to roadway safety can be classified into several categories: 

driving simulations, non-driving simulator laboratory testing, and focus groups. 

For one such investigation, a non-driving simulator laboratory testing environment was used.(16)

For this study, researchers filmed a 27 minute drive and had 200 licensed drivers view the film 

while their eye movements were recorded. Billboards generated greater levels of visual attention 

than suggested by measures of recall. Billboards were viewed by individuals whether they were 

in the “target” audience or not and regardless of whether the billboard was of high or low 

interest. In addition, billboards located close to official highway signs received more attention 

than those that were farther away. 

In a driving simulation laboratory, Crundall et al. compared street level advertisements (SLAs), 

such as those on bus shelters, to raised level advertisements (RLAs), which include elevated ads 

on poles or streetlights.(17) The study was based on the understanding that, in undemanding 

situations, drivers have spare attentional capacity; however, when cognitive demands increase, 

spare capacity diminishes. As a result, eye movements must focus on the driving task at hand. 
10

Based on their prior research, Crundall et al. believe that if an advertisement is within the 

driver’s visual field during a search for hazards, it will attract visual fixations and distract 

attention needed to safely perform the driving task.(17) Because the most relevant information for 

hazard detection is distributed along a horizontal plane, the authors believe that the majority of 

visual fixations will fall within this plane when the driver is looking for driving-relevant 

information. Thus, if an advertisement is located within this window, it will receive more 

fixations than will advertisements located outside this window. The principal research 

hypotheses tested were that during conditions when drivers were looking for hazards, SLAs 

would receive the most attention. When spare capacity was greater, the attention given to RLAs 

would increase. The results supported these hypotheses. A post-drive survey showed that SLAs 

were judged more hazardous than RLAs. 

Young and Mahfoud used a driving simulator in which subjects drove three routes in the 

presence and absence of billboards.(18) The presence of billboards adversely affected driving 

performance in terms of lateral control and crashes. Billboards also had an adverse impact on 

driver attention in terms of the number of glances made to them, and they were associated with a 

higher subjective mental workload. In addition, the recall of official road signs was adversely 

affected by billboards, which the authors interpreted to mean that drivers were attending to 

billboards instead of relevant road signs. The authors reached a “persuasive overall conclusion 

that advertising has adverse effects on driving performance and driver attention” (p. 18).(18)

In a recent study using a driving simulator, Chan and her colleagues compared the impacts of invehicle versus external-to-vehicle distractors on performance of inexperienced versus 

experienced drivers.(19) The authors were particularly concerned with young, novice drivers 

because of the elevated crash risk for this segment of the driving population. They were also 

concerned because the researchers believed that distraction could adversely affect the novice 

drivers’ poorly developed hazard detection and avoidance skills. Chan et al. theorized that 

external distraction may be more harmful than internal distraction because when drivers are 

looking within the vehicle, it should be obvious to them that they are not processing relevant 

roadway information. However, when drivers are looking at sources outside the vehicle, it is 

likely that the forward roadway is still somewhere within the field of view. Thus, it may not be 

obvious to drivers (particularly inexperienced drivers) that this important information is not 

being fully processed since it is peripheral, unattended, or both. 

Chan et al. were primarily interested in the longest glances away from the forward roadway since 

these have been implicated in prior studies (e.g., Horrey and Wickens(20)) as major contributors 

to crashes. Thus, they used as their dependent measure the maximum time that drivers spent 

continuously looking away from the forward roadway during a specific distraction task. In terms 

of in-vehicle distractors, as hypothesized, inexperienced drivers showed a consistent pattern of 

looking away from the roadway for longer periods of time than experienced drivers. However, 

the findings about external distractions were quite different and unexpected in two key ways. 

There was very little difference in the duration of distraction episodes between the experienced 

and inexperienced drivers, and the maximum distraction durations were significantly longer for 

the out-of-vehicle tasks than for the in-vehicle tasks. The two experience groups showed little 

differences in the percentage of distraction episodes longer than 2.0 s, 2.5 s, and 3.0 s, in all 

cases longer for the external than for the in-vehicle distractors. The study also demonstrated that, 

“drivers are more willing to make extended glances external to the vehicle than internal to the 
11

vehicle” (p. 17).(19) Chan et al. conclude that, “it is likely that our out-of-vehicle tasks (which not 

only engage attention but also draw the eyes and visual attention away from in front of the 

vehicle) would have quite significant detrimental effects on processing the roadway in front of 

the vehicle” (p. 22).(19)

Three of the laboratory investigations of possible distraction effects mentioned above employ 

indirect measures of driver attention (eye glances) in the context of a driving simulation 

experimental approach. The interactive driving simulator approach offers considerable 

experimental control over stimulus parameters, like the size, number, proximity, and change rate 

of CEVMS or other advertising display. The simulator is also well suited for executing 

parametric studies of the effects of these variables on possible driver distraction. However, the 

approach suffers from all of the sources of artificiality found in the on-road instrumented vehicle 

approach for conducting field research mentioned earlier. Also, the approach adds the important 

source of virtual driving as opposed to real driving. Although the vehicle cab of the driving 

simulator may have certain degrees of motion (pitch, roll, heave, etc.) to enhance the sense of 

virtual driving, the vehicle cab does not move down the roadway. The visual scene passes by 

while the driver and vehicle remain stationary. This degree of artificiality requires considerable 

adaptation on the part of the research participants, most of whom need some amount of training 

to become accustomed to the differences between driving in a simulator and driving on a real 

road. Moreover, in the case of CEVMS, present driving simulators do not have sufficient visual 

dynamic range, image resolution, and contrast ratio capability to produce the compelling visual 

effect of a bright, photo-realistic LED-based CEVMS on a natural background scene. 

One laboratory investigation had research participants watch films of driving scenes containing 

billboards while their eye movements were being recorded.(16) This study represents an example 

of a non-driving simulator laboratory method. It suffers from all of the aforementioned 

limitations of laboratory CEVMS or billboard research. In addition, it does not measure the 

participants’ response while engaged in a driving task. 

2.5 PREVIOUS LITERATURE REVIEWS 

Garvey summarizes the literature on sign visibility, legibility, and conspicuity on behalf of the 

advertising industry.(21) One of his recommendations bears on the issue of distraction from 

billboards. He suggests that signs need not be detectable at distances greater than the minimum 

required legibility distance. Specifically, he states, “if a sign is detected before it is legible, the 

driver will take numerous glances at the sign in attempts to read it” before it becomes legible, 

and “these momentary diversions are inefficient and potentially dangerous” (p. 1).(21) 

Cairney and Gunatillake, working on behalf of the Government of Victoria, Australia, undertook 

a review of the literature with the goal of generating recommendations for guidelines for the 

control of outdoor advertising in that State.(22) They cited two prior reviews by Wachtel and 

Netherton in the United States and by Andreassen in Australia as the basis of their review.(2,23)

Since these earlier studies, the technology used for the display of roadside advertising and the 

addition of in-vehicle distractors has changed. Cairney and Gunatillake conclude that the 

principal concern remains the effects that a sign may have on a driver’s visibility of other road 

users, the roadway, and traffic control devices, particularly at high-demand locations, such as 

interchanges. They suggest several research approaches, including case studies, site 
12

investigations, and laboratory simulations to address these newer technologies. They conclude 

that the best of the studies conducted to date demonstrate that when all confounding variables are 

controlled statistically, sites with advertising signs have higher crash rates than sites without 

them. However, large, well-controlled studies will be required to detect significant effects 

because the effect size is small. They further conclude that changeable message signs may have a 

more direct bearing on crash rate than static signs. The findings of the study suggest that 

unregulated roadside advertising has the capability of creating a significant safety problem. The 

conclusions from their review run counter to Andreassen’s conclusion that, “there is no current 

evidence to say that advertising signs, in general, are causing accidents” (p. 4).(23) 

On behalf of the Scottish government, Wallace undertook the most extensive and critical 

review of the literature since the two earlier FHWA studies.(24) The study concludes that driver 

distraction from attention-getting sources can occur even when the driver is concentrating 

on the driving task. Furthermore, there is abundant evidence that billboards can function as 

distractors, particularly in areas of visual clutter. Billboards can distract in “low information” 

settings, and distraction from external factors is likely to be underreported and underrepresented 

in crash databases. 

The Dutch National Road Safety Research Institute reviewed the recent literature for the Dutch 

authorities and emphasized some of the stronger, more consistent points made in other studies, 

such as billboards should not be placed near challenging road settings, especially at or near 

intersections. Also, they should not resemble official traffic signs in pattern or color.(25)

Furthermore, dynamic signs that display motion or include moving parts should not be permitted. 

A key conclusion was that, “precisely in a dangerous situation it is important for the driver to 

have his attention on the road; an advertising billboard can slow the driver’s reaction time, which 

increases the chance of a crash” (p. 2).(25)

The WisDOT sponsored a study which summarizes available information about the safety 

impacts of outdoor electronic billboards and tri-vision signs.(26) Similar to Crundall, et al. and 

Wallace, the authors of this study determined that greater visual complexity associated with a 

high-volume location, such as intersections, required drivers to search the environment more 

than at lower-volume locations.(17,26) The authors stated, “it can be conjectured that additional 

visual stimuli such as billboards may add additional demand to driver workload in high-volume 

intersections” (p. 6).(26) 

Bergeron, on behalf of the Government of Quebec, Canada, re-reviewed many of the studies 

originally examined by Wachtel and Netherton and added reviews of several studies conducted 

subsequent to 1980.(2,27) His findings and conclusions, similar to those of other researchers, 

indicate that attentional resources needed for the driving task are diverted by the irrelevant 

information presented on advertising signs. This distraction leads to degradation in oculomotor 

performance, which adversely affects reaction time and vehicle control capability. The study 

concludes that when the driving task imposes substantial attentional demands that might occur 

on a heavily traveled, high-speed urban freeway, billboards can create an attentional overload 

that can have an impact on micro and macroperformance requirements of the driving task. 
13

2.6 REVIEWS OF PRACTICE 

Bergeron also performed a site review at a major elevated expressway in Montreal, Canada, 

which was proposed for two future billboards.(28) By reviewing the scene and considering various 

parameters such as traffic volumes, road geometry, and traffic control devices, Bergeron 

concludes that this 1.1 km section was already causing excessive cognitive demands, particularly 

for the many unfamiliar drivers. He concluded that the billboards would be inadvisable for 

several reasons. First, the location creates a substantial demand on drivers’ mental workloads 

because of its complex geometry, heavy traffic, high traffic speeds, merging and diverging 

traffic, and the presence of signs and signals that require drivers to make rapid decisions. Also, at 

the perceptual level, the billboards would add confusion to the visual environment, thus 

impairing drivers’ visual search, tracking, and reaction time. In addition, at an attention level, 

billboards could distract drivers. Last, the billboards could add to a driver’s mental workload in a 

setting where workload is already quite high. In a road situation such as this one, Bergeron 

concludes that the billboard is a “useless drain on limited attentional resources” (p. 5), and it 

could lead to reduced performance through inattention errors by overloading the driver’s 

information processing abilities.(28) 

du Toit and Coetzee address the current regulatory process for advertising signs visible from 

national roads.(29) The authors report that the South African government engages in careful 

scrutiny of proposed advertising signs before they are approved for use. All applications receive 

a desktop review followed by a site visit. If a decision cannot be made at this point, the 

authorities evaluate crash statistics for the proposed location to determine that if it is hazardous. 

Key questions asked as part of the review include the following: 

• Will the proposed sign obscure the view of an official road sign? 

• Will the sign cause a disruption of information flow to the driver? 

• Will the sign’s location distract the driver’s attention at merge/diverge areas, curves, and 

interchanges? 

A clear system exists in South Africa that requires certain spacing between road signs, 

particularly those that are close to interchanges; proposed advertising signs must fit within the 

parameters. This system, as codified in the South African Road Traffic Signs Manual 

(SARTSM), is intended, “to allow adequate time for the driver to read, interpret and react on the 

information on the road sign” (p. 7).(29) The authors report that for a recent review period, 

86.7 percent of all applications were rejected. Of those, 40.8 percent were rejected because the 

advertisement was too close to existing road signs, 20 percent were rejected because the sign 

disrupted the flow of information to the driver, and 7.5 percent were rejected because the sign 

was too close to a ramp gore. 

As a result of his work cited immediately above, Coetzee reviewed literature, performed a 

regulatory analysis, and recommended changes to regulations for outdoor advertising control in 

South Africa.(30) Although superficially similar to regulations in the United States, billboard 

control in South Africa goes much further, regulating the design and amount of information (in 

bits) that can be displayed on a given sign, as well as the proximity of two or more advertising 
14

signs to one another and to road features, such as official signs and interchanges. In South 

Africa, message sequencing, visual clutter, and sign size are restricted for different display 

technologies. This document includes a description of the terms critical event and critical zone, 

and it demonstrates how regulations would control advertising signs in these applications. 

Coetzee finds support from the earlier work of Ogden and the experiments of Johnston and Cole, 

concluding that, whereas drivers may be able to ignore advertisements when the driving task 

requires attention, it is possible that an attention-getting sign can assume primary importance and 

interfere with not only any spare capacity that a driver might have but also the information 

processing capacity reserved for primary task performance.(31,32) The danger arises, according to 

Coetzee, when processing the information on the advertisement interferes with the driver’s 

principal vehicle control task in situations that demand attention and rapid reactions.(30) The 

Coetzee report is the only work in the present review of the literature that has attempted to 

establish the parameters of billboard location and content based on theories of information 

processing and cognitive demand. 

2.7 CONCLUSIONS FROM LITERATURE REVIEW 

2.7.1 Basic Research Question 

The basic research question being addressed in the present report is whether the presence of 

CEVMS used for outdoor advertising is associated with a reduction in driving safety for the 

public. When regarded from a scientific perspective, the present literature review does not 

provide an adequate answer to this question. The studies reviewed are inconclusive. 

The present literature review reveals a disjointed array of isolated studies revealing sometimes 

contradictory and inconclusive results. Some studies show statistically significant driver safety 

concerns or distraction effects, but not all levels of distraction have negative safety impacts. 

Some studies go one step further and compare a statistically significant distraction with a 

criterion level of distraction claimed to represent the threshold of negative safety performance. 

This approach represents a substantial improvement, but it depends heavily upon the veridicality 

of the chosen criterion level of distraction. Other studies show no statistically significant safety 

or distraction effects at all, or they show mixed results. Some studies which show no statistically 

significant safety or distraction effects have been demonstrated to have serious flaws in their 

experimental and/or statistical designs. These studies are often plagued with two intrinsic 

methodological problems. First, they may not have sufficient measurement accuracy and 

precision to distinguish CEVMS distraction from noise in the data. Second, they may not have 

sufficient statistical power to reveal a small but important distraction effect which may really 

exist; i.e., they have not sampled enough events, drivers, or conditions to demonstrate an effect 

which may be obscured by variability due to sampling. In summary, from the perspective of 

strict statistical hypothesis testing, the present literature review is inconclusive with regard to 

demonstrating a possible relationship between driver safety and CEVMS exposure. From this 

perspective, the more stringent restrictions on the placement of billboards found in other 

countries might be regarded as a conservative precautionary measure, erring on the side of 

protecting public health from a possible but unproven threat and not as a response to an 

established driving safety hazard. That is not to say that such a conservative approach is 

inappropriate, but it should be acknowledged as such. 
15

The present literature review does reveal a preponderance in the number of studies (5:1) which 

show some driver safety effects due to traditional billboards and CEVMS in comparison with the 

number of studies that show no driver safety effects at all due to these stimuli. In addition, four 

other studies show mixed results. Three lists were prepared below to demonstrate this outcome. 

These lists included only empirical research studies, regardless of the methodology employed. 

Studies that reviewed literature or practice were not included unless they also contained an 

original research component. Studies previously reviewed in the earlier FHWA projects were 

also not included. 

The following research studies reported potential adverse safety effects for all dependent 

measures: 

• Wisconsin Department of Transportation.(4)

• Young.(16)

• Crundall, et al.(17)

• Young and Mahfoud.(18)

• Chan, et al.(19)

The research study by Tantala and Tantala(8) reported no adverse safety effect on any dependent 

measure. 

The following research studies reported potential adverse safety effects using some dependent 

measures and no effects using other dependent measures: 

• Lee, McElheny, and Gibbons.(12)

• Beijer, Smiley, and Eizenman.(14)

• Beijer.(15)

• Smiley et al.(7)

Such an outcome could lead one to conclude that there is more evidence for a possibly 

meaningful negative safety impact than evidence against such an impact. This conclusion is not 

warranted for at least two reasons. First, a simple tally of the number of studies which support a 

given research hypothesis compared with the number of studies which do not support the 

hypothesis may be misleading. Such a tally neglects to weight the various studies for their 

intrinsic strength of experimental design, statistical power, and care of execution. One strong 

landmark study with a robust experimental design and a sufficiently large sample of cases or 

drivers can topple a host of weaker investigations with fewer credentials. Yet, credentialing and 

weighting studies can become a subtle and subjective matter. It is difficult to judge studies on 

their relative strengths because it requires experience and judgment. While it may be relatively 
16

easy to identify the champion study and give that study a strong weighting, it is more difficult to 

evaluate the weaker studies at the middle and bottom of the list. 

Second, there is a strong propensity in scientific research to search for differences. The current 

Western model of reductionist scientific inquiry, coupled with its reliance on the paradigm of 

parametric statistics, is aligned against supporting the null hypothesis. This hypothesis states that 

there are no observed differences between two or more different treatments, i.e., that matters 

under scientific scrutiny are due to chance. This propensity to search for differences is so strong 

that when anticipated results are small or subtle, researchers often seek out conditions in nature 

that are worst case examples to find any affect at all. This causes the results to suffer from a lack 

of generalization when the entire population becomes the frame of reference. Thus, the present 

literature review acknowledges a possible natural and intrinsic bias toward including more 

studies that show a possible distraction effect of CEVMS exposure than studies that do not. Once 

these two considerations are recognized—a lack of weightings for comparing studies and a 

propensity to emphasize differences—the present literature review realigns to its original 

inconclusive outcome. In summary, present scientific techniques are not adapted to providing 

proof that CEVMS do not distract drivers; they only afford opportunities to demonstrate that they 

do distract drivers and possibly to what extent. If the demonstrated extent of distraction is minor 

and below the accepted criterion to interfere with safe driving, then the safety impact may be 

considered negligible. 

2.7.2 Methodological Implications 

The inconclusive literature review findings suggest the need for carefully controlled and 

methodologically sound investigations of the relationships between CEVMS, driver distraction, 

and safety. The review also suggests several factors that need to be considered in future research. 

One plausible model posits that drivers often have spare attentional capacity, and they can afford 

to divert their visual attention away from the driving task to look at objects irrelevant to the 

driving task, such as CEVMS. According to this model, when driving demand increases because 

of fixed hazards (such as dangerous roadway geometry or complex interchanges) or transient 

hazards (such as slowing traffic, vehicle path intrusion, or adverse weather), spare capacity is 

reduced or eliminated, and the driver devotes more capacity to the driving task. In this model, 

driver workload emerges as an important issue. By applying this model, in some countries, 

outdoor advertisements are not allowed in areas where known fixed hazards exist. Such locations 

include, but are not limited to, sharp horizontal or vertical curves and areas where high cognitive 

demand is imposed by the roadway, traffic, or environment, like intersections, interchanges, and 

locations of merging or diverging traffic. In some countries, billboards are also not allowed 

where they might interfere with the processing of important information from official road signs. 

These prohibitions do not in themselves prove that distraction is worse in high driver workload 

situations. However, they do point to the need to consider conditions of differing driver workload 

in an effective future research program on possible safety effects from CEVMS exposure. 

When scanning for hazards, drivers’ eye movements tend to fall within a horizontal window 

centered on the focus of expansion in the forward view. This focus of expansion is related to the 

visual flow of the moving scene where points and objects all emerge from a single point. 

Because an attention-getting billboard may be able to attract a driver’s glance even 

unintentionally, a CEVMS that falls within this scanning pattern can interrupt the pattern and 
17

cause a distraction at an inopportune time. Furthermore, research suggests that the distraction 

from a roadside billboard may be unconscious. Consequently, drivers may not be aware that they 

are being distracted, and they are unable to verbalize that any distraction occurred. Although 

where someone’s eyes look may not be the same as where his or her attention is focused, a 

theoretical connection may be implied. Through this connection, measurements of eye glance 

behavior permit the researcher to gain potential entrance into this realm of unconscious 

allocation of attention. This allocation of attention should play an important role in an effective 

program for future research. 

In addition, it cannot be assumed that all CEVMS are equal, even those of the same size, height, 

and LED technology to display their images. The impact of a CEVMS in an undeveloped area 

with relatively low levels of nighttime ambient lighting may be quite different from that of a 

CEVMS in a more urban context among other buildings and structures in an area with high 

nighttime illumination levels. Furthermore, characteristics of the CEVMS displays may, in and 

of themselves, lead to measurable differences in distraction, such as information density, colors 

of figure and background, character size and font, and message content. These characteristics 

cannot be assumed to be equivalent for purposes of comparisons. One possible solution to this 

problem may be for future research studies to exercise a certain degree of experimental control 

over the CEVMS message itself. This may require a deeper level of cooperation with the 

billboard industry than has been encountered in previous studies. Such increased cooperation 

could be beneficial in establishing a collaborative research environment among industry, 

government, and university stakeholders. 

Finally, a frequently changing CEVMS, which can generally be seen long before it can be 

read, raises a particular concern for distraction. This is because drivers may continue to 

glance at the CEVMS to observe changes in varying content with various sizes of lettering 

until the sign content can be read. The implication here is that future studies may need to 

embrace longer viewing distances. 

19 

3.0 KEY FACTORS AND MEASURES 

The study of possible CEVMS effects on driver safety represents a complex research endeavor. 

There are numerous key factors affecting a driver’s response to CEVMS. Many of these 

influential factors may be designated as independent research variables in need of specification 

or control within a given research design. Likewise, there are numerous inferred measures of 

driver safety which may serve as possible dependent variables for observation and measurement. 

Depending upon the specific research design, some of these independent and dependent variables 

may swap places. 

3.1 KEY FACTORS (INDEPENDENT VARIABLES) 

For classification purposes, the key factors, or major independent variables, may be categorized 

into various types. The list of key factors shown below gives some of the independent variables 

which might be considered in the study of possible safety effects of CEVMS. These key 

independent variables were selected from a more comprehensive analysis by means of a process 

to be described later. This analysis grouped all of the independent variables into five major 

categories according to source as follows: 

• Billboard. 

• Roadway. 

• Vehicle. 

• Driver. 

• Environment. 

After this initial analysis, a subsequent evaluation selected only the most important, or key, 

factors or variables. Each category lists the key independent variables which belong to that 

category. The lists below contain independent variables from four of the five above mentioned 

categories. The vehicle category is missing because all of the variables belonging to that 

category were eliminated in the selection process. For cross reference purposes, the decimal 

number shown in brackets to the right of each variable gives the outline number from the more 

detailed analysis upon which the selection was based (see table 1 in appendix A). In parentheses 

to the right of certain variables are given some examples and explanations which serve to clarify 

that particular variable. 

The following are the key factors relating to the billboard: 

• Location [1.1] (lat./long., GPS, mile marker, survey location, reference location). 

• Sight distance [1.1.3]. 

• Resolution [1.2.3] (dpi, LEDs/inch, crispness). 
20 

• Luminance [1.2.4] (brightness). 

• Contrast ratio [1.2.4]. 

• Day/night settings [1.2.4]. 

• Change rate [1.3.2] (image changes). 

• Dwell time [1.3.2]. 

• Change time [1.3.2]. 

• Sequencing [1.3.2] (apparent motion). 

• Full motion video [1.3.4]. 

• Engagement value [1.3.5] (ability to hold attention). 

• Message [1.4]. 

The following are the key factors relating to the roadway: 

• Category [2.1.1] (two-lane rural, collector, arterial, freeway). 

• Geometry [2.2.2] (curve radius: horizontal, vertical). 

• Intersection [2.2.3] (signalized, stop controlled). 

• Interchange [2.2.4]. 

• Exit [2.2.4]. 

• Entrance [2.2.4]. 

• Merge [2.2.4]. 

• Gore [2.2.4]. 

• Traffic [2.3] (average daily traffic, peak traffic, level of service). 

The following are the key factors relating to the driver: 

• Age [4.1]. 

• Gender [4.1]. 

• Demographics [4.1]. 
21 

• Years driving [4.2]. 

• Route familiarity [4.2]. 

• State [4.3] (alert, fatigue, alcohol, drugs). 

The following are the key factors relating to the environment: 

• Visual clutter [5.1.1]. 

• Nearby billboards [5.1.1]. 

• Ambient lighting [5.1.1]. 

• Official signs [5.2] (illuminated, luminous (VMS), retro-reflective). 

• On-premise signs [5.3] (conventional, tri-vision, digital, full motion video). 

The combined list of key factors given above represents a subset of the most influential 

independent variables in terms of importance to a future program of research. This subset of 

variables was selected from a more extensive list of the major independent variables which 

might play a role. As mentioned previously, the list of all major independent variables may 

be found in outline form in table 1 in appendix A. The bracketed decimal numbers in the list 

of key factors refer to the corresponding outline numbers in table 1. In addition, the table cites 

some of the advantages and disadvantages of employing that particular variable. The combined 

list of key factors presents the 32 variables which were judged to be the most influential 

variables from table 1. 

The more comprehensive and detailed analysis represented in table 1 identifies considerably 

more possible independent variables. The approximately 60 types of variables listed in the table 

are further broken down into 185 specific subtypes or levels of independent variables which 

could play an important role in studying the possible effects of CEVMS on driver distraction and 

roadway safety. It is encouraged to carefully examine the many independent variables and their 

advantages and disadvantages, as described in table 1 in appendix A, to gain a greater 

appreciation of the complexity of the research problem. With such a profusion of important 

factors affecting the study of CEVMS effects, no single experiment could possibly answer all of 

the relevant scientific or engineering questions. 

The key independent variables were selected from the expanded list represented in table 1 by 

three senior research psychologists, all coauthors of the present report and familiar with CEVMS 

research. The criterion for selection was the importance of that factor in conducting research on 

CEVMS effects. Thus, the list of key factors indicates critical independent variables which need 

to be considered in any proposed program of research. The brightness and crispness, or photo 

realism, of the CEVMS images are extremely important. Any image changes, apparent motion or 

video motion in the CEVMS, and location parameters are also critical factors. The next level of 

importance relates to environmental factors. Two distinct classes of variables must be taken into 

account: general visual clutter and the presence of other off-premise commercial CEVMS 
22 

(nearby billboards). In particular, compelling information from CEVMS used for advertising 

may conflict with important roadway safety information conveyed by nearby traffic control 

devices (official signs). The question should also be raised concerning possible enhanced 

distraction caused by the urgency of Amber Alerts and other public safety messages displayed on 

CEVMS. Any contextual links among the messages from several sequential CEVMS, as well as 

any specific user interactions with the CEVMS must be taken into account. Factors to consider 

for drivers include their familiarity with the driving route and the expected presence or absence 

of CEVMS. Lastly, the complexity of the roadway geometry and the volume of traffic are likely 

to play significant roles. 

3.2 KEY MEASURES (DEPENDENT VARIABLES) 

The study of driver safety is a complex area of investigation. There are numerous objective, 

inferred, and subjective measures of driver behavior which might serve as dependent variables in 

a program of proposed research on the possible safety effects of CEVMS. As demonstrated in the 

discussion concerning independent variables, the key measures or dependent variables may be 

categorized into types. The list of key measures shown below gives 28 key measures, or 

dependent variables, which might be considered possible safety effects of CEVMS. As was the 

case for the list of key factors (independent variables), the list of key measures represents a down 

selection from a more extensive list of the major dependent variables of interest (see table 2 in 

appendix A). The dependent variables are grouped into the following four major categories: 

• Vehicle behavior. 

• Driver and vehicle interactions. 

• Driver attention and distraction. 

• Crashes. 

The structure of the list of key measures for dependent variables is similar to that for the list of 

key factors for independent variables. In the case of dependent variables, the major variable 

categories of driver and vehicle interactions and crashes found in table 2 are missing from the list 

of key measures below because all of the variables belonging to these two categories were 

eliminated in the selection process. 

Key measures relating to vehicle behavior are as follows: 

• Speed [1.1] (continuous, exceeding speed, speed variance). 

• Lane position [1.2] (continuous, lane excursions, lane variance). 

• Acceleration [1.3] (longitudinal, lateral, heave). 

• Other vehicle interactions [1.4]. 

• Headway [1.4.1] (time to collision). 
23 

• Gap acceptance [1.4.2] (merge, passing). 

• Conflicts [1.4.3] (near-crashes). 

• Violations [1.4.4] (red light running, failure to yield, failure to stop). 

• Errors [1.4.5] (missed exit, wrong lane). 

• Timing [1.4.6] (late movements, premature movements). 

• Infrastructure interactions [1.5]. 

• Response to roadway geometry [1.5.1] (swerves, sudden braking). 

• Response to traffic control devices [1.5.2] (misses, delays). 

• Pedestrian interactions [1.5.3] (yields). 

Key measures relating to driver attention/distraction are as follows: 

• Eye glance behavior [3.1.1] (number and duration of glances, glance object). 

• Distractor performance [3.1.2] (secondary task). 

• Visual occlusion [3.1.3]. 

• Feature detection [3.1.4]. 

• Feature recognition [3.1.5]. 

• Driver workload [3.1.6] (task performance). 

• Head turning [3.1.7]. 

• Driver errors [3.1.8]. 

• Reaction time [3.1.9] (perception-reaction time). 

• Surprise [3.2.1] (orienting response). 

• Conspicuity [3.2.2] (attention grabbing). 

• Search patterns [3.2.3]. 

• Capacity [3.2.4] (self-regulated attention, spare capacity). 

• Subjective measures [3.3]. 
24 

As mentioned above, the more detailed analysis underlying the combined list of key measures 

shown above may be found in table 2 in appendix A. Table 2 for the dependent variables 

has the same general structure as table 1 for the independent variables. The approximately 65 

types of dependent variables listed in table 2 are further broken down into 105 specific subtypes 

or levels of variables which could play an important role in measuring the possible effects of 

CEVMS on driver distraction. As noted before, it is encouraged to carefully examine the 

many dependent variables and their advantages and disadvantages, as described in table 2 in 

appendix A, to gain a greater appreciation of the wide variety of ways that driver safety can 

be measured as they relate to possible influences from CEVMS. With so many potential 

measurement techniques available, care must be taken in selecting appropriate dependent 

variables for any proposed program of research. 

Only the key dependent variables are listed in the combined list of 28 key measures given above. 

They were selected by the same process used to select the key independent variables in the list of 

key factors. As indicated before, the criterion for selection was importance in conducting 

research on CEVMS effects. Thus, the list of key measures indicates critical measures which 

need to be considered in future research. Eye glance behavior can serve as a particularly 

important potential indicator of specific visual distractions. The concept of self-regulated 

attention is very important for establishing excessive levels of distraction, despite difficulties in 

establishing a criterion threshold. This concept refers to attention that is under the driver’s 

conscious control, as opposed to involuntary attention, which may compel the driver to glance 

away from the road for an excessive amount of time. Increases in driving conflicts and errors are 

likewise effective measures of safety. The next level of importance relates to other observations 

of vehicle behaviors, including determinations of acceleration, lane position, and speed. 

Similarly important infrastructure interactions, such as driver responses to roadway geometry 

and traffic control devices, need to be considered. 
25 

4.0 RESEARCH STRATEGIES 

To successfully investigate the potential safety effects of CEVMS, the key factors (independent 

variables) and key measures (dependent variables) described in the previous section need to be 

selected, combined, and integrated into an effective research strategy. There are a number of 

possible research strategies that could address the basic research question. The list of 

recommended research strategies shown below lists eight key research approaches that might be 

considered. This list was generated from a more comprehensive and detailed analysis of the 

research strategies which might be of interest. This comprehensive analysis of research strategies 

was divided into six major groups (see table 3 in appendix A). The first group focuses on 

observing or counting actual motor vehicle crashes as they might occur or have occurred in the 

field. This field portion includes retrospective crash data base studies. The second group entails 

observing motor vehicle crashes as they might occur in a driving simulator. The third group 

involves observing safety surrogate measures as they might actually occur in the field. The 

fourth group focuses on observing safety surrogate measures as they might occur in a driving 

simulator. The fifth and sixth groups relate to social surveys and analytical studies. In this 

instance, the down-selection process eliminated all research strategies concerning crashes, social 

surveys, and analytical studies. Within the parentheses next to each strategy are some selected 

advantages and disadvantages associated with using that type of strategy in conducting research. 

Only the key strategies are shown in the list of recommended research strategies. They were 

selected by the same process used to select the key independent and dependent variables, with 

one important exception. This exception involves the incorporation of several assumptions which 

were derived from the antecedent analysis of potential independent and dependent variables. 

First, the brightness, sharpness, photo realism, and visual context of the CEVMS are extremely 

important. Since these characteristics are difficult to reproduce in a laboratory, laboratory 

methods tended to be judged low. In addition, certain participant-related variables, in particular 

eye glance behavior, are highly effective measures of distraction and workload. Any research 

method that supported the measurement of such variables tended to be judged high. Last, crash 

data involve rare events with multiple causal factors, making them difficult to measure. The 

CEVMS technology is too new to have an adequate crash heritage. In general, crash estimation 

methods tended to be judged low. 

After incorporation of the above assumptions, the following final list of recommended research 

strategies was developed. This final list included strategies from only two of the original six 

groups of strategies. 

The recommended research strategies for the safety surrogate field group include the following: 

• Unobtrusive observation [3.1] (natural driving context/no eye glance data, expensive). 

• Naturalistic driving [3.2] (natural driving context/insensitive eye glance data, expensive). 

• On-road instrumented vehicle [3.3] (experimental control, sensitive eye glance data, 

efficient, cost effective/artificial drive purpose). 
26 

• Closed-course test track [3.4] (stimulus control, efficient, cost effective/out of context 

driving). 

• Commentary driving [3.5] (easy/artificial response, interfere with driving). 

• Non-vehicle based field testing [3.6] (easy/artificial, out of context). 

The recommended research strategies for the safety surrogate laboratory group include the 

following: 

• Driving simulator [4.1] (experimental control, sensitive eye glance data, efficient/limited 

stimulus, artificial). 

• Non-simulator laboratory [4.2] (relatively easy/artificial, out of context). 

The more detailed analysis underlying the above combined list of recommended research 

strategies may be found in table 3 in appendix A. In the table, the more comprehensive analysis 

of research strategies is further broken down into approximately 55 specific categories and 

165 subtypes or levels of these categories. The reader is encouraged to carefully examine the 

many strategies and their advantages and disadvantages, as described in the table, to gain a 

greater appreciation of the wide variety of potentially relevant research methods which might be 

employed to study possible CEVMS effects. 

Table 3 can be used to discriminate among potential candidate research strategies. Certain 

research strategies can be eliminated from further consideration. Analytical studies cannot fill 

knowledge gaps and consequently often fall prey to reliance on unfounded assumptions. Social 

surveys are based on memory and opinion, and they are generally administered far from the 

event of interest both in terms of time and space. Crash rates, whether observed in the field or in 

the laboratory, represent extremely rare events, which are often the result of multiple complex 

causes and thereby difficult to evaluate. CEVMS technology has not been deployed long enough 

to accumulate a sufficient number of proximal motor vehicle crashes to make reliable estimates 

concerning population crash statistics in the field. Driving simulators used to measure safety 

surrogates have the advantage of careful control over stimulus parameters and testing conditions, 

but they suffer the disadvantage of being unnatural and artificial. More importantly, driving 

simulators have difficulty reproducing the luminance contrast and bright photorealism of the new 

CEVMS technology. In a similar manner, the closed-course test track and non-vehicle based 

field testing techniques represent a comparatively artificial and out-of-context experimental 

environment even though they are conducted in the field. Finally, commentary driving also 

affords natural billboard stimuli, but the driving task becomes somewhat artificial. 

The three research strategies which were judged to be the most effective were the on-road 

instrumented vehicle, the naturalistic driving, and the unobtrusive observation method, which 

were all used to measure driver distraction and safety surrogates. Thus, the outcome of the 

present investigation of research strategies recommends three primary candidates for 

consideration in any program of future research to study the possible effects of CEVMS on 

driver distraction and roadway safety. Each of the three study methods represented has its own 

unique advantages and disadvantages. All three of these top candidate research strategies should 
27 

be considered in developing any future research program on CEVMS effects. They provide the 

basis for selecting a recommended first stage study in such a program. 

This is not to say that other research strategies do not have a significant role to play in a 

comprehensive research program directed toward a common goal. For example, if significant 

negative CEVMS safety effects have already been found using one of the primary research 

strategies, subsequent driving simulator experiments might be employed to systematically vary 

certain billboard location, timing, or spacing parameters in a controlled and consistent manner to 

establish billboard placement guidance. In addition, combinations of research strategies can 

result in synergistic efficiency. For example, both the unobtrusive observation and the 

naturalistic driving methods naturally support the simultaneous collection of crash, near-crash, or 

safety surrogate data. The analysis of crash data will also be needed to relate measures of driver 

distraction to more direct determinants of roadway safety. 

29 

5.0 FUTURE RESEARCH PROGRAM 

As stated previously, it is not possible to answer all of the critical questions concerning possible 

attention, distraction, and safety impacts from CEVMS in a single experiment. Instead, a 

carefully crafted program of research needs to be conceived and implemented to embrace a series 

of interrelated experiments and studies directed at answering different facets of this complex 

issue. This section describes the important elements of a recommended research program. This 

research program is broadly defined to provide a background and context for more concrete 

alternative first stage studies outlined in section 6.0. This section describes a long-range 

multistudy research program covering a number of years. Section 6.0 will outline three methods 

for implementing the first stage of that program. 

5.1 STAGES 

The proposed research program would have the following three stages: 

• Stage 1—The attention and distraction effects of CEVMS would be investigated to 

determine whether any observed or measured distractions due to CEVMS is sufficient to 

interfere with attentional criteria for safe driving. This stage is directed at discovering 

whether or not distraction from CEVMS represents a potential driving hazard. Initial 

CEVMS parameters must be chosen carefully so as not to bias the result from the outset. 

• Stage 2—If potential interfering distraction is observed, it would be necessary to 

investigate the relationship between the observed distraction and various CEVMS 

parameters (e.g., luminance, change rate, distance, CEVMS spacing, engagement level of 

sign content, and road geometry) to determine possible limitations on CEVMS 

deployment and operation which might reduce distraction to noninterfering levels. This 

stage is directed at developing empirical data to support the development of possible 

restrictions or regulation of CEVMS to reduce potential driving hazards. 

• Stage 3—As related to CEVMS, researchers would have to investigate the relationship 

between distraction, defined in terms of eye glance behavior and safety surrogate 

measures (driving conflicts, errors, etc.), and safety, defined more directly in terms of 

crashes, fatalities, injuries, and property damage. This stage focuses on validating the eye 

glance and safety surrogate measures used to infer attention and distraction effects of 

CEVMS through the primary safety criterion of protecting life, health, and property. 

The above stages of the proposed research program are to be pursued sequentially. The initial 

stage is directed at determining whether or not a potentially harmful CEVMS distraction effect 

exists. To demonstrate such a distraction effect, an independent and objective threshold criterion 

of excessive distraction must be employed. If no potentially harmful distraction is shown, at least 

as far as driving safety is concerned, there would be little need to pursue the second stage of 

developing a basis for regulating CEVMS or the third stage of relating CEVMS distraction to 

more direct measures of safety (crashes). If potentially harmful distraction is shown in the first 

stage, the second and third stages would be implemented in order. The order of the last two 

stages may appear to be reversed. Normally, it would seem desirable to establish a relationship 
30 

between CEVMS distraction and crashes before developing a basis for regulation. However, in 

this instance, the LED-based digital CEVMS technology is so new that it will not be possible to 

reliably measure crashes for some time. Meanwhile, if possible distraction is shown, the 

community of practitioners engaged in outdoor advertising control will need near-term technical 

information on the luminance, contrast, change rates, and spacing of CEVMS to minimize that 

distraction. For this reason, the stages have been proposed in the order given above. 

5.2 APPROACH 

The literature review update in section 2.0 points to some important principles that should be 

incorporated into the proposed program of research to enhance the probability that the program 

can successfully achieve its goals. These principles can be regarded as lessons learned from the 

experience of previous research. First, empirical studies should employ CEVMS stimuli, as well 

as a variety of comparison stimuli, including standard (non-digital) billboards, built objects of 

casual visual interest (e.g., houses, barns), and natural background control scenery (e.g., trees, 

fields). This principle establishes a relevant visual context against which to contrast CEVMS 

stimuli. Next, empirical studies should be constructed so as to compare the effects of CEVMS 

and the effects of the various comparison stimuli. This principle implies that some measurable 

(statistically significant) effect should be demonstrated for as many of the comparison stimuli as 

possible, at least for the standard billboards. It is necessary to show some distraction effect for 

both CEVMS and standard billboards relative to a baseline to be sure that the study is not just 

measuring random noise in the data. In addition, for the case of distraction and safety surrogate 

performance measures, the measured effects of CEVMS and standard billboards need to be 

compared with each other and with an independently determined criterion of potentially harmful 

consequences. The application of this criterion needs to incorporate the concept of self-regulated 

attention, as indicated in section 3.0. Last, to the degree possible, direct experimental control 

should be exerted over the CEVMS stimuli. In the first stage of determining a meaningful 

distraction effect, this control can be limited to turning the CEVMS on and off for predetermined 

periods according to a strict experimental protocol. In the second stage of establishing possible 

parameter limitations, this control may need to be expanded to changing the luminance, message 

change rate, or some other CEVMS characteristic according to an experimental protocol. 

These four principles define the basic approach for implementing the proposed research 

program. They provide guidance and direction to the proposed program. It should be emphasized 

that only a systematic multiyear broad program of research can adequately answer the important 

questions posed by the community interested in outdoor advertising control concerning the 

possible distraction effects and safety implications of CEVMS. No single experiment can 

provide the solution. It should also be emphasized that all stages of the research program must be 

sensitive to the practical needs of the outdoor advertising community, which includes highway 

engineers, traffic engineers, the outdoor advertising industry, environmental advocates, and 

outdoor advertising regulators. Even though the second stage is where most of these practical 

needs are addressed, at all stages of the research, investigators need to try to provide practical 

information on the luminance, contrast, change rate, display size, display spacing, or other 

parameters over which the outdoor advertising community could possibly exert some control. 

Administrators concerned with issuing permits for billboards need practical engineering results 

to assist them in there daily jobs. 
31 

5.3 STRUCTURE 

As outlined above, the proposed research program consists of three stages. The first stage 

focuses on determining the potential existence of harmful distraction effects due to CEVMS. The 

second stage involves determining limitations or restrictions to CEVMS parameters which could 

reduce or eliminate the implied potentially harmful distracting effects. The third stage focuses on 

relating the reduction in implied potentially harmful distraction to actual safety benefits of 

decreasing crashes, fatalities, injuries, and property damage on the roadway. The sections below 

describe these stages in more detail. 

5.3.1 Stage 1—Determination of Distraction 

The first stage, to determine the potential existence of harmful CEVMS distraction, may be 

implemented in many different ways. According to the analysis of research strategies in 

section 4.0, the three most effective approaches are the on-road instrumented vehicle, the 

naturalistic driving, and the unobtrusive observation methods. 

The on-road instrumented vehicle method is sensitive to a wide range of variables, including 

accurate eye glance measurements. It affords the opportunity to ensure that the test participants 

drive by many CEVMS and comparison sites in a structured and reproducible manner. 

The naturalistic driving method is similar to the on-road instrumented vehicle technique, but it 

has less control since the test participants drive their own vehicles according to their own 

personal daily schedules. As a result, the participants may pass few, if any, billboards. 

Furthermore, the naturalistic driving method has difficulty supporting accurate eye glance 

measurements, and it requires considerably more effort and expense. However, the naturalistic 

driving method is less artificial and has a high degree of face validity. 

Although the unobtrusive observation method also involves considerable effort and expense, the 

data collected are based on the observation of vehicles rather than individual drivers. The 

unobtrusive observation method is the least artificial of the three because with this technique, 

research participants are generally unaware of being observed. 

This first stage of the research program would employ one or more of these study approaches as 

a first step. A single method could be selected, or more than one approach could be combined. 

For example, the on-road instrumented vehicle and the unobtrusive observation method could 

make an effective combination, but the cost would be high. In either case, this first stage should 

also be designed to answer, at least in a preliminary manner to whatever degree possible, some of 

the practical questions of interest to the community concerned with outdoor advertising control. 

5.3.2 Stage 2—Basis for Regulation 

If the results of the first stage reveal a CEVMS driver distraction effect sufficient for public 

concern, then the second stage of the proposed research program would be implemented to 

provide an initial technical basis for possible regulation. This stage would consist of a series of 

eye glance and safety surrogate evaluations in the field and in the laboratory designed to 

investigate the various parameters of CEVMS which contribute to driver distraction. Although 

field methods can capture the realism of the CEVMS stimulus, they do not allow the researcher 
32 

to independently vary a variety of CEVMS parameters one at a time so as to isolate the effect of 

that variable, as some of the laboratory techniques would. For example, this second stage might 

begin with attempts to estimate the gross effects of certain salient CEVMS parameters in the 

field. Throughout this section, the brightness of the CEVMS will be used as an example, but the 

approach can be adapted to many other relevant CEVMS characteristics. For example, many 

current CEVMS displays adjust their brightness for day and night. If the outdoor advertising 

industry would agree to adjust the brightness of several installations both during the day and at 

night for the purposes of experimentation, partial estimates of the effects of brightness on eye 

glance behavior might be elaborated for selected luminance levels. 

To obtain a more complete functional relationship between eye glance distraction and CEVMS 

luminance, a test track or driving simulator experiment might be devised. If it were possible to 

erect an experimental CEVMS installation at a test track location, the test track experiment 

would have realistic brightness and contrast levels, as well as controlled exposure conditions. 

However, it would suffer from a highly constrained and unnatural driving environment. The 

driving simulator experiment could easily portray a wide variety of driving environments with 

realistic contexts, but it would suffer from a severely restricted range of luminance and contrast 

ratios. Nonetheless, to overcome these disadvantages, correction factors or transformations might 

be applied to the test track data to account for discrepancies in level of attention and to the 

driving simulator data to account for photometric discrepancies. The incorporation of such 

correction factors or transformations to relate test track and laboratory data to driving data on 

real roads underscores the necessity of conducting a combination of field and laboratory testing 

environments in this stage of the proposed research program. Some degree of field validation 

needs to be a part of any laboratory component of the research during this stage. 

This second stage of the research program must be designed to answer, to the degree possible, 

the practical questions of the community interested in outdoor advertising control. This is the 

stage of research which addresses functional relationships regarding the effects of CEVMS 

luminance (brightness), change rates, size, display spacing, and other variables on driver 

distraction and roadway safety. These functional relationships could subsequently be translated 

by outdoor advertising administrators and regulators into concrete rules which protect the safety 

of the driving public while at the same time allowing commercial growth and the rights of the 

outdoor advertising industry. To be fully successful, this stage of the research program must be 

pursued with active participation from all stakeholders, which include industry, 

environmentalists, researchers, and regulators alike. 

5.3.3 Stage 3—Relationship to Crashes 

The third stage of the proposed research program relates changes in potentially harmful 

distraction effects due to various CEVMS parameters to changes in actual roadway safety 

(crashes and their consequent fatalities, injuries, and property damage). This stage is directed at 

validating the earlier findings with regard to CEVMS distraction based on eye glance and safety 

surrogate measures in the context of retrospective crash data. This stage of the program would 

likely employ the Empirical Bayes, or Bayesian, method of analyzing crash statistics. The 

Bayesian approach formally incorporates prior knowledge into the process of current research, 

and it translates probabilistic calculations into statements of belief concerning statistical 

hypotheses in place of the classical confidence interval concept employed in parametric 
33 

statistics. The Empirical Bayes method also incorporates the crash history of other control sites 

with similar traits to account for extraneous factors which may be influencing the crash data at 

the site of interest. In short, the Empirical Bayes method possesses distinct statistical advantages 

over the naïve before/after technique and even the before/after technique with a simple control. 

The Empirical Bayes method is well suited for the task of estimating vehicle crash rates along 

different stretches of roadway, including those stretches with CEVMS. The prediction of 

baseline crash rates, and their potential increase or decrease with the introduction of CEVMS, is 

essential to this final stage of the proposed research program. This final stage should also be 

designed to answer, to whatever degree possible based on crash statistics, some of the practical 

questions of interest to the community concerned with outdoor advertising control. Because of 

the low numbers of crashes and their susceptibility to multiple determining causes, considerable 

effort, time, and expense will likely have to be expended on this final stage. 

35 

6.0 RECOMMENDED FIRST STAGE STUDY 

The first stage of the research program, determination of distraction, provides the context for 

selecting the recommended next study. The first goal of this stage of the program is to determine 

whether any observed or measured distraction due to CEVMS is sufficient to interfere with 

attentional criteria for safe driving. The second goal is to provide some preliminary practical 

technical information that could be of help to the community interested in outdoor advertising 

control. This goal could consist of furnishing initial indications of the possible distraction effects 

produced by one or more of the concrete variables over which the community might exert some 

control, such as luminance (brightness), change rate, display size, and display spacing. 

According to the analysis summarized in section 4.0, to provide an initial answer to these types 

of questions, the three most effective research strategies are the on-road instrumented vehicle, 

the naturalistic driving, and the unobtrusive observation methods. In the present section, one 

possible preliminary study is briefly described using each of these three approaches. A more 

detailed description of each study approach is given in appendix B. This detailed description 

includes more specific information on the general method, factors and measures employed, 

advantages and disadvantages, and budgetary cost. After project initiation, a more 

comprehensive work plan and more in-depth budget will need to be developed. That 

comprehensive work plan should receive inputs from all of the important stakeholders in 

CEVMS research, which include industry, environmentalists, researchers, and regulators alike. 

After careful and thorough deliberation, the final details of that comprehensive work plan and 

budget may differ considerably from what is suggested in this section or in appendix B. 

6.1 SUMMARY OF STUDY APPROACHES 

6.1.1 On-Road Instrumented Vehicle 

The on-road instrumented vehicle method employs an instrumented vehicle which is brought to 

the study site. The study site is a location where there are one or more CEVMS installations 

along a public access roadway. Each research participant drives the instrumented vehicle along a 

prescribed route, which includes CEVMS installations, standard (non-digital) billboards, objects 

of casual visual interest (e.g., houses and barns), and natural background control scenery (e.g., 

trees and fields). Each participant completes several such drives. The instrumented vehicle is 

capable of measuring vehicle speed, vehicle lane position, longitudinal acceleration, lateral 

acceleration, GPS time and position, and driver eye glance direction and duration. The 

instrumented vehicle is also equipped with accurate vehicle-mounted or head-mounted eyetracking equipment, video cameras (forward and cab views), and a voice recorder. The major 

independent variable in the study is the presence or absence of CEVMS and other comparison 

visual stimuli along the driving path. If possible, the CEVMS should be capable of being turned 

off and on or changing along some other dimension like luminance or change rate, according to a 

prearranged experimental design. Other important independent variables are the time of day 

(day/night), traffic conditions (peak, nonpeak) and driver variables (age, gender, and route 

familiarity). The primary dependent variables are the frequency, direction, and duration of driver 

eye glances. Secondary dependent measures are safety surrogate indicators associated with driver 

errors and other measures of driver performance, such as speed changes, headway, lane 
36 

deviation, and traffic conflicts. A rough budgetary estimate for conducting such an on-road 

instrumented vehicle study is between $400,000 and $800,000 (see appendix B for more details). 

6.1.2 Naturalistic Driving 

The naturalistic driving method employs a standardized instrument package which is installed in 

each participant’s own private vehicle or in a vehicle loaned to the participant. The participant’s 

vehicle appears and performs as it normally would. Participants drive their vehicles as part of 

their daily life routines, making control of CEVMS exposure difficult. The instrument package is 

capable of measuring speed, lane position, acceleration, GPS time and position, driver eye glance 

frequency, direction, and duration. However, because of the unobtrusive nature of the 

experimental technique, this method cannot support the use of accurate head-mounted or vehiclemounted eye-tracking equipment. Once the participant’s vehicle has been instrumented, data are 

collected by means of automatic wireless downloads without participant awareness or 

involvement. The major independent variable is the presence or absence of CEVMS and other 

comparison visual stimuli (standard billboards, buildings, control settings, etc.) along the driven 

path. If possible, the CEVMS should be controlled according to a prearranged experimental 

protocol. Secondary independent variables could include the type of vehicle (sedan, pickup, or 

SUV) and driver characteristics (age, gender, and route familiarity). The primary measures or 

dependent variables are the frequency, direction, and duration of the driver’s eye glances. 

However, as a result of the lower degree of accuracy in eye movement recording, this study 

method depends more heavily on secondary dependent variables. Safety surrogate measures 

associated with driver errors and other measures of driver performance (headway, lane deviation, 

conflicts, and erratic maneuvers) are of increased importance in this method. Additional 

dependent variables may include the time of day (day/night), traffic conditions (peak, nonpeak), 

in-vehicle distractions (eating, cell phone use), state of fatigue, etc. A rough budgetary estimate 

for conducting such a naturalistic driving study is between $2 million and $4 million (see 

appendix B for more details). 

6.1.3 Unobtrusive Observation 

The unobtrusive observation method employs an array of static cameras or other sensors 

mounted near the locations of the CEVMS and other comparison stimuli. The cameras are 

capable of recording the behavior of vehicles passing the various relevant visual stimuli as a part 

of the natural flow of traffic. The drivers are usually completely unaware that their vehicles are 

being observed. Post-hoc analysis of the video recordings from these cameras can yield data 

similar to some of that obtained by the on-road instrumented vehicle and naturalistic driving 

methods including vehicle speed, lane position, acceleration, and time. However, the data from 

distal video cameras are usually far less accurate and reliable than what can be collected by 

instruments on board the vehicle. Moreover, with present measurement technology, such video 

recordings cannot yield any data concerning driver eye glance movements. The major 

independent variable is the presence or absence of CEVMS and other comparison visual stimuli 

(standard billboards, buildings, etc.) along the driving path. If possible, the CEVMS should be 

controlled according to a prearranged experimental protocol. 

Some secondary independent variables might include the time of day (day/night) and traffic 

conditions (peak, nonpeak). This study method depends completely on safety surrogate measures 
37 

associated with driver errors and other measures of driver performance (headway, lane deviation, 

and erratic maneuvers), and it requires a large camera array over a long distance recording 

for extended periods, as well as extensive data analysis. A rough budgetary estimate for 

conducting such an unobtrusive observation study is between $1 million and $3 million (see 

appendix B for more details). 

6.2 COMPARISON OF STUDY ALTERNATIVES 

This section has introduced and described three different candidate approaches for the 

recommended next study, which include the on-road instrumented vehicle method, the 

naturalistic driving method, and the unobtrusive observation method. Each study method would 

be capable of addressing the two-part basic research question to determine whether any observed 

or measured distraction due to CEVMS is sufficient to interfere with attentional criteria for safe 

driving, and to provide some preliminary practical technical information that could be of help to 

the community interested in outdoor advertising control. However, each method has certain 

advantages and disadvantages with regard to its ability to address these two questions. 

The on-road instrumented vehicle method was judged the best, having the advantage of being 

sensitive to a wide range of participant variables, including accurate eye glance measurements 

with real CEVMS stimuli in natural settings. The degree of experimental control afforded by this 

method makes it the most productive of the three. Driving scenarios can be selected with a 

number of CEVMS and standard billboard stimuli along a single drive, which can be repeated 

both within and across research participants. To the degree that accurate measurements of visual 

distraction and eye glance behavior are pivotal dependent variables, the on-road instrumented 

vehicle method has the clear advantage. The high degree of experimental control ensures that 

exposure to CEVMS and to comparing visual stimuli is uniform and consistent. The on-road 

instrumented vehicle approach is the most productive research method for producing quality data 

in the shortest amount of time for the least cost. 

The naturalistic driving method was judged the second best, offering some similar advantages to 

the on-road instrumented vehicle method. However, it suffered from less experimental control 

over CEVMS exposure, less ability to capture participant-related variables, and more logistical 

complication and expense. Both of these methods are somewhat related from the perspective of 

the research participant. In both cases, the research participant is driving in an instrumented 

vehicle on a real road. Both allow the determination of driver eye glance behavior to some 

degree, but the increased level of experimental control exercised in the on-road instrumented 

vehicle method gives this technique a distinct advantage, both in terms of more accurate eye 

glance measurements and more consistent driver exposure. 

Finally, unobtrusive observation of safety surrogate measures involves no direct contact with the 

driver, thus preserving a completely natural driving environment. However, this method is not 

sensitive to participant variables. In particular, it is not possible to measure eye glance behavior 

with this method. This method depends solely on safety surrogate measures. Furthermore, since 

these safety surrogate measures are relatively subtle to detect at a distance, this method can be 

costly and time-consuming to implement. 
38 

The on-road instrumented vehicle method has a strong advantage in productivity and efficiency. 

The major advantage of the other two methods is the natural and unobtrusive nature of the study 

procedure from the perspective of the research participants. However, some degree of artificiality 

may be a small price to pay to gain the cost effectiveness of the on-road instrumented vehicle 

method. In the final analysis, the present report recommends the on-road instrumented vehicle 

method as the best choice for the first stage study. This recommendation is made on the basis of 

scientific merit, timeliness of producing a meaningful result, and cost. 
39 

7.0 CONCLUSIONS 

The present report reviews the possible safety effects of CEVMS. The report consists of an 

update of earlier published work, an investigation of applicable research methods and techniques, 

recommendations for future research, and an extensive reference list and bibliography. The 

literature review update covers recent post-hoc crash studies, field investigations, laboratory 

investigations, previous literature reviews, and reviews of practice. The conclusion of the 

literature review is that the current body of knowledge represents an inconclusive scientific result 

with regard to demonstrating detrimental driver safety effects due to CEVMS exposure. This 

outcome points toward the importance of conducting carefully controlled and methodologically 

sound future research on the issue. 

The present report also analyzes the key factors or independent variables affecting a driver’s 

response to CEVMS and the key measures or dependent variables which serve as indicators of 

driver safety. These key factors and measures are selected, combined, and integrated into a set of 

optimal research strategies. Based on these strategies, as well as on lessons learned from the 

literature review update, a proposed long-term program of research has been developed to 

address the problem. This research program consists of three stages, which include determination 

of distraction, basis for possible regulation, and relationship of distraction to crashes. 

The present report only addresses the first stage of the proposed research program in detail. For 

this first stage, three candidate studies, which are an on-road instrumented vehicle study, a 

naturalistic driving study, and an unobtrusive observation study, have been introduced and 

compared. An analysis of the relative advantages and disadvantages of each study indicate that 

the on-road instrumented vehicle study is the best choice as the recommended first stage in 

answering the basic research question.

41 

APPENDIX A—EXPANDED TABLES 

A.1 KEY FACTORS (INDEPENDENT VARIABLES) 

Table 1. Expanded key factors (independent variables). 

Variable Ref. # Advantages Disadvantages 

1.0 Billboard 

1.1 Location 8, 129, 

38, 15, 

44, 32 

 

1.1.1 Lat./long.; GPS; mile 

marker; survey location; 

reference location; mobile 

13, 53, 

160 

Important to define stimulus; 

Easy to measure. 

Likely to require travel 

expenses. 

1.1.2 Distance from 

roadway; setback 

 Less important. 

1.1.3 Sight distance; visual 

occlusions; distance first 

detected 

13, 53 Determines exposure time. 

1.1.4 Orientation; angle to 

road; side of road; twosided 

144 Less important. 

1.2 Display 144 

1.2.1 Type: Conventional; 

Digital; Tri-vision 

125, 48 Digital type stands out. Tri-vision likely to disappear. 

1.2.2 Size; length; height; 

visual angle; mounting 

height 

129, 32 Off-premise sizes somewhat 

standard. 

On-premise sizes variable. 

1.2.3 Resolution; dpi; 

LEDs/in 

95, 48, 

53 

Crispness (sharpness) of 

image important. 

1.2.4 Luminance; contrast 

ratio; day/night settings 

48, 53, 

144 

Brightness (luminance) 

extremely important. 

Night setting may depend 

upon background 

illumination. 

1.3 Dynamics 31 
42 

Variable Ref. # Advantages Disadvantages 

1.3.1 Type: static; changing 158, 

129, 26 

Changing images extremely 

important. Static serves as 

control. 

1.3.2 Change rate; dwell 

time; change time; 

sequencing 

48, 50, 

158, 94 

Change pattern important. 

Easy to measure. 

1.3.3 Special effects: wipe, 

dissolve, scintillate 

 Adds to uniqueness and 

conspicuity. 

More difficult to measure. 

1.3.4 Full motion video 125, 

126 

Full motion video extremely 

compelling. 

Difficult to specify exact 

content seen. 

1.3.5 Engagement value: 

ability to hold attention 

 Important overall distraction 

variable 

Difficult to measure; requires 

subjective rating. 

1.3.6 Sound 

1.4 Message 129, 

44, 

144, 53 

 

1.4.1 Type: text; graphics; 

mixed; targeted 

32, 31 Particular message may be 

secondary. 

1.4.2 Text: word count; 

font size; color; content; 

legibility; affect 

32, 48 Many variations. Less 

important. 

1.4.3 Graphics: size; 

complexity; color; content; 

affect 

31, 50 Difficult to specify. Many 

varieties. 

1.4.4 Public safety alerts Social benefit. May be more distracting than 

advertising. 

1.4.5 Interactive: 

encourages driver response 

 Interactive may require more 

attention. 

2.0 Roadway 

2.1 Type 

 
43 

Variable Ref. # Advantages Disadvantages 

2.1.1 Category: two-lane 

rural; collector; arterial; 

freeway 

13, 15 

71, 54 

Important determinate of 

driver workload. 

Many variations even in 

single category. 

2.1.2 Lanes: number; 

width; markings; medians; 

shoulders; rumble strips 

 Less important. 

2.1.3 Speed: posted; 

advisory; 85th percentile; 

median 

50 Changes urgency of correct 

driving responses. 

2.1.4 Condition: dry, wet, 

ice, rain; oil slick 

 Important to driver control 

over vehicle. 

2.1.5 Traction: coefficient 

of friction 

 

2.2 Complexity 15 

2.2.1 Tangent: level; grade Less important. 

2.2.2 Curve: horizontal; 

vertical 

13, 44, 

118 

May place sudden demand on 

driver attention. 

2.2.3 Intersection: 

signalized; stop controlled 

129, 

38, 48 

Increased driver workload. Wide variety of intersection 

complexities. 

2.2.4 Interchange: exit, 

entrance, merge, gore 

26, 44, 

32, 48 

Controlled access. More 

carefully engineered. 

2.2.5 Driveway; entrance Less important. 

2.2.6 Lane change: merge; 

diverge; lane drop 

 May place sudden demand on 

driver attention. 

2.2.7 Other: bicycle lane; 

fire house 

 Less important. 

2.3 Traffic 158, 

38, 15, 

113, 

 

 
44 

Variable Ref. # Advantages Disadvantages 

2.3.1 Average daily traffic; 

peak traffic; level of 

service 

118 Likely to increase driver 

workload. 

2.3.2 Traffic mix: cars, 

trucks, buses, motorcycles 

 Less important. 

2.3.3 Pedestrians Mainly only in urban 

settings. 

3.0 Vehicle 59 

3.1 Type: automobile; 

SUV; truck; motorcycle 

 Motorcycle has least 

obstructed view. 

3.2 Condition: response; 

vehicle dynamics 

 Hard to determine in field. 

3.3 Windshield: size; 

tinting; field of view 

 Defines some stimulus 

exposure characteristics. 

4.0 Driver 10 

4.1 Characteristics: age; 

gender; demographics 

53, 23, 

12, 54 

 Less important. 

4.2 Experience: years 

driving; route familiarity 

15, 100 Route familiarity extremely 

important. 

4.3 State: alert; fatigue; 

alcohol; drugs 

 Difficult to measure. 

4.4 Distractions: 

conversation; eating; cell 

phone 

24, 90, 

25 

 

5.0 Environment 

5.1 Visual—general 113 

5.1.1 Visual clutter; nearby 

billboards; ambient lighting 

160, 

15, 32, 

44 

Complexity of visual 

environment extremely 

important. 

Difficult to specify. 

 
45 

Variable Ref. # Advantages Disadvantages 

5.1.2 Day/night viewing: 

dawn; dusk; sun-glare 

53 Nighttime viewing of bright 

images important. 

5.1.3 Visual flow Less important. 

5.2 Official signs 160, 2, 

26, 100 

 

5.2.1 Type: regulatory, 

advisory, navigational 

94 Regulatory most important. 

5.2.2 Location: left, right, 

overhead 

44, 15 Billboard can conflict with 

sign. 

5.2.3 Lighting: illuminated; 

luminous (VMS); retroreflective 

 Luminous (VMS) signs most 

important. 

5.2.4 Density: number in 

view, type mix 

15 Many variations in urban 

settings. 

5.2.5 Dynamics: change 

rate; motion; video 

 Extremely important point of 

possible conflict. 

Motion and video not yet 

allowed. 

5.2.6 Message: text; 

graphics 

 Less important 

5.3 On-premise signs 

5.3.1 Type: conventional; 

Tri-vision; digital; full 

motion video 

144 Digital and video most 

important. 

Tri-vision likely to disappear. 

5.3.2 Location: left, right, 

high, low 

144 

5.3.3 Lighting: illuminated; 

luminous; LED 

144 Bright, high resolution very 

compelling. 

Difficult to measure. 

5.3.4 Density: number in 

view, type mix 

 Can add to visual clutter. Many variations possible. 

5.3.4 Dynamics: change 

rate; motion; video; sound 

144 Extremely important variable. 
46 

Variable Ref. # Advantages Disadvantages 

5.3.5 Message: text; 

graphics; interactive 

 Interactive important. Text and graphics less 

important. 

5.4 Geographic 15 

5.4.1 Population: urban; 

suburban; rural 

13, 71 Can affect visual clutter. Many variations. 

5.4.2 Terrain: mountain; 

valley; desert; hilly; near 

water 

 Can affect driver workload. Many variations. 

5.4.3 Area: city; state; 

region 

 Less important. 

5.5 Meteorological 

5.5.1 Temperature; 

humidity; cloud cover 

53 Less important. 

5.5.2 Precipitation: rain; 

snow; fog; ice; visibility 

53 Can affect driver workload. 
47 

A.2 KEY MEASURES (DEPENDENT VARIABLES) 

Table 2. Expanded key measures (dependent variables). 

Variable Ref. # Advantages Disadvantages 

1.0 Vehicle Behavior 48 

1.1 Speed 125, 50 

1.1.1 Continuous More accurate profile. Large amounts of data. 

Expensive. 

1.1.2 Discrete locations Less data. Cheaper. 

1.1.3 Speed exceedances: 

high; low 

 Distraction indicator. 

1.1.4 Speed variance Distraction indicator. Best with continuous data. 

1.2 Lane position 161, 48, 

54 

 

1.2.1 Continuous More accurate profile. Large amounts of data. 

Expensive. 

1.2.2 Discrete locations Less data. Cheaper. 

1.2.3 Lane excursions: 

right; left 

23 Distraction indicator. More difficult to measure. 

1.2.4 Lane variance Distraction indicator. Best with continuous data. 

1.3 Acceleration 48, 54 

1.3.1 Longitudinal: hard 

braking; delayed 

acceleration; braking 

without cause 

 Excellent surrogate for 

distraction. 

1.3.2 Lateral: swerves 39 Good surrogate for 

distraction. 

1.3.3 Heave: bumps 125, 48 Not important. 

1.4 Other vehicle 

interactions 

39 
48 

Variable Ref. # Advantages Disadvantages 

1.4.1 Headway (car 

following); time to 

collision 

125, 48, 

118 

Good surrogate for 

distraction. 

1.4.2 Gap acceptance: 

merge; passing 

 Good surrogate for 

distraction. 

Difficult to measure. 

1.4.3 Conflicts; nearcrashes 125 Extremely important 

measure. 

1.4.4 Violations: red light 

running; failure to yield; 

failure to stop 

 Low probability events. 

1.4.5 Errors: missed exit; 

wrong lane 

 Good surrogate for 

distraction. 

1.4.6 Timing: late 

movements; premature 

movements 

 Difficult to measure. 

1.5 Infrastructure 

interactions 

 

1.5.1 Response to roadway 

geometry: swerves; sudden 

braking 

118, 15 Surrogate for distraction. 

1.5.2 Response to traffic 

control devices: misses, 

delays 

15 Surrogate for distraction. 

1.5.3 Pedestrian 

interactions; yields 

 Only in urban settings. 

1.6 Signals 39 

1.6.1 Brake light 125 Indication of sudden 

deceleration. 

1.6.2 Turn signals Less important. 

1.6.3 Other: backup lights Not important. 

 
49 

Variable Ref. # Advantages Disadvantages 

2.0 Driver/Vehicle

Interactions

 

2.1 Steering 

2.1.1 Gross movements: 

curves; turns 

 Surrogate for distraction. 

2.1.2 Fine movements: lane 

keeping 

60 Difficult to measure. 

2.2 Throttle 

2.2.1 Pedal press; pedal 

position; duration 

 Less important. 

2.2.2 Pedal release; 

duration 

 Less important. 

2.3 Brake 125 

2.3.1 Pedal press; duration; 

excursion 

 Surrogate for distraction. 

2.3.2 Pedal release Less important. 

2.4 Shift (manual only) 

2.4.1 Gear selection (speed) Not important. 

2.4.2 Gear transitions 

(shifts) 

 Not important. 

2.5 Displays 154 

2.5.1 Speedometer Secondary visual distractor. 

2.5.2 Other: gauges; radio Less important. 

2.6 Other controls 154, 25 

2.6.1 Safety: windshield 

wipers; instrument lights; 

horn; turn signals 

54 Less important, except turn 

signals. 
50 

Variable Ref. # Advantages Disadvantages 

2.6.2 Entertainment: radio; 

CD player 

48, 24, 

54 

Secondary distractor. 

2.6.3 Auditory/vocal: voice 

actuated 

154 Low probability of 

occurrence. 

3.0 Driver Attention / 

Distraction

79, 113, 

32, 146, 

145 

 

3.1 Objective measures 129 

3.1.1 Eye glance behavior: 

eye movements; number of 

glances; duration of 

glances; glance object 

129, 42, 

125, 53, 

160, 83, 

161, 78 

Excellent measure of 

unconscious attention / 

distraction. 

Delicate, expensive 

equipment. Difficult to 

calibrate. Expensive to 

analyze data. 

3.1.2 Distractor 

performance; secondary 

task 

83, 53 Excellent measure of 

distraction. 

Can increase risk in field 

experiments. Can be 

artificial. 

3.1.3 Visual occlusion 15 Good measure of 

distraction. 

Can increase risk in field 

experiments. Unnatural 

driving task. 

3.1.4 Feature detection 48 

3.1.5 Feature recognition 48 Good measure. 

3.1.6 Driver workload; task 

performance 

38, 15, 

113 

Excellent indicator of 

distraction. 

Complicated to measure. 

3.1.7 Head turning 78 Easy to measure. Less important. 

3.1.8 Driver errors 83 Excellent measure of 

distraction. 

Many varieties. Low 

probability of occurrence. 

3.1.9 Reaction time; 

perception-reaction time 

15 Good indicator of 

distraction. 

Difficult to measure. 

3.2 Inferred measures 

3.2.1 Surprise; orienting 

response 

 Difficult to measure. 
51 

Variable Ref. # Advantages Disadvantages 

3.2.2 Conspicuity; attention 

grabbing 

 Difficult to measure. 

3.2.3 Search patterns 15 Indicative of visual 

hypotheses. 

3.2.4 Capacity: selfregulated attention; spare 

capacity 

15 Extremely important 

concept. 

Hard to establish criterion 

threshold. 

3.3 Subjective measures 161 

3.3.1 Conversational drive Good possible method. Lots of extraneous data. 

3.3.2 Rating scale Inexpensive. Imprecise. 

3.3.3 Questionnaire Inexpensive. Imprecise. 

3.3.4 Survey 125 Relatively inexpensive. Sampling frame difficult. 

3.3.5 Focus group Small sample. Lots of data. Confounding social 

variables. 

4.0 Crashes 158, 125, 

26, 44, 

128, 161, 

95, 121 

 

4.1 Type: head-on; 

sideswipe; rear-end; 

backing; run-off-road; 

pedestrian 

39 Very important 

discriminator variable. 

Related to ultimate goal. 

Rare events. Many 

contributing factors. Difficult 

to estimate statistically. 

4.2 Severity: fatal; injury; 

property damage; 

unreported 

 Important to determine 

impact. 

Rare events. Many factors. 

Difficult to estimate 

statistically. 

4.3 Method of 

measurement 

 Rare events. Hard to 

estimate. 

4.3.1 Direct observation: 

simulator; field camera 

42 Best studied in simulator. 

No chance of injury. 

4.3.2 Before/after study 39, 158 Most common study type. No control site. Regression 

toward mean. 
52 

Variable Ref. # Advantages Disadvantages 

4.3.3 Before/after with 

control 

 Control adds rigor. Regression toward mean. 

4.3.4 Before/after/before More convincing causal 

effect. 

Regression toward mean. 

4.3.5 Regression model Directly account for 

multiple factors 

Large amounts of data on 

many variables 

4.3.6 Empirical Bayes Control for regression 

toward mean. 

More complicated statistical 

model. 

4.3.7 Full Bayes More complete treatment of 

conditional probabilities. 

Not widely used. 
53 

A.3 KEY RESEARCH STRATEGIES 

Table 3. Expanded key research strategies. 

Method Ref. # Advantages Disadvantages 

1.0 Crashes: Field 97, 95, 

21 

 

1.1 Unobtrusive observation 

1.1.1 Participant: random, 

uncontrolled; usually unknown 

49 No sampling bias. Do not know participant sample.

1.1.2 Experimenter: usually 

absent; remote observation; 

unknown to participant 

49 No artificial participant 

behaviors due to 

experimenter. 

1.1.3 Stimuli: natural, ordinary, 

in context; variable, 

uncontrolled 

49 Natural stimuli. Stimuli not uniform; e.g., 

weather effects. 

1.1.4 Responses: crashes; 

antecedent vehicle behaviors; 

rare; few participant variables 

49 Directly related to the safety 

goal. 

Extremely rare events; 

insensitive to participant 

variables. 

1.1.5 Scenario: natural route 

and purpose; uses own vehicle 

49 Completely natural 

experimental context; uses 

own vehicle. 

Long-term monitoring required. 

1.2 Naturalistic driving 

1.2.1 Participant: selected, 

sampled 

79, 78, 

42 

Know participant sample. Possible sampling bias. 

1.2.2 Experimenter: absent; 

remote observation; known to 

participant 

79, 78, 

42 

Possible artificial participant 

behaviors. 

1.2.3 Stimuli: natural, ordinary, 

in context; variable, 

uncontrolled 

79, 78, 

64, 42 

Natural stimuli. Stimuli not uniform; e.g., 

weather effects. 

1.2.4 Responses: crashes; 

antecedent vehicle and 

participant behaviors; rare 

79, 78, 

64, 42 

Directly related to ultimate 

goal; sensitive to some 

participant variables. 

Extremely rare events; difficult 

to collect adequate sample of 

crashes. 

 
54 

Method Ref. # Advantages Disadvantages 

1.2.5 Scenario: natural route 

and trip purpose; uses own 

vehicle 

79, 78, 

64, 42 

Mostly natural experimental 

context; uses own or 

borrowed vehicle. 

Participant aware of test status; 

may be injured or killed; vehicle 

may be damaged or destroyed; 

expensive. 

1.3 Retrospective database: 

fatal, injury, property damage 

87, 49, 

128, 

14, 58, 

Directly related to ultimate 

goal. 

Crashes are rare events; difficult 

to estimate. 

1.3.1 Before-after study 158, 1, 

130 

Most common study type. No control site; regression 

toward mean. 

1.3.2 Before-after study with 

control 

120 Control adds rigor. Regression toward mean. 

1.3.3 Before-after-before study More convincing causal 

effect. 

Regression toward mean. 

1.3.4 Regression model Directly account for multiple 

factors. 

Large amounts of data on many 

variables. 

1.3.5 Empirical Bayes Control for regression toward 

mean. 

More complicated statistical 

model. 

1.3.6 Full Bayes More complete treatment of 

conditional probabilities. 

Not widely used. 

2.0 Crashes: Laboratory 

2.1 Driving simulator 

2.1.1 Participant: selected, 

sampled 

70 Know participant sample. Possible sampling bias. 

2.1.2 Experimenter: remotely 

present, unobtrusive 

observation 

70 More experimenter control. Possible artificial participant 

behaviors. 

2.1.3 Stimuli: simulated, 

artificial; consistent, controlled 

70 Extremely repeatable 

stimulus conditions. 

Artificial stimuli; hard to 

simulate conspicuity and 

legibility. 

 
55 

Method Ref. # Advantages Disadvantages 

2.1.4 Responses: programmed 

crashes; antecedent participant 

and vehicle behaviors; can be 

more frequent crashes 

70 Some control over crashes; 

can program more frequent 

crash opportunities. 

Lack of negative consequences 

can unnaturally alter frequency 

of crashes. 

2.1.5 Scenario: contrived route, 

artificial; unnatural vehicle and 

environment; safe from harm 

70 Control over driving 

scenario; participant safe 

from harm. 

Unnatural vehicle and 

environment; artificial scenario; 

simulator sickness. 

2.2 Non-simulator laboratory 87 

2.2.1 Crash scenarios: movies, 

pictures, acting out 

 Relatively easy; less 

resources. 

Artificial, out-of-context testing 

environment. 

2.2.2 Crash reconstructions: 

questionnaires, focus groups 

 Relatively easy; focus groups 

more expensive. 

Artificial, out-of-context testing 

environment; focus group social 

biases. 

3.0 Safety Surrogate: Field 34, 85 

3.1 Unobtrusive observation 

3.1.1 Participant: random, 

uncontrolled; usually unknown 

15 No sampling bias. Do not know participant sample.

3.1.2 Experimenter: usually 

absent; remote observation; 

unknown to participant 

15 No artificial participant 

behaviors due to 

experimenter. 

3.1.3 Stimuli: natural, ordinary, 

in context; variable, 

uncontrolled 

15 Natural stimuli. Stimuli not uniform; e.g., 

weather effects. 

3.1.4 Responses: crash 

precursors; antecedent vehicle 

behaviors; more frequent; few 

participant variables 

15 More frequent events than 

crashes; can collect more 

data with less risk. 

Crash precursors only indirect 

indicators; insensitive to 

participant variables. 

3.1.5 Scenario: natural route 

and trip purpose; uses own 

vehicle 

15 Completely natural 

experimental context; uses 

own vehicle. 

3.2 Naturalistic driving 

 
56 

Method Ref. # Advantages Disadvantages 

3.2.1 Participant: selected, 

sampled 

79, 78, 

42 

Know participant sample. Possible sampling bias. 

3.2.2 Experimenter: absent; 

remote observation; known to 

participant 

79, 78, 

42 

Possible artificial participant 

behaviors. 

3.2.3 Stimuli: natural, ordinary, 

in context; variable, 

uncontrolled 

79, 78, 

42 

Natural stimuli. Stimuli not uniform; e.g., 

weather effects. 

3.2.4 Responses: crash 

precursors; antecedent vehicle 

and participant behaviors; more 

frequent events 

79, 78, 

42 

More frequent events than 

crashes; can collect more 

data with less risk. 

Crash precursors only indirect 

indicators. 

3.2.5 Scenario: natural route 

and trip purpose; uses own 

vehicle 

79, 78, 

118, 42 

Mostly natural experimental 

context; uses own or longterm borrowed vehicle. 

Participant aware of test status; 

may be injured or killed; vehicle 

may be damaged or destroyed; 

expensive. 

3.3 On-road instrumented 

vehicle 

14 

3.3.1 Participant: selected, 

sampled 

54, 18 Know participant sample. Possible sampling bias. 

3.3.2 Experimenter: present; 

direct observation and 

interaction 

83 More experimenter control; 

increased experiment safety. 

Possible artificial participant 

behaviors. 

3.3.3 Stimuli: selected; natural, 

in context 

83, 18 Natural stimuli. Stimuli not uniform; e.g., 

weather effects. 

3.3.4 Responses: crash 

precursors; antecedent vehicle 

and participant behaviors; more 

frequent 

54, 18 More frequent events than 

crashes; can collect more 

data with less risk. 

Crash precursors only indirect 

indicators. 

3.3.5 Scenario: natural route, 

artificial trip purpose; uses 

experimental vehicle 

54, 83, 

18 

Semi-natural experimental 

context; more safe. 

Artificial trip purpose; 

unfamiliar vehicle. 

3.4 Closed-course test track 
57 

Method Ref. # Advantages Disadvantages 

3.4.1 Participant: selected, 

sampled 

136 Know participant sample. Possible sampling bias. 

3.4.2 Experimenter: present; 

direct observation and 

interaction 

136 More experimenter control; 

increased experiment safety. 

Possible artificial participant 

behaviors. 

3.4.3 Stimuli: selected; out of 

context 

136 Semi-natural stimuli. Stimuli not uniform; some 

possible control. 

3.4.4 Responses: crash 

precursors; antecedent vehicle 

and participant behaviors; more 

frequent 

136 More frequent events than 

crashes; can collect more 

data with less risk. 

Crash precursors only indirect 

indicators. 

3.4.5 Scenario: unnatural route, 

artificial trip purpose; uses 

experimental vehicle 

136 Low probability of harm to 

participant or vehicle. 

Unnatural experimental context. 

3.5 Commentary driving 

3.5.1 Participant: selected, 

sampled 

36 Know participant sample. Possible sampling bias. 

3.5.2 Experimenter: present; 

direct observation; extensive 

interaction 

36 More experimenter control; 

increased experiment safety. 

Possible artificial participant 

behaviors. 

3.5.3 Stimuli: selected; natural, 

in context 

36 Natural stimuli. Stimuli not uniform; e.g., 

weather effects. 

3.5.4 Responses: extensive 

driver commentary; running 

verbal description; crash 

precursors observable 

 Collect large amounts of 

data; direct observation of 

gross attention. 

Commentary could interfere 

with driving task; artificial task. 

3.5.5 Scenario: natural route, 

artificial trip purpose 

 Semi-natural experimental 

context; more safe. 

Artificial trip purpose. 

3.6 Non-vehicle based field 

testing 

 

3.6.1 Roadside interviews 14, 

125, 85 

Relatively easy; less 

resources. 

Artificial, distal testing 

environment. 
58 

Method Ref. # Advantages Disadvantages 

3.6.2 Fuel station, nearby mall 

interviews 

 Relatively easy; less 

resources. 

Artificial, out-of-context testing 

environment. 

4.0 Safety Surrogate: 

Laboratory 

36 

4.1 Driving simulator 

4.1.1 Participant: selected, 

sampled 

161, 4, 

70, 82 

Know participant sample. Possible sampling bias. 

4.1.2 Experimenter: remotely 

present, unobtrusive 

observation 

161, 4, 

70, 82 

More experimenter control. Possible artificial participant 

behaviors. 

4.1.3 Stimuli: simulated, 

artificial; consistent, controlled 

161, 4, 

70, 82 

Extremely repeatable 

stimulus conditions. 

Artificial stimuli; hard to 

simulate conspicuity and 

legibility. 

4.1.4 Responses: programmed 

crash precursors; antecedent 

participant and vehicle 

behaviors; can have more 

frequent events 

10, 82, 

4 

Some control over nearcrashes; can program more 

frequent near-crash 

opportunities. 

Lack of negative consequences 

can unnaturally alter frequency 

of near-crashes. 

4.1.5 Scenario: contrived route, 

artificial; unnatural vehicle and 

environment; safe from harm 

161, 4, 

70, 82 

Control over driving 

scenario; participant safe 

from harm. 

Unnatural vehicle and 

environment; artificial scenario; 

simulator sickness. 

4.2 Non-simulator laboratory 75 

4.2.1 Pre-crash scenarios: 

movies, pictures, acting out 

160, 36 Relatively easy; less 

resources. 

Artificial, out-of-context testing 

environment; weak response 

measure. 

4.2.2 Pre-crash reconstructions: 

questionnaires, focus groups 

36 Relatively easy; focus groups 

more expensive. 

Artificial, out-of-context testing 

environment; weak response 

measure; focus group social 

biases. 

5.0 Social Survey 14, 125 

5.1 Telephone survey Less resources; personal 

interviewer; more flexible. 

Out of context; opinions only; 

more labor intensive; smaller 

scale. 
59 

Method Ref. # Advantages Disadvantages 

5.2 Mail survey Less resources; standardized; 

larger scale. 

Out of context; opinions only. 

5.3 E-mail survey Less resources; standardized; 

large scale. 

Out of context; opinions only; 

internet user bias. 

6.0 Analytical Study 

6.1 Literature review 53, 38, 

26, 

129, 52 

Benefit from previous 

knowledge and mistakes. 

Based on old information; 

abstract; hard to apply. 

6.2 Review of practice 15, 44 Socially oriented, practical, 

legal. 

Based on old information; not 

scientific; possibly misleading. 

6.3 Deductive-inductive 

reasoning study 

26 Less resources; no need for 

new data. 

Must often make dangerous 

assumptions; cannot fill in 

knowledge gaps. 

61 

APPENDIX B—DETAILED DESCRIPTION OF STUDIES 

B.1 ON-ROAD INSTRUMENTED VEHICLE APPROACH 

The most effective research strategy to emerge from the analysis undertaken in section 6.0 is the 

on-road instrumented vehicle method. The following describes one possible study which might 

be conducted using this method. 

B.1.1 Method 

The on-road instrumented vehicle method employs an instrumented vehicle which is brought to 

the study site, along with a crew of about two or three researchers. The study site is a location 

where there is at least one CEVMS installation along a public access roadway. Preferably, there 

would be several CEVMS installations at the location so that a single test driving scenario might 

pass a few different CEVMS in the course of about half an hour of driving. The investigation 

should include at least two or three study sites which already have CEVMS in place. At each 

study site, approximately 20 to 30 research participants would be recruited from the local area. 

Each research participant would drive the instrumented vehicle along a prescribed route, which 

includes CEVMS installations, standard (non-digital) billboards, human-constructed objects of 

casual visual interest (houses, barns, etc.), and natural background control scenery (trees, fields, 

etc.). Each drive takes less than 1 hour (preferably about 30 minutes), and each participant would 

return for several drives on different days. Other aspects would vary as well, such as the time of 

day, traffic density, and CEVMS conditions (e.g., CEVMS turned on versus CEVMS turned off). 

Each participant would complete between three and six such drives. The instrumented vehicle 

and crew would usually remain at a given study site for about 1 to 2 months. The crew would 

consist of an experimenter and a safety observer, who would both be present in the instrumented 

vehicle. The safety observer would also serve as a research assistant or technician. The 

instrumented vehicle is capable of measuring vehicle speed, vehicle lane position, longitudinal 

acceleration, lateral acceleration, GPS time and position, and driver eye glance direction and 

duration. The instrumented vehicle is also equipped with accurate vehicle-mounted or headmounted eye-tracking equipment, video cameras (forward and cab views) and a voice recorder. 

B.1.2 Factors and Measures 

The major factors or independent variables in the study are the presence or absence of CEVMS 

and other comparison visual stimuli (standard billboards, buildings, etc.) along the driving path. 

If possible, the CEVMS should be capable of being turned off and on or changed along some 

other dimension like luminance or change rate, according to a prearranged experimental design. 

The period of time that the CEVMS is off or changed could be kept relatively brief and carefully 

controlled since the study will follow a strict protocol. Other important independent variables are 

the time of day (day/night), traffic conditions (peak and nonpeak), and driver variables (age, 

gender, and route familiarity). One or more of the primary CEVMS variables of interest to the 

community concerned with outdoor advertising control should be represented by varying levels 

along the driving route (e.g., different degrees of luminance, change rate, or display spacing) as 

much as possible. Direct experimental control would be preferable to site selection in this regard. 
62 

The primary measure or dependent variable in this study is the frequency, direction, and duration 

of driver eye glances, which serves as an indication of visual attention and distraction. The 

fundamental hypothesis is that drivers have limited attention; they self-regulate their attention to 

perform demanding tasks. In the case of the driving task, a certain proportion of their attention 

needs to be concentrated on the roadway scene ahead. To the degree that eye glance behavior can 

serve as a measure of visual attention, eye glances need to be concentrated on the roadway 

ahead. If the frequency and duration of eye glances away from the roadway ahead exceed 

accepted norms or criteria for keeping a driver’s eyes on the road, then driver safety may be 

compromised. Thus, eye glance behavior is the primary dependent variable in the study. Eye 

glance behavior has an intuitive connection to visual attention and is sensitive to subtle visual 

search strategies, including those which are below the level of conscious awareness (see 

section 2.7.2). Depending upon the type of eye glance measuring instrumentation selected, the 

act of measuring eye glance behavior may prove to be a more or less significant distraction to the 

driver in itself. This experimentally-induced artifact can be controlled by selecting a minimally 

intrusive measurement method or by ensuring adequate adaptation to the instrumentation on the 

part of the research participant. 

This study includes another class of secondary dependent variables. These are safety surrogate 

measures associated with driver errors and other measures of driver performance, such as speed 

changes, headway, lane deviation, and traffic conflicts. These secondary variables can be 

measured by instrumentation in the vehicle in terms of speed, acceleration, and lane position. 

These secondary variables can also be directly observed and noted by the experimenter and/or 

safety observer in the instrumented vehicle for later analysis in terms of sudden braking, 

inadequate headway, swerving, and conflicts. Thus, events indicative of possible driver error or 

other maladaptive behavior can be flagged by human observers. Also, for these events, only 

objective vehicle performance data needs to be analyzed, saving considerable effort and expense 

by eliminating the need to analyze large amounts of continuous vehicle performance data. 

B.1.3 Advantages/Disadvantages 

One advantage of this method is its ability to implement accurate eye-tracking measurements 

which afford the opportunity to observe subtle and often unconscious eye movements. This 

ability to measure unconscious eye movements correlates with unconscious distraction facilitates 

incorporation of the notion of self-regulated attention into the experimental paradigm. When a 

driver is attempting to concentrate on the roadway ahead, a distractor, which unconsciously 

diverts attention away from the roadway against the driver’s will, may have a more severe safety 

consequence than a distractor which can be maintained under conscious and voluntary control. 

Thus, in addition to being able to measure distraction which is both conscious and voluntary, 

accurate eye-tracking determinations have the potential to probe other phenomena, such as 

unconscious and involuntary distraction as they relate to CEVMS exposure. 

Another advantage of this method is the ability to structure driving scenarios to have an 

appropriate number of CEVMS, standard billboard, and other visual stimuli all located on a 

controlled course, which all research participants drive in a consistent manner. The ability to 

choose and structure the test drive assures adequate and uniform exposure to CEVMS and other 

relevant visual stimuli. The ability to exert experimental control is a valuable asset to this 

method. It facilitates a clean and robust statistical analysis of the data because all of the 
63 

participants are exposed to all of the experimental conditions the same number of times in a 

relatively controlled manner. Experimental control ensures a high level of CEVMS exposure, 

thereby contributing to the productivity and cost effectiveness of this technique. 

However, examined from a different perspective, such a degree of experimental control may also 

be regarded as a disadvantage. A certain amount of artificiality is introduced into the driving 

situation thereby. Research participants are definitely aware that they are participating in a 

controlled experiment, driving someone else’s car on a contrived route which does not serve a 

personal purpose related to daily life. In addition, with the experimenter riding along with the 

participants in the vehicle, there may be a tendency for the participants to try to please the 

experimenter and to drive in some unnatural way. The introduction of eye-tracking equipment 

adds to the artificiality of the situation. Wearing head-mounted eye-tracking gear definitely 

represents unnatural driving attire. However, most research participants rapidly adapt to the gear 

with time, and they often report that they are unaware of its presence after a short drive. Vehiclemounted eye-tracking equipment can be far less intrusive, although the tedious calibration 

procedures and the presence of the cameras in the car remind participants that their head and eye 

movements are constantly being monitored. These are all valid experimental concerns; however, 

none of these interventions is likely to profoundly alter the driving behavior, much less the eye 

glance movements, of the research participants, as long as they are not informed of the purpose 

of the study. The enhanced experimental efficiency that this approach has to offer far outweighs 

its artificiality drawbacks. 

B.1.4 Budgetary Cost 

A rough budgetary estimate for conducting such an on-road instrumented vehicle study is 

between $400,000 and $800,000. The main cost drivers for this method are the eye glance 

measuring technology and the crew needed to implement the experiment at the study sites. The 

range in this estimate relates to the number of study sites, adequacy of the sites, length of the 

experimental drive, number of experimental drives, number of research participants, difficulty in 

obtaining research participants, ability to turn the CEVMS off and on, and numerous other 

factors which cannot be determined without further planning. 

B.2 NATURALISTIC DRIVING APPROACH 

The naturalistic driving method is similar to the on-road instrumented vehicle method. The major 

difference is that the participants drive their own vehicles (or loaned vehicles) for their own 

personal purposes. The method typically employs a large number of such vehicles. The 

following describes one possible study which might be conducted using this method. 

B.2.1 Method 

The naturalistic driving method employs a standardized instrument package which is installed in 

the participant’s own private vehicle or in a vehicle loaned to the participant. The installation is 

made as unobtrusive as possible so that the participant’s vehicle appears and performs as it 

normally would. The instrument package is capable of measuring many of the same variables as 

the on-road instrumented vehicle, such as speed, lane position, acceleration, GPS time and 

position, driver eye glance frequency, direction, and duration. The instrument package is also 
64 

connected to the vehicle data bus so that additional vehicle-related measures of engine, braking, 

and steering performance are also recorded. However, because of the unobtrusive nature of the 

experimental technique, this method cannot support the use of extremely accurate head-mounted 

or vehicle-mounted eye-tracking equipment. In the present state of technology, these accurate 

eye movement instruments involve careful calibration procedures with the driver. With this 

method, the eye-tracking system is mounted in the dashboard in a manner which involves little or 

no driver interaction. Once the participant’s vehicle has been instrumented, data are collected by 

means of automatic wireless downloads without participant awareness or involvement. The 

instrumentation is left in the vehicle for a period of 3 to 6 months, during which time the 

participant drives the vehicle for normal personal or business use. 

The fact that participants drive their own vehicles for their own use reduces control and adds 

uncertainty to the study. It is difficult to control where the participants are going to drive and 

when. The study site must be selected carefully so that participants are likely to drive by at least 

some of the target CEVMS installations. The participants must be selected carefully so that they 

are likely to take the selected roadway with some reasonable frequency. As a result of this 

increased uncertainty, the number of study sites must be increased to 4 and 5, the number of 

research participants selected at each site must be increased to 50 and 75, and the duration of 

measurement for each participant must be increased to 3 and 6. In this study, it is even more 

important that there are several CEVMS installations at each study site. As was the case for the 

on-road instrumented vehicle study, each study site needs to include CEVMS installations, 

standard (non-digital) billboards, objects of casual visual interest (houses, barns, etc.), and 

natural background control scenery (trees, fields, etc.). 

B.2.2 Factors and Measures 

As with the on-road instrumented vehicle study, the major factors or independent variables are 

the presence or absence of CEVMS and other comparison visual stimuli (standard billboards, 

buildings, control settings, etc.) along the driven path. If possible, the CEVMS should be turned 

off and on or changed in some other way, according to a prearranged experimental design. 

However, in this instance, the CEVMS would have to be turned off or changed for longer periods 

of time because it is not certain when the instrumented test vehicles might pass. These are the 

primary independent variables. Secondary independent variables could include the type of 

vehicle (sedan, pickup, or SUV) and driver characteristics (age, gender, and route familiarity). 

In addition, as much as possible, one or more of the primary CEVMS variables of interest to the 

community concerned with outdoor advertising control should be represented by varying levels 

in the selection of CEVMS stimuli. 

As in the on-road instrumented vehicle study, the primary measure or dependent variable is the 

frequency, direction, and duration of driver eye glances. The fundamental hypothesis of selfregulated attention which needs to be concentrated on the roadway scene ahead remains the 

same. As before, if the frequency and duration of eye glances away from the roadway ahead 

exceed accepted norms or criteria, then driver safety is assumed be compromised. Thus, eye 

glance behavior is the primary dependent variable in this study, as well. However, the particular 

unobtrusive and disengaged dashboard-mounted eye-tracking device may not be capable of 

making as accurate measurements of eye-movements as can other more delicate vehicle-mounted 

or head-mounted devices which require periodic participant calibration. Consequently, this study 
65 

method depends more heavily on secondary dependent variables. Safety surrogate measures 

associated with driver errors and other measures of driver performance (headway, lane deviation, 

conflicts, and erratic maneuvers) become increasingly important in this method. Since the 

participants will be driving according to their own personal schedules, additional dependent 

variables may include the time of day (day/night), traffic conditions (peak and nonpeak), invehicle distractions (eating and/or cell phone use), and state of fatigue. 

B.2.3 Advantages/Disadvantages 

The naturalistic driving method possesses one major advantage over the on-road instrumented 

vehicle method: the driving scenario, driving task, and driving purpose are all completely 

natural. The research participants drive their own vehicles (or ones loaned to them) on their own 

personal schedules along personally selected routes to meaningful destinations. Although to a 

lesser degree, the naturalistic driving method shares another advantage with the on-road 

instrumented vehicle method: its ability to implement eye-tracking measurements. In fact, the 

dashboard-mounted eye-tracking device is far less intrusive to the driver than the head-mounted 

eye-tracking device sometimes employed in the on-road instrumented vehicle method. 

Unfortunately, some dashboard-mounted eye-tracking devices may not be as sensitive and 

accurate as a head-mounted device. Also, they may not be able to track extensive head 

movements or measure subtle eye glances indicative of unconscious distraction. The useful field 

of view can also be an issue with certain unobtrusive vehicle-mounted eye-tracking equipment. 

Consequently, this experimental method may be less effective in its ability to probe the subtle 

phenomena of unconscious and involuntary distraction as they relate to CEVMS exposure. 

Another disadvantage of this method is its inherent lack of structured driving scenarios. Since 

participants drive whenever and wherever they want, it is difficult to ensure adequate and 

uniform exposure to CEVMS and other relevant visual stimuli. This lack of experimental control 

and higher degree of uncertainty necessitate an increase in the number of study sites, research 

participants, and duration of the study, which negatively impacts the productivity and cost 

effectiveness of the technique. For example, this method typically requires the instrumentation of 

a relatively large number of vehicles at any given study site instead of the instrumentation of just 

one vehicle which is shared by many research participants. Another minor disadvantage is that 

research participants are aware that they are participating in an experiment, even if the study is 

minimally intrusive in terms of daily life routine. 

B.2.4 Budgetary Cost 

A rough budgetary estimate for conducting such a naturalistic driving study is between 

$2 million and $4 million. The main cost drivers for this method include increasing the number 

of study sites, installing instruments in a large number of vehicles at a single site, and collecting 

and analyzing data covering a long period of time. The range in this budgetary estimate relates to 

the number of study sites, adequacy of the sites, number of vehicles which need to be 

instrumented at one time, number of research participants, difficulty in obtaining research 

participants, driving patterns of the research participants, length of the study at any given site, 

ability to turn the CEVMS off and on, and numerous other factors which cannot be determined 

without further planning. 
66 

B.3 UNOBTRUSIVE OBSERVATION APPROACH 

The unobtrusive observation method is different from the on-road instrumented vehicle 

method and the naturalistic driving method. The major distinction is that no study participants 

are selected, and all data are obtained from the natural flow of traffic past the CEVMS and 

other comparison stimuli. The following describes one possible study which might be 

conducted using this method. 

B.3.1 Method 

The unobtrusive observation method employs an array of static cameras or other sensors 

mounted near the locations of the CEVMS and other comparison stimuli. The other sensors may 

include loops, tubes, or radar to measure vehicle passes and driving parameters. The present 

report will focus on video recording of traffic. The cameras are capable of recording the behavior 

of vehicles passing the various relevant visual stimuli as a part of the natural flow of traffic. The 

drivers are usually completely unaware that their vehicles are being observed. Post-hoc analysis 

of the video recordings from these cameras can yield data similar to some of that obtained by the 

on-road instrumented vehicle and naturalistic driving methods, which include vehicle speed, lane 

position, acceleration, and time. However, the data from distal video cameras are usually far less 

accurate than what can be collected by instruments onboard the vehicle. Moreover, with present 

measurement technology, such video recordings cannot yield any data concerning driver eye 

glance frequency, direction, and duration. The camera arrays are usually left in place for a period 

of several months to 1 year at each study site. There would typically be three to four such sites in 

the study. At each study site, separate camera arrays would need to be installed at the locations 

of all selected CEVMS displays, standard (non-digital) billboards, objects of casual visual 

interest (houses, barns, etc.), and natural background control scenery (trees, fields, etc.). 

B.3.2 Factors and Measures 

As in the on-road instrumented vehicle and naturalist driving studies, the major independent 

variables are the presence or absence of CEVMS and other comparison visual stimuli (standard 

billboards, buildings, etc.) along the driving path. If possible, the CEVMS should be controlled 

according to a prearranged experimental protocol. However, in this instance, the CEVMS 

would have to be changed for longer durations because it is possible to predict when vehicles 

might pass. In addition, one or more of the primary CEVMS variables of interest to the 

community concerned with outdoor advertising control should be represented by varying levels 

in the selection of CEVMS stimuli. These constitute the primary independent variables. Since 

continuous video recording will be employed, the experimenter can decide to select different 

times of data collection for further analysis. This capability can provide insight into some 

secondary independent variables such as time of day (day/night) and traffic conditions 

(peak, nonpeak). 

In contrast to the on-road instrumented vehicle and naturalistic driving studies, the primary 

dependent variable is not driver eye glance behavior. Instead, this study method depends 

completely on safety surrogate measures associated with driver errors and other measures of 

driver performance (headway, lane deviation, and erratic maneuvers). These are subtle driving 

behaviors to measure by means of distal cameras mounted along the roadway. Unless the 
67 

cameras are mounted very high, multiple vehicle images may occlude each other. For a long 

stretch of roadway, such as might required for CEVMS exposure, a relatively large array of 

cameras may be needed. Thus, a large amount of data needs to be collected and analyzed in such 

a study. Automatic machine vision video analysis algorithms can help in the data analysis 

process, but such algorithms are not yet sufficiently sensitive and robust to reliably identify all of 

the subtle indicators of driver errors, conflicts, or maladaptive performance which might 

accompany CEVMS exposure. The use of other sensors instead of or in addition to cameras may 

mitigate some of these data analysis problems to a certain extent. 

 B.3.3 Advantages/Disadvantages 

The unobtrusive observation method possesses one major advantage over the other two methods: 

the data are derived from the natural flow of traffic. Other than erecting camouflaged camera 

arrays at various locations along the roadway, the experimenter does not disturb the natural flow 

of human driving. As opposed to the other two methods, the vast majority of drivers are 

completely unaware that they are part of a study depending on how well the camera camouflage 

works. Other sensors used for this application can also be hidden and made extremely hard to 

detect. This is the major advantage of the unobtrusive observation method. Another strong 

advantage is the large number of vehicles which pass by the CEVMS and other comparison 

stimuli every day. Sample sizes can be relatively large. 

Like the other techniques, the unobtrusive observation method has disadvantages as well. First, 

with present technology, it is not possible to implement eye-tracking measurements in such a 

study. The inability to measure eye glance behavior makes it difficult to investigate important 

constructs, like self-regulated attention and unconscious distraction as they relate to CEVMS 

exposure. The method is left to rely on safety surrogate measures, such as driver errors and 

maladaptive maneuvers. These relatively subtle pre-crash and near-crash driving behaviors are 

difficult to measure by means of distal video cameras. Such driving behaviors also occur very 

seldom and need to be observed over great distances, leading to the necessity to collect large 

amounts of video data from extended camera arrays over long periods of time. The collection, 

reduction and analysis of such large amounts of data tend to make this method time-consuming 

and expensive. 

B.3.4 Budgetary Cost 

A rough budgetary estimate for conducting such an unobtrusive observation study is between 

$1 million and $3 million. The main cost drivers for this method include designing camera arrays 

which can measure subtle vehicle maneuvers, installing camera arrays to record a large extent of 

roadway for all CEVMS and comparison stimuli, and collecting and analyzing data covering a 

long period of time. The range in this budgetary estimate relates to the number of study sites, 

adequacy of the sites, number and location of cameras in an array, method of recognizing safety 

surrogate measures, length of the study at any given site, ability to turn the CEVMS off and on, 

and numerous other factors which cannot be determined without further planning.

69 

ACKNOWLEDGEMENTS 

The present project benefited from the contributions of many people. Vaughan Inman, Stephen 

Fleger, Jason Kennedy, and Erin Dagnall provided valuable research, editorial, and technical 

input. From FHWA Research and Development, Paul Tremont made significant technical and 

editorial suggestions. From the FHWA Office of Real Estate Services, Catherine O’Hara, Janis 

Gramatins, Edward Kosola, and Gerald Solomon provided essential stewardship and guidance 

for the overall effort. Members of the Transportation Research Board (TRB) Subcommittee on 

Digital Signage graciously provided outside technical review. Members of the National Alliance 

of Highway Beautification Agencies (NAHBA) furnished helpful background, context, and 

perspective for the project. Appreciated contributions came from representatives of the outdoor 

advertising industry, including the Outdoor Advertising Association of America, Inc.; 

representatives of environmental advocacy groups, including Scenic America; and from various 

State and local officials engaged in outdoor advertising control. Inputs from the broad 

community interested in outdoor advertising control, including industry, environmental 

advocates, and regulators, were especially helpful in ensuring that the present research effort 

was directed at serving the needs of the user community for such research. The authors are 

grateful to these and many other unmentioned individuals and organizations who directly 

or indirectly provided support.

71 

REFERENCES 

1. Farbry, J., Wochinger, K., Shafer, T., Owens, N, and Nedzesky, A. (2001). “Research 

Review of Potential Safety Effects of Electronic Billboards on Driver Attention and 

Distraction (Final Report).” Federal Highway Administration. Washington, DC. 

2. Wachtel, J. and Netherton, R. (1980). “Safety and Environmental Design Considerations 

in the Use of Commercial Electronic Variable-Message Signage.” Report No. FHWARD-80-051. Federal Highway Administration. Washington, DC. 

3. Massachusetts Outdoor Advertising Board. (1976). “Decision in the matter of John 

Donnelly & Sons, Permittee, Telespot of New England, Inc., Intervenor, and Department 

of Public Works, Intervenor, with respect to permit numbered 19260, as amended.” 

Boston, MA. 

4. Wisconsin Department of Transportation District 2, Freeway Operations Unit. (1994). 

“Milwaukee County Stadium Variable Message Sign Study: Impacts of an Advertising 

Variable Message Sign on Freeway Traffic.” 

5. Stutts, J.C., Reinfurt, D.W., Staplin, L., and Rodgman, E.A. (2001). “The Role of Driver 

Distraction in Traffic Crashes.” Report Prepared for AAA Foundation for Traffic Safety. 

Washington, DC. 

6. Goodman, M., Bents, F.D., Tijerina, L., Wierwille, W., Learner, N., and Benel, D. 

(1997). “An Investigation of the Safety Implications of Wireless Communications in 

Vehicles.” Report DOT HS 808-635. National Highway Traffic Safety Administration. 

Washington, DC. 

7. Smiley, A., Persaud, B., Bahar, G., Mollett, C., Lyon, C., Smahel, T., and Kelman, W.L. 

(2005). “Traffic Safety Evaluation of Video Advertising Signs.” TRB, No. 1937. 

Transportation Research Record. Journal of the Transportation Research Board, 

105–112. Washington, DC. 

8. Tantala Sr., A.M. and Tantala, M.W. (2007). “A Study of the Relationship Between 

Digital Billboards and Traffic Safety in Cuyahoga County Ohio.” Foundation for Outdoor 

Advertising Research and Education. Washington, DC. 

9. Wachtel, J. (2008). “A Critical, Comprehensive Review of Two Studies Recently 

Released by the Outdoor Advertising Association of America—Final Report.” Maryland 

State Highway Administration, Project No. AX137A51. Hanover, MD. Obtained from 

http://www.sha.state.md.us/UpdatesForPropertyOwners/oots/outdoorSigns/FINALREPO

RT10-18-GJA-JW.pdf. Accessed September 27, 2008. 

10. Klauer, S.G., Neale, V.L., Dingus, T.A., Ramsey, D., and Sudweeks, J. (2005). “Driver 

Inattention: A Contributing Factor to Crashes and Near-Crashes.” Proceedings of the 

Human Factors and Ergonomics Society 49th Annual Meeting. Human Factors and 

Ergonomics Society. 1922–1926. Santa Monica, CA. 
72 

11. Klauer, S.G., Dingus, T.A., Neale, V.L., Sudweeks, J.D., and Ramsey, D.J. (2006). “The 

Impact of Driver Inattention on Near-Crash/Crash Risk: An Analysis Using the 100-Car 

Naturalistic Driving Study Data.” Report DOT HS 810 594. National Highway Traffic 

Safety Administration. Washington, DC. 

12. Lee, S.E., McElheny, M.J., and Gibbons, R. (2007). “Driving Performance and Digital 

Billboards.” Report prepared for Foundation for Outdoor Advertising Research and 

Education. Virginia Tech Transportation Institute. Blacksburg, VA. 

13. Dingus, T.A., Klauer, S.G., Neale, V.L., Petersen, A., Lee, S.E., Sudweeks, J., et al. 

(2006). “The 100-Car Naturalistic Driving Study: Phase II—Results of the 100-Car Field 

Experiment.” Report No. DOT HS 810 593. National Highway Traffic Safety 

Administration. Washington, DC. 

14. Beijer, D.D., Smiley, A., and Eizenman, M. (2004). “Observed Driver Glance Behavior 

at Roadside Advertising.” Transportation Research Record, No. 1899. 96–103. 

15. Beijer, D.D. (2002). “Driver Distraction due to Roadside Advertising.” Department of 

Mechanical and Industrial Engineering. University of Toronto. 

16. Young, E. (1984). “Visibility Achieved by Outdoor Advertising.” Journal of Advertising 

Research, 24, 19–21. 

17. Crundall, D., Van Loon, E., and Underwood, G. (2006). “Attraction and Distraction of 

Attention With Roadside Advertisements.” Accident Analysis and Prevention, 38(4), 

671–677. 

18. Young, M.S. and Mahfoud, J.M. (2007). “Driven to Distraction: Determining the Effects 

of Roadside Advertising on Driver Attention.” Final Report of a Study Funded by The 

Rees Jeffreys Road Fund. West London: Brunel University. 

19. Chan, E., Pradhan, A.K., Knodler, M.A., Pollatsek, A., and Fisher, D.L. (2008). 

“Evaluation on a Driving Simulator of the Effect of Drivers’ Eye Behaviors from 

Distractions Inside and Outside the Vehicle.” Human Factors. 

20. Horrey, W.J. and Wickens, C.D. (2007). “In-Vehicle Glance Duration: Distributions, 

Tails and a Model of Crash Risk.” Proceedings of the 2007 Transportation Research 

Board Meeting. Washington, DC. TRB. http://hmil.cs.drexel.edu/papers/CSC02.pdf. 

21. Garvey, P.M. and Mace, D.J. (1996). “Changeable Message Sign Visibility.” Report No. 

FHWA-RD-94-077. Federal Highway Administration. Washington, DC. 

22. Cairney, P. and Gunatillake, T. (2000). Roadside Advertising Signs—A Review of the 

Literature and Recommendations for Policy. Contract Report for RACV (Royal 

Automobile Club of Victoria). 

23. Andreassen, D.C. (1984). “Traffic Accidents and Advertising Signs.” Australian Road 

Research Board Internal Report AIR 000-213. 
73 

24. Wallace, B. (2003). “External-to-Vehicle Driver Distraction.” Research Findings 

No.168/2003. Scottish Executive Social Research. Development Department Research 

Programme. 

25. SWOV (Dutch National Road Safety Research Institute). (2006). “Advertising and 

Information Alongside the Road.” Fact Sheet. Leidschendam, The Netherlands. 

26. CTC & Associates. (2003). “Electronic Billboards and Highway Safety.” Transportation 

Synthesis Report. Bureau of Highway Operations. Division of Transportation 

Infrastructure Development. Wisconsin Department of Transportation. 

27. Bergeron, J. (1996a). “An Evaluation of the Influence of Roadside Advertising on Road 

Safety.” Document prepared for the Ministere des Transports, Government of Quebec. 

28. Bergeron, J. (1996b). “Road Safety Survey Regarding the Effects of Billboards that 

Centre RCA SEC Has Proposed to Install In Proximity to the Ville-Marie Expressway.” 

Document prepared for the Ministere des Transports, Government of Quebec. 

29. du Toit, E.M. and Coetzee, J.L. (2001). “Advertising Boards On or Visible from National 

Roads.” 20th South African Transport Conference: Meeting the Transport Challenges in 

Southern Africa. 

30. Coetzee, J.L. (2003). “The Evaluation of Content on Outdoor Advertisements.” 

Innovative Traffic Solutions (Pty) Ltd. Pretoria, South Africa. 

31. Ogden, K.W. (1989). “Human Factors in Traffic Engineering.” Clayton, Victoria, 

Australia: Department of Civil Engineering. Monash University. 

32. Johnston, A.W. and Cole, B.L. (1976). “Investigation of Distraction by Relevant 

Information.” Australian Road Research, 6(3) 32–33. 

75 

BIBLIOGRAPHY 

1. Ady, R.W. (1967). “An Investigation of the Relationship between Illuminated 

Advertising Signs and Expressway Accidents.” Traffic Safety Research Review, 11(1), 

9–11. 

2. Akagi, Y., Seo, T., and Motoda, Y. (1996). “Influence of Visual Environments on 

Visibility of Traffic Signs.” National Academy Press. Transportation Research Record 

No. 1553. 52–58. Washington, DC. 

3. Allen, T.M., Smith, G.M., Janson, M.H., and Dyer, F.M. (1966). “Sign Brightness In 

Relation to Legibility.” Michigan State Highway Commission, Office of Testing and 

Research, Research Report R-581. Lansing, MI. 

4. Alm, H. and Nilsson, L. (1994). “Changes in Driver Behavior as a Function of Handsfree 

Mobile Phones—A Simulator Study.” Accident Analysis and Prevention, 26(4), 441–451. 

5. American Sign and Indicator Corporation. (1976). “Legal; Design and Economic 

Considerations: Electronic Information Displays.” Spokane, WA. 

6. Andreassen, D.C. (1984). “Traffic Accidents and Advertising Signs.” Australian Road 

Research Board Internal Report AIR, 000-213. 

7. Arkansas Highway Department. (1967). “Regulations for Control of Outdoor Advertising 

Policy.” Little Rock, Arkansas Highway Department. 

8. Association of Automobile Manufacturers. (2000). “Statement of Principles on Human 

Machine Interface (HMI) for In-Vehicle Information and Communication Systems.” 

(Draft.) 

9. Australian Road Research Board. “For Your Information: Advertising Signs and Road 

Safety.” Nunawading, Australia. 

10. Babbitt Kline, T.J., Ghali, L.M., and Kline, D.W. (1990). “Visibility Distance of 

Highway Signs Among Young, Middle-Aged and Older Observers: Icons Are Better 

Than Text.” Human Factors, 32(5) 609–619. 

11. Ball, K. and Owsely, C. (1993). “The Useful Field of View Test: A New Technique for 

Evaluating Age-Related Declines in Visual Function.” Journal of American Optometric 

Association, 64(1), 71–79. 

12. Barr, R.A. and Eberhard, J.W. (1991). “Special Issue Preface.” Human Factors, 33(5), 

497–498. 

13. Beijer, D.D. (2002). “Driver Distraction Due to Roadside Advertising.” University of 

Toronto, Department of Mechanical and Industrial Engineering. 
76 

14. Beijer, D.D., Smiley, A., and Eizenman, M. (2004). “Observed Driver Glance Behavior 

at Roadside Advertising.” Transportation Research Record, No. 1899. 96–103. 

15. Bergeron, J. (1996a). “An Evaluation of the Influence of Roadside Advertising on Road 

Safety.” Document Prepared for the Ministere des Transports, Government of Quebec. 

16. Bergeron J. (1996b). “Road Safety Survey Regarding the Effects of Billboards That 

Centre RCA SEC has Proposed to Install in Proximity to the Ville-Marie Expressway.” 

Document Prepared for the Ministere des Transports, Government of Quebec. 

17. Bhise, V.D. and Rockwell, T.H. (1972). “Development of a Driver-InformationAcquisition Based Operational Tool for the Evaluation of Highway Signs.” Presented to 

the 1973 Annual Meeting of the Highway Research Board, Washington, DC. 

18. Bhise, V.D. and Rockwell, T.H. (1973). “Development of a Methodology for Evaluating 

Road Signs.” Ohio University Experiment Station, Report No. 315B. Columbus, OH. 

19. Blanche, E.E. (1963). Written comments on Madigan-Hyland Report, included as Exhibit 

A in Congressional Record, May 9, 1963, 109, Part 6-House, 8173. 

20. Blanche, E.E. (1965). “The Roadside Distraction.” Traffic Safety, 65(11), 24–25, 

36–37. 

21. Blanche, E.E. “A Study of Accidents on the New Jersey Garden State Parkway.” 

22. Brody, L. (1963). Letter on Madigan-Hyland Report, included as Exhibit B in 

Congressional Record, May 9, 1963, 109, Part 6-House, 8173–8174. 

23. Brouwer, W.H., Waterink, W., van Wolffelaar, P.C., and Rothengatter, T. (1991). 

“Divided Attention in Experienced Young and Old Drivers: Lane Tracking and Visual 

Analysis in a Dynamic Driving Simulator.” Human Factors, 33(5), 573–582. 

24. Brown, I.D., Tickner, A.H., and Simmonds, D.C.V. (1969). “Interference between 

Concurrent Tasks of Driving and Telephoning.” Journal of Applied Psychology, 53(5), 

419–424. 

25. Cain, A. and Burris, M. (1999). “Investigations of the Use of Mobile Phones While 

Driving.” Center for Urban Transportation Research. University of South Florida. 

26. Cairney, P. and Gunatillake, T. (2000). “Roadside Advertising Signs—A Review of the 

Literature and Recommendations for Policy.” Contract Report for RACV (Royal 

Automobile Club of Victoria). 

27. Chan, E., Pradhan, A.K., Knodler, M.A., Pollatsek, A., and Fisher, D.L. (2008). 

“Evaluation on a Driving Simulator of the Effect of Drivers’ Eye Behaviors from 

Distractions inside and Outside the Vehicle.” Human Factors. 
77 

28. Claus, K.E. (1974). “Psychological Research and Government Control: The Case of 

Electronic Information Displays.” Claus Research Associates. Palo Alto, CA. 

29. Claus, K.E. and Claus, R.J. (1974). “Visual Communication Through Signage.” Signs of 

the Times Publishing Company, 1. Cincinnati, OH. 

30. Claus, R., Oliphant, R.M., and Claus, K. (1972). “Signs. Legal Rights and Aesthetic 

Considerations.” Signs of the Times Publishing Company. Cincinnati, OH. 

31. Claus, R.J. and Claus, K.E. (1971). “Visual Environment: Sight, Sign and By-Law.” The 

MacMillan Company. New York, NY. 

32. Coetzee, J.L. (2003). “The Evaluation of Content on Outdoor Advertisements.” 

Innovative Traffic Solutions (Pty) Ltd. Pretoria, South Africa. 

33. Colan, O.R. (1978). “Evaluation of National Standards for Directional and Official 

Signs.” Federal Highway Administration, Letter Progress Report, Contract FH-11-9372, 

March 1978. Washington, DC. 

34. Cole, G.L. and Hughes, P.K. (1984). “A Field Trial of Attention and Search 

Conspicuity.” Human Factors, 26(3), 299–313. 

35. Craford, M., Holonyak, N., and Kish Jr., F. (2001). “In Pursuit of the Ultimate Lamp.” 

Scientific American, 284, 62–67. 

36. Crundall, D., Van Loon, E., and Underwood, G. (2006). “Attraction and Distraction of 

Attention with Roadside Advertisements.” Accident Analysis and Prevention, 38(4), 

671–677. 

37. Crundall, D.E. and Underwood, G. (1998). “Effects of Experience and Processing 

Demands on Visual Information Acquisition in Drivers.” Ergonomics, 41(4), 448–458. 

38. CTC & Associates. (2003). “Electronic Billboards and Highway Safety.” Transportation 

Synthesis Report. Bureau of Highway Operations. Division of Transportation 

Infrastructure Development. Wisconsin Department of Transportation. 

39. Curriden, M. (2000). “Juries That Take Action Beyond the Law Have Deep Roots.” The 

Dallas Morning News. Obtained from 

http://www.dallasnews.com/juries/101414_jurytwo_ 25buss.html. Last accessed on: 

April 11, 2008. 

40. Decina, L.E., Gish, K.W., Staplin, L., and Kirchner, A.H. (1996). “Feasibility of New 

Simulation Technology to Train Novice Drivers.” Publication No. DTNH22-95-C05104. National Highway Traffic Safety Administration. Washington, DC. 

41. Decision in the matter of John Donnelly & Sons, Permitee, Telespot of New England, 

Inc., Intervenor, and Department of Public Works, Intervenor, with respect to permit 
78 

numbered 19260, as amended. (1976). Outdoor Advertising Board. January 13, 1976. 

Boston, MA. 

42. Dingus, T.A., Klauer, S.G., Neale, V.L., Petersen, A., Lee, S.E., Sudweeks, J., et al. 

(2006). “The 100-Car Naturalistic Driving Study: Phase II – Results of the 100-Car Field 

Experiment.” Report No. DOT HS 810 593. National Highway Traffic Safety 

Administration. Washington, DC. 

43. Dorsey, W. (1977) “Variable Message Signing for Traffic Surveillance and Control: A 

State of the Art Report.” U.S. Department of Transportation, Report No. RD-77-98. 

Washington, DC. 

44. du Toit, E.M. and Coetzee, J.L. (2001). “Advertising Boards on or Visible from National 

Roads.” 20th South African Transport Conference: Meeting the Transport Challenges in 

Southern Africa. 

45. Dudek, C.L. and Messer, C.J. (1971). “Study for Design Considerations for Real-Time 

Freeway Information Systems.” Highway Research Record No. 363, 1971, 1–17. 

46. Elwood, P.H. (1951). “Highway Accidents in Relation to Roadside Business and 

Advertising.” Highway Research Board Bulletin No. 30, 44–49. 

47. Farber, E., Blanco, M., Foley, J., Curry, R., Greenberg, J.A., and Serafin, C.P. (2000). 

“Surrogate Measures of Visual Demand While Driving.” Ford Motor Company-Scientific 

Research Laboratory. Dearborn, MI. 

48. Farbry, J., Wochinger, K., Shafer, T., Owens, N., and Nedzesky, A. (2001). “Research 

Review of Potential Safety Effects of Electronic Billboards on Driver Attention and 

Distraction (Final Report).” Federal Highway Administration. Washington, DC. 

49. Faustman, D.J. (1961). “A Study of the Relationship Between Advertising Signs and 

Traffic Accidents on U.S. 40 between Vallejo and Davis.” Roadside Council. Report 

CRC No. 165. San Francisco, CA. 

50. Federal Highway Administration (2000). “Manual on Uniform Traffic Control Devices 

(MUTCD).” Federal Highway Administration. Washington, DC. 

51. Forbes, T.W., Snyder, T., and Pain, R. (1965). “Traffic Sign Requirements I: Review of 

Factors Involved, Previous Studies, and Needed Research.” Highway Research Record 

No. 70. Highway Research Board, 48–56. Washington, DC. 

52. Garvey, P.M., Thompson-Kuhn, B., and Pietrucha, M.T. (1995). “Sign Visibility 

Literature Review: Final Report.” Report Submitted to United States Sign Council. 

Pennsylvania Transportation Institute. University Park, PA. 

53. Garvey, P.M. and Mace, D.J. (1996). “Changeable Message Sign Visibility.” Report No. 

FHWA-RD-94-077. Federal Highway Administration. Washington, DC. 
79 

54. Gellatly, A.W. and Kleiss, J.A. (2000). “Visual Attention Demand Evaluation of 

Conventional and Multifunction In-Vehicle Information Systems.” In Proceedings of the 

IEA 2000/HFES 2000 Congress. Human Factors and Ergonomics Society, (3)282–285. 

Santa Monica, CA. 

55. Glaze, A.L. and Ellis, J.M. (2003). “Pilot Study of Distracted Drivers.” Transportation 

Safety Training Center for Public Policy. Virginia Commonwealth University. 

Richmond, VA. 

56. Goodman, M., Bents, F.D., Tijerina, L., Wierwille, W., Learner, N., and Benel, D. 

(1997). “An Investigation of the Safety Implications of Wireless Communications in 

Vehicles.” Report DOT HS 808-635. National Highway Traffic Safety Administration. 

Washington, DC. 

57. “Guide to the Management of Roadside Advertising.” (2002). TERS Product No. 80.500, 

Edition 1.0. Brisbane, Australia: Queensland Government, Department of Main Roads. 

58. Hall, J.W. and Lorenz, V.M. (1989). “Characteristics of Construction Zone Accidents.” 

Transportation Research Record, 1230, 20–27. 

59. Hanowski R.J., Wierwille W.W., and Dingus T.A. (2003). “An On-Road Study to 

Investigate Fatigue in Local/Short Haul Trucking.” Accident Analysis and Prevention, 

35(2), 153–160. 

60. Harbluk, J.L., Noy, Y.I, and Eizenman, M. (2002). “The Impact of Cognitive Distraction 

on Driver Visual Behaviour and Vehicle Control.” Report No. TP 13889 E. Transport, 

Canada. 

61. Henderson, Hon. D.N. (1963). Remarks on outdoor advertising and traffic safety, in 

Congressional Record, May 9, 1963, 109, Part 6-House, 8172–8173. 

62. Highway Research Board (Ed). (1971). “The Changeable-Message Concept of Traffic 

Control.” Highway Research Board Special Report No. 129. 

63. Hoffman, J.E. and Subramaniam, B. (1995). “The Role of Visual Attention in Saccadic 

Eye Movements.” Perception and Psychophysics, 57(6), 787–795. 

64. Holahan, C.J., Campbell, M.D., Culler, R.E., and Verselka, C. (1978). “Relationship 

between Roadside Signs and Traffic Accidents: A Field Investigation.” Paper presented 

at the annual meeting of the Transportation Research Board. Washington, DC. 

65. Holahan, C.J., Culler, R.E., and Wilcox, B.L. (1978). “Effects of Visual Distraction on 

Reaction Time in a Simulated Traffic Environment.” Human Factors, 20(4), 409–413. 

66. Holahan, C.J. (1979). “An Evaluation of the Utilization of Psychological Knowledge 

Concerning Potential Roadside Distractors—Research Report 64.” University of Texas at 

Austin. Austin, TX. 
80 

67. Holdsworth, G. (2005). “Report Review: Driving Performance in the Presence and 

Absence of Billboards.” Prepared for Foundation for Outdoor Advertising Research and 

Education by Lee, S.E., Olsen, E.C.B., and DeHart, M.C. 

68. Hornbeck, P.L. and Okerlund, G.A., Jr. (1973). “Visual Values for the Highway User: 

An Engineers Workbook.” U.S. Department of Transportation. Washington, DC. 

69. Horrey, W.J. and Wickens, C.D. (2004). “Focal and Ambient Visual Contributions and 

Driver Visual Scanning in Lane Keeping and Hazard Detection.” Proceedings of the 

Human Factors and Ergonomics Society 48th Annual Meeting. Human Factors and 

Ergonomics Society. Santa Monica, CA. 

70. Horrey, W.J. and Wickens, C.D. (2007). “In-Vehicle Glance Duration: Distributions, 

Tails and a Model of Crash Risk.” Proceedings of the 2007 Transportation Research 

Board Meeting. Washington, DC. TRB. http://hmil.cs.drexel.edu/papers/CSC02.pdf. 

71. Hughes, P.K. and Cole, B.L. (1985). “What Attracts Attention When Driving?” 

Australian Road Research Board Internal Report # AIR 377-1. 

72. Hughes, P.K. and Cole, B.L. (1984). “Search and Attention Conspicuity of Road Traffic 

Control Devices.” Australian Road Research, 14(1), 1–9. 

73. Jamson, S.L. and Tate, F.N. (2005). “Evaluation of the Effects of Bilingual Traffic Signs 

on Driver Performance and Safety.” Ergonomics, 48(15), 1734–1748. 

74. Johnson, L. and Lauer, A.R. (1937). “A Study of the Effect of Induced Manual 

Handicaps on Automotive Performance in Relation to Reaction Time.” Journal of 

Applied Psychology, 21(1), 85–93. 

75. Johnston, A.W. and Cole, B.L. (1976). “Investigation of Distraction by Relevant 

Information.” Australian Road Research, 6(3), 32–33. 

76. Kipp, O.L. (1952). “Final Report on the Minnesota Roadside Study.” Highway Research 

Board Bulletin, 55, 33–37. 

77. Kircher, K. (2007). “Driver Distraction: A Review of the Literature.” VTI rapport 594A. 

Linkoping, Sweden. 

78. Klauer, S.G., Dingus, T.A., Neale, V.L., Sudweeks, J.D., and Ramsey, D.J. (2006). “The 

Impact of Driver Inattention on Near-Crash/Crash Risk: An Analysis Using the 100-Car 

Naturalistic Driving Study Data.” Report No. DOT HS 810 594. National Highway 

Traffic Safety Administration. Washington, DC. 

79. Klauer, S.G., Neale, V.L., Dingus, T.A., Ramsey, D., and Sudweeks, J. (2005). “Driver 

Inattention: A Contributing Factor to Crashes and Near-Crashes.” Proceedings of the 

Human Factors and Ergonomics Society 49th Annual Meeting. Human Factors and 

Ergonomics Society, 1922–1926. Santa Monica, CA. 
81 

80. Kuhn, B.T. (1999). “The Impact of Illumination on Typical On-Premise Sign Visibility.” 

ITE Journal, 4, 64. 

81. Lauer, A.R. and Kotvis, H.L. (1934). “Automotive Manipulation in Relation to Vision.” 

Journal of Applied Psychology, 18(3), 422–431. 

82. Lauer, A.R. and McMonagle, C.J. (1955). “Do Roadside Signs Affect Accidents?” 

Traffic Quarterly, 9(3), 322–329. 

83. Lee, S.E., McElheny, M.J., and Gibbons, R. (2007). “Driving Performance and Digital 

Billboards.” Report prepared for Foundation for Outdoor Advertising Research and 

Education. Virginia Tech Transportation Institute. Blacksburg, VA. 

84. Lee, S.E., Olsen, E.C.B., and DeHart, M.C. (2003). “Driving Performance in the 

Presence and Absence of Billboards.” Report prepared for Foundation for Outdoor 

Advertising Research and Education. Virginia Tech Transportation Institute. 

Blacksburg, VA. 

85. Lehtimaki, R. (1974). “The Effect of Billboards (Roadside Advertising) on Traffic 

Safety.” (Translation from Finnish in January 1980). Liikenneturva. Helsinki, Finland. 

86. Lerner, N.D., Tornow, C. E., Freedman, M., Llaneras, R.E., Rabinovich, B.A., and 

Steinberg, G.V. (1999). “Preliminary Investigations of Highway Design Countermeasures 

to Aid Drivers with Limited Experience: Literature Review and Crash Data Analysis.” 

Draft FHWA Report (Unpublished). Federal Highway Administration. Washington, DC. 

87. Madigan-Hyland, Inc. (1963). “New York State Thruway Authority: Relationship 

between Accidents and the Presence of Advertising Devices.” 

88. Massachusetts Outdoor Advertising Board. (1976). “Decision Performance and Digital 

Billboards.” Report prepared for Foundation for Outdoor Advertising Research and 

Education. Virginia Tech Transportation Institute. Blacksburg, VA. 

89. McGee, H.W., Moore, W., Knapp, B.G., and Sanders, J.H. (1978). “Decision Sight 

Distance for Highway Design and Traffic Control Requirements.” Report FHWA-RD78–78. Government Printing Office. Washington, DC. 

90. McKnight, J. and McKnight, A.S. (1991). “The Effect of Cellular Phone Use Upon 

Driver Attention.” National Public Services Research Institute. Landover, MD. 

91. McMonagle, J.C. (1951). “Accident Analysis—Telegraph Road 1947–1948.” Highway 

Research Board Bulletin, 30, 29–41. 

92. McMonagle, J.C. (1963). Statement on Madigan-Hyland Report, included as Exhibit D, 

in Congressional Record, 109, May 9, 1963, Part 6-House, 8174–8175. 

93. McMonagle, J.C. (1952). “Traffic Accidents and Roadside Features.” Highway Research 

Board Bulletin, 55, 38–48. 
82 

94. McNees, R.W. and Messer, C.J. (1981). “Evaluating Urban Freeway Guide Signing.” 

Report No. FHWA/TX-81/5+220-3. Federal Highway Administration. Washington, DC. 

95. Michigan State Highway Department. (1952). “Accident Experience in Relation to Road 

and Roadside Features.” Final Report on the Michigan Study. Lansing, MI. 

96. Miltenburg, P.G.M. and Kuiken, M.J. (1991). “The Effect of Driving Experience on 

Visual Search Strategies.” In: M.J. Kuiken and J.A. Groeger, (Eds.), Feedback 

Requirements and Performance Differences of Drivers. Haren, the Netherlands. Traffic 

Research Centre. University of Groningen. 

97. Minnesota Department of Highways. (1951). “Minnesota Rural Trunk Highway 

Accident, Access Point and Advertising Sign Study.” 

98. Mourant, R.R. and Rockwell, T.H. (1970). “Mapping Eye-Movement Patterns to the 

Visual Scene in Driving: An Exploratory Study.” Santa Human Factors Society. Human 

Factors, 12(1), 81–87. Santa Monica, CA. 

99. Mourant, R.R. and Rockwell, T.H. (1972). “Strategies of Visual Search by Novice and 

Experienced Drivers.” Human Factors Society. Human Factors, 14(4), 325–335. Santa 

Monica, CA. 

100. Mourant, R.R., Rockwell, T.H., and Rackoff, N.J. (1969). “Drivers’ Eye Movements and 

Visual Workload.” Highway Research Record, No. 292, 1–10. National Academy Press. 

Washington, DC. 

101. National Research Council. (1988). “Transportation in an Aging Society (Vols.1 & 2).” 

Transportation Safety Board, National Academy Press. Washington, DC. 

102. National Standards for Regulation by States of Outdoor Advertising Signs, Displays and 

Devices Adjacent to the National System of Interstate and Defense Highways. (1960). 23 

F.R. 8793, November 1, 1958, as amended 25 F.R. 218, January 12, 1960, 25 F.R. 2575, 

March 26, 1960, sec. 20.8. 

103. Nygardhs, S. and Helmers, G. (2007). “Vms-Variable Message Signs: A Literature 

Review.” VTI rapport 570A. Linkoping, Sweden. 

104. Olsson, S. and Burns, P.C. (2000). “Measuring Driver Visual Distraction with a 

Peripheral Detection Task.” Obtained from The National Highway Traffic Safety 

Administration Driver Distraction Internet Forum. Obtained from: 

http://www.nrd.nhtsa.dot.gov/departments/nrd-13/driver-distraction/Papers.htm. 

Site last updated August 11, 2008. Site last accessed September 22, 2008. 

105. Ogden, K.W. (1989). “Human Factors in Traffic Engineering.” Department of Civil 

Engineering. Monash University. Clayton, Victoria, Australia. 
83 

106. Parkes, A.M, Ward, N.J., and Vaughan, G. (2001). “A Human Factors Evaluation of a 

Novel Display and Control Concept for In-Vehicle Audio Systems: A Case Study.” 

International Journal of Vehicle Design, 25(4), 339–352. 

107. Pottier, A. (1988). “Influence of the Conspicuous Nature of Road Signs, of the 

Surroundings and of the Functional Field of Vision to Facilitate their Observation.” 

International Ergonomics Association, 10th International Congress, 581–583. Sydney, 

Australia. 

108. Pottier, A. (1990). “Functional Field of Vision, Road Sign Conspicuity, and 

Surrounding.” (Summary Translation from French). Arcueil, Cedex, France: INRETS. 

109. Pottier, A. (1998). “Perceptual Visual Workload as a Function of Static Visual Noise 

Level During Car Driving.” 24th International Congress of Applied Psychology. San 

Francisco, CA. 

110. Pottier, A. (Unknown). “Effect of the Road Environmental Complexity on the Visual 

Comportment of Dependent/Independent Field Drivers.” (Summary Translation from 

French). Arcueil, Cedex, France, INRETS. 

111. Pottier, A. and Pottier, M. (1988). “Motorist’s Ability to Notice Signs in Their Peripheral 

Field of Vision According to the Dependence-Independence Field.” International 

Ergonomics Association. 10th International Congress, 590–592. Sydney, Australia. 

112. Prince, J.H., Blackwell, H.R., and Ohmart, J.G. (Undated). “Comparative Legibility of 

Highway and Advertising Signs under Dynamic Conditions—Project 886.” The Ohio 

State University Institute for Research in Vision. Columbus, OH. 

113. Rahimi, M., Briggs, R., and Thorn, D. (1990). “A Field Evaluation of Driver Eye and 

Head Movement Strategies Toward Environmental Targets and Distractors.” Applied 

Ergonomics, 21(4), 267–274. 

114. Rama, P., Luoma, J. and Harjula, V. (1999). “Distraction Due to Variable Speed Limits.” 

Traffic Engineering and Control, 40(9), 428–430. 

115. Redelmeier, D.A. and Ticshirani, R.J. (1997). “Association Between Cellular-Telephone 

Calls and Motor Vehicle Collisions.” The New England Journal of Medicine, 336(7), 

453–458. 

116. Restudy of the Highway Beautification Program. (1970). Committee Print 91-40, U.S. 

House of Representatives, 91st Congress, 2nd Session, September 1970. 

117. Road Safety Committee. (2006). “Inquiry into Driver Distraction—Report of the Road 

Safety Committee on the Inquiry into Driver Distraction.” Parliamentary Paper No. 209 

Session 2003–2006. Parliament of Victoria. Victoria, Australia. 
84 

118. Rockwell, T.H. (1988). “Spare Visual Capacity in Driving-Revisited (New Empirical 

Results for an Old Idea).” In Proceeding of Vision in Vehicles II (317-324). Gale, A.G. et 

a1. (Editors). Elsevier Science Publishers B.V. (North-Holland). 

119. Rumar, K. (1990). “The Basic Driver Error: Late decision.” Ergonomics, 33(10/11), 

1281–1290. 

120. Rusch, W.A. (1951). “Highway Accident Rates as Related to Roads Business and 

Advertising.” Highway Research Board. Highway Research Board Bulletin, 30, 46–50. 

Washington, DC. 

121. Rykken, K.B. (1951). “Minnesota Roadside Survey: Progress Report on Accident, 

Access Point and Advertising Sign Study in Minnesota.” Highway Research Board 

Bulletin, 30, 42–43. 

122. Schollerer, E., Stricker, D., Sury, P., Groner, R., and Groner, M. (2007). “Driving and 

Advertisements: A Simulator Study with Eye Movements Recorded.” Universitat Bern. 

Bern, Switzerland. 

123. Serafin, C., Wen, C., Paelke, P., and Green, P. (1993). “Car Phone Usability: A Human 

Factors Laboratory Test.” Proceedings of the Human Factors and Ergonomics Society 

Annual Meeting. Human Factors and Ergonomics Society, 220–224. Santa Monica, CA. 

124. Shoaf, R.T. (1955). “Are Advertising Signs Near Freeways Traffic Hazards?” Traffic 

Engineering, 26(2), 71–76. 

125. Smiley, A., Persaud, B., Bahar, G., Mollett, C., Lyon, C., Smahel, T., et al. (2005). 

“Traffic Safety Evaluation of Video Advertising Signs.” Transportation Research Record. 

Journal of the Transportation Research Board, No.TRB.1937, 105–112. 

Washington, DC. 

126. Smiley, A., Smahel, T., and Eizenman, M. (2004). “Impact of Video Advertising on 

Driver Fixation Patterns.” Transportation Research Record, 1899, 76–83. 

127. Staffeld, P.R. (1953). “Accidents Related to Access Points and Advertising Signs in 

Study.” Traffic Quarterly, 7(1), 59–74. 

128. Stutts, J.C., Reinfurt, D.W., Staplin, L., and Rodgman, E.A. (2001). “The Role of Driver 

Distraction in Traffic Crashes.” Report Prepared for AAA Foundation for Traffic Safety. 

Washington, DC. 

129. SWOV. (2006). “Advertising and Information Alongside the Road.” SWOV (Institute for 

Road Safety Research) Fact Sheet. Leidschendam, The Netherlands. 

130. Tantala Sr., A.M. and Tantala, M.W. (2007). “A Study of the Relationship Between 

Digital Billboards and Traffic Safety in Cuyahoga County Ohio.” Foundation for Outdoor 

Advertising Research and Education. Washington, DC. 
85 

131. Tantala, M. and Tantala, P. (2005). “An Examination of the Relationship Between 

Advertising Signs and Traffic Safety.” Presented at the 84th Annual Meeting of the 

Transportation Research Board. Washington, DC. 

132. Theeuwes, J. (1996). “Visual Search at Intersections: An Eye-Movement Analysis.” In: 

A.G. Gale, I. Brown, C. Haslegrave, and S. Taylor (Eds.), Vision in Vehicles: VI. North 

Holland Press, Elsevier Science Publishers. New York, NY. 

133. Theeuwes, J. and Hagenzieker, P. (1993). “Visual Search of Traffic Scenes: On The 

Effect of Location Expectations.” Vision in Vehicles—IV, A.G. Gale et al. editors, 

Elsevier Science Publishers BV. 

134. Thompson-Kuhn, B., Garvey, P.M., and Pietrucha, K.M. (1997). “Model Guidelines for 

Visibility of On-Premise Advertisement Signs.” National Academy Press. Transportation 

Research Record, No. 1605. Washington, DC. 

135. Tijerina, L., Kiger, S. M., Rockwell, T.H., and Tornow, C. (1995). “Workload 

Assessment of In-Cab Text Message System and Cellular Phone Use by Heavy Vehicle 

Drivers on the Road.” In Proceedings of the Human Factors and Ergonomics Society 39th 

Annual Meeting. Human Factors and Ergonomics Society, 1117–1121. 

Santa Monica, CA. 

136. Tijerina, L., Palmer, E.B., and Goodman, M.J. (1999). “Individual Differences and InVehicle Distraction While Driving: A Test Track Study and Psychometric Evaluation.” In 

Proceedings of the Human Factors and Ergonomics Society 43rd Annual Meeting. Human 

Factors and Ergonomics Society, 982–986. Santa Monica, CA. 

137. Transportation Environment Consultants. (1989). “Review of Roadside Advertising 

Signs. Roads and Traffic Authority.” Sydney, Australia. 

138. Transportation Environment Consultants. (1990). “Evaluation of Banner Advertising for 

Safety Promotion.” Roads and Traffic Authority. Sydney, Australia. 

139. Treat, J.R., Tumbas, N.S., McDonald, S.T., Shinar, D., Hume, R.D., Mayer, R.E., et al. 

(1979). “Tri-Level Study of the Causes of Traffic Accidents.” National Highway Traffic 

Safety Administration. Washington, DC. 

140. TRL Information Centre (2007). “Variable Message Signs Update. Current Topics in 

Transport.” TRL Limited. Berkshire, United Kingdom. 

141. Violanti, J.M. (1996). “Cellular Phones and Fatal Traffic Collisions.” Accident Analysis 

and Prevention 30(4), 519–524. 

142. Wachtel, J. (1981). “Electronic Advertising Along Highways—Concern for Traffic 

Safety.” Public Roads, 45(1), 1–5. 

143. Wachtel, J. (2008). “A Critical, comprehensive Review of Two Studies Recently 

Released by the Outdoor Advertising Association of America—Final Report.” Maryland 
86 

State Highway Administration. Project No. AX137A51. Hanover, MD. Obtained from: 

http://www.sha.state.md.us/UpdatesForPropertyOwners/oots/outdoorSigns/FINALREPO

RT10-18-GJA-JW.pdf. Accessed September 27, 2008. 

144. Wachtel, J. and Netherton, R. (1980). “Safety and Environmental Design Considerations 

in the Use of Commercial Electronic Variable-Message Signage.” Report No. FHWARD-80-051. Federal Highway Administration. Washington, DC. 

145. Wallace, B. (2003). “Driver Distraction by Advertising: Genuine Risk or Urban Myth?” 

Proceedings of the Institution of Civil Engineers. Municipal Engineer, 156 Issue ME3, 

185–190. 

146. Wallace, B. (2003). “External-to-Vehicle Driver Distraction.” Research Findings 

No.168/2003, Scottish Executive Social Research, Development Department Research 

Programme. 

147. Waller, P.F. (1991). “The Older Driver.” Human Factors, 3(5), 499–505. 

148. Walton & Associates (1987). “The Effects of Billboards Adjacent to the New Jersey 

Turnpike.” Preliminary Draft Report. 

149. Wang, J.H. and Cao, Y. (2005). “Study of the Interface Issues Between Motorists and 

Intelligent Highway System Through Variable Message Signs.” International Journal of 

Vehicle Design, 1(1/2), 106–118. 

150. Wang, J., Knipling, R., and Goodman, M. (2000). “The Role of Driver Inattention in 

Crashes: New Statistics from the 1995 Crashworthiness Data System.” Obtained from the 

Driver Distraction Internet Forum sponsored by the National Highway Traffic Safety 

Administration. Obtained from: http://www.nrd.nhtsa.dot.gov/departments/nrd-13/driverdistraction/Links.htm. Site last updated August 11, 2008. Site last accessed on 

September 22, 2008. 

151. Waugh, J.D., Glumm, M.M., Kilduff, P.W., Tauson, R.A., Smyth, C.C., and Pillalamarri, 

R.S. (2000). “Cognitive Workload While Driving and Talking on a Cellular Phone or to a 

Passenger.” In Proceedings of the IEA 2000/HFES 2000 Congress. Human Factors and 

Ergonomics Society, 6, 276–279. Santa Monica, CA. 

152. Weckesser, P.M. (1978). “The Effect of Outdoor Advertising Adjacent to the New Jersey 

Turnpike.” New Jersey Turnpike Authority. 

153. Weiner, S. (1973). Review of Report: “A Study of the Relationship Between Advertising 

Signs and Traffic Accidents on U.S. 40 Between Vallejo and Davis by D. Jackson 

Faustman, 1961.” Unpublished Internal Memorandum. Federal Highway Administration. 

Environmental Design and Control Division. Washington, DC. 

154. Wierwille, W.W. (1993). “Visual and Manual Demands of In-Car Controls and 

Displays.” In Peacock, B. and Karwowski, W. (Eds.). Taylor & Francis. Automotive 

Ergonomics, 299–320. Washington, DC. 
87 

155. Wierwille, W.W., Antin, J.F., Dingus, T.A., and Hulse, M.C. (1988). “Visual Attentional 

Demand of an In-Car Navigation Display System.” In Gale, A G., Freeman, M.H., 

Haslegrave C.M., Smith, P., and Taylor, S.P. (Eds.). North Holland Press. Vision in 

Vehicles II, 307–316. Amsterdam, The Netherlands. 

156. Wikman, A., Nieminen, T., and Summala, H. (1998). “Driving Experience and TimeSharing During In-Car Tasks on Roads of Different Width.” Ergonomics, 4,242(3), 

358–372. 

157. Williams, L.G. (1996). “Target Conspicuity and Visual Search.” Human Factors, 8(1), 

80–92. 

158. Wisconsin Department of Transportation District 2, Freeway Operations Unit. (1994). 

“Milwaukee County Stadium Variable Message Sign Study: Impacts of an Advertising 

Variable Message Sign on Freeway Traffic.” 

159. Woods, D.L. and Rowan, N.J. (1969). “Driver Communications.” Texas Transportation 

Researcher, 5(1), 14–16. 

160. Young, E. (1984). “Visibility Achieved by Outdoor Advertising.” Journal of Advertising 

Research, 24, 19–21. 

161. Young, M.S. and Mahfoud, J.M. (2007). “Driven to Distraction: Determining the Effects 

of Roadside Advertising on Driver Attention.” Final Report of a Study Funded by The 

Rees Jeffreys Road Fund. West London: Brunel University. 

162. Zwahlen, H.T., Adams, C.C., and DeBald, D.P. (1988). “Safety Aspects of CRT Touch 

Panel Controls in Automobiles.” In Gale, A.G., Freeman, M. H., Haslegrave, C. M., 

Smith, P., and Taylor, S. P. (eds.). Elsevier. Vision in Vehicles II, 335–344. 

Amsterdam, The Netherlands. 

163. Zwahlen, H.T. (1988). “Safety Aspects of Cellular Telephones in Automobiles.” (Paper 

No. 88058). Paper presented at the International Symposium on Automotive Technology 

and Automation (ISATA), May, 1988. Florence, Italy.
HRDS-07/02-09(WEB)E