a

Breakthroughs in 

Vision and Visibility 

for Highway Safety

The Exploratory Advanced Research Program

Workshop Summary Report • August 13–14, 2
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Technical Report Documentation Page 

i
ii
iii

On August 13–14, 2014, at the Turner–Fairbank Highway Research Center in McLean, VA, the 

Federal Highway Administration’s (FHWA’s) Office of Safety Research and Development 

(R&D) and the Office of Safety, with support from the Exploratory Advanced Research (EAR) 

Program, convened a 2-day workshop, “Breakthroughs in Vision and Visibility for Highway Safety.” 

Michelle Arnold of FHWA’s Office of Safety R&D Human Factors Team provided a brief introduction 

describing the purpose of the workshop, after which Monique Evans, FHWA’s Office Director for Safety 

R&D, formally welcomed workshop participants. In her welcome address, Evans stated that investigators have conducted research in a variety of areas surrounding visibility issues, including efforts exploring 

retroreflectivity and pavement-marking signs, and legibility of fonts; however, much of this work has 

been tapering off. Evans addressed the need to identify the role for FHWA in this particular field, what 

is needed, and where FHWA fits in.

Next, David Kuehn, EAR Program Manager, briefly discussed the purpose of the EAR Program. Kuehn 

began by stating that the EAR Program not only focuses on finding advances in science and engineering 

that have not been applied in transportation research, but also uses these advances to enhance the highway transportation safety system. He mentioned that there has been a lot of research conducted relating to visibility but that this research has focused on the energy sector and the vehicle side, as opposed 

to transportation infrastructure. Kuehn also noted that there have been several advances in sight and 

cognition research that move beyond the existing processes and framework used in highway visibility.

During day one of the workshop, participants observed presentations from five expert speakers operating 

in different fields related to visibility research. The speakers covered various topics, including FHWA’s 

previous research, roadway-lighting limitations, and eye-movement analysis. Following the presentations, the panel of speakers and audience members discussed current issues in this area of research and 

identified research gaps that could help move the field forward.

On day two of the workshop, Cathy Satterfield at FHWA’s Office of Safety provided workshop participants 

with a recap of day one and summarized the research that was presented by the five speakers. Following 

the recap, the workshop participants divided into two groups to discuss in detail the following two topics: (1) what exploratory research do we need to conduct to bring us into the future; and (2) how do we 

coordinate across disciplines?

The facilitator for the second day of activities asked each group to discuss what applied research is 

needed and identify next steps for future research. Following this, the workshop participants visited 

FHWA’s Arens Photometric Visibility Laboratory. Researchers have used this laboratory to conduct a 

variety of studies, including evaluations of the photometric and colorimetric properties of traffic control 

devices. Researchers have also used the laboratory to investigate signage and pavement-marking materials 

and traffic signal lights. The workshop participants discussed possible ideas for use of the laboratory in 

the future. 

Executive Summary
iv

Key discussion points from the workshop are summarized as follows:

•	 Establishing standards. Visibility standards and guidelines currently being used for new technologies 

(e.g., virtual windshields and head-up-displays that project information onto the windshield) and 

the roadway implications of these technologies (e.g., pavement markings, sign clutter, and billboards) 

need to be revisited and reestablished. 

•	 Researching decisionmaking. Driver, pedestrian, and night simulation research are needed to provide 

insight into driver decisionmaking processes when visibility is low. 

•	 Understanding the impact of technologies. Investigators need to conduct research that studies the 

effect of active safety and partial automation technologies on highway visibility (e.g., adaptive cruise 

control and lane-departure systems) and driver risk assessment. 

•	 Looking to future technologies. Investigators need to identify research that bridges the gap between 

technology today (e.g., partial automation) and future technology (e.g., full vehicle automation).

•	 Communicating research. Government agencies, universities, industry, and other countries need 

more communication and research coordination to create a clearinghouse of current, ongoing, and 

relevant visibility research.
v

Table of Contents

INTRODUCTION 1

PART ONE: PRESENTATIONS 3

Lighting the Infrastructure and the Environment: Progress and Issues 

in Roadway Lighting 4

Overview 4

Summary 4

Interaction of Vehicle Lighting with Traffic Control Devices (Retroreflectivity) 6

Overview 6

Summary 6

Vehicles of the Future and Visibility 8

Overview 8

Summary 8

A Unified Contrast Sensitivity Function-Based Framework for 

Edge Detection and Edge Visibility 10

Overview 10

Summary 10

Human Visual System—Eye-Movement Analysis 12

Overview 12

Summary 12

PART TWO: DISCUSSION 15

Expert Panel Discussion 16

Luminance and the Effect of Speed on Crash Rate 16

Driver Behavior and Visibility Effects From Glare 16

Virtual Windshield and Driver Perception 16

Gaps in Human Factors Visibility Research 17

Smart Vehicle Technology 17

Breakout Group Discussions 19

Potential Research Topics and Critical Questions 19

APPENDICES 23

Appendix A: Agenda 25

Appendix B: About the Presenters 26

Appendix C: Attendees 28
List of Figures

Figure 1. Control system topologies. 4

Figure 2. Driver crash rate and luminance. 5

Figure 3. Roadway visibility concepts. 11

Figure 4. Eye movements navigating complex mazes. 12

Figure 5. Proposed framework for visibility research. 21

List of Acronyms and Abbreviations

CALTRANS California Department of Transportation

DOT Department of Transportation

EAR Exploratory Advanced Research

FHWA Federal Highway Administration

GPS global positioning system

HUD head-up display

IFSTTAR French Institute of Science and Technology for Transport, 

Development, and Networks

LED light-emitting diodes

MUTCD Manual on Uniform Traffic Control Devices

NCHRP National Cooperative Highway Research Program

R&D Research and Development

SEMs saccadic eye movements

TTI Texas A&M Transportation Institute

V2V vehicle-to-vehicle

vi
1

On August 13–14, 2014, at the Turner–Fairbank Highway Research Center in McLean, VA, the 

Federal Highway Administration’s (FHWA’s) Office of Safety Research and Development (R&D) 

and Office of Safety, with support from the Exploratory Advanced Research (EAR) Program, 

convened a 2-day workshop, “Breakthroughs in Vision and Visibility for Highway Safety.” The purpose 

of this workshop was to identify gaps in highway visibility research and brainstorm about innovative 

tools and techniques to fill those gaps. FHWA’s Office of Safety R&D invited speakers from universities 

and research companies across the globe to present their research and to provide insights into next 

steps in highway visibility. The speakers also participated in a panel discussion with the other workshop 

participants to discuss their research and to answer questions. The group then identified and discussed 

specific research areas that would bring FHWA’s research into the next 5 years, 10 years, 20 years, and 

beyond. This workshop summary report captures highlights from the workshop and summarizes the 

discussions that took place.

Introduction
2
3

Part One

Presentations
4

Overview

Dr. Gibbons began his presentation with a 

brief introduction to the evolution of outdoor lighting over the years (Gibbons, 2014). 

He mentioned that two key developments 

have occurred, solid-state lighting and 

control systems. These developments have 

led to a lighting revolution primarily driven 

by the convergence of these two technologies. Dr. Gibbons presented research and 

findings from two projects conducted at 

the Virginia Tech Transportation Institute, 

“Spectral Effects of Light Sources” and 

“Adaptive Lighting.” He then discussed potential 

areas of future visibility research.

Summary

Solid-state lighting is a type of lighting that offers 

little flexibility or control; typically only on or off 

on a timer. Control systems offer more flexibility 

and control, take advantage of light-emitting diode 

(LED) technology, and create energy efficient, dimmable light-system management. Figure 1 presents 

a topology of how a control system works. 

For Dr. Gibbons’ first project, “Spectral Effects 

of Light Sources,” he investigated the interaction of 

headlamps and overhead lighting, color recognition, and pedestrian object detection. Because the 

human visual system adapts well to blue light at 

night, and LEDs can now provide all colors of the 

spectrum, there is a potential to have a white light 

source, which could greatly increase visibility for 

night driving. Dr. Gibbons’ research showed that 

lighting levels on roadways could be lowered and a 

shift in the broad spectrum to blue could decrease 

energy consumption, while maintaining or even 

increasing visibility. 

Lighting the Infrastructure and the Environment: 

Progress and Issues in Roadway Lighting

Presenter: Dr. Ron Gibbons

Project Team: Virginia Tech Transportation Institute

For Dr. Gibbons’ second project, “Adaptive 

Lighting,” he investigated the ability to adapt roadway lighting systems to the needs of the environment. An adaptive luminaire system would reduce 

energy consumption and allow municipalities to 

install the systems where needed, reducing the 

costs associated with lamp replacement. To study 

whether adjusting the luminaire intensity affects 

crash rates, Dr. Gibbons’ tested vehicles that were 

driven with various types of lighting systems, while 

accounting for traffic volume, weather, lighting 

conditions, and pedestrian usage. He then compared data involving 3,200 lane-km (2,000 lane-mi) 

of lighting with 23,000 crashes and identified that 

there are situations when lighting levels could be 

changed while maintaining safe levels of driving 

performance. Figure 2 provides the ratio of nightto-day crash rate and the corresponding horizontal 

luminance levels. 

This analysis did not remove crashes attributed 

to impaired driving, and the number of crashes 

was stratified to determine whether lighting had 

a differential effect on impaired drivers compared 

with crashes involving pedestrians or objects. 

Figure 1. Control system topologies. 
5

Dr. Gibbons showed that the results were not 

significant and more lighting and crash data are 

needed for further investigation. He also described 

some potential areas for future research focusing 

on lighting systems and their effects on infrastructures, which are summarized as follows: 

•	 Use geographic information system databases

and collect information on roadway lighting, 

linking it to crashes on the same roadways. 

•	 Determine the effects that lack of maintenance

could have on detection and crash rates on the 

roadways and sidewalks. An increasing number 

of cities and municipalities are interested in 

looking at the effects of switching to LED systems, such as Anchorage, AK, and San Jose, CA. 

Both cities have instituted adaptable lighting 

systems (dimmable) and have maintained the 

same detection levels as when using a solid state 

system; however, cities still struggle to determine 

specifications for control system infrastructure 

(e.g., lens, expected life expectancy, cleaning, 

and maintenance). Data gathered in Boston, MA; 

Cambridge, MA; and Minneapolis, MN, measured 

light output from LED luminaries and showed 

how cleaning or changing lighting systems can 

affect the measureable output. 

•	 Research how connected vehicles could be used

to implement “lighting on demand” functionality 

for roadways, which would turn the lights on 

and off as a vehicle drives along the roadway.

Figure 2. Driver crash rate and luminance. 
6

Overview

Dr. Carlson presented areas of completed and 

ongoing research related to retroreflectivity, pavement markings, and signage (Carlson, 2014). He 

also discussed topics for potential future research. 

These research areas included brightness and legibility of signage; placement, width, and materials 

used in pavement markings; and ways to expand on 

current performance values outlined in the Manual 

on Uniform Traffic Control Devices (MUTCD). In 

addition, Dr. Carlson provided examples where 

research could be expanded to establish retroreflectivity specifications and expected life cycles of 

signs and pavement markings.

Summary

Dr. Carlson explained that retroreflectivity is a 

passive technology and needs lighting to function 

properly. There have been many studies conducted 

that have investigated different aspects of signs as 

they pertain to retroreflectivity. For example, 

FHWA investigated sign brightness, retroreflectivity measurement biases, and the use of flashing 

signs; Minneapolis Department of Transportation 

(DOT) investigated fonts on guide signs; Florida 

DOT investigated sign lighting and the materials 

that should be used for roadway signs; researchers 

for National Cooperative Highway Research Program 

(NCHRP) Synthesis 431: Practices to Manage Traffic 

Sign Retroreflectivity explored and identified 

methods and best practices for traffic sign reflectivity that States are using to be in compliance 

with Federal regulations; American Association 

of State Highway and Transportation Officials’ 

Subcommittee on Traffic Engineering conducted 

a survey to update NCHRP’s reflectivity devices 

Interaction of Vehicle Lighting with Traffic Control 

Devices (Retroreflectivity)

Presenter: Dr. Paul Carlson

Project Team: Texas A&M Transportation Institute

practices; and the Georgia Institute of Technology 

worked with Georgia DOT to assess light detection 

and ranging retroreflectivity.

Dr. Carlson also described previous pavementmarkings research. FHWA published a study that 

tested pavement-marking performance in harsh 

environments (Alaska and Tennessee); NCHRP 

developed a new recommended procedure to test 

the retroreflectivity of glass beads, for which a 

specification is currently being developed; Missouri 

DOT investigated the safety of marking width, 

retroreflectivity, brightness, and placement; and 

the American Traffic Safety Services Association, 

in collaboration with FHWA, investigated the 

safety of pavement markings’ retroreflectivity and 

pavement at night. 

Dr. Carlson highlighted that the MUTCD established performance value sets for traffic devices. 

Researchers for NCHRP 05-20 are also working to 

expand and update the standards set in the 

MUTCD to describe how much light is needed to 

illuminate guide signs. To achieve this, the 

researchers worked to break down the complexity 

of the highway scene. By using images, they developed a program that would output a background 

complexity rating. Dr. Carlson explained that the 

complexity rate is calculated by using a static 

image, digitizing it to determine edge detection, 

and then assessing every pixel within the image. 

By using this complexity rating, the goal is to set 

standards and help determine when to light guide 

signs and how much light is needed. 

Dr. Carlson also reviewed ongoing pavementmarking research. FHWA is working to develop 

standards to help select pavement markings for 

specific situations and environments; Illinois DOT 
7

is working to develop laboratory test methods to 

mimic the wear and tear of pavement markings in 

the field to accelerate performance testing for new 

technologies before installation on highways and 

roadways; and researchers for NCHRP 05-21 are 

investigating the safety and performance of raised 

pavement markings when paired with retroreflective pavement markings, in addition to determining 

additional benefits. Researchers for NCHRP Topic 

46-13 are also studying rumble strips and profile 

markings to understand performance. 

Dr. Carlson described several potential areas for 

research that range from establishing requirements 

for minimum retroreflectivity to investigating the 

usage and effect of digital signage along roadways. 

The following research areas were discussed:

•	 Establish requirements for minimum retroreflectivity. Researchers should specify a predicted 

life cycle of signs and identify when replacement 

would be necessary. The manufacturer’s warranty period is not a good benchmark. 

•	 Establish a link between the use and degree of

retroreflectivity of signs and safety. 

•	 Improve mobile measurements of retroreflectivity in many different ways. This could lead 

to variation among measurement methods. A 

better understanding is needed to develop test 

methods for these data-collection devices. 

•	 Develop guidance relating to the brightness of

luminaires for beacon and LED-enhanced signage and the amount of brightness used for 

these traffic control devices. The sign’s message 

could be confused or lost if the luminosity is too 

bright (causing glare) or not bright enough 

(reducing visual acuity). 

•	 Establish guidelines on appropriate usage of

digital sign technology.

•	 Research how a driver internalizes the information presented on signage with different 

levels and types of retroreflectivity to operate 

the vehicle safely. This could be a multifaceted 

research project, beginning with when drivers 

read a sign, moving into comprehension and 

application of the information, and then looking at luminance curves to predict and define 

performance levels.
8

Overview

During his presentation, Dr. Ferreira described 

virtual windshields, vehicle-to-vehicle (V2V) connectivity, and new infrastructure technology 

(Ferreira, 2014). He explained that he has focused 

his research on the implications of virtual and 

electronic windshields on transportation infrastructure. These implications, as well as potential 

areas for future research, are described in the 

following section.

Summary

Dr. Ferreira noted that a driver’s visibility is 

primarily affected by weather conditions and vehicle 

design (e.g., the windshield, dashboard, and pillars). 

Virtual windshields can be used to augment a driver’s 

perception of the roadway. To achieve this, a 

computer uses the driver’s perspective to overlay 

an image in their field of view and enhance the 

physical world as seen by the driver. Vehicles 

currently augment the driver’s reality through the 

use of side- and rearview mirrors. That is, mirrors 

are used to augment the perception of what is going 

on behind the driver. These augmentations may 

improve the driver’s visibility and awareness of his 

or her surrounding environment. 

Dr. Ferreira explained that virtual windshields 

can be implemented through superimposed images 

on a head-up display (HUD) or other information 

display. Virtual environment technology includes 

parking assistance, cruise-control adaptability, 

lane-departure warning, and crash-avoidance systems. Vehicle manufacturers recently have begun 

removing the sideview mirrors and replacing them 

with cameras that display the side views on the 

centrally-mounted rearview mirror. 

Vehicles of the Future and Visibility

Presenter: Dr. Michel Ferreira

Project Team: University of Porto

Dr. Ferreira highlighted how electronic 

windshields offer “see-through” visibility technology by using cameras to capture the environment and a computer to create digital content, 

which is displayed on the windshield. Dashboard 

information, global positioning system (GPS) navigation, and information from other vehicles can 

then be superimposed on the windshield view. 

For example, a truck could send its window view to 

the following vehicle so that driver can make a 

safe decision as to whether to try to pass the truck. 

Dr. Ferreira noted some potential issues with this 

technology. For instance, there could be delays in 

the image projection between vehicles, thereby 

increasing the risk of drivers making maneuver 

decisions with incorrect (i.e., late) information. 

Moreover, if one vehicle loses the ability to connect 

with other vehicles, then messages and information would not be shared, which may create blind 

spots for other vehicles. 

Dr. Ferreira stated that there is a potential to use 

wireless technology and to synchronize a driver’s 

smart phone with the vehicle’s virtual windshield. 

The car would become a platform for a smart 

phone, but with a larger screen, and create a 

connected and an immersive ambient experience. 

He also stated that using wireless technology 

allows for more accurate information to be shared 

and increases the ability for V2V connectivity. 

In this scenario, every vehicle on the road would 

have a virtual traffic light that travels with the 

vehicle and would always be visible to the driver 

through the HUD. The interconnected vehicles on 

the road would monitor and sense area traffic when 

approaching an intersection and help govern traffic 

flow and safety. 
9

Dr. Ferreira then described some potential areas 

for research in virtual windshields and visibility, 

as follows:

•	 Investigate the effect of augmented reality on

a driver’s decisionmaking performance. For 

example, “see-through” visibility technology 

could affect a driver’s risk assessment, creating 

a false sense of safety. 

•	 Identify the amount andplacementofinformation

on virtual windshields and HUDs. With increasing amounts of information available to drivers 

(e.g., GPS and dashboard information), there 

are questions as to how much information is 

too much information to be helpful and to facilitate safe vehicle operation. 
10

Overview

Dr. Hautière presented his research on developing 

an edge-detection formula to aid in driver visibility 

during less-than-ideal conditions (e.g., fog and 

rain; Hautière, 2014). He developed this formula 

using photometrical visibility standards to analyze 

images without a priori information about target 

characteristics. He modeled the driver’s perception and computed highway visibility through 

contrast estimation and measurement of the retroreflected luminance coefficient. Details about Dr. 

Hautière’s research and areas for future research 

are described in the following section.

Summary

Researchers at the French Institute of Science and 

Technology for Transport, Development, and 

Networks (IFSTTAR) developed a mathematical 

formula to calculate edge detection and assist 

drivers by filling in the missing information from 

a driver’s windshield view when visibility is poor. 

Three types of visibility are used to achieve this: 

(1) geometric visibility that relies on the geometry 

of the highway design and the presence of fixed 

and moving obstacles; (2) atmospheric visibility 

that relies on rain or fog intensity, granulometry, 

pavement properties, and vehicle velocity; and 

(3) photometric visibility that relies on lighting 

conditions and the color and photometry of objects. 

Figure 3 provides additional information related to 

these three types of visibility. 

The research team at IFSTTAR was able to estimate the photometrical visibility through image 

A Unified Contrast Sensitivity Function-Based 

Framework for Edge Detection and Edge Visibility

Presenter: Dr. Nicolas Hautière

Project Team: IFSTTAR

analysis without any a priori information about 

target characteristics. Dr. Hautière explained that 

the driver’s perception was modeled and highway 

visibility computed through contrast estimation 

and measurement of the retroreflected luminance 

coefficient. The research team validated the contrast model by using human subject testing. The 

subjects were able to reproduce better results than 

were the calculated results, making the model 

conservative and demonstrating the efficiency of 

this approach in real-world applications.

Dr. Hautière noted that this model could be 

used to assist the driver in fog conditions. The 

system would detect objects, apply the contrast 

model, and then represent the image on the HUD 

to improve the driver’s reaction time through 

improved clarity and quality of visible cues. 

Dr. Hautière then discussed potential new areas 

for visibility research, as follows:

•	 Investigate how this technology could be used

with “intelligent roadways” that contain smart 

cameras installed along the highway infrastructure to detect, characterize, and share 

visibility conditions with vehicles approaching 

the area. This cooperative system could be 

used to implement vehicle velocity control to 

match visibility conditions.

•	 Research how pedestrians would fit into the

model. New driving simulations could be 

developed to account for this type of scenario 

and test the ability of the model to account 

for moving objects.
11

Figure 3. Roadway visibility concepts. 

© IFSTTAR
12

Overview

Dr. Kowler presented research that focused on eye 

movement and the cognitive effort needed to make 

correct and efficient decisions (Kowler, 2014). Her 

research focused on human ability to complete 

computer-generated mazes of varying complexity 

by using different cognitive functions. The following 

section summarizes Dr. Kowler’s discussion of how 

this applies to roadway visibility infrastructure and 

outlines other possible research areas to explore. 

Summary

Dr. Kowler explained that saccadic eye movements 

(SEMs) are rapid jumps of the eye and that SEM 

scan patterns occur a couple of times per second. 

She noted that human cognition of the visual field 

decreases with eccentricity of the SEMs, that is, 

even when luminance cues are given, they are not 

always followed or recognized. Dr. Kowler mentioned that there is extensive research related to 

how people scan their visual field, retain, and make 

decisions based on this information. 

Through human subject testing, Dr. Kowler 

showed that some individuals do not put forth the 

amount of effort needed to analyze the location of 

Human Visual System—Eye-Movement Analysis

Presenter: Dr. Eileen Kowler

Project Team: Rutgers University

the luminance signal and the most efficient path to 

reach the location. For example, in a maze task, 

researchers asked participants to complete a randomly selected maze as fast as possible and to use 

the computer mouse to trace the path through the 

maze. Results showed that some participants used 

their eyes to explore the maze before moving the 

mouse; however, there were other participants 

who immediately started using the mouse instead 

of visually exploring the maze. Dr. Kowler’s 

research indicated that the latter group of participants made more mistakes and took longer than 

did those who had visually explored the maze 

before tracing the path with the mouse. Figure 4 

shows that although the subjects had ample opportunity to explore the maze, many did not. 

Dr. Kowler suggested that the question of why 

people did not explore the entire maze relates to 

memory. The cost of exploration equals the amount 

of memory needed to retain the information, 

and some people do not use this cognitive tool. 

Dr. Kowler noted that human decisionmaking 

outweighs visibility and that adding a time pressure element to make a decision can make the task 

extremely difficult. 

Figure 4. Eye movements navigating complex mazes.

© Rutgers University
13

Dr. Kowler discussed potential areas for visibility 

research as they relate to roadway infrastructure, 

as follows:

•	 Research individual differences in visual acuity

and attention (e.g., attention deficit hyperactivity 

disorder). These differences could be confounding variables in visibility technology systems.

•	 Investigate how to measure when a person is

seeing an object and when they actually process 

the information. In driving, there are SEMs 

because it is a dynamic environment with many 

tasks. Natural driving affects attention; when 

demands are low, there is better attention and 

vice versa.

Part Two

Discussion
16

Expert Panel Discussion

At the end of the first day, the presenters 

participated in a panel discussion and 

answered questions from the other 

workshop participants. The workshop participants 

directed general questions to all five presenters 

and also posed specific questions to individual presenters for their response. A summary of the panel 

discussion is outlined in the following sections. 

Luminance and the Effect of Speed 

on Crash Rate 

The panelists noted that when traveling on highspeed roads (e.g., interstate highways), the major 

visual task for the driver is to be aware of the vehicles ahead. More light is needed on slow-speed 

roads because of complexities (e.g., intersections 

and narrow and winding road curvature) associated 

with such roads. According to the panelists, older 

drivers tend to decrease the time they spend driving 

on unfamiliar or high-speed roads at night. In 

terms of visual capabilities, the panelists suggested 

that younger drivers have limited experience but 

have the best vision, whereas older drivers have the 

most experience but have impaired vision. The 

panelists mentioned that there is a gap in research 

in how changes in roadway infrastructure affect 

drivers familiar with the roadway and that there 

are various elements that could be included in the 

redesign to address this issue.

Driver Behavior and Visibility Effects 

from Glare

During the discussion, the panelists noted that 

there are hours of eye-glance data that need to 

be mined from the second Strategic Highway 

Research Program’s naturalistic driving study. 

The panelists also highlighted that the California 

DOT (i.e., CALTRANS) is currently expanding its 

research on managing lanes. CALTRANS do not 

want to put up glare screens or glare walls and 

are investigating how much lighting could be 

installed to help drivers avoid looking at the glare 

of oncoming vehicles. 

The panelists mentioned that researchers for a 

study conducted over a 3-year period in Finland 

collected data from drivers in high-speed and lowspeed situations (Kallberg, 2014). Halfway through 

the experiment, the researchers installed reflector 

posts. In the high-speed situation, they observed 

no difference in driver behavior; however, in the 

low-speed situation, the reflectorization resulted 

in an increase in crash rates because drivers maintained a higher speed even though the road was 

complex. Researchers for this study theorized that 

reflector posts created a false sense of safety. This 

meant that drivers felt that they could keep their 

speeds high instead of decreasing them to appropriately and safely maneuver through the terrain.

Virtual Windshield and Driver 

Perception

The panelists spent part of the discussion focusing on virtual windshields and driver perception. 

They noted that the HUD reduces a driver’s 

peripheral vision and acuity. Moreover, it can even 

create a hazard by inhibiting the driver’s ability to 

refocus when the image being broadcast onto 

the screen brings his or her attention “in” instead 

of “out” (e.g., viewing the world outside of the 

vehicle). The panelists suggested that this may be 

worse than looking at the instrument cluster in a 

vehicle’s dashboard. They also noted that the use 

of these virtual windshields is becoming more 

widely available. There is new technology moving 

toward interconnected vehicles and infrastructure that is leading the way for these windshields 

to project traffic signs and speed limits directly in 

the driver’s immediate field of view. According to 

the panelists, this creates an increase in information workload and a new environment that the 

driver needs to adjust to. There is a significant 

need for human factors research and involvement 
17

to ensure high levels of safety with the emergence 

and adoption of these new technologies. 

The panelists mentioned that there are individual differences when it comes to a person’s 

ability to focus and respond to visual information. 

For example, when the driver has two sets of 

information (i.e., the projected and the real-world 

view), the human eye needs to choose which set 

of information to focus on. When there are two 

surfaces, including one that is transparent to the 

other view, people tend to choose to focus on 

the closest surface. In this scenario, that would be 

the information projected on the virtual windshield. Panelists noted the importance of a low 

contrast between surfaces when there is low 

illumination because there is less ability for the 

human eye to clearly focus on a specific view. 

Gaps in Human Factors 

Visibility Research 

The panelists also discussed gaps in human factors 

visibility research. They noted that the interaction 

between cars and connectivity is an important 

innovation, particularly in terms of driver perception. Vehicles will be able to send messages to other 

vehicles without any dependence on conditions. 

This is because intervehicle communication relies 

on established infrastructure, including lights, 

signs, markings, and sounds (e.g., horns). The 

panelists suggested that the loop needs to be closed 

between visibility devices and the capabilities of 

different drivers. More specifically, individual 

differences need to be studied and accounted for to 

ensure that these new visibility technologies can 

adapt to a wide variety of drivers. The panelists 

mentioned that researchers should study young, 

old, experienced, and novice drivers, and analyze 

their varying visibility requirements and mental 

capacity to understand the world around them. 

According to the panelists, the infrastructure 

currently available encompasses the environment 

as a system of parts. These parts (e.g., street signs, 

traffic lights, and lane markings) are not “interconnected,” but they work together to ensure safe 

highway and roadway travel. The panelists mentioned that one goal is to tighten up this system of 

parts by taking inputs from vehicles as part of 

future Intelligent Transportation System installations to form a cohesive system. During the 

discussion, the panelists also noted that researchers 

have previously conducted studies to analyze the 

effects of lighting on driver performance to model 

behaviors. The researchers focused on the direction of drivers’ vision and which components of the 

visual system aided or inhibited a driver’s visible 

acuity. When considering visibility and interconnectivity as a whole system, the panelists suggested 

that information silos need to be identified and broken down. The panelists put forward two specific 

questions that need to be answered: (1) does really 

good retroreflectivity mean that more or less lighting 

is needed; and (2) is it a better investment for 

municipalities to install dimmable systems that can 

be increased or decreased in energy consumption, 

rather than repainting pavement markings every 

3–6 months? 

The panelists agreed that there needs to be a better systematic approach to nighttime visibility. For 

example, the geometries for daytime visibility are 

different for pavement markings, retroreflectivity, 

signs, and raised pavement markings. The panelists 

suggested that research needs to be focused on 

identifying other performance metrics given that 

nighttime visibility is integrated. In addition, they 

agreed that nighttime visibility needs to be better 

defined, because current research is based on daytime conditions and assumptions. Although driver 

behavior, specifically in regard to speed, does not 

generally change between day and night driving, 

there are many other things that do change at night 

that are not documented in the MUTCD. The panelists highlighted that local and State governments 

are looking for objective performance data to justify 

new lighting infrastructure or to maintain existing 

surface infrastructure. At this time, it is not known 

if it is more cost-effective to spend money to install 

dimmable lighting or to spend money on maintaining existing pavement markings.

Smart Vehicle Technology 

The panelists went on to discuss smart vehicle technology. With new “smarter” technology becoming 
18

increasingly more available (e.g., rear-visibility 

cameras, lane-keeping assist, and blind-spot monitoring), the panelists asked why accidents are still 

happening. They questioned what it is that the 

human element in this mix is failing to do and asked 

if onboard data recorders could be used to examine 

vehicle crashes after the fact and determine the 

fault. Panelists suggested that augmented systems 

could possibly help identify this missing link. They 

agreed that further research is needed to identify 

the shortfalls of these technologies and to find solutions to enhance their effect on safety.
19

Breakout Group Discussions

Potential Research Topics and 

Critical Questions 

For the second half of this workshop, workshop 

participants split into two small groups to brainstorm and answer two different, but related, 

topics. The first session charged the groups to 

answer the questions, “What exploratory research 

do we need to do to get us to the future, and how 

do we coordinate across disciplines?” While the 

groups had the charge to consider exploratory and 

cross-disciplinary research, the discussion for the 

most part was on applied research with a narrower 

highway focus.

Session One: 

What exploratory research do we need to 

do to get us to the future, and how do we 

coordinate across disciplines?

•	 Roadside

– Develop MUTCD standards. Research is crucial for amending and developing standards 

for the MUTCD to account for adaptive lighting and minimum retroreflectivity levels. 

– Evaluate distractions. There is a need to evaluate standards in terms of private land jurisdiction, brightness, and the amount of light 

from billboards allowed on the roadway and 

the distraction it may cause.

– Prioritize information. There are no concrete 

data on what constitutes and defines “sign 

clutter.” Standards are needed to prioritize 

the information displayed and to analyze this 

type of infrastructure on the roadway. 

•	 Vehicles

– Prepare for the future. Investigators need to 

conduct research to define and prepare for 

future technologies. Vehicle automation is on 

the horizon, and investigators need to identify research areas between partial automation and full automation. 

– Implement monitoring. There is a concern for 

the lack of implementation of monitoring 

technologies across passenger car fleets. The 

installation of black boxes in vehicles is a 

growing trend in the industry, which can provide information on such factors as speed, 

timing, and response to infrastructure.

– Streamline processes. There are concerns 

about the number of different agencies that 

influence the approval of headlamp designs. 

•	 Driver

– Investigate drivers. With increasingly more 

safety technology on the market, there may 

be some unintended consequences. For example, drivers may be placing too much trust in 

these technologies and thus may neglect their 

own responsibilities. Additional research 

could explore the timespan needed for a 

driver to make a decision and assess risk. 

– Research older drivers. Research could investigate how driver performance changes with age 

and identify how visibility standards may help 

to evaluate whether a sign failed to warn older 

drivers as a result of visual or sign clutter.

•	 Cross-Cutting and Other Research Areas

– Coordinate disciplines. There is related research 

in other areas (e.g., aviation and medicine) 

that relates directly to visibility, cognition, 

perception, and safe operation of vehicles. 

There must be coordination between the different disciplines and an emphasis on staying 

aware of new research. 

– Identify pedestrians at night. It is difficult for 

drivers to identify pedestrians and bicycles at 

nighttime. Infrared technologies, bio-motion, 

and lighting at night could be considered as 

options to identify heat, movement, and 

luminance of pedestrians and bicyclists. 

– Focus research efforts. The focus of future 

infrastructure needs should be made clear: 
20

the focus should be on either the driver or the 

machine. Automation and new technologies 

are pushing highway research to shift focus 

from the driver to the vehicle. Because of 

this, investment in roadways may be directed 

to pavement markings, because sensor systems 

will be relying on this type of infrastructure. 

Researchers should still consider the driver 

when implementing virtual windshields and 

the amount of information (i.e., clutter) that 

is safe to present to the driver. 

– Study work zones. Researchers need to focus 

more attention on the topic of visibility of 

work zones at night for drivers. 

– Influence behaviors. The role of education in 

promoting safety and influencing behavior is an 

important factor to include in future research; 

however, it was noted by participants that 

much of this is outside of FHWA’s jurisdiction. 

– Protect motorcyclists. There is an increasing 

need for programs to address motorcycle 

fatalities. Potential solutions could include 

lighting systems embedded in helmets, technologies displayed on the windshield, and 

protective wear.

Session Two: 

Needed Applied Research and Next Steps 

The second session focused on identifying and 

creating concrete next steps to move research 

toward addressing the ideas discussed in the first 

brainstorming session. These are outlined in the 

following sections. 

1. Adopt FHWA Visibility Vision Statement 

and Goals

Workshop participants said that FHWA has 

the potential to facilitate the focus of upcoming 

research by producing a vision statement. The 

direction set by this statement includes quantification of safety measurements and acceptance of 

new technology, and enables FHWA to react 

efficiently to new technology as it is introduced 

and available to the public. The group proposed 

a draft vision statement as a consensus of the 

different suggestions discussed. This vision 

statement communicates research objectives 

across infrastructure, vehicle, and user as follows:

FHWA Vision

“To provide the safest and most costeffective visual environment for all users 

through full integration of infrastructure 

and technology.”

2. Create a Framework for FHWA’s 

Visibility Research

The workshop participants proposed a framework (figure 5) in support of the aforementioned 

vision statement that identifies three main 

research components: infrastructure, vehicle, 

and user. Among the three components, workshop participants said that infrastructure is the 

component over which FHWA has the most 

influence. This framework correlates factors that 

can be controlled by researchers and practitioners 

and can be used as a reference to identify 

research needs. 

Figure 5 indicates consistent standards across 

infrastructure, vehicles, and users and consistent 

communications systems across infrastructure, 

vehicles, and users. Under this research framework, workshop participants suggested that 

projects in the next 5 years perform a benefit–

cost analysis and assess the effect a study will 

have on vehicle-to-infrastructure and V2V 

communications.

3. Develop a Clearinghouse of Research in 

Other Disciplines and Countries

Workshop participants suggested that a framework that brings together research and 

information is needed. The strategic program 

for visibility should include stakeholders and 

agencies that could contribute their respective 

research and help define uniform safety measurements and correlation factors. The workshop 

participants said that this research plan needs 

to be promoted to obtain inputs from stakeholders and to refine research needs based on 
21

visibility. Participants mentioned that a clearinghouse could be developed of relevant vision, 

human cognition and perception, and vehicle 

automation technology research. The workshop participants suggested the following list 

of key potential stakeholders:

•	 Transportation Research Board’s Standing

Committee on Visibility.

•	 American Association of State Highway and

Transportation Officials.

•	 National Highway Traffic Safety

Administration.

•	 Intelligent Transportation Systems Joint

Program Office. 

•	 FHWA Resource Center Innovative

Finance Team.

•	 Academia.

•	 Automotive Industry (Alliance of Automobile

Manufacturers and Japanese Automobile 

Standards Internationalization Center).

•	 Association for Unmanned Vehicle Systems

International.

4. Explore Driver, Pedestrian, and Night 

Simulation Training

Workshop participants discussed limitations in 

previous simulator research, specifically night 

simulation and pedestrian and driver interaction 

simulation. IFSTTAR has conducted some 

pedestrian and nighttime research, but workshop participants suggested that more is needed 

to understand driver behavior in the decisionmaking process, particularly when there is 

limited visual acuity, and to test new technologies. 

5. Identify Infrastructure Investments

During the discussion, workshop participants 

said that investment in new types of highway 

infrastructure may be needed over the next 20 

years. They suggested that new infrastructure 

may be inclined toward automated driving and 

will incorporate vehicle and infrastructure 

sensors that do not rely on human vision but on 

machine–vision systems. Workshop participants mentioned that long-term investments 

should focus on providing the infrastructure 

elements and technology that will complement 

the entire integrated system.

6. Investigate and Establish the Effectiveness 

of Retroreflectivity

Workshop participants discussed technologies 

that are already influenced by FHWA, including monitoring the driver and enhancing the 

visibility of the road through retroreflectivity 

STANDARDS INFRASTRUCTURE

Lights

Signs

Markings

Base Map

Road Geometry

Complexity

of Scenario

Lighting

Sensor 

Technology

Fleet 

Turnover

Display

Capabilities

Acceptance

Education

Training

License

VEHICLE

VISION

USER

COMMUNICATION

SYSTEMS

Figure 5. Proposed framework for visibility research. 
22

and lighting. Given that the effectiveness of 

retroreflectivity and lighting is not currently 

known, workshop participants said that more 

research needs to be conducted. This will help 

to determine whether there is a correlation 

between retroreflectivity, lighting, and a particular scenario of interest. Workshop participants 

suggested that FHWA could play a role as a 

facilitator and ensure roadways remain a focus 

of research. 

7. Update MUTCD and the Highway 

Safety Manual

The final research area discussed by workshop 

participants related to how Congress mandates 

safety performance measures and crashmodification factors. These are used as predictive 

tools to guide expectations regarding reductions 

in crashes. Workshop participants mentioned 

that this requirement funds research based on 

the financial investment of the infrastructure. 

Participants highlighted that States have been 

charged with performance-based decisionmaking, whereas researchers use the available data 

to create these standards, even if they are not 

complete or of high quality. Workshop participants suggested that a next step would be to 

redefine and reestablish the minimum safety 

requirements set within the MUTCD and 

Highway Safety Manual using new technology 

specifications. They said that this type of 

research is an initial point, or a datum, for 

research over the next 5 years.
Appendices

25

Appendix A—Agenda

EAR Program Convening Workshop: Breakthroughs in Vision and Visibility for Highway Safety

Turner–Fairbank Highway Research Center, McLean, VA

Wednesday, August 13, 2014 

1 p.m. Welcome, Introduction, EAR Program Overview

Monique Evans, Federal Highway Administration

Michelle Arnold, Federal Highway Administration

David Kuehn, Federal Highway Administration

1:15 p.m. Lighting the Infrastructure and the Environment: Progress and Issues in Roadway Lighting

Dr. Ron Gibbons, Virginia Tech Transportation Institute

1:45 p.m. Interaction of Vehicle Lighting with Traffic Control Devices (Retroreflectivity)

Dr. Paul Carlson, Texas A&M Transportation Institute

2:15 p.m. Vehicles of the Future and Visibility

Dr. Michel Ferreira, University of Porto

2:45 p.m. Break

3 p.m. A Unified Contrast Sensitivity Function-Based Framework for Edge Detection and 

Edge Visibility

Dr. Nicolas Hautière, IFSTTAR

3:30 p.m. Human Visual System—Eye-Movement Analysis

Dr. Eileen Kowler, Rutgers University

4 p.m. Panel Discussion

4:45 p.m. Adjourn

Thursday, August 14, 2014 

8 a.m. Day 1 Recap and Breakout Topic Introduction

Cathy Satterfield, Federal Highway Administration

8:15 a.m. Navigating the Transition Effectively—Breakout Groups

Facilitated by Cathy Satterfield and Abdul Zineddin

9:15 a.m. Present Findings to the Large Group

9:45 a.m. Break

10 a.m. Navigating the Transition Effectively—Breakout Groups

Facilitated by Michelle Arnold and Joseph Cheung

11 a.m. Present Findings to the Large Group

11:30 a.m. Arens Photometric and Visibility Laboratory Visit

12 p.m. Adjourn
26

Appendix B—About the Presenters

Ron Gibbons 

Dr. Ron Gibbons is the director of the Center for 

Infrastructure Based Safety Systems at the Virginia Tech 

Transportation Institute. He is also the Institute’s lead 

lighting research scientist and is responsible for lightingand visibility-associated research projects and projects 

that consider roadway safety as they relate to infrastructure. Dr. Gibbons is currently the principal investigator 

on multiple projects, including studies on the effect of 

lighting design on roadway safety, the effect of headlamp 

design on safety and wet night visibility, and the performance of alternative light sources in roadway lighting. 

Dr. Gibbons is the author of several published papers on 

roadway lighting, photometry, and target visibility. He is 

a past president of the Illuminating Engineering Society 

of North America. Gibbons obtained his doctorate degree 

from the University of Waterloo, Canada. 

Paul Carlson 

Dr. Paul Carlson is a research engineer at the Texas A&M 

Transportation Institute (TTI) and Division Head of the 

Operations and Design Division. Dr. Carlson leads TTI’s 

Visibility Research Laboratory, located in TTI’s new 

State Headquarters and Research Building. Dr. Carlson’s 

primary areas of interest are traffic engineering, highway 

safety, vision science, traffic control devices, geometric 

design, and human factors. He has been a principal or 

co-principal investigator for numerous research studies, 

dealing with topics such as traffic-sign and pavementmarking retroreflectivity, highway safety, nighttime 

driver visibility needs, centerline and edge-line rumble 

strips, traffic-signal warrants, and operational effects of 

geometric design. Dr. Carlson holds a doctorate of 

philosophy in civil engineering from Texas A&M 

University and a master of science and bachelor of 

science degree, both in civil engineering, from The 

Pennsylvania State University.

Michel Ferreira 

Dr. Michel Ferreira is a faculty member of the Department 

of Computer Science at the University of Porto, Portugal, 

and a researcher at the Porto Laboratory of the Instituto 

de Telecomunicações. He is a lead scientist in Intelligent 

Transportation Systems and principal investigator in 

several research projects. Dr. Ferreira currently leads the 

Geo-Networks group, and his main research interest is 

in the area of Intelligent Transportation Systems, in 

which he is especially interested in cooperative 

Intelligent Transportation Systems, where intervehicle 

communication plays an important role. Vehicular ad 

hoc networks, mobility simulation, and spatio-deductive 

databases are important topics in his current research. 

A major goal in his research is the efficient design of 

large-scale distributed systems that use infrastructureless communication to self-organize, based on spatial 

reasoning. He received his undergraduate degree in 

computer science from the University of Porto in 1994, 

a master’s degree in computer engineering from the 

University of Minho in 1996, and a doctorate degree in 

computer science from the University of Porto in 2002. 

Nicolas Hautière 

Dr. Nicolas Hautière is a researcher and program manager for IFSTTAR, the French Institute of Science and 

Technology for Transport, Development, and Networks. 

He received a master’s degree in civil engineering from 

the National School of State Public Works, and a master’s 

and doctorate degree in computer vision from the 

University Jean Monnet, Saint-Etienne, France, in 2002 

and 2005, respectively. He received the habilitation to 

supervise research, HDR, in 2011 from the Université 

Paris-Est and the specialized master in political science 

and sustainable development in 2013 from Ecole des 

Ponts ParisTech. His research interests cover modelling 

of the meteorological phenomena reducing highway 
27

visibility, detection of adverse visibility conditions, and 

the estimation of visibility range. The applications range 

from road operation, including advanced driver assistance systems and video traffic sensors, to meteorological 

observation. Since September 2013, Dr. Hautière has 

been a Project Director at the Department Components 

and Systems, IFSTTAR, and leader of the French program “Route 5ème Génération.” 

Eileen Kowler 

Dr. Eileen Kowler is Distinguished Professor of Psychology 

at Rutgers University and Associate Dean of the Graduate 

School. Her research includes the areas of perception, 

attention, and motor control. Dr. Kowler received her 

doctorate in psychology from the University of Maryland 

in 1978 and joined the psychology faculty at Rutgers in 

1980 after postdoctoral work at New York University. 

She is a member of the graduate faculty of Biomedical 

Engineering and is on the Executive Committee of the 

Rutgers Center for Cognitive Science. She edited the 

reference work “Eye Movements and Their Role in 

Visual and Cognitive Processes” and served as section 

editor for “Behavioral Physiology and Visuomotor 

Control” for the journal Vision Research from 1995–2004. 

Dr. Kowler has served on the editorial board of the 

Journal of Vision and Cognitive Brain Research. 
28

Appendix C—Attendees

Attendee Organization

Roya Amjadi Federal Highway Administration

Carl Andersen Federal Highway Administration

Michelle Arnold Federal Highway Administration

Stacy Balk Leidos

Paul Carlson Texas A&M Transportation Institute

Clayton Chen Federal Highway Administration

Joseph Cheung Federal Highway Administration

Ann Do Federal Highway Administration

Monique Evans Federal Highway Administration

Michel Ferreira University of Porto

Brian Fouch Federal Highway Administration

Ellie L. Francis Ellie L. Francis, Ph.D., O.D.

Philip Garvey Pennsylvania State University

Ron Gibbons Virginia Tech Transportation Institute

Nicolas Hautière French Institute of Science and Technology for Transport, 

 Development, and Networks

Eileen Kowler Rutgers University

David Kuehn Federal Highway Administration

Alan Lewis International Commission on Illumination

Paul Lutkevich Parsons Brinckerhoff

Catherine McInnis Volpe Center

George Merritt Federal Highway Administration Resource Center

Cameron Miller National Institute of Standards and Technology

Fred Owens Franklin and Marshall College

Matthew Palmer Virginia Tech Transportation Institute

William Perez Leidos

Cathy Satterfield Federal Highway Administration

Greg Schertz Federal Highway Administration

Caroline Trueman Federal Highway Administration

David Yang Federal Highway Administration

Abdul Zineddin Federal Highway Administration
29

References

1. Gibbons, R. (2014, August). Lighting the 

infrastructure and the environment: progress 

and issues in roadway lighting. Paper presented 

at the Exploratory Advanced Research Program 

Workshop, “Breakthroughs in Vision and 

Visibility for Highway Safety,” McLean, VA. 

2. Carlson, P. (2014, August). Interaction of 

vehicle lighting with traffic control devices 

(retroreflectivity). Paper presented at the 

Exploratory Advanced Research Program 

Workshop, “Breakthroughs in Vision and 

Visibility for Highway Safety,” McLean, VA. 

3. Ferreira, M. (2014, August). Vehicles of the 

future and visibility. Paper presented at the 

Exploratory Advanced Research Program 

Workshop, “Breakthroughs in Vision and 

Visibility for Highway Safety,” McLean, VA.

4. Hautière, N. (2014, August). A unified contrast 

sensitivity function-based framework for edge 

detection and edge visibility. Presented at the 

Exploratory Advanced Research Program 

Workshop, “Breakthroughs in Vision and 

Visibility for Highway Safety,” McLean, VA. 

5. Kowler, E. (2014, August). Human visual 

system—eye-movement analysis. Presented at 

the Exploratory Advanced Research Program 

Workshop, “Breakthroughs in Vision and 

Visibility for Highway Safety,” McLean, VA. 

6. Kallberg, V-P. (1993). Reflector posts—signs of 

danger? Transportation Research Record, No. 1403,

pp. 57–66.

About the EAR Program

Federal legislation establishes an Exploratory Advanced Research (EAR) Program for transportation to 

address longer term, higher risk, breakthrough research with the potential for dramatic long-term 

improvements to transportation systems, improvements in planning, building, renewing, and operating safe, 

congestion-free, and environmentally sound transportation facilities. The Federal Highway Administration’s 

(FHWA’s) EAR Program secures broad scientific participation and extensive coverage of advanced ideas 

and new technologies through stakeholder engagement, topic identification, and sponsored research. 

The uncertainties in the research approach and outcomes challenge organizations and researchers to 

be innovative problem-solvers, which can lead to new research techniques, instruments, and processes 

that can be applied to future high-risk and applied research projects.

For more information, please visit the EAR Program Web site at http://www.fhwa.dot.gov/

advancedresearch/.
Office of Safety Research and Development

Turner-Fairbank Highway Research Center

6300 Georgetown Pike

McLean, VA 22101-2296

Publication No. FHWA-HRT-15-067

HRTM-30/08-15(WEB)E