Research, Development, and Technology

Turner-Fairbank Highway Research Center

6300 Georgetown Pike

McLean, VA 22101-2296

PUBLICATION NO. FHWA-HRT-22-088 SEPTEMBER 2022 

Comprehension and Legibility 

of Selected Symbol Signs Phase IV
FOREWORD

The objective of the Transportation Pooled Fund Program’s Traffic Control Device (TCD) 

Consortium is to assemble regional, State, and local entities, appropriate organizations, and the 

Federal Highway Administration (FHWA) to establish a systematic procedure to select, test, and

evaluate existing and new TCDs that will support changes to the Manual on Uniform Traffic 

Control Devices and interim approvals. 

This report documents an FHWA project examining the comprehension and legibility of existing 

and new signs. In 2016, the TCD Pooled Fund Study panel selected the following sign messages 

for symbol development and evaluation: Toll Plaza Electronic Toll Interoperability, Lane 

Reduction Treatment, Temporary Traffic Control Bicycle/Pedestrian Access, Flashing Yellow 

Arrow, Blind Hill Warning, Rail/Flangeway Gap Bicycle Warning, Vehicle Prohibition, Bicycle 

Passing Law, Passenger Ferry, Midblock Hybrid Beacon Pedestrian Crossings (Driver), 

Alternative Fuels, and Recreational and Cultural Interest.

This report is of interest to engineers, planners, and other researchers and practitioners concerned 

with road users’ ability to see and understand signs. Information on the comprehension of 

Recreational and Cultural Interest signs may be of interest to local, regional, State, and park 

authorities as they evaluate their existing and planned public information strategies.

Brian P. Cronin, P.E. 

Director, Office of Safety and Operations 

Research and Development

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation 

(USDOT) 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. 

Recommended citation: Federal Highway Administration, Comprehension and Legibility of 

Selected Symbol Signs Phase IV (Washington, DC: 2022) https://doi.org/10.21949/1521917. 
TECHNICAL REPORT DOCUMENTATION PAGE

1. Report No.

FHWA-HRT-22-088

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

4. Title and Subtitle

Comprehension and Legibility of Selected Symbol Signs 

Phase IV

5. Report Date

September 2022

6. Performing Organization Code:

7. Author(s)

Stacy A. Balk (ORCID: 0000-0003-3886-5117), Erin Kissner, 

and Bryan Katz (ORCID: 0000-0003-2813-8098) 

8. Performing Organization Report No.

9. Performing Organization Name and Address

Leidos, Inc. 

6300 Georgetown Pike

McLean, VA 22101

10. Work Unit No.

11. Contract or Grant No.

DTFH61-13-D-00024

12. Sponsoring Agency Name and Address

Office of Safety and Research

Federal Highway Administration

6300 Georgetown Pike

McLean, VA 22101-2296

13. Type of Report and Period Covered

March 2016–December 2017

14. Sponsoring Agency Code

HRDS-30

15. Supplementary Notes

The Contracting Officer’s Representative and Human Factors Team Leader was Brian Phillips (HRDS-30; 

ORCID: 0000-0002-8426-0867).

16. Abstract

The traffic control device (TCD) pooled fund study (PFS) addresses human factors and operations issues through 

the systematic evaluation of existing and new TCDs. As a part of this effort, the Federal Highway Administration 

Human Factors Team evaluated sets of existing and proposed traffic signs for driver comprehension and legibility. 

The TCD PFS panel selected the following sign messages for evaluation: Lane Reduction Treatment, Temporary 

Traffic Control Bicycle/Pedestrian Access, Flashing Yellow Arrow, Alternative Fuels, Midblock Hybrid Beacon 

Pedestrian Crossings, Passenger Ferry, Bicycle Passing Law, Vehicle Prohibition, Rail/Flangeway Gap Bicycle 

Warning, Blind Hill Warning, Toll Plaza Electronic Toll Interoperability, and Recreation and Cultural Interest. The 

research team used open-ended responses, multiple-choice responses, and subjective rankings to assess sign 

comprehension and then tested the legibility of each sign. The study provides recommendations on the specific 

signs road users are most able to understand, as well as sign groups for which additional public education and sign 

testing would be recommended. 

17. Key Words

Traffic control devices, symbol sign, human factors, 

safety, transportation 

18. Distribution Statement

No restrictions. This document is available to the public 

through the National Technical Information Service, 

Springfield, VA 22161.

http://www.ntis.gov

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Unclassified

21. No. of Pages

65 

22. Price

N/A

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

TABLE OF CONTENTS

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

Literature Review ................................................................................................................... 1

Research Goals and Selected Signs ....................................................................................... 3

Research Approach................................................................................................................. 4

Sign Categories ........................................................................................................................ 4

Lane Reduction Treatment.................................................................................................. 4

Temporary Traffic Control Bicycle/Pedestrian Access ...................................................... 4

Flashing Yellow Arrow....................................................................................................... 5

Alternative Fuels ................................................................................................................. 5

Midblock Hybrid Beacon Pedestrian Crossings (Driver) ................................................... 5

Passenger Ferry ................................................................................................................... 5

Bicycle Passing Law ........................................................................................................... 5

Vehicle Prohibition ............................................................................................................. 5

Rail/Flangeway Gap Bicycle Warning ............................................................................... 5

Blind Hill Warning ............................................................................................................. 6

Recreational and Cultural Interest ...................................................................................... 6

Toll Plaza Electronic Toll Interoperability ......................................................................... 6

CHAPTER 2. METHOD .............................................................................................................. 7

Comprehension ....................................................................................................................... 7

Legibility .................................................................................................................................. 7

Participants .............................................................................................................................. 8

CHAPTER 3. RESULTS .............................................................................................................. 9

Lane Reduction Treatment .................................................................................................... 9

Comprehension ................................................................................................................... 9

Legibility ........................................................................................................................... 12

Temporary Traffic Control Bicycle/Pedestrian Access ..................................................... 13

Comprehension ................................................................................................................. 13

Legibility ........................................................................................................................... 14

Flashing Yellow Arrow ......................................................................................................... 15

Comprehension ................................................................................................................. 15

Legibility ........................................................................................................................... 17

Alternative Fuels ................................................................................................................... 17

Comprehension ................................................................................................................. 17

Legibility ........................................................................................................................... 20

Midblock Hybrid Beacon Pedestrian Crossing .................................................................. 21

Comprehension ................................................................................................................. 21

Legibility ........................................................................................................................... 23

Passenger Ferry ..................................................................................................................... 24

Comprehension ................................................................................................................. 24

Legibility ........................................................................................................................... 25

Bicycle Passing Law .............................................................................................................. 25

Comprehension ................................................................................................................. 26

Legibility ........................................................................................................................... 28
iv

Vehicle Prohibition ............................................................................................................... 29

Comprehension ................................................................................................................. 29

Legibility ........................................................................................................................... 30

Rail/Flangeway Gap Bicycle Warning ................................................................................ 30

Comprehension ................................................................................................................. 31

Legibility ........................................................................................................................... 32

Blind Hill Warning ............................................................................................................... 33

Comprehension ................................................................................................................. 33

Legibility ........................................................................................................................... 34

Recreation and Cultural Interest ........................................................................................ 35

Comprehension ................................................................................................................. 36

Legibility ........................................................................................................................... 36

Comprehension of Additional Recreation Signs............................................................... 37

Toll Plaza Electronic Toll Interoperability......................................................................... 37

Comprehension ................................................................................................................. 37

CHAPTER 4. RECOMMENDATIONS, DISCUSSION, AND CONCLUSIONS ................ 41

Lane Reduction Treatment .................................................................................................. 41

Recommendations for Lane Reduction Treatment ........................................................... 41

Temporary Traffic Control Bicycle/Pedestrian Access ..................................................... 42

Recommendations for Temporary Traffic Control Bicycle/Pedestrian Access ................ 42

Flashing Yellow Arrow ......................................................................................................... 42

Recommendations for Flashing Yellow Arrow ................................................................ 43

Alternative Fuels ................................................................................................................... 43

Recommendations for Alternative Fuels .......................................................................... 43

Midblock Hybrid Beacon Pedestrian Crossings ................................................................ 43

Recommendations for Midblock Hybrid Beacon Pedestrian Crossings ........................... 44

Passenger Ferry ..................................................................................................................... 44

Recommendations for Passenger Ferry ............................................................................ 44

Bicycle Passing Law .............................................................................................................. 45

Recommendations for Bicycle Passing Law ..................................................................... 45

Vehicle Prohibition ............................................................................................................... 45

Recommendations for Vehicle Prohibition ....................................................................... 45

Rail/Flangeway Gap Bicycle Warning ................................................................................ 46

Recommendations for Rail/Flangeway Gap Bicycle Warning ......................................... 46

Blind Hill Warning ............................................................................................................... 46

Recommendations for Blind Hill Warning ....................................................................... 47

Recreational and Cultural Interest ..................................................................................... 47

Recommendations for Recreational and Cultural Interest ................................................ 48

Toll Plaza Electronic Toll Interoperability......................................................................... 48

Recommendations for Toll Plaza Electronic Toll Interoperability ................................... 48

APPENDIX. ADDITIONAL RECREATION SIGNS RESULTS ......................................... 49

REFERENCES ............................................................................................................................ 57
v 

LIST OF FIGURES

Figure 1. Graph. Percentage of participants selecting each Lane Reduction Treatment sign 

alternative at each ranking value. ........................................................................................ 12

Figure 2. Graph. Percentage of participants selecting each Flashing Yellow Arrow sign 

alternative at each ranking value. ........................................................................................ 16

Figure 3. Graph. Percentage of participants selecting each Bicycle Passing Law sign 

alternative at each ranking value. ........................................................................................ 28

Figure 4. Graph. Percentage of participants selecting each Rail/Flangeway Gap Bicycle 

Warning sign alternative at each ranking value. ................................................................. 32

Figure 5. Graph. Percentage of participants selecting each Blind Hill Warning sign 

alternative at each ranking value. ........................................................................................ 34

Figure 6. Screenshot. Example of an in-context photo displaying a toll interoperability 

sign. ..................................................................................................................................... 38
vi 

LIST OF TABLES

Table 1. Lane Reduction Treatment sign alternatives selected for evaluation. .............................. 9

Table 2 Percentage of participant responses within each coded category for each Lane 

Reduction Treatment sign alternative. ................................................................................ 10

Table 3. Percentage of participants responding to each Lane Reduction Treatment sign 

category. .............................................................................................................................. 10

Table 4. Percentage of responses to when participants stated they would begin to 

merge/switch lanes. ............................................................................................................. 11

Table 5. Mean response distance by Lane Reduction Treatment sign alternative. ....................... 12

Table 6. Temporary Traffic Control Bicycle/Pedestrian Access sign alternatives selected 

for evaluation. ...................................................................................................................... 13

Table 7. Percentage of participant responses within each coded category for each 

Temporary Traffic Control Bicycle/Pedestrian Access sign alternative. ............................ 13

Table 8. Percentage of participant responses when participants imagined they were a 

bicyclist within each coded category for each Temporary Traffic Control 

Bicycle/Pedestrian Access sign alternative. ........................................................................ 14

Table 9. Percentage of participants who selected each mode of transportation, divided by 

alternative. ........................................................................................................................... 14

Table 10. Mean response distance by Temporary Traffic Control Bicycle/Pedestrian 

Access sign alternative. ....................................................................................................... 15

Table 11. Flashing Yellow Arrow sign alternatives selected for evaluation. ............................... 15

Table 12. Percentage of participant responses within each coded category for each Flashing 

Yellow Arrow sign alternative, by flashing state. ............................................................... 16

Table 13. Mean response distance by Flashing Yellow Arrow sign alternative. .......................... 17

Table 14. Alternative Fuels sign alternatives selected for evaluation. ......................................... 17

Table 15. Percentage of participant responses within each coded category for each 

Alternative Fuels sign alternative. ....................................................................................... 18

Table 16. Paired comparison results examining Alternative Fuels signs with versus without 

supplemental placards. ........................................................................................................ 18

Table 17. Percentage of participant responses by sign alternative to the statement, “I would 

expect this service to be provided at a traditional fueling station.” .................................... 19

Table 18. Percentage of participant responses by sign alternative to the statement, “If I 

were looking for typical unleaded fuel, I would be able to find it at this service 

station.” ............................................................................................................................... 19

Table 19. Percentage of participant responses by sign alternative to the question, “At this 

service station, what else might you expect to find?” ......................................................... 20

Table 20. Mean response distance by Alternative Fuels sign alternative. .................................... 20

Table 21. Summary of paired comparison differences by Alternative Fuels sign alternative. ..... 21

Table 22. Midblock Hybrid Beacon Pedestrian Crossings sign alternatives selected for 

evaluation. ........................................................................................................................... 21

Table 23. Percentage of participant responses within each coded category for each 

Midblock Hybrid Beacon Pedestrian Crossings sign alternative, by flashing state. ........... 22

Table 24. Percentage of participant responses within each coded category for each 

Midblock Hybrid Beacon Pedestrian Crossings sign alternative when a pedestrian 

was waiting to cross the street, by flashing state. ................................................................ 23
vii 

Table 25. Mean response distance by Midblock Hybrid Beacon Pedestrian Crossings sign 

alternative. ........................................................................................................................... 24

Table 26. Passenger Ferry sign alternatives selected for evaluation. ........................................... 24

Table 27. Percentage of participant responses within each coded category for each 

Passenger Ferry sign alternative. ......................................................................................... 24

Table 28. Percentage of participant responses by sign alternative to the question, “Who can 

ride this ferry?” .................................................................................................................... 25

Table 29. Mean response distance by Passenger Ferry sign alternative. ...................................... 25

Table 30. Bicycle Passing Law sign alternatives selected for evaluation..................................... 26

Table 31. Percentage of participant responses, from the perspective of a motorist, within 

each coded category for each Bicycle Passing Law sign alternative. ................................. 26

Table 32. Percentage of participant responses, from the perspective of a bicyclist, within 

each coded category for each Bicycle Passing Law sign alternative. ................................. 27

Table 33. Percentage of participant responses by sign alternative to the question, “Which 

of these statements is true?” ................................................................................................ 27

Table 34. Mean response distance by Bicycle Passing Law sign alternative. .............................. 29

Table 35. Vehicle Prohibition sign alternatives selected for evaluation. ...................................... 29

Table 36. Percentage of participant responses within each coded category for each Vehicle 

Prohibition sign alternative. ................................................................................................ 29

Table 37. Percentage of participant responses by sign alternative to the question, “Which 

types of transportation are prohibited?” .............................................................................. 30

Table 38. Mean response distance by Vehicle Prohibition sign alternative. ................................ 30

Table 39. Rail/Flangeway Gap Bicycle Warning sign alternatives selected for evaluation. ........ 31

Table 40. Percentage of participant responses within each coded category for each 

Rail/Flangeway Gap Bicycle Warning sign alternative. ..................................................... 31

Table 41. Participant responses to the question, “Would you dismount your bike before 

crossing the tracks?”............................................................................................................ 32

Table 42. Mean response distance by Rail/Flangeway Gap Bicycle Warning sign 

alternative. ........................................................................................................................... 33

Table 43. Blind Hill Warning sign alternatives selected for evaluation. ...................................... 33

Table 44. Percentage of participant responses within each coded category for each Blind 

Hill Warning sign alternative. ............................................................................................. 34

Table 45. Mean response distance by Blind Hill Warning sign alternative.................................. 35

Table 46. Recreation and Cultural Interest sign alternatives selected for evaluation, and 

response percentages. .......................................................................................................... 35

Table 47. Mean response distance by Recreation and Cultural Interest sign alternative. ............ 37

Table 48. Toll Interoperability sign alternatives selected for evaluation...................................... 37

Table 49. Percentage of participant responses within each coded category for each Toll 

Plaza Electronic Toll Interoperability sign alternative. ....................................................... 38

Table 50. Percentage of participants responding that they could pay the toll using a toll 

transponder for each lane. ................................................................................................... 39

Table 51. Percentage of participants responding that they could pay a toll without a toll 

transponder for each lane. ................................................................................................... 40

Table 52. Recreation sign results. ................................................................................................. 49
viii

LIST OF ABBREVIATIONS

Alt. alternative

ANSI American National Standard Institute

ATV all-terrain vehicle

DOT department of transportation 

FHWA Federal Highway Administration

MSe mean squared error

MUTCD Manual on Uniform Traffic Control Devices

PFS pooled fund study 

TCD traffic control device
1 

CHAPTER 1. INTRODUCTION

Traffic signs are an important communication tool that convey regulatory, warning, and guidance 

information to road users. The process of understanding user requirements for new signs is 

particularly important for symbol signs, which rely on a common nonverbal interpretation by a 

large and diverse population of drivers. 

The traffic control device (TCD) pooled fund study (PFS) focuses on a systematic evaluation of 

new TCDs, employing a process that addresses human factors and operations issues for each 

TCD idea. As part of the TCD PFS effort, the Federal Highway Administration (FHWA) Human 

Factors Team evaluated driver comprehension and legibility for sets of sign alternatives for both 

existing and proposed traffic signs. For some sets, participants were also asked to rank the 

effectiveness of the alternatives.

By pooling resources and expertise, rather than performing several independent research studies 

across the country, the TCD PFS provides local and State agencies faster responses to their needs

and new technologies using effective assessment skills and tools that enable consistent TCD idea 

identification and evaluation. The TCD PFS efforts address TCD issues identified by local and 

State jurisdictions, industries, and organizations and aid in the compliance to the Manual on 

Uniform Traffic Control Devices (MUTCD) rulemaking process and incorporation of novel 

TCDs into the MUTCD.(1)

TCD PFS members have selected various sign concepts to include as phase IV of a study to 

evaluate the effectiveness of concepts for new signs, most of which contain symbols. The 

remainder of this report describes the study effort. 

LITERATURE REVIEW

Traffic symbol signs communicate important messages to the driver or road user using an icon or 

graphical representation rather than words. A well-designed symbol can communicate 

instructions to the driver quickly and accurately, but ambiguous designs may be misunderstood 

and have potentially dangerous consequences. The current review examines a brief history of 

symbol signs, the advantages of well-designed symbol signs, and criteria for evaluating the 

effectiveness of a symbol sign. The evaluation criteria presented in this report informed the 

dependent measures that were assessed in this study. 

The concept of symbol signs has its early origins in Paris with the Convention on the 

International Circulation of Motor Vehicles held in 1909.(2) Because of this meeting, several 

European countries recommended adoption of four road sign warnings (hump, curve, road 

crossing, and railroad crossing). In 1949, the United Nations developed a new protocol on road 

signs in which 50 signs were specified and adopted by 30 countries.(2) This protocol was revised 

in 1953 and 1968 and adopted by more European, Asian, and South American countries. 

Although the United States had primarily used word signs, by 1970 the United States began the 

use of symbol signs, many of which came from the 1968 United Nations standards.(2)

The advantages to a well-designed symbol, in lieu of text, are numerous. Symbol signs can be 

identified at greater distances, providing drivers with important information from further away 
2 

and thus giving them more time to react to changing situations. Additionally, these signs can be 

identified quickly and more accurately at a glance, which is critical given the dynamic nature of 

the driving environment and the oftentimes cluttered visual scene. Symbol signs are better 

identified in adverse weather conditions (e.g., fog), where, due to the degraded visual conditions, 

focal vision (or recognition vision)—which is required to discern fine detail like text—would be 

impaired. Importantly, given the increasingly diverse makeup of nonnative drivers on the 

roadway, symbol signs have the advantage of being understood even by drivers who do not 

understand the language of the country. 

However, symbol signs may be rendered ineffective and potentially dangerous when the 

meaning of the sign is not adequately conveyed by the selected symbol. In a study by Ogden, 

Womack, and Mounce, motorists were surveyed regarding their understanding of work zone 

signing.(3) The researchers found that these motorists had some difficulty interpreting both word 

and symbol messages on signs. Dewar, Kline, and Swanson found that at the time of their study, 

only 16 out of 85 of the standard traffic symbols used in the United States were understood by 

more than 95 percent of the drivers in their sample.(4)

 Additionally, for 10 of the signs they 

examined, comprehension was less than 40 percent. In another study, several motorists 

interpreted the No Entry For Motorcycles sign and the End Speed Limit sign exactly opposite of 

the intended meaning for these signs.(5)

 A sign that is not comprehended or interpreted with the 

intended meaning can create a hazard for road users.

Despite the importance of well-designed symbol signs, there is no universally accepted standard

for evaluating the effectiveness of a design, nor a consistently applied comprehension accuracy 

criteria. Although there is not a definitive list of requirements for evaluating symbol signs, 

several researchers have proposed factors critical to the design and evaluation of symbol signs. 

Dewar proposed six criteria important to the design and evaluation of symbol signs listed and 

defined in this report:(6)

• Understandability: The ease with which the symbol can be understood. 

• Legibility distance: The greatest distance at which the symbol can be clearly read. 

• Conspicuity: The extent to which a sign can be easily detected or seen in a visually

complex environment. 

• Learnability: The extent to which the meaning of a symbol can be learned and 

remembered. 

• Glance legibility: The ease with which the symbol can be read when it is seen for only a 

fraction of a second. 

• Reaction time: How quickly the meaning of the sign can be identified. 

Additionally, Dewar, Kline, and Swanson had transportation experts rate the relative importance 

of these six criteria.(4) In their study, comprehension was prioritized as the most important 

criteria, followed closely by conspicuity. Reaction time and legibility distance were rated as 

equally important, and learnability was rated as least important. Indeed, this prioritization makes 
3 

logical sense in that a symbol that is both easy to understand and conspicuous should allow 

drivers to respond from greater distances and with faster reaction times. Previous symbol sign 

studies conducted for the TCD PFS have used Dewar’s list as guidance for symbol sign 

evaluation (e.g., the study by Katz, Dagnall, and O’Donnell).(7)

In addition to standards for sign evaluation, examining criteria for sign design is also important. 

Several symbol sign alternatives will be designed in the current study, and looking at human 

factors principles for sign design will be useful. Sanders and McCormick proposed five 

ergonomic principles for the design of symbol signs, which are highlighted as follows:(8)

• Spatial compatibility: The physical arrangement in space, relative to the position of 

information and directions. 

• Conceptual compatibility: The extent to which symbols and codes conform to people’s 

association. 

• Physical representation: The similarity between the content of the sign and the reality it

represents. 

• Familiarity: The extent to which the driver is familiar with the sign from his/her driving 

experience. 

• Standardization: The extent to which the codes used for different dimensions, such as 

color and shape, are consistent for all signs. 

Both Shinar et al.

(9)

 and Ben-Bassatt and Shinar(5) examined the topic of sign comprehension as it 

relates to the ergonomic principles listed in the preceding bulleted list. In both studies, there were 

high and significant correlations between the probability of sign comprehension and the extent to 

which the sign complied with the ergonomic principles of compatibility, familiarity, and 

standardization. Signs designed according to these principles should be easier for drivers to 

understand and make an appropriate response. 

RESEARCH GOALS AND SELECTED SIGNS

The FHWA Human Factors Team conducted phase IV of the symbol signs study series to 

develop and evaluate proposed alternatives for new traffic signs. The goals of this study were as 

follows: 

• Evaluate driver comprehension of selected signs. 

• Measure the legibility distance of selected signs.

• Provide recommendations on signs that merit consideration for addition to the 

MUTCD.(1)

The TCD PFS panel selected the following sign messages for symbol development and 

evaluation (see section, Sign Categories, for detailed descriptions of each sign type):
4 

• Lane Reduction Treatment. 

• Temporary Traffic Control Bicycle/Pedestrian Access. 

• Flashing Yellow Arrow. 

• Alternative Fuels. 

• Midblock Hybrid Beacon Pedestrian Crossings (Driver). 

• Passenger Ferry. 

• Bicycle Passing Law. 

• Vehicle Prohibition. 

• Rail/Flangeway Gap Bicycle Warning. 

• Blind Hill Warning. 

• Recreational and Cultural Interest. 

• Toll Plaza Electronic Toll Interoperability. 

RESEARCH APPROACH

The TCD PFS focuses on the systematic evaluation of new TCDs and employs a consistent 

process to research and address human factors and operations issues for these TCDs. As part of 

this effort, the FHWA Human Factors Team evaluated a selection of proposed symbols to ensure 

their effectiveness for driver comprehension and legibility distance. The research objectives of 

this study were to: 

• Perform a literature review examining the current state of practice for effective symbol

sign design. 

• Develop a set of symbol sign alternatives. 

• Perform a laboratory test to determine driver comprehension and legibility distance of the 

experimental symbol signs. 

• Provide recommendations on the symbol signs alternatives that should be considered for 

inclusion in the next edition of the MUTCD. 

SIGN CATEGORIES

The following sign categories for symbol development and evaluation were selected by the PFS

panel. Images of each of the sign alternatives are presented in chapter 3, Results. 

Lane Reduction Treatment

The current study results will be used in a future investigation of both the signing and lane 

markings best suited for lane reduction treatments or situations where one lane is ending. 

Temporary Traffic Control Bicycle/Pedestrian Access

Growing interest in pedestrian and bicycle safety has made bicycle and/or pedestrian pathways 

more common. As large public works projects displace paths and routes, special detour routes for 

bicycles and/or pedestrians will become more prevalent. The team assessed bicyclist and 
5 

pedestrian comprehension of such signs based on how users perceive the route use and choose a 

route appropriate for their mode of travel. 

Flashing Yellow Arrow 

The Flashing Yellow Arrow sign informs drivers that they are expected to yield at a flashing 

yellow traffic signal. Adequately conveying dynamic “flashing” in a static symbol is a challenge. 

This study investigated the most appropriate symbol to portray a flashing yellow arrow.

Alternative Fuels 

New alternative fuels (specifically hydrogen, liquid propane gas, biodiesel, and fast 

charging/slow charging electric vehicle stations) may require signing, alerting drivers to the 

location where these fuels can be obtained. 

Midblock Hybrid Beacon Pedestrian Crossings (Driver) 

Drivers may not understand what action to take when encountering hybrid beacon pedestrian 

crosswalks. Signs instructing drivers of the appropriate action to take at this type of crosswalk 

were investigated by the team. 

Passenger Ferry

The MUTCD has an approved sign to indicate a vehicle ferry.

(1) However, simply removing the 

vehicle symbol from this sign to indicate a passenger ferry would not be in conformance with the 

MUTCD standard. A symbol sign that indicates a passenger ferry was developed and evaluated

by the team. 

Bicycle Passing Law 

More than 20 States have passed legislation requiring motorists to provide a minimum of 3 ft of

clearance when passing bicyclists on the roadway.(10) However, there is not currently a standard 

sign that alerts motorists of this law. Many States and local highway agencies have developed 

their own signs to convey this message. These existing signs and several alternatives were tested 

for comprehension and legibility. 

Vehicle Prohibition 

Vehicle Prohibition signs indicate that certain vehicles (e.g., golf carts, motorcycles, jet skis, or 

all-terrain vehicles [ATVs]) are not permitted on bicycle or pedestrian pathways or trails. Some 

current symbols used by State and local highway agencies do not match existing symbols on 

signs compliant with the MUTCD. Additionally, some entities have expressed interest in

combining several symbols into a single sign. 

Rail/Flangeway Gap Bicycle Warning 

Given the expansion of fixed guideway transit networks throughout the country and an increase 

in bicycle travel, rails have been embedded into the roadway, creating a flush surface allowing 
6 

roadway users other than motor vehicles to share this same space. This design, although fine for 

motor vehicle traffic, is problematic for bicyclists, as bicycle tires can drop into the flangeway 

gap if the bicyclist does not cross the gap at an appropriate angle, creating a dangerous situation 

for the bicyclist. Additionally, the top of the rail can become slippery in wet conditions. There is 

currently no MUTCD-approved sign to warn bicyclists about this potential hazard, although 

some States and local highway agencies have developed signs for this purpose. Some of the signs 

display a regulatory or guidance-related message on a diamond-shaped warning sign. This usage

is inappropriate, as the diamond shape and yellow color are reserved for warning signs. 

Blind Hill Warning

Vertical curves can obscure key roadway features or activity that might lie ahead of an unaware 

driver and therefore represent a critical safety event. There is no well-accepted TCD for warning 

drivers of vertical curvature. The Hill Blocks View sign and Limited Sight Distance sign have 

demonstrated limited success in conveying messages related to limited sight distance. A test of 

signs for blind hill warning will evaluate user understanding of the specific hazard indicated by 

the sign and may produce an output that can also be applied to the limited sight distance 

applications as well.

Recreational and Cultural Interest

These signs direct road users to general areas of interest or to specific facilities or activities 

within these areas. These signs may be used to alert the road user to the attraction from the 

roadway or may guide users once already inside a park or other recreational or cultural area. The 

team investigated the understandability of specific signs in this category. 

Toll Plaza Electronic Toll Interoperability

To meet Moving Ahead for Progress in the 21st Century (MAP-21) requirements for federally 

funded facilities, the International Bridge, Tunnel and Turnpike Association began efforts toward 

designing technologies and business practices to implement national electronic toll 

interoperability within the United States.(11) Symbol signs to communicate that a specific toll has 

national interoperability capabilities were evaluated by the team.
7 

CHAPTER 2. METHOD

Data were collected both at the Turner-Fairbank Highway Research Center and in a mobile 

laboratory. The use of the mobile laboratory allowed the team to collect data from participants 

from outside of the Washington, DC, metropolitan area. Participants sat approximately 5 ft from 

a 60-inch LCD display. Signs were evaluated for comprehension and legibility. 

COMPREHENSION

The first portion of the study evaluated driver comprehension of each sign alternative in the 

different sign categories. This process consisted of multiple stages in which participants provided 

open-ended responses, multiple-choice responses, and subjective rankings of the signs. The 

open-ended and multiple-choice sections were between-subject factors, in which participants saw 

only one sign alternative from each sign category. Participants were shown one sign at a time in 

an appropriate and relevant context. Larger, physical print versions of each sign were provided to 

participants to allow for more detailed inspection. Specific questions were tailored for each sign 

type, which are detailed in chapter 3, Results. 

Some, but not all, sign sets were ranked by perceived effectiveness. In the ranking section, 

participants were shown all sign alternatives for a given category and then ranked each sign on 

how well each alternative would work to show the intended meaning of the sign. Participants 

completed all comprehension questions before completing the ranking questions to ensure that 

the exposure to alternatives did not influence their response. 

LEGIBILITY

Next, legibility distance (the maximum distance at which the participant can read text or

decipher the elements of the sign) was assessed. For the legibility distance evaluation, eight 

participants viewed the same individual signs and answered comprehension questions for each 

sign. 

For the test, each sign was shown one at a time and on a black background. The sign presentation 

began at a simulated distance of 1,000 ft (304.8 m). The sign expanded in size to simulate an 

approach speed of 45 mph. Participants were instructed to keep their eyes on the sign and to 

press a button on the table in front of them as soon as the sign became legible (i.e., as soon as 

they could identify the elements of the sign). When the button was pressed, the sign disappeared,

and the distance was recorded. The participant then described the sign aloud. If the participant 

was correct, the researcher began a new trial with a different sign. If the participant was

incorrect, the same sign reappeared and continued to increase in size, giving the participant 

another opportunity to press the button when the sign became legible. 

Correctness was deemed as anything that confirmed that the sign was legible to the participant. If 

the sign size reached the full screen without a correct response, the trial was terminated, and the 

next trial began. 
8 

PARTICIPANTS

Two hundred people participated. Half of these participants were recruited from the Washington, 

DC, metropolitan area and completed the experiment at the Turner-Fairbank Highway Research 

Center. The remaining 100 participants completed participation in the mobile lab (which traveled 

to locations in central and coastal Virginia and an area near Orlando, FL). In all cases, no 

differences in responses were found based on data collection location. As a result, all data were 

combined. Participants were at least 18 yr of age, possessed a valid U.S. driver’s license, and 

passed a visual acuity test with a minimum of 20/40 binocular vision, corrected if necessary. 

Before the start of the experiment, participants were asked to read and sign the informed consent 

form. Participants were paid $40 for their time.
9 

CHAPTER 3. RESULTS

This section describes the results for each of the sign types tested. The information provided in 

this section is specific to the context of this research study. Tested signs and sign assemblies do 

not necessarily comply with MUTCD provisions. State departments of transportation (DOTs) 

and local jurisdictions are required to use MUTCD-compliant signs and sign assemblies. If a 

State DOT and/or local jurisdiction is interested in using a new TCD or a different application of 

an existing device, it must receive approval to experiment from FHWA using the MUTCD 

experimentation process.

(1)

LANE REDUCTION TREATMENT

Table 1 presents all alternatives for Lane Reduction signs. Sign alternative (Alt.) 1, Alt. 2, and 

Alt. 3 are not in the MUTCD, whereas Alt. 4, Alt. 5, and Alt. 6 are already included in the 

MUTCD.

(1)

 The results of the comprehension, ranking, and legibility tasks are presented in the 

following subsections. 

Table 1. Lane Reduction Treatment sign alternatives selected for evaluation. 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6

All photos source: FHWA.

(1)

Comprehension 

Participants were presented with an image of a lane reduction roadway with a sign placed in the

appropriate context location. Participants were only exposed to a single lane reduction sign and 

were asked, “Imagine you are driving along the roadway and encounter this sign. What does this 

sign mean?” Open-ended responses were coded based on participants’ response of lane ending, 

merge, lane ends and merge combined, lane narrowing, or some other response. 

Table 2 gives the percentage of participant responses in each coded category by sign alternative. 

For example, 46.7 percent of the responses to Alt. 1 were coded as lane ending. Nonparametric 

analyses were performed to determine whether differences in responses varied by sign 

alternative. Statistically significant differences are noted by a p value of 0.05 (i.e., less than 

5 percent chance that the results would occur by chance) and are presented in bold font with an 

asterisk in the tables. Here, the percentage of participants who mentioned the lane was ending 

only (no mention of the need to merge) was significantly influenced by sign alternative. The 

percentage of participants who mentioned the need to merge (without mentioning that the lane 

was ending) also varied significantly as a function of sign alternative. No significant difference 

was found across sign alternatives in the percentage of participants who mentioned both the lane 

ending and the need to merge, the percentage of participants who indicated that the lane was 

narrowing, or the percentage of participants who gave incorrect responses. 
10 

Table 2 Percentage of participant responses within each coded category for each Lane 

Reduction Treatment sign alternative.

Sign 

Alternative 

Lane Ending 

Only (Percent) 

Merge Only 

(Percent)

Lane Ending

and Merge 

(Percent)

Lane 

Narrowing

(Percent) 

Other/ 

Incorrect

(Percent) 

Alt. 1 46.7 3.3 40.0 0.0 10.0 

Alt. 2 40.0 12.5 45.0 2.5 0.0 

Alt. 3 13.3 40.0 36.7 0.0 10.0 

Alt. 4 40.0 10.0 36.7 6.7 6.7 

Alt. 5 16.7 10.0 70.0 0.0 3.3 

Alt. 6 12.5 20.0 62.5 0.0 5.0 

p Value 0.011* 0.009* >0.05 >0.05 >0.05 

*Statistically significant difference. 

To better capture their understanding of the sign, participants were then asked to mark

checkboxes to indicate what they felt the sign meant. Results are presented in table 3. 

Participants could select more than one response (the total for each row will sum to more than 

100 percent). Nonparametric tests were performed to determine whether responses differed based 

on sign alternative.

Table 3. Percentage of participants responding to each Lane Reduction Treatment sign 

category. 

Sign 

Alternative 

Right Lane 

Closed 

(Percent) 

Left Lane 

Closed 

(Percent) 

Right Lane 

Ends (Percent) 

Left Lane Ends 

(Percent) 

Traffic Merging 

Ahead (Percent) 

Alt. 1 6.7 3.3 73.3 26.7 70.0 

Alt. 2 10.0 0.0 67.5 25.0 62.5 

Alt. 3 36.7 13.3 83.3 13.3 83.3 

Alt. 4 13.3 0.0 83.3 0.0 86.7 

Alt. 5 23.3 0.0 93.3 0.0 73.3 

Alt. 6 27.5 0.0 90.0 5.0 77.5 

p Value 0.018* 0.003* 0.045* <0.001* 0.206 

*Statistically significant difference. 

Paired comparison tests were performed to determine where differences existed. Significantly

more people responded that Alt. 3 meant that the right lane was closed than Alt. 1 (p = 0.003), 

Alt. 2 (p = 0.005), and Alt. 4 (p = 0.021). Similarly, significantly more people responded that 

Alt. 6 meant that the right lane was closed than Alt. 1 (p = 0.027) and Alt. 2 (p = 0.045). No 

other statistically significant differences between signs believed to indicate that the right lane 

was closed were found. Those who saw Alt. 3 were more likely to respond that the sign meant 

the left lane was closed than any other sign alternative (p < 0.05). No other significant 

differences were found for this response. 

Those who saw Alt. 2 were significantly less likely to indicate that the sign meant that the right 

lane ends than those who saw signs Alt. 5 (p = 0.006) and Alt. 6 (p = 0.009). Those who saw 
11 

Alt. 1 were significantly less likely than those who saw Alt. 5 (p = 0.044) to indicate that the sign 

meant that the right lane was ending. Those who saw signs Alt. 1, Alt. 2, and Alt. 3 were 

significantly more likely than those who saw signs Alt. 4, Alt. 5, or Alt. 6 to believe that the left 

lane was ending (p < 0.01). No differences were found between responses to signs Alt. 1, Alt. 2, 

and Alt. 3. This finding could have notable implications for driver behavior. 

Next, participants were asked about their actions/behaviors in the presence of the sign. They 

were asked, “Assume that you are traveling in the rightmost lane. When should you move out of 

the lane that is ending?” Table 4 presents the percentage of participants selecting each response 

by sign alternative. No statistically significant differences between sign alternatives were found. 

Table 4. Percentage of responses to when participants stated they would begin to 

merge/switch lanes.

Sign 

Alternative 

As Soon As

Possible 

(Percent) 

Somewhere Between 

Seeing the Sign and 

Where the Lane Begins

to Taper (Narrow) 

(Percent) 

When the Lane 

Begins to Taper 

(Narrow) 

(Percent) 

Follow the Lane Until It 

Ends and Transitions into 

a Single Lane (i.e., Follow 

the White Line) (Percent) 

Alt. 1 66.7 23.3 0.0 10.0 

Alt. 2 62.5 35.0 2.5 0.0 

Alt. 3 73.3 16.7 10.0 0.0 

Alt. 4 66.7 16.7 10.0 6.7 

Alt. 5 76.7 10.0 3.3 10.0 

Alt. 6 72.5 22.5 2.5 2.5 

p Value 0.771 0.057 0.615 0.748 

Finally, participants were told the intended meaning of the Lane Reduction sign. All alternatives 

were presented, and participants were asked to rank them in terms of perceived effectiveness

(figure 1). When only the top choice indicated by the participants was considered (ranking = 1), 

Alt. 5 was selected as the top choice by 34.5 percent (69/200) of the participants, and Alt. 4 was 

selected as the top choice by 26.5 percent (53/200) of the participants. There was a statistically 

significant difference in the rankings of each alternative, χ2(25) = 484.38, p < 0.001. 
12 

Source: FHWA.

Lane reductions 1–6 = Alt. 1–6, respectively.

Figure 1. Graph. Percentage of participants selecting each Lane Reduction Treatment sign 

alternative at each ranking value. 

Legibility 

Participants were presented with the same single Lane Reduction sign as they had previously 

seen. The sign slowly became larger on a television screen to simulate approaching a sign along 

the roadway. The sign was presented in isolation. Participants pressed a button to indicate that 

they could determine the content of the sign. A verbal response confirmed that the participant did 

indeed determine the sign content. Table 5 presents the mean simulated response distances for 

each of the signs. Mean response distance varied significantly by sign alternative, F(5) = 16.76, 

mean squared error (MSe) = 6,576.25, p < 0.001. 

Table 5. Mean response distance by Lane Reduction Treatment sign alternative. 

Sign Alternative Mean Distance (ft)

Alt. 1 446.97 

Alt. 2 432.78 

Alt. 3 459.10 

Alt. 4 551.81 

Alt. 5 408.81 

Alt. 6 379.58 

Pairwise comparison follow-up testing revealed Alt. 4 was recognized at a distance significantly 

greater than those for all other alternatives (p < 0.05). Alt. 6 was recognized at a distance 

significantly shorter than those for all other signs (p < 0.05). These results are not surprising, 

given that symbol signs generally contain more robust and less fine detail than worded signs. 
13 

The finer the detail, the more challenging it is to determine content at a distance.

TEMPORARY TRAFFIC CONTROL BICYCLE/PEDESTRIAN ACCESS 

Table 6 presents all alternatives for Temporary Traffic Control signs. All sign alternatives are 

already included in the MUTCD.(1)

 The results of the comprehension and legibility tasks are 

presented in the following subsections. 

Table 6. Temporary Traffic Control Bicycle/Pedestrian Access sign alternatives selected for 

evaluation. 

Alt. 1 Alt. 2 Alt. 3

 

All photos source: FHWA.(1)

Comprehension

Participants were only exposed to a single temporary TCD sign and were asked, “Imagine you 

are driving and encounter this sign. What does this sign mean?” The sign was placed in context 

in a location that was ambiguous as to whether it pertained to a bicycle/pedestrian path or the 

main roadway. Open-ended responses were coded based on responses of a detour plus the person 

or persons toward which the sign is directed (e.g., pedestrians, cyclists, vehicles).

The sign alternative significantly affected participant response, χ2(10) = 96.30, p < 0.001. 

Table 7 presents the percentage of participant responses coded to each category. Given the 

ambiguity of the sign placement, paired comparisons for this question were not performed. 

Notably, however, some of the responses did not fall into a category specifically related to a 

detour: e.g., “Construction ahead proceed with caution,” or “Drive through there with caution in 

case someone is walking. You could park there and walk if you wanted to.” 

Table 7. Percentage of participant responses within each coded category for each 

Temporary Traffic Control Bicycle/Pedestrian Access sign alternative.

Sign 

Alternative 

Detour Plus 

Specific Vehicle 

Types (Percent)

Detour 

Only 

(Percent)

Pedestrian 

Only, No 

Detour

(Percent)

Bike Only, 

No Detour 

(Percent)

Vehicle Only, 

No Detour

(Percent)

Other 

Response 

(Percent)

Alt. 1 0.0 84.3 0.0 0.0 2.9 12.9 

Alt. 2 54.3 11.4 1.4 11.4 2.9 18.6 

Alt. 3 41.7 33.3 1.7 1.7 0.0 21.7 

The same question was asked again, but this time participants were asked to imagine that they 

were a bicyclist: “Imagine you are bicycling and encounter this sign. What does this sign mean?” 

Once again, sign alternative significantly affected participant response, χ2(10) = 41.32, p < 0.001. 

Table 8 presents the percentage of participant responses coded to each category. 
14 

Table 8. Percentage of participant responses when participants imagined they were a 

bicyclist within each coded category for each Temporary Traffic Control 

Bicycle/Pedestrian Access sign alternative.

Sign 

Alternative 

Detour Plus

Specific Vehicle 

Types (Percent) 

Detour Only 

(Percent) 

Pedestrian 

Only, No 

Detour

(Percent) 

Bike Only, 

No Detour

(Percent) 

Vehicle Only, 

No Detour

(Percent) 

Other 

Response

(Percent) 

Alt. 1 8.6 57.1 0.0 10.0 11.4 12.9 

Alt. 2 17.1 31.4 0.0 21.4 1.4 28.6 

Alt. 3 31.7 30.0 1.7 5.0 1.7 30.0 

Finally, to assess more clearly their understanding of which road users should use an alternate 

route, participants were asked, “Imagine traveling along the roadway and encounter this sign. 

Which of these statements is true? (check all that apply).” Options were: “Motorists should use 

an alternate route,” “Bicyclists should use an alternate route,” and “Pedestrians should use an 

alternate route.”

Table 9 presents the percentage of participants who selected each mode that must use an 

alternate route by sign alternative. Nonparametric tests revealed that for each mode of 

transportation, sign type significantly influenced response: motorists, χ2(2) = 119.50, p < 0.001; 

bicyclists, χ2(2) = 64.62, p < 0.001; and pedestrians, χ2(2) = 54.33, p < 0.001. 

Table 9. Percentage of participants who selected each mode of transportation, divided by 

alternative.

Sign Alternative Motorists (Percent) Bicyclists (Percent) Pedestrians (Percent) 

Alt. 1 94.3 71.4 47.1 

Alt. 2 10.0 97.1 94.3 

Alt. 3 20.0 31.7 91.7 

p Value <0.001* <0.001* <0.001*

*Statistically significant difference. 

Supplemental pairwise comparisons revealed that significantly more participants responded that 

the motorists should use an alternate route with Alt. 1 than with the other two alternatives 

(p < 0.001). When asked about bicyclists, all three alternatives performed significantly 

differently from one another (p < 0.001). When asked about pedestrians, significantly fewer 

participants responded that pedestrians should use an alternate route with Alt. 1 than with the 

other two alternatives (p < 0.001). 

Legibility

The same legibility procedure was used as described in the Lane Reduction Treatment, Legibility

subsection. Mean response distances are presented in table 10. Mean response distance varied 

significantly by sign alternative, F(2) = 21.69, MSe = 7,856.06, p < 0.001. Pairwise comparison 

follow-up testing revealed that Alt. 1 generated significantly greater recognition distances than 

Alt. 2 and Alt. 3 (p < 0.05). No significant difference between Alt. 2 and Alt. 3 was found 

(p > 0.05). 
15 

Table 10. Mean response distance by Temporary Traffic Control Bicycle/Pedestrian Access 

sign alternative. 

Sign Alternative Mean Distance (ft)

Alt. 1 574.50 

Alt. 2 480.20 

Alt. 3 499.50 

FLASHING YELLOW ARROW 

Table 11 presents all alternatives for Flashing Yellow Arrow signs. Alt. 1 is compliant with the 

MUTCD, as creation of word message-only signs is allowed to address traffic situations not 

addressed by other standard signs.(1) Alt. 2 and Alt. 3 are not compliant with the MUTCD as they 

include a symbol. A condition in which no sign was placed next to the signal mast was also 

included. This option was designed to provide insight as to whether the sign is necessary to 

properly interpret the signal. The results of the comprehension, ranking, and legibility tasks are 

presented in the following subsections. 

Table 11. Flashing Yellow Arrow sign alternatives selected for evaluation. 

Alt. 1 Alt. 2 Alt. 3 Alt. 4

(no sign) 

All photos source: FHWA. 

Comprehension 

Participants were only exposed to a single Flashing Yellow Arrow sign and were asked, 

“Imagine you are driving and encounter this sign. You want to make a left turn and are 

positioned in the proper lane. How would you proceed?” The sign was placed in context next to 

the signal face on the mast arm. The yellow arrow was presented as animated (i.e., flashing), on, 

(i.e., steady and not flashing), and off (blank). Open-ended responses were coded based on the 

following responses: acknowledgment that the driver did not have the right of way and needed to 

watch for oncoming traffic, driver needed to use caution only, or some other response. 

Participant responses as percentages are presented in table 12. When all data were explored, no 

statistically significant differences between sign alternatives were found, nor was there a 

significant interaction between the flashing state of the signal mast and the sign alternative 

(p > 0.05). However, the flashing state of the signal was found to significantly affect response. 

Significantly more people who saw the animated flashing yellow arrow verbally indicated that 

they did not have the right of way and needed to yield to oncoming traffic (p < 0.05). This result 

suggests the flashing of the light itself is meaningful to drivers. 
16 

Table 12. Percentage of participant responses within each coded category for each Flashing 

Yellow Arrow sign alternative, by flashing state. 

Flashing State

Sign 

Alternative

Yield to Oncoming 

Traffic (Percent)

Use Caution Only 

(Percent)

Other 

(Percent)

Off Alt. 1 80.0 0.0 20.0 

Alt. 2 65.0 10.0 25.0 

Alt. 3 75.0 5.0 25.0 

Alt. 4 65.0 20.0 15.0 

On (steady) Alt. 1 65.0 20.0 15.0 

Alt. 2 75.0 5.0 20.0 

Alt. 3 60.0 20.0 20.0 

Alt. 4 45.0 30.0 25.0 

Animated (flashing) Alt. 1 70.0 30.0 0.0 

Alt. 2 100.0 0.0 0.0 

Alt. 3 85.0 5.0 10.0 

Alt. 4 70.0 30.0 0.0 

Next, participants were told the intended meaning of the Flashing Yellow Arrow sign. The three 

sign alternatives were presented (i.e., no blank sign was shown for ranking). Participants were 

asked to rank the signs in terms of perceived effectiveness (figure 2). When only the top choice 

indicated by the participants was considered (ranking = 1), Alt. 3 was selected as the top choice 

by 47.5 percent (95/200) of the participants, and Alt. 2 was selected as the top choice by 

34.0 percent (68/200) of the participants. There was a statistically significant difference in the 

rankings of each alternative, χ2(4) = 121.44, p < 0.001. Alt. 1 (all text) was consistently rated the 

least effective sign (p < 0.05). 

Source: FHWA.

Yellow flashing arrows 1–3 = Alt. 1–3, respectively.

Figure 2. Graph. Percentage of participants selecting each Flashing Yellow Arrow sign 

alternative at each ranking value. 
17 

Legibility

The same legibility procedure was used as described in the Lane Reduction Treatment, Legibility 

subsection. Mean response distances are presented in table 13. Mean response distance did not 

vary significantly by sign alternative, F(2) = 0.80, MSe = 3,455.212, p > 0.05. In other words, all 

signs were read at a similar distance.

Table 13. Mean response distance by Flashing Yellow Arrow sign alternative. 

Sign Alternative Mean Distance (ft)

Alt. 1 376.07 

Alt. 2 379.38 

Alt. 3 389.97 

ALTERNATIVE FUELS 

Table 14 presents all alternatives for Alternative Fuels signs. Alt. 7 is already included in the 

MUTCD.(1) All other sign alternatives are not MUTCD compliant. The results of the 

comprehension and legibility tasks are presented in the following subsections. 

Table 14. Alternative Fuels sign alternatives selected for evaluation. 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6

Alt. 7 Alt. 8 Alt. 9 Alt. 10 Alt. 11 Alt. 12 

 

All photos source: FHWA.(1)

BD = biodiesel; LNG = liquefied natural gas; M = methanol; HYD = hydrogen; H2 = hydrogen; CNG = compressed 

natural gas.

Comprehension 

Participants were only exposed to a single alternative fuel sign and were asked, “Imagine you are 

driving along the roadway and encounter this sign. What service is available at this exit?” 

Open-ended responses were coded as correct, partially correct, or incorrect/some other response. 

For example, for Alt. 3, a response of “fuel” would be considered partially correct because 

biodiesel is a type of fuel, but the response does not specify which specific type of fuel. The 

percentage of responses coded as correct, partially correct, and incorrect are displayed in 
18 

table 15. Note that p values are not available for Alt. 3 and Alt. 6, as all participants gave 

partially correct responses for these signs. 

Table 15. Percentage of participant responses within each coded category for each 

Alternative Fuels sign alternative.

Sign Alternative 

Correct 

(Percent)

Partially 

Correct 

(Percent)

Incorrect/Other 

Response 

(Percent) p Value 

Alt. 1 25.0 75.0 0.0 0.025*

Alt. 2 (supplemental placard) 60.0 40.0 0.0 0.527 

Alt. 3 0.0 100.0 0.0 + 

Alt. 4 (supplemental placard) 40.0 60.0 0.0 0.527 

Alt. 5 0.0 100.0 0.0 + 

Alt. 6 (supplemental placard) 40.0 55.0 5.0 0.019*

Alt. 7 5.0 95.0 0.0 < 0.001*

Alt. 8 (supplemental placard) 50.0 45.0 5.0 0.026*

Alt. 9 20.0 80.0 0.0 0.058 

Alt. 10 (supplemental placard) 50.0 50.0 0.0 1.0 

Alt. 11 10.0 35.0 55.0 0.047*

Alt. 12 10.0 20.0 70.0 0.045*

*Statistically significant difference. +p Values not available. 

Each alternative was evaluated with and without the supplemental placard. Overall, alternatives 

with the supplemental placard resulted in significantly more completely correct responses than 

those without (p < 0.001). Follow-up paired comparison analyses were performed, and summary 

results are presented in table 16. 

Table 16. Paired comparison results examining Alternative Fuels signs with versus without

supplemental placards.

No Placard Supplemental Placard p Value 

Alt. 1 Alt. 2 0.061 

Alt. 3 Alt. 4 0.002*

Alt. 5 Alt. 6 0.003*

Alt. 7 Alt. 8 0.003*

Alt. 9 Alt. 10 0.114 

*Statistically significant difference. 

Participants were also asked questions to assess more clearly their interpretation and 

understanding of the signs. Participant responses to the question, “I would expect this service to 

be provided at a traditional fueling station,” are found in table 17. Participant responses to the 

question, “If I were looking for typical unleaded fuel, I would be able to find it at this service 

station,” are found in table 18. Participant responses to the question, “At this service station, 

what else might you expect to find?” are presented in table 19. 
19 

Table 17. Percentage of participant responses by sign alternative to the statement, “I would 

expect this service to be provided at a traditional fueling station.” 

Sign Alternative Yes (Percent) No (Percent) 

Alt. 1 70.0 30.0

Alt. 2 (supplemental placard) 50.0 50.0

Alt. 3 18.0 82.0

Alt. 4 (supplemental placard) 50.0 50.0

Alt. 5 85.0 15.0

Alt. 6 (supplemental placard) 45.0 55.0

Alt. 7 60.0 40.0

Alt. 8 (supplemental placard) 25.0 75.0

Alt. 9 70.0 30.0

Alt. 10 (supplemental placard) 55.0 45.0

Alt. 11 35.0 65.0

Alt. 12 30.0 70.0

Table 18. Percentage of participant responses by sign alternative to the statement, “If I 

were looking for typical unleaded fuel, I would be able to find it at this service station.” 

Sign Alternative Yes (Percent) No (Percent)

Alt. 1 80.0 20.0

Alt. 2 (supplemental placard) 60.0 40.0

Alt. 3 90.0 10.0

Alt. 4 (supplemental placard) 20.0 80.0

Alt. 5 95.0 5.0

Alt. 6 (supplemental placard) 40.0 60.0

Alt. 7 70.0 30.0

Alt. 8 (supplemental placard) 40.0 60.0

Alt. 9 70.0 30.0

Alt. 10 (supplemental placard) 40.0 60.0

Alt. 11 50.0 50.0

Alt. 12 30.0 70.0
20 

Table 19. Percentage of participant responses by sign alternative to the question, “At this 

service station, what else might you expect to find?” 

Sign Alternative 

An Attendant 

(Percent Response 

of Yes)

Public Restroom

(Percent 

Response of Yes) 

Concessions 

(Percent 

Response of 

Yes)

Alt. 1 35.0 45.0 45.0

Alt. 2 (supplemental placard) 20.0 70.0 50.0

Alt. 3 60.0 75.0 35.0

Alt. 4 (supplemental placard) 60.0 50.0 30.0

Alt. 5 70.0 65.0 70.0

Alt. 6 (supplemental placard) 65.0 70.0 50.0

Alt. 7 45.0 6.0 55.0

Alt. 8 (supplemental placard) 75.0 70.0 55.0

Alt. 9 70.0 60.0 50.0

Alt. 10 (supplemental placard) 55.0 65.0 50.0

Alt. 11 30.0 50.0 35.0

Alt. 12 50.0 70.0 30.0

Legibility 

The same legibility procedure was used as described in the Lane Reduction Treatment, Legibility 

subsection. Mean response distances are presented in table 20. Mean response distance varied 

significantly by sign alternative, F(11) = 6.12, MSe = 32,579.22, p < 0.001. Pairwise comparison 

follow-up testing revealed a multitude of differences. Those differences are summarized in 

table 21. 

Table 20. Mean response distance by Alternative Fuels sign alternative. 

Sign Alternative Mean Distance (ft)

Alt. 1 478.55

Alt. 2 (supplemental placard) 350.7

Alt. 3 479.08

Alt. 4 (supplemental placard) 433.74

Alt. 5 479.91

Alt. 6 (supplemental placard) 407.02

Alt. 7 478.84

Alt. 8 (supplemental placard) 392.13

Alt. 9 489.05

Alt. 10 (supplemental placard) 389.57

Alt. 11 457.06

Alt. 12 407.91
21 

Table 21. Summary of paired comparison differences by Alternative Fuels sign alternative. 

Sign 

Alternative

Alt. 

1 

Alt. 

2 

Alt. 

3 

Alt. 

4 

Alt. 

5 

Alt. 

6 

Alt. 

7 

Alt. 

8 

Alt. 

9 

Alt. 

10 

Alt. 

11 

Alt. 

12 

Alt. 9 – * – – – * – * – * – * 

Alt. 5 – * – – – * – * – * – * 

Alt. 3 – * – – – * – * – * – * 

Alt. 7 – * – – – * – * – * – * 

Alt. 1 – * – – – * – * – * – * 

Alt. 11 – * – – – * – * – * – – 

Alt. 4 – * – – – – – – – – – – 

Alt. 12 * – * – * – * – * – – – 

*Statistically significant difference. 

–No difference. 

MIDBLOCK HYBRID BEACON PEDESTRIAN CROSSING

Table 22 presents all alternatives for Hybrid Beacon Crossing signs. None of the signs are 

compliant with the MUTCD. A condition in which no sign was placed next to the signal mast 

was also included. This action was designed to provide insight as to whether the sign is 

necessary to properly interpret the signal. The results of the comprehension and legibility tasks 

are presented in the following subsections. 

Table 22. Midblock Hybrid Beacon Pedestrian Crossings sign alternatives selected for 

evaluation. 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5

(no sign) 

All photos source: FHWA

Comprehension 

Participants were only exposed to a single Hybrid Beacon Pedestrian Crossing sign and were 

asked, “Imagine you are driving and encounter this signal. What does this sign mean?” The sign 

was placed in context next to the signal face on the mast arm. The signal was presented as off, 

flashing red, solid/steady red, or flashing yellow. In an additional condition, each of the signal 

statuses were shown without any sign. Participant responses are summarized in table 23. 

Responses were coded as correct based on the signal that was shown to each participant (e.g., a 

flashing red means stop, then proceed according to the rules applicable at a stop sign). As can be 

seen in the table, there were also people who provided a response that was not incorrect but did 

not address the question at hand (e.g., “It is a pedestrian crossing.”). 
22 

Table 23. Percentage of participant responses within each coded category for each Midblock Hybrid Beacon Pedestrian 

Crossings sign alternative, by flashing state. 

Flashing State 

Sign 

Alternative 

Correct 

Response 

(Percent)

Stop Only

(Percent)

Emergency 

Signal 

(Percent)

Responded to a 

Different Question

(Percent)

Caution 

(Percent)

Other 

Incorrect

(Percent)

Off Alt. 1 10.0 10.0 0.0 70.0 10.0 0.0

Alt. 2 10.0 20.0 0.0 70.0 0.0 0.0

Alt. 3 0.0 20.0 0.0 70.0 10.0 0.0

Alt. 4 10.0 30.0 0.0 50.0 0.0 10.0

Alt. 5 20.0 0.0 10.0 40.0 10.0 20.0

Flashing red Alt. 1 30.0 50.0 0.0 20.0 0.0 0.0

Alt. 2 20.0 60.0 0.0 0.0 0.0 20.0

Alt. 3 60.0 20.0 0.0 10.0 0.0 10.0

Alt. 4 20.0 50.0 0.0 20.0 0.0 10.0

Alt. 5 0.0 90.0 10.0 0.0 0.0 0.0

Steady red Alt. 1 90.0 10.0 0.0 0.0 0.0 0.0

Alt. 2 90.0 10.0 0.0 0.0 0.0 0.0

Alt. 3 70.0 30.0 0.0 0.0 0.0 0.0

Alt. 4 90.0 10.0 0.0 0.0 0.0 0.0

Alt. 5 90.0 0.0 10.0 0.0 0.0 0.0

Flashing yellow Alt. 1 0.0 40.0 20.0 10.0 0.0 30.0

Alt. 2 0.0 0.0 40.0 10.0 0.0 50.0

Alt. 3 40.0 0.0 60.0 0.0 0.0 0.0

Alt. 4 10.0 10.0 30.0 0.0 0.0 50.0

Alt. 5 0.0 0.0 90.0 0.0 10.0 0.0
23 

When all data are explored, no statistically significant differences between sign alternatives were 

found, χ2(20) = 28.80, p > 0.05. However, the light state of the signal was found to significantly 

affect response, χ2(15) = 210.78, p < 0.001. Given the large number of participants who did not 

provide a response and who answered the question presented, this result was not explored 

further. Next, participants were asked, “Imagine you are driving and encounter this signal. There 

is a pedestrian waiting to cross the street. How would you proceed?” Participant responses were 

coded as one of three responses: yield/stop for pedestrian, no indication of yielding/stopping, or 

other (table 24). 

Table 24. Percentage of participant responses within each coded category for each 

Midblock Hybrid Beacon Pedestrian Crossings sign alternative when a pedestrian was 

waiting to cross the street, by flashing state. 

Flashing State 

Sign 

Alternative

Yield/Stop 

(Percent)

No Yield/Stop 

(Percent)

Other 

(Percent)

Off Alt. 1 90.0 10.0 0.0

Alt. 2 60.0 20.0 20.0

Alt. 3 70.0 10.0 20.0

Alt. 4 90.0 10.0 0.0

Alt. 5 70.0 30.0 0.0

Flashing red Alt. 1 90.0 10.0 0.0

Alt. 2 100.0 0.0 0.0

Alt. 3 90.0 10.0 0.0

Alt. 4 100.0 0.0 0.0

Alt. 5 90.0 10.0 0.0

Steady red Alt. 1 100.0 0.0 0.0

Alt. 2 100.0 0.0 0.0

Alt. 3 80.0 20.0 0.0

Alt. 4 90.0 0.0 10.0

Alt. 5 100.0 0.0 0.0

Flashing yellow Alt. 1 80.0 20.0 0.0

Alt. 2 80.0 20.0 0.0

Alt. 3 80.0 20.0 0.0

Alt. 4 80.0 20.0 0.0

Alt. 5 90.0 10.0 0.0

When all data were explored, no statistically significant differences between sign alternatives 

were found, χ2(8) = 7.05, p > 0.05. However, the light state of the signal was found to affect 

response significantly, χ2(6) = 17.45, p = 0.008. 

Legibility 

The same legibility procedure was used as described in the Lane Reduction Treatment, Legibility 

subsection. Mean response distances are presented in table 25. Mean response distance varied 

significantly by sign alternative, F(3) = 10.16, MSe = 45,907.07, p < 0.001. Pairwise comparison 

follow-up testing revealed that Alt. 3 was recognized at a significantly shorter distance than 
24 

Alt. 1 and Alt. 2 (p < 0.05). Alt. 2 was recognized at a significantly longer distance than Alt. 3 

and Alt. 4 (p < 0.05). 

Table 25. Mean response distance by Midblock Hybrid Beacon Pedestrian Crossings sign 

alternative.

Sign Alternative Mean Distance (ft) 

Alt. 1 399.72 

Alt. 2 408.08 

Alt. 3 340.89 

Alt. 4 371.96 

PASSENGER FERRY 

Table 26 presents all alternatives for the Passenger Ferry signs. None of the alternatives are 

MUTCD compliant. The results of the comprehension and legibility tasks are presented in the 

following subsections. 

Table 26. Passenger Ferry sign alternatives selected for evaluation. 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 

 

All photos source: FHWA.

Comprehension 

Participants were asked to “Imagine you are driving and encounter this sign. What does this sign 

mean?” Participant responses were coded by response category: ferry, other recreational boat, 

and other. Responses by sign alternative are summarized in table 27. Nonparametric tests 

revealed that sign alternative significantly affected participant response, χ2(8) = 57.45, p < 0.001. 

Table 27. Percentage of participant responses within each coded category for each 

Passenger Ferry sign alternative.

Sign Alternative Ferry (Percent) 

Other Recreational Vehicle 

(Percent) Other (Percent) 

Alt. 1 77.5 7.5 15.0 

Alt. 2 50.0 37.5 12.5 

Alt. 3 30.0 55.0 15.0 

Alt. 4 72.5 2.5 25.0 

Alt. 5 85.0 10.0 5.0 
25 

Next, participants were asked to specify who could ride the ferry (check all that apply). A 

summary of these results is presented in table 28. Significant differences were found across sign 

alternatives in the percentage of people who indicated passenger vehicles, pedestrians, bicyclists, 

motorcyclists, freight vehicles, and transit vehicles were allowed on the ferry. 

Table 28. Percentage of participant responses by sign alternative to the question, “Who can 

ride this ferry?” 

Sign 

Alternative 

Passenger 

Vehicle 

(Percent 

Response of 

Yes) 

Pedestrians 

(Percent 

Response of 

Yes) 

Bicyclists 

(Percent 

Response of 

Yes) 

Motorcyclists 

(Percent 

Response of 

Yes) 

Freight 

Vehicles 

(Percent 

Response of 

Yes) 

Transit 

Vehicles 

(Percent 

Response of 

Yes) 

Alt. 1 95.0 32.5 27.5 40.0 95.0 27.5 

Alt. 2 7.5 95.0 97.5 7.5 0.0 0.0 

Alt. 3 5.0 100.0 2.5 0.0 0.0 0.0 

Alt. 4 25.0 15.0 15.0 15.0 95.0 12.5 

Alt. 5 97.5 42.5 35.0 52.5 7.5 5.0 

p Value <0.001* <0.001* <0.001* <0.001* <0.001* <0.001*

*Statistically significant difference. 

Legibility 

The same legibility procedure was used as described in the Lane Reduction Treatment, Legibility 

subsection. Mean response distances are presented in table 29. Mean response distance did not 

significantly vary by sign alternative, F(4) = 1.71, MSe = 12,166.63, p > 0.05.

Table 29. Mean response distance by Passenger Ferry sign alternative.

Sign Alternative Mean Distance (ft) 

Alt. 1 432.89 

Alt. 2 417.51 

Alt. 3 458.90 

Alt. 4 457.03 

Alt. 5 434.44 

BICYCLE PASSING LAW 

Table 30 presents all alternatives for Bicycle Passing Law signs. None of the alternatives are in 

the MUTCD. The results of the comprehension, ranking, and legibility tasks are presented in the 

following subsections. 
26 

Table 30. Bicycle Passing Law sign alternatives selected for evaluation. 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6

All photos source: FHWA. 

Comprehension 

Comprehension questions were presented in the context of a participant imagining 

himself/herself as both a motorist and a bicyclist. These questions were presented in a 

randomized order. Results as the motorist are presented first. Participants were asked, “Imagine 

you are driving along the roadway and encounter this sign near a bicyclist. What does this sign 

mean?” Responses were coded based on who participants reported should leave space while 

passing laterally, or if the sign was interpreted as a rule for longitudinal passing. Nonparametric 

tests revealed that sign alternative significantly affected participant response, χ2(25) = 41.35, 

p = 0.021. A summary of the percentage of each response type by sign alternative is presented in 

table 31. 

Table 31. Percentage of participant responses, from the perspective of a motorist, within 

each coded category for each Bicycle Passing Law sign alternative.

Sign 

Alternative 

Car Leaves 

Space, 

Lateral

(Percent) 

Bike Leaves 

Space, 

Lateral

(Percent) 

No Indicator of 

Who Leaves 

Space, Lateral

(Percent) 

Bike Passing 

Bike

(Percent) 

Longitudinal 

Space, 

Following

(Percent) 

Other 

(Percent) 

Alt. 1 53.3 0.0 10.0 3.3 3.3 30.0 

Alt. 2 70.0 0.0 0.0 0.0 0.0 30.0 

Alt. 3 90.0 3.3 0.0 0.0 0.0 3.3 

Alt. 4 76.6 3.3 3.3 0.0 0.0 16.7 

Alt. 5 65.0 5.0 10.0 0.0 0.0 20.0 

Alt. 6 56.7 0.0 3.3 0.0 0.0 40.0 

The same question was posed to participants from the perspective of a bicyclist: “Imagine you 

are bicycling along the roadway and encounter this sign near a motorist. What does this sign 

mean?” Responses were coded similarly. Nonparametric tests revealed that sign alternative 

significantly affected participant response, χ2(25) = 64.46, p < 0.001. A summary of the 

percentage of each response type by sign alternative is presented in table 32. 
27 

Table 32. Percentage of participant responses, from the perspective of a bicyclist, within 

each coded category for each Bicycle Passing Law sign alternative.

Sign 

Alternative 

Car Leaves 

Space, 

Lateral

(Percent) 

Bike Leaves 

Space, 

Lateral 

(Percent) 

No Indicator of 

Who Leaves 

Space, Lateral 

(Percent) 

Bike Passing 

Bike

(Percent) 

Longitudinal 

Space, 

Following 

(Percent) 

Other 

(Percent) 

Alt. 1 50.0 6.7 0.0. 6.7 3.3 33.3 

Alt. 2 47.5 17.5 0.0 0.0 0.0 35.0 

Alt. 3 86.7 3.3 0.0 0.0 3.3 6.7 

Alt. 4 50.0 16.7 3.3 0.0 0.0 30.0 

Alt. 5 37.5 17.5 17.5 0.0 0.0 27.5 

Alt. 6 26.7 16.7 0.0 0.0 0.0 56.7 

Next, to capture participant understanding of the sign more clearly, a multiple-choice question 

was presented: “Imagine traveling along the roadway and you encounter this sign. Which of 

these statements is true? (check all that apply).” 

A. As a motorist, I should provide at least 3 ft of space for bicyclists while passing. 

B. As a bicyclist, I should provide at least 3 ft of space for motorists to pass. 

C. As a motorist, I could receive a ticket for not providing 3 ft of space while passing a 

bicyclist. 

D. As a bicyclist, I could receive a ticket for not providing 3 ft of space for motorists to pass. 

A summary of responses, including significant differences between sign alternatives, are 

presented in table 33. 

Table 33. Percentage of participant responses by sign alternative to the question, “Which of 

these statements is true?” 

Sign Alternative

A. Motorist 

Leaves Space 

(Percent 

Response of 

Yes)

B. Bicyclist 

Leaves Space

(Percent 

Response of 

Yes)

C. Motorist 

Receives Ticket

(Percent 

Response of 

Yes)

D. Bicyclist 

Receives Ticket

(Percent 

Response of 

Yes)

Alt. 1 96.7 33.3 43.3 13.3 

Alt. 2 97.5 25.0 75.0 12.5 

Alt. 3 96.7 20.0 70.0 16.7 

Alt. 4 93.3 80.0 70.0 43.3 

Alt. 5 97.5 72.5 62.5 32.5 

Alt. 6 93.3 66.7 50.0 30.0 

p Value 0.908 <0.001* 0.056 0.017*

*Statistically significant difference. 

Next, participants were told the intended meaning of the Bicycle Passing sign. The six sign 

alternatives were presented, and participants were asked to rank them in terms of perceived 

effectiveness. When only the top choice indicated by the participants was considered 

(ranking = 1), Alt. 2 was selected as the top choice by 28.0 percent (56/200) of the participants, 
28 

and Alt. 4 was selected as the top choice by 22.5 percent (45/200) of the participants. There was 

a statistically significant difference in the rankings of each alternative, χ2(25) = 311.64, 

p < 0.001. Alt. 1 was consistently rated the least effective sign (p < 0.05). In general, data show 

that the bike signs were usually preferred by the participants in the following order: Alt. 4 or Alt.

2 or Alt. 5, Alt. 6 or Alt. 3, and Alt. 1. Figure 3 summarizes the percentage of time participants 

selected each of the sign alternatives at each ranking level.

Source: FHWA.

Bikes 1–6 = Alt. 1–6, respectively.

Figure 3. Graph. Percentage of participants selecting each Bicycle Passing Law sign 

alternative at each ranking value. 

Legibility 

The same legibility procedure was used as described in the Lane Reduction Treatment, Legibility 

subsection. Mean response distances are presented in table 34. Mean response distance 

significantly varied by sign alternative, F(5) = 20.77, MSe = 5,433.43, p < 0.001. Follow-up 

paired comparisons show that Alt. 1, Alt. 5, and Alt. 4 did not result in statistically significantly 

different legibility distances (p > 0.05). However, all three (Alt. 1, Alt. 5, and Alt. 4) were read at 

a distance significantly greater than that for Alt. 3, Alt. 2, and Alt. 6. Alt. 6 was more legible than 

Alt. 3 (p < 0.05). No difference between Alt. 2 and Alt. 3 was found (p > 0.05). 
29 

Table 34. Mean response distance by Bicycle Passing Law sign alternative.

Sign Alternative Mean Distance (ft)

Alt. 1 452.73 

Alt. 2 376.15 

Alt. 3 328.11 

Alt. 4 470.49 

Alt. 5 470.25 

Alt. 6 385.23 

VEHICLE PROHIBITION 

Table 35 presents all alternatives for Vehicle Prohibition signs that were evaluated. None of the 

alternatives are included in the MUTCD. The results of the comprehension and legibility tasks 

are presented in the following subsections. 

Table 35. Vehicle Prohibition sign alternatives selected for evaluation.

Alt. 1 Alt. 2 Alt. 3 

 

All photos source: FHWA. 

Comprehension

Participants were only exposed to a single Vehicle Prohibition sign and were asked, “Imagine 

you encounter this sign. What does this sign mean?” The sign was placed in context, near an 

entrance to a trail from a parking lot. Participant responses were coded into several categories: 

prohibition plus the specific pictured mode, prohibition plus an adjacent but not pictured 

category, prohibition plus general motorized vehicle, or other. A common response for an 

adjacent but not pictured category was “no jet skis.” Participant responses are summarized in 

table 36. Nonparametric analyses revealed that sign alternative influenced participant response, 

χ2(6) = 24.53, p < 0.001. 

Table 36. Percentage of participant responses within each coded category for each Vehicle 

Prohibition sign alternative.

Sign Alternative 

No Pictured Mode

(Percent) 

No Nonpictured 

Mode (Percent) 

No Motorized 

Vehicles (Percent) 

Other 

(Percent) 

Alt. 1 61.7 20.0 15.0 3.3 

Alt. 2 55.7 15.7 21.4 7.1 

Alt. 3 47.1 42.9 2.9 7.1 
30 

Next, to capture participant understanding of the sign more clearly, a multiple-choice question 

was presented: “Imagine you encounter this sign. Which types of transportation are prohibited 

(not allowed on trail)? (check all that apply).” Table 37 shows the percentage of participants who 

responded that bicyclists, motorcycles, ATVs, and snowmobiles were prohibited for each sign 

type. Significant differences were found between sign types for all response types. 

Table 37. Percentage of participant responses by sign alternative to the question, “Which 

types of transportation are prohibited?” 

Sign 

Alternative 

Bicyclists (Percent 

Response of Yes) 

Motorcycles 

(Percent 

Response of Yes)

ATVs (Percent 

Response of 

Yes) 

Snowmobiles 

(Percent Response 

of Yes)

Alt. 1 21.7 100.0 58.3 43.3 

Alt. 2 2.9 71.4 90.0 44.3 

Alt. 3 0.0 11.4 24.3 97.1 

p Value <0.001* <0.001* <0.001* <0.001*

*Statistically significant difference. 

Legibility 

The same legibility procedure was used as described in the Lane Reduction Treatment, Legibility 

subsection. Mean response distances are presented in table 38. Mean response distance did not 

significantly vary by sign alternative, F(2) = 1.49, MSe = 7,117.44, p > 0.05. 

Table 38. Mean response distance by Vehicle Prohibition sign alternative.

Sign Alternative Mean Distance (ft) 

Alt. 1 442.31 

Alt. 2 451.78 

Alt. 3 462.62 

RAIL/FLANGEWAY GAP BICYCLE WARNING 

Table 39 presents all alternatives For Rail Flangeway Gap signs that were evaluated. None of the 

alternatives are in the MUTCD. The results of the comprehension, ranking, and legibility tasks 

are presented in the following subsections. 
31 

Table 39. Rail/Flangeway Gap Bicycle Warning sign alternatives selected for evaluation. 

Alt. 1 Alt. 2 Alt. 3 Alt. 4

All photos source: FHWA. 

Comprehension 

Participants were only exposed to a single Rail Flangeway sign and were asked, “What does this 

sign mean?” The sign was placed in context, near a rail crossing. Participant responses fell into 

multiple categories: 

A. Use caution/care when crossings plus tracks plus bicycles. 

B. Use caution/care when crossings plus tracks plus bicycles plus need to cross tracks 

perpendicularly. 

C. Bike hazard or some other unspecified issue. 

D. Tracks ahead. 

E. Other. 

Participant responses are summarized in table 40. Nonparametric analyses revealed that sign 

alternative influenced participant response, χ2

(12) = 79.11, p < 0.001. 

Table 40. Percentage of participant responses within each coded category for each 

Rail/Flangeway Gap Bicycle Warning sign alternative.

Sign 

Alternative 

A. Bikes Use

Caution When 

Crossing

(Percent) 

B. Bikes Use Caution 

When Crossing Plus 

Need to Cross 

Perpendicularly

(Percent) 

C. Bike Hazard 

or Some Other 

Unspecified 

Issue (Percent) 

D. Tracks 

Ahead 

(Percent) 

E. Other 

(Percent) 

Alt. 1 22.0 8.0 8.0 54.0 8.0 

Alt. 2 66.0 2.0 4.0 4.0 24.0 

Alt. 3 22.0 12.0 2.0 18.0 46.0 

Alt. 4 24.0 8.0 0.0 16.0 52.0 

To gain better insight into participant understanding of the sign, each was asked, “Imagine that 

you are traveling by bicycle and encounter this sign. Would you dismount your bike before 

crossing the tracks?” Participant responses are summarized in table 41. Nonparametric analyses 

revealed that sign alternative did not influence participant response, χ2(3) = 4.27, p > 0.05. 
32 

Table 41. Participant responses to the question, “Would you dismount your bike before 

crossing the tracks?” 

Sign Alternative Yes (Percent) No (Percent) 

Alt. 1 36.0 64.0 

Alt. 2 50.0 50.0 

Alt. 3 56.0 44.0 

Alt. 4 48.0 52.0 

Next, participants were told the intended meaning of the Rail Flangeway sign. The four sign 

alternatives were presented, and participants were asked to rank them in terms of perceived 

effectiveness. Sign alternative significantly affected ranking, χ2(9) = 293.96, p < 0.001. When 

only the top choice indicated by the participants was considered (ranking = 1), Alt. 2 was 

selected as the top choice by a majority of the participants. The data suggests that the tracks signs 

were usually preferred by the participants in the following order: Alt. 2, Alt. 1, Alt. 3 or Alt. 4. 

Figure 4 summarizes the percentage of time participants selected each of the sign alternatives at 

each ranking level.

Source: FHWA.

Tracks 1–4 = Alt. 1–4, respectively.

Figure 4. Graph. Percentage of participants selecting each Rail/Flangeway Gap Bicycle 

Warning sign alternative at each ranking value. 

Legibility 

The same legibility procedure was used as described in the Lane Reduction Treatment, Legibility 

subsection. Mean response distances are presented in table 42. Mean response distance 

significantly varied by sign alternative, F(3) = 16.23, MSe = 3,114.21, p < 0.001. Follow-up 

paired comparisons revealed that Alt. 1 was recognized at a distance significantly shorter than 
33 

that for Alt. 2, Alt. 3, and Alt. 4 (p < 0.001). No differences between Alt. 2, Alt. 3, and Alt. 4 

were found (p > 0.05). 

Table 42. Mean response distance by Rail/Flangeway Gap Bicycle Warning sign 

alternative.

Sign Alternative Mean Distance (ft)

Alt. 1 320.91 

Alt. 2 375.86 

Alt. 3 389.67 

Alt. 4 386.31 

BLIND HILL WARNING 

Table 43 presents the alternative Blind Hill Warning signs that were evaluated. Alt. 1 is already 

included in the MUTCD.(1) All other signs are not MUTCD compliant. The results of the 

comprehension, ranking, and legibility tasks are presented in the following subsections. 

Table 43. Blind Hill Warning sign alternatives selected for evaluation. 

Alt. 1 Alt. 2 Alt. 3 Alt. 4

 

All photos source: FHWA.(1)

Comprehension 

Participants were posed an open-ended question to assess comprehension of the Blind Hill 

Warning sign. The sign was placed in-context near the crest of a hill. The first question was, 

“Imagine you are driving and encounter this sign. What does this sign mean?” Participant 

responses were coded based on the following: 

A. Mention of a sight obstruction and a hill/mountain/similar. 

B. Mention of a hill (but no sight obstruction). 

C. Mention of a sight obstruction (but no hill). 

D. Use caution (but no specifics as to why). 

E. Other. 

Nonparametric analyses revealed that sign alternative influenced participant response, 

χ2

(12) = 113.75, p < 0.001. A summary of responses is presented in table 44. 
34 

Table 44. Percentage of participant responses within each coded category for each Blind 

Hill Warning sign alternative.

Sign 

Alternative 

A. Sight 

Obstruction Plus

Hill (Percent) 

B. Hill 

(Percent) 

C. Sight 

Obstruction 

(Percent) 

D. Use 

Caution 

(Percent) 

E. Other 

(Percent) 

Alt. 1 58.0 2.0 28.0 8.0 4.0 

Alt. 2 14.0 84.0 0.0 0.0 2.0 

Alt. 3 50.0 16.0 12.0 18.0 4.0 

Alt. 4 34.0 38.0 6.0 10.0 12.0 

Next, participants were told the intended meaning of the Blind Hill Warning sign. The four sign 

alternatives were presented, and participants were asked to rank them in terms of perceived 

effectiveness (figure 5). Sign alternative significantly affected ranking, χ2(9) = 323.52, p < 0.001. 

When only the top choice indicated by the participants was considered (ranking = 1), Alt. 1 was 

selected as the top choice by the majority of participants 65.5 percent (131/200). The data show 

that the Blind Hill Warning signs were usually preferred by the participants in the following 

order: Alt. 1, Alt. 3, Alt. 2, and Alt. 4. 

Source: FHWA.

Hills 1–4 = Alt. 1–4, respectively.

Figure 5. Graph. Percentage of participants selecting each Blind Hill Warning sign 

alternative at each ranking value. 

Legibility 

The same legibility procedure was used as described in the Lane Reduction Treatment, Legibility 

subsection. Mean response distances are presented in table 45. Mean response distance 

significantly varied by sign alternative, F(3) = 14.88, MSe = 4,445.71, p < 0.001. Follow-up 

paired comparisons revealed that Alt. 1 and Alt. 2 were recognized at a distance significantly 
35 

greater than that for Alt. 3 and Alt. 4 (p < 0.01). No other statistically significant differences 

were found (p > 0.05). 

Table 45. Mean response distance by Blind Hill Warning sign alternative.

Sign Alternative Mean Distance (ft)

Alt. 1 439.14 

Alt. 2 424.89 

Alt. 3 371.71 

Alt. 4 367.29 

RECREATION AND CULTURAL INTEREST 

Table 46 presents all alternative Recreation and Cultural Interest signs that were evaluated. All 

signs are already included it the MUTCD, except for Alt. 11, which includes the trailer camping 

symbol from D9-3a (a General Service sign) on the brown background of a Recreation and 

Cultural Interest sign.(1)

 The results of the comprehension and legibility tasks are presented in the 

following subsections. 

Table 46. Recreation and Cultural Interest sign alternatives selected for evaluation, and 

response percentages. 

Sign 

Alternative Alternative Image Response 

Coded Response 

(Percent) 

Alt. 1

 

Camping 32.7 

Camping plus trailer 17.3 

Other 50.0 

Alt. 2

 

Camping 25.0 

Camping plus recreational 

vehicle 23.1 

Other 51.9 

Alt. 3 Parking 86.0 

Police station 12.0 

Other 2.0 

Alt. 4

 

Lighthouse 91.7 

Other 8.3 

Alt. 5

 

First aid 66.7 

Hospital 29.2 

Urgent care 2.1 

Other 2.1 
36 

Sign 

Alternative Alternative Image Response 

Coded Response 

(Percent) 

Alt. 6

 

Boat ramp 58.0 

Boating activity 24.0 

Other 18.0 

Alt. 7

 

Marina 24.0 

Anchor 58.0 

Other 18.0 

Alt. 8

 

Winter recreation area 10.0 

Specific winter recreation area 54.0 

Snow area 12.0 

Other 24.0 

Alt. 9

 

Sanitary waste disposal for 

recreational vehicle 

8.0 

Camping 64.0 

Other 28.0 

Alt. 10 

 

Picnic area 94.0 

Snack bar/food area 2.0 

Other 4.0 

Alt. 11 

 

Camping 18.0 

Specific type of camping 48.0 

Other 34.0 

Alt. 12 Camping 46.0 

Specific type of camping 46.0 

Other 8.0 

All photos source: FHWA.(1)

Comprehension 

Participants were presented with an in-context interest sign for Lincoln State Park positioned 

along the side of the roadway and were asked, “What amenities are available at Lincoln State 

Park?” Responses were coded and are presented in table 46. 

Legibility 

The same legibility procedure was used as described in the Lane Reduction Treatment, Legibility 

subsection. Mean response distances are presented in table 47. Mean response distance 

significantly varied by sign alternative, F(3) = 14.88, MSe = 4,445.71, p < 0.001. 
37 

Table 47. Mean response distance by Recreation and Cultural Interest sign alternative. 

Sign Alternative Mean Distance (ft)

Alt. 1 420.76 

Alt. 2 434.09 

Alt. 3 564.60 

Alt. 4 437.04 

Alt. 5 535.74 

Alt. 6 421.22 

Alt. 7 480.11 

Alt. 8 517.28 

Alt. 9 430.89 

Alt. 10 518.73 

Alt. 11 471.97 

Alt. 12 528.13 

Comprehension of Additional Recreation Signs 

Seventy-two additional Recreation signs were also evaluated for comprehension as part of a 

separate task. These additional signs were those that may not be commonly used or seen as 

appropriate for highway signing, but rather would likely be used in parks or recreation areas. 

Participants were told that they would be presented with a series of signs that they might see in 

or near a park or recreation area. They were shown one sign at a time on a plain black 

background and were instructed to indicate the meaning of each sign or what service the sign 

was telling them was available. The responses were coded and are presented in the appendix. 

TOLL PLAZA ELECTRONIC TOLL INTEROPERABILITY 

Table 48 presents all alternatives for Toll Interoperability signs that were evaluated. None of 

these alternatives are compliant with the MUTCD. The results of the comprehension tasks are 

presented in the following subsections. 

Table 48. Toll Interoperability sign alternatives selected for evaluation. 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6

 

All photos source: FHWA. 

Comprehension 

Participants were presented with an in-context photo (see figure 6 as an example). Each 

participant was only shown one of the Interoperability signs and was asked, “Imagine you are 

driving on a toll road and encounter this sign. What does this sign mean?” Participants were 
38 

directed to the individual Interoperability sign as the focus of their response. Participant 

responses were coded as one of four major responses: transponder, a multistate transponder (or 

acknowledgment that the transponder could be used at any toll plaza), or don’t know/other. 

Participant responses are summarized in table 49. Nonparametric statistics revealed that sign 

alternative did not affect participant responses, χ2

(10) = 16.25, p > 0.05. 

Source: FHWA.

Figure 6. Screenshot. Example of an in-context photo displaying a toll interoperability sign. 

Table 49. Percentage of participant responses within each coded category for each Toll 

Plaza Electronic Toll Interoperability sign alternative. 

Sign Alternative 

Transponder 

(Percent)

Multistate Transponder 

(Percent)

Don’t Know/Other 

(Percent)

Alt. 1 75.0 0.0 25.0 

Alt. 2 56.7 0.0 43.3 

Alt. 3 83.3 3.3 13.3 

Alt. 4 36.0 0.0 35.0 

Alt. 5 63.3 0.0 36.7 

Alt. 6 86.7 0.0 13.3 

Next the potential effects of education about interoperability were explored. One-third of the 

participants were told, “You’ve recently received a letter in the mail stating that there is a new 

effort to allow interoperability between different toll roads and toll transponder brands. This 

interoperability will allow you to pay tolls on any compatible toll road with any transponder 

brand. This special symbol will indicate toll road compatibility.” The remaining participants did 

not receive this education.
39 

Participants were then asked, “Imagine you are driving on a toll road and encounter this sign. 

You have an E-ZPass® brand toll transponder. Which lane(s) can you use to pay the toll? (select 

all that apply).” A summary of responses is presented in table 50. See figure 6 for an example of 

lane labeling. For this section only, a seventh alternative was included that did not have an 

Interoperability sign. Overall (independent of education), the Interoperability sign that 

participants saw did not influence their lane choices (p > 0.05). The education itself, however, 

did influence participant response. Participants who received the education were significantly 

more likely to select lane 1 than those who did not receive the education (p = 0.016). No other 

comparisons were statistically significant.

Table 50. Percentage of participants responding that they could pay the toll using a toll 

transponder for each lane.

Education 

Sign 

Alternative 

Lane 1 

(Percent)

Lane 2 

(Percent)

Lane 3 

(Percent)

No education Alt. 1 100.0 0.0 0.0

Alt. 2 80.0 10.0 10.0

Alt. 3 100.0 0.0 0.0

Alt. 4 90.0 30.0 30.0

Alt. 5 100.0 30.0 20.0

Alt. 6 100.0 40.0 30.0

Alt. 7 80.0 20.0 10.0

Education Alt. 1 100.0 0.0 0.0

Alt. 2 100.0 20.0 20.0

Alt. 3 100.0 20.0 20.0

Alt. 4 100.0 0.0 0.0

Alt. 5 100.0 10.0 0.0

Alt. 6 100.0 0.0 0.0

Alt. 7 100.0 40.0 20.0

Finally, the participants’ general understanding of toll transponder use was explored. One-third 

of the participants were asked, “Imagine you are driving on a toll road and encounter this sign. 

You do not have a toll transponder. Which lane(s) can you use to pay the toll? (select all that 

apply).” As expected, the Interoperability sign did not significantly affect lane choice across all 

three lanes (p > 0.05). As can be seen in table 51, participants clearly understood that they could 

not travel in lane 1 without a transponder. 
40 

Table 51. Percentage of participants responding that they could pay a toll without a toll 

transponder for each lane.

Sign Alternative Lane 1 (Percent) Lane 2 (Percent) Lane 3 (Percent)

Alt. 1 0.0 100.0 100.0

Alt. 2 0.0 100.0 90.0

Alt. 3 0.0 100.0 100.0

Alt. 4 0.0 100.0 100.0

Alt. 5 0.0 100.0 90.

Alt. 6 0.0 100.0 100.0
41 

CHAPTER 4. RECOMMENDATIONS, DISCUSSION, AND CONCLUSIONS

This section summarizes the results for each of the tested sign types and provides 

recommendations based on those results. The tested signs and sign assemblies do not necessarily 

comply with MUTCD provisions. As noted in chapter 3, State DOTs and local jurisdictions are 

required to use MUTCD-compliant signs and sign assemblies. If a State DOT and/or local 

jurisdiction is interested in using a new TCD or a different application of an existing device, they 

must receive approval from FHWA to experiment using the MUTCD experimentation process.(1)

LANE REDUCTION TREATMENT

According to the open-ended responses, between 86.7 and 97.5 percent of participants in each 

signing category responded that a lane was ending and/or there would be merging traffic ahead. 

However, when the researchers looked at the responses for the multiple-choice question, the 

participants seemed to be confused about which lane was ending, depending on the signing 

alternative that they viewed. Even though all sign alternatives were intended to indicate that the 

right lane was ending, participants who viewed Alt. 1, Alt. 2, and Alt. 3 were significantly more 

likely than those who saw Alt. 4, Alt. 5, or Alt. 6 to believe that the left lane was ending. 

Therefore, the use of arrows could possibly be contributing to this confusion regarding which 

lane is ending. 

The signing alternatives also influenced whether participants were likely to indicate that a lane 

was closed (rather than ending). Participants who viewed Alt. 3 were more likely to indicate that 

the sign meant that the left lane was closed than those who viewed any other sign alternative. 

Participants who viewed Alt. 3 were also more likely than those who viewed Alt. 1, Alt. 2, or 

Alt. 4 to report that the right lane was closed. Participants who viewed Alt. 6 were more likely 

than those who viewed Alt. 1 or Alt. 2 to report that the right lane was closed. 

Based on these responses, it is evident that Alt. 4 and Alt. 5 performed the best in terms of 

conveying the intended meaning (right lane ends) and not conveying unintended meaning (e.g., 

right lane closed, left lane closed, left lane ends). More participants reported that the right lane 

ends when viewing Alt. 5 (93.3 percent) than when viewing Alt. 4 (83.3 percent), and Alt. 5 was 

selected as the top choice by more participants (34.5 percent) than Alt. 4 (26.5 percent). Alt. 6 

also performed well in terms of comprehension; however, it had a significantly shorter legibility 

distance than all other alternatives.

Recommendations for Lane Reduction Treatment

Although Alt. 5 may be slightly easier for participants to understand than Alt. 4, they both had 

high comprehension, and both are currently allowed in the MUTCD. Furthermore, Alt. 4 was 

recognized at a legibility distance significantly greater than all other alternatives. This result is 

not surprising, as symbol signs tend to have longer legibility distances than text signs. Therefore, 

either Alt. 4 or Alt. 5 would be acceptable for use. Alt. 6 also performed well in terms of 

comprehension and is currently allowed in the MUTCD; however, it had significantly shorter 

legibility distances than all other alternatives.
42 

TEMPORARY TRAFFIC CONTROL BICYCLE/PEDESTRIAN ACCESS 

As shown in table 6, the primary difference between the three sign alternatives is whether, and 

what, specific mode(s) of transportation are shown on the sign. The results shown in table 9

indicate that if a specific mode of transportation is not shown on the sign (Alt. 1), the majority of 

participants (94.3 percent) believed that motorists should use an alternative route. Participants 

generally assumed (71.4 percent) that bicyclists would also follow the detour. Only 47.1 percent 

of participants believed that pedestrians should follow the detour as well. When both pedestrians 

and bicycles are shown on the sign (Alt. 2), 94.3 percent of participants indicated that pedestrians 

should use an alternate route, and 97.1 percent indicated that bicyclists should use an alternate 

route. When only a pedestrian is shown on the sign (Alt. 3), 91.7 percent of participants believed 

pedestrians should use an alternate route, and only 31.7 percent of participants believed 

bicyclists should use an alternate route. However, when participants are shown the bicycle and/or 

pedestrian symbols, motorists may still interpret the sign as applicable to them as well. For 

example, Alt. 3 shows a pedestrian on the sign, but 20.0 percent of participants who viewed this 

sign still responded that motorists should take the detour. 

Recommendations for Temporary Traffic Control Bicycle/Pedestrian Access 

In general, participants tended to indicate that the detour applies to the transportation mode(s) 

shown on the sign. However, motorists may still believe the sign applies to them, even when the 

sign does not indicate it (table 9, Alt. 3 example). Therefore, although the signs appear to be 

generally effective, this type of sign may not be completely clear as evaluated. The contextual 

placement of the sign for this study was intentionally ambiguous. However, this ambiguous 

placement could be representative of some real-world situations where a path cannot be seen 

from the location of the sign. Therefore, the sign should ideally be placed and angled in such a 

way that it is clear that the sign is directed only toward pedestrians and bicyclists. Additionally, 

although Alt. 1 had significantly higher legibility distances than Alt. 2 and Alt. 3, including the 

pedestrian and bicycle symbols is likely acceptable, as pedestrians and bicyclists are generally 

traveling at lower speeds on sidewalks or trails. 

FLASHING YELLOW ARROW

As indicated in the results, there were no significant differences between sign alternatives, nor 

was there a significant interaction between the flashing state of the signal mast and sign 

alternative. Regardless of sign alternative or flashing state, between 75.0 and100.0 percent of 

participants reported that the driver needed to yield to oncoming traffic or use caution. This 

outcome was also true for participants who viewed Alt. 4 (no sign), signifying that even with no 

sign at all, people would choose to either yield to oncoming traffic or use caution. The results 

also indicated that significantly more people who saw the animated flashing yellow arrow 

verbally indicated that they did not have the right of way and needed to yield to oncoming traffic. 

This result is important because it suggests that the flashing light carries meaning to drivers. 

When the participant rankings of the signs are considered, participants generally preferred Alt. 3 

and Alt. 2 over Alt. 1. All three signs had similar legibility distances. Although there were no 

statistically significant differences, more participants selected Alt. 3 as their top choice than 
43 

Alt. 2. Alt. 3 also had a slightly longer legibility distance (although, again, the difference was not 

significant).

Recommendations for Flashing Yellow Arrow 

With only 70.0 percent of participants reporting that they need to yield to oncoming traffic when 

viewing the animated flashing yellow arrow with no sign, not using a sign at all may be 

premature. However, in the future, signs may not be needed or may be able to be removed after a 

certain period of time. Alt. 3 or Alt. 2 are both acceptable signs to use. 

ALTERNATIVE FUELS

As indicated in table 15, participants were, in general, more likely to be partially correct (e.g., 

indicating “fuel” without specifying what type of fuel) than fully correct (i.e., indicating the 

correct type of fuel that was available). Keep in mind, however, that, depending on the goals of 

the driver (i.e., the specificity of the type of fuel the driver is trying to find), a partially correct 

response could mislead the driver to make an incorrect decision. As such, these results should be 

interpreted with caution. Additionally, participants were more likely to be fully correct (i.e., 

understand what type of fuel is available) when viewing signs with the supplemental placards 

than when viewing signs without the supplemental placards. Participants viewing the signs with 

the supplemental placards were also less likely to expect the service to be provided at a 

traditional fueling station and/or expect that they would also be able to find unleaded fuel at that 

service station. Although the signs without the placards tended to have higher legibility distances 

than the signs with the placards, the placards are necessary for comprehension of the signs. 

Participants had particular difficulty partially understanding Alt. 11 and Alt. 12, presumably 

because these signs include only the abbreviations and do not include the gas pump symbol. This 

result suggests that the gas pump symbol is helpful. 

Participants were not asked if they use any of these types of alternative fuels. Presumably, people 

who use such alternative fuels may be more familiar with the abbreviations for these fuels, and 

thus results may have been varied if alternative fuel users, specifically, were included in the 

study. 

Recommendations for Alternative Fuels 

Alternative Fuels signs should include the gas pump symbol and a supplemental placard 

indicating the type of alternative fuel that is offered. 

MIDBLOCK HYBRID BEACON PEDESTRIAN CROSSINGS 

When told that there was a pedestrian waiting to cross the street and asked how they would 

proceed, the majority of participants said that they would yield or stop for pedestrians (table 24). 

There were no significant differences between sign alternatives. However, the state of the signal 

(off, flashing red, steady red, or flashing yellow) was found to significantly affect responses. 

Participants who experienced the off or flashing yellow signals were generally likely to report 

that they would stop or yield, but slightly less so than those who saw the flashing red or steady 

red signals. 
44 

Although responses did not differ significantly by sign alternative (including Alt. 5, for which no 

sign was presented at all), some interesting findings are presented in table 23. For example, when 

the flashing red state in table 23 is considered, Alt. 3 seems to do the best job conveying to 

drivers that they can proceed after stopping when the crosswalk is clear. All other sign 

alternatives seem to tell participants that they must stop on flashing red, regardless of whether 

there is a pedestrian present or not, with 90.0 percent of participants who viewed Alt. 5 (no sign) 

reporting only that they should stop (table 23). Additionally, 90.0 percent of participants who 

saw Alt. 5 (no sign) with a flashing yellow signal indicated it was an emergency signal. 

Participants indicating that the flashing yellow indicates an emergency signal does not 

necessarily present a safety hazard, as they would likely proceed with caution and/or check for 

approaching vehicles. These examples do highlight the need for a sign, at least initially, while 

people are learning what the different flashing states mean.

Although Alt. 3 resulted in a higher correct response rate for the flashing red and flashing yellow 

states, it resulted in a slightly lower correct response rate for the off and steady red states 

compared with other signing alternatives (table 23). Furthermore, the legibility testing indicated 

that Alt. 3 was recognized at significantly shorter (worse) distances than Alt. 1 and Alt. 2, and 

that Alt. 2 was recognized a significantly longer distance than Alt. 3 and Alt. 4. 

Recommendations for Midblock Hybrid Beacon Pedestrian Crossings 

Since there is no statistical difference between signing alternatives in terms of decision to yield 

and stop, any of the alternatives would be adequate. However, Alt. 1 and Alt. 2 had higher 

legibility distances.

PASSENGER FERRY 

The results of the open-ended questions (table 27) indicate that, in general, participants 

understand any of the sign alternatives to indicate the presence of a ferry. However, the 

alternatives that included the image of a motorized vehicle (Alt. 1, Alt. 4, and Alt. 5) resulted in 

higher percentages of participants indicating that a ferry was present than alternatives that only 

included the images of pedestrians or pedestrians and bicycles on the ferry (Alt. 2 and Alt. 3).

When participants were asked to select all who could ride the ferry (table 28), they generally 

tended to respond that only the modes of transportation shown in the sign were able to use the 

ferry. For example, for Alt. 4, 95.0 percent of participants reported that freight vehicles were 

allowed; however, only 25.0 percent reported that passenger vehicles were allowed and 

15.0 percent reported that motorcyclists were allowed. Although it may be assumed that 

participants understand that the sign would show the largest type of vehicle allowed on the ferry 

(thus implying that smaller motorized vehicles are also allowed), participant responses indicate 

that confusion exists concerning who can ride the ferry, unless the information is explicitly 

shown on the sign. 

Recommendations for Passenger Ferry 

If the intent of the sign is to convey that multiple user types can use the ferry, then the sign 

should include each user type so people understand who can use the ferry. 
45 

BICYCLE PASSING LAW 

When the first open-ended question (from the perspective of the driver) is considered, Alt. 3, 

Alt. 4, and Alt. 2 had the highest comprehension with 90.0, 76.6, and 70.0 percent, respectively, 

indicating that the car should leave lateral space (table 31). When the second open-ended 

question (from the perspective of the bicyclist) is considered, Alt. 3, Alt. 4, Alt. 1, and Alt. 2 had 

the highest comprehension with 86.7, 50.0, 50.0, and 47.5 percent, respectively, indicating that 

the car should leave lateral space (table 32). Once participants received the multiple-choice

question (table 33), nearly all participants (between 93.3 and 97.5 percent) reported that the 

motorist should leave lateral space. However, many people also reported that the bicyclist should 

leave space and/or could receive a ticket. In this question, more people who viewed Alt. 4, Alt. 5, 

and Alt. 6 reported that the bicyclist should leave space and/or could receive a ticket than those 

who viewed Alt. 1, Alt. 2, and Alt. 3. Therefore, the use of the arrows in Alt. 4, Alt. 5, and Alt. 6 

might be leading participants to believe that the bicyclists should also leave space. 

When the results of both the open-ended and multiple-choice questions are considered, Alt. 2 and 

Alt. 3 would be considered the best in terms of comprehension, followed by Alt. 1 or Alt. 4. 

However, Alt. 1 was consistently ranked as the least effective sign by participants, while most 

participants (28.0 percent) selected Alt. 2 as their top choice, followed by 22.5 percent of 

participants who selected Alt. 4 as their top choice. 

Somewhat contrary to the comprehension results, the mean legibility distances for Alt. 1, Alt. 5, 

and Alt. 4 were significantly greater than those for Alt. 3, Alt. 2, and Alt. 6. 

Recommendations for Bicycle Passing Law 

When comprehension, legibility, and ranking are considered, Alt. 3 is the most effective.

VEHICLE PROHIBITION

Participants generally understood that the mode of transportation that was presented on the sign 

was prohibited, with 61.7, 55.7, and 47.1 percent of participants viewing Alt. 1, Alt. 2, and 

Alt. 3, respectively, indicating that the pictured modes were prohibited in their open-ended 

responses. However, participants are less likely to assume that these signs mean that other modes 

of transportation not depicted on the sign are prohibited as well (table 36 and table 37). For 

example, as shown in the multiple-choice results in table 37, between 90.0 and 100.0 percent of 

participants selected that the mode of transportation shown on the sign was prohibited. Fewer 

participants, ranging from 0.0 percent to 58.3 percent, indicated that modes other than the one 

shown on the sign were also prohibited. The only exception to this finding is that for Alt. 2, 

71.4 percent of participants indicated that motorcycles were prohibited (when the sign shows an 

ATV). However, the symbol in Alt. 3 may have simply been mistaken for a motorcycle. 

Recommendations for Vehicle Prohibition 

As stated previously, between 47.1 and 61.7 percent of participants indicated in their open-ended 

responses that the pictured mode of transportation was prohibited. This level of comprehension 

indicates that the symbols may not accurately indicate what the purpose of the sign might be. 

Although participants tended to understand more that the pictured mode was prohibited in the 
46 

multiple-choice question, they were less likely to say that other modes were also prohibited. 

Therefore, text signs may be better for these types of signs. Or, if a symbol is used, text should 

also be included to clarifying the intent.

RAIL/FLANGEWAY GAP BICYCLE WARNING 

As shown in table 40, the sign alternative had a significant influence on participant response. 

Only 30.0, 34.0, and 32.0 percent of participants who viewed Alt. 1, Alt. 3, and Alt. 4, 

respectively, reported that bicyclists should use caution when crossing tracks, or that they should 

cross perpendicularly, whereas 68.0 percent of participants who viewed Alt. 2 indicated that 

bicyclists should use caution when crossing tracks or should cross perpendicularly. When 

providing subjective rankings of the signs’ effectiveness, Alt. 2 was also selected as the top 

choice by the majority (56.0 percent) of participants, followed by Alt. 1, Alt. 3, and Alt. 4. Sign 

alternative had no significant difference on whether participants reported that they would 

dismount their bike before crossing the tracks. Alt. 3 and Alt. 4 were presumably confusing for 

participants, as 46.0 percent and 52.0 percent, respectively, of their responses fell into the 

“other” category.

Alt. 1 was recognized at a significantly shorter (worse) legibility distance than Alt. 2, Alt. 3, and 

Alt. 4. However, there were no significant differences between the legibility distances of Alt. 2, 

Alt. 3, and Alt. 4. 

Recommendations for Rail/Flangeway Gap Bicycle Warning 

Of the signs tested, Alt. 2 is the best option for signing for a rail/flangeway gap bicycle warning. 

BLIND HILL WARNING 

Although it is important that motorists understand that this sign is conveying the presence of a 

hill, it is more important that they understand that the hill is causing a sight obstruction, or that 

they simply recognize that there may be a sight obstruction. When participants who at least 

mentioned that there was a sight obstruction (may or may not have also mentioned a hill) are 

considered, Alt. 1 had the highest comprehension (86.0 percent) followed by Alt. 3 

(62.0 percent). Alt. 4 and Alt. 2 had relatively low comprehension (40.0 and 14.0 percent, 

respectively). When the participants who mentioned a sight obstruction and a hill in their 

responses are considered, Alt. 1 had the highest comprehension (58.0 percent) followed by Alt. 3 

(50.0 percent). The ranking data show that participants usually preferred the signs in the 

following order: Alt. 1, Alt. 3, Alt. 2, and Alt. 4. Alt. 1 was selected as the top choice by the 

majority (65.5 percent) of participants. 

One of the primary reasons to use a symbol sign instead of a text sign is that symbols typically 

result in better legibility (longer distances). Interestingly, Alt. 1 (the text sign) had the highest 

mean legibility distances of all four alternatives. The results indicated that Alt. 1 and Alt. 2 were 

recognized at significantly greater distances than Alt. 3 and Alt. 4. 
47 

Recommendations for Blind Hill Warning 

Alt. 1 had the highest comprehension, legibility distance, and subjective ranking of effectiveness. 

Therefore, the researchers recommended that Alt. 1 (which is currently in the MUTCD) continue 

to be used. 

RECREATIONAL AND CULTURAL INTEREST 

Although there are varying criterion for determining appropriate sign comprehension, the 

American National Standards Institute (ANSI) develops standards for the design, application, 

and use of signs, colors, and symbols and suggests a strict criteria of 85.0 percent 

comprehension. The results presented in table 46 indicate that Alt. 3, Alt. 4, and Alt. 10 are 

easily understood by participants and are acceptable for continued use. Alt. 12 was also deemed 

acceptable for continued use in that the participants who answered “camping” were assumed to 

imply camping in a tent or other nonvehicular means. On the other hand, there was some 

confusion about Alt. 1, Alt. 2, Alt. 6, Alt. 7, Alt. 8, Alt. 9, and Alt. 11. Therefore, it is 

recommended that these signs be evaluated to determine the most appropriate symbol to convey 

the intended meaning of each sign. 

The results presented in the appendix are ordered from the signs that received the highest 

percentage of completely correct responses to the signs with the lowest percentage of completely 

correct responses. As these signs were not meant to be compared with each other, the 

recommendations were based on the comprehension scores of each individual sign. 

Using the ANSI criteria, the following signs had at least 85.0 percent complete comprehension 

and, thus, are recommended for continued use: 

• Golfing. 

• Restrooms. 

• Tennis. 

• Trash Dumpster. 

• Swimming. 

• Motor Boating. 

• Archery. 

• Horse Trail. 

• Picnic Shelter. 

• Fishing Area. 

• Tunnel. 

• Baseball. 

• Falling Rocks. 

• Hiking Trail. 

• Viewing Area. 

• Chair Lift or Ski Lift. 

• Cross-Country Skiing. 

• Sleeping Shelter. 

• Post Office. 
48 

• Dog Sledding. 

• Nature Study Area. 

• Scuba Diving. 

• Bus Stop. 

Recommendations for Recreational and Cultural Interest

For all additional signs, it is recommended that further testing be conducted to determine the best 

symbol for conveying each intended message. 

TOLL PLAZA ELECTRONIC TOLL INTEROPERABILITY 

When viewing the different sign alternatives, participants generally understood that the symbols 

meant a toll transponder, but they did not understand that the transponder could be used in 

multiple States, or that it could be used at any toll plaza (table 49). Sign alternative did not 

significantly affect participant responses. 

Even with no education on the toll transponder interoperability, participants tended to understand 

that if they had an E-ZPass transponder, then they could use lane 1. However, the participants 

who received the education were significantly more likely to select lane 1 than those who did not 

receive the education. Additionally, the sign alternative viewed by participants did not influence 

lane choices, and participants clearly understood that they could not travel in lane 1 without a 

transponder, regardless of which sign alternative was used. Therefore, it is presumed that 

education, rather than the actual symbol or sign that is used, is the more important component in 

conveying interoperability. 

Recommendations for Toll Plaza Electronic Toll Interoperability 

Regardless of which symbol is selected, education will be key in ensuring that road users 

understand the concept of interoperability. Based on the results, no symbol is recommended over 

another, since none was statistically significant. However, should some symbols be considered, 

Alt. 1, Alt. 3, and Alt. 6 did have slightly higher comprehension than the other alternatives for 

the open-ended question (table 49) and for the lane-choice question when no education was 

given (table 50).
49 

APPENDIX. ADDITIONAL RECREATION SIGNS RESULTS 

Table 52 give the results for the 72 additional recreation signs that were evaluated for 

comprehension. Participants were instructed to indicate the meaning of each sign or what service 

the sign was telling them was available.

Table 52. Recreation sign results.

Sign Name Sign Image 

Completely 

Correct (Percent)

Partially Correct 

(Percent)

Incorrect 

(Percent)

Golfing 100.0 0.0 0.0 

Restrooms 100.0 0.0 0.0 

Tennis 99.0 0.0 1.0 

Trash dumpster 98.0 2.0 0.0 

Swimming 98.0 0.0 2.0 

Motor boating 98.0 1.0 1.0 

Archery 

 

98.0 0.0 2.0 

Horse trail 96.0 3.0 1.0 
50 

Sign Name Sign Image 

Completely 

Correct (Percent)

Partially Correct 

(Percent)

Incorrect 

(Percent)

Picnic shelter 95.0 0.0 5.0 

Fishing area 

 

95.0 0.0 5.0 

Tunnel 93.0 0.0 7.0 

Baseball 93.0 6.0 1.0 

Falling rocks 93.0 5.0 2.0 

Hiking trail 91.0 1.0 8.0 

Viewing area 

 

90.0 0.0 10.0 

Chair lift or ski lift 90.0 5.0 5.0 

Cross-country 

skiing 

89.0 1.0 10.0 
51 

Sign Name Sign Image 

Completely 

Correct (Percent)

Partially Correct 

(Percent)

Incorrect 

(Percent)

Sleeping shelter 88.0 4.0 8.0 

Post office 87.0 0.0 13.0 

Dog sledding 87.0 4.0 9.0 

Nature study area 86.0 5.0 9.0 

Scuba diving 86.0 0.0 14.0 

Bus stop 85.0 6.0 9.0 

Waterskiing 84.0 7.0 9.0 

Theater 84.0 1.0 15.0 

Wildlife viewing 84.0 0.0 16.0 
52 

Sign Name Sign Image 

Completely 

Correct (Percent)

Partially Correct 

(Percent)

Incorrect 

(Percent)

Tramway 

 

83.0 0.0 17.0 

Hand launch or 

small boat launch 

82.0 2.0 16.0 

Recycling 81.0 0.0 19.0 

Snow tubing 79.0 1.0 20.0 

Whale viewing 77.0 15.0 8.0 

Climbing 77.0 22.0 1.0 

Beach 77.0 14.0 9.0 

Sledding 76.0 3.0 21.0 

All-terrain trail 76.0 10.0 14.0 
53 

Sign Name Sign Image 

Completely 

Correct (Percent)

Partially Correct 

(Percent)

Incorrect 

(Percent)

Jet ski or personal 

watercraft 

76.0 7.0 17.0 

Snowshoeing 75.0 1.0 24.0 

Canoeing 74.0 22.0 4.0 

Deer viewing area 72.0 23.0 5.0 

Seal viewing 71.0 15.0 14.0 

Sailing 67.0 30.0 3.0 

Stable 66.0 2.0 32.0 

Surfing 64.0 0.0 36.0 

Grocery store 64.0 6.0 30.0 
54 

Sign Name Sign Image 

Completely 

Correct (Percent)

Partially Correct 

(Percent)

Incorrect 

(Percent)

Mechanic 63.0 4.0 33.0 

Ice skating 

 

62.0 14.0 24.0 

Snowmobiling 61.0 1.0 38.0 

Diving 60.0 39.0 1.0 

Hang gliding 59.0 7.0 34.0 

Kennel 59.0 1.0 40.0 

Kayaking 55.0 28.0 17.0 

Row boating 51.0 47.0 2.0 

Off-road vehicle 

trail 

51.0 9.0 40.0 
55 

Sign Name Sign Image 

Completely 

Correct (Percent)

Partially Correct 

(Percent)

Incorrect 

(Percent)

Snowboarding 

 

51.0 0.0 49.0 

Fishing pier 48.0 51.0 1.0 

Wind surfing 48.0 51.0 1.0 

Tour boat 47.0 3.0 50.0 

Downhill skiing 38.0 56.0 6.0 

Corral 34.0 65.0 1.0 

Ski jumping 31.0 47.0 23.0 

Ranger station 30.0 12.0 58.0 

Dam 26.0 2.0 72.0 
56 

Sign Name Sign Image 

Completely 

Correct (Percent)

Partially Correct 

(Percent)

Incorrect 

(Percent)

Radiator water 

 

26.0 33.0 42.0 

Ice fishing 17.0 77.0 6.0 

Rafting 16.0 78.0 6.0 

Amphitheater

 

10.0 2.0 88.0 

Fish ladder 5.0 3.0 92.0 

Fish hatchery 3.0 6.0 91.0 

Driving tour 0.0 1.0 99.0 

Cultural interest 

area

0.0 0.0 100.0 

Point of interest 0.0 0.0 100.0 

All photos source: FHWA.(1)
57 

REFERENCES

1. FHWA. 2009. Manual of Uniform Traffic Control Devices for Streets and Highways. 

Washington, DC: Federal Highway Administration. 

2. Dewar, R., D. Kline, F. Scheiber, and A. Swanson. 1997. Symbol Signing Design for 

Older Drivers. Report No. FHWA-RD-94-069. Washington, DC: Federal Highway 

Administration.

3. Ogden, M. A., K. N. Womack, and J. M. Mounce. 1990. “Motorist Comprehension of 

Signing Applied in Urban Arterial Work Zones.” Transportation Research Record: The 

Journal of the Transportation Research Board 1281: 127–135. 

4. Dewar, R., D. Kline, and H. Swanson. 2001. “Age differences in comprehension of 

traffic symbols.” Accident Reconstruction Journal 12, no. 1: 37–41. 

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HRSO-30/09-22(WEB)E Recycled

Recyclable

Recommended citation: Federal Highway Administration,

Comprehension and Legibility of Selected Symbol Signs Phase IV 

(Washington, DC: 2022) https://doi.org/10.21949/1521917.