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Use of Hazard Pictorials/Symbols

in the Minerals Industry

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U S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Building Technology

Illuminating Engineering Group

Building Physics Division

Washington, DC 20234

September 1983

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NBSIR 83-2732

USE OF HAZARD PICTORIALS/SYMBOLS

IN THE MINERALS INDUSTRY

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Belinda Lowenhaupt Collins

U S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Building Technology

Illuminating Engineering Group

Building Physics Division

Washington, DC 20234

September 1983

Sponsored by

Bureau of Mines

U S. Department of Interior

Washington, DC 20241

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler. Director
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ABSTRACT

This report documents a three-phase research effort on the evaluation of the

effectiveness of safety symbols and hazard pictorials for use In mining and

milling operations. In the first phase, applicable codes and standards were reviewed, along with documentation of typical mining hazards, to determine

relevant safety messages. This phase included site visits to eight mine sites

to document existing sign practice and common mining hazards. In the second

phase, the effectiveness of two sets of symbols for 40 different safety messages was evaluated with 267 miners from 10 sites at disparate geographical

locations. This evaluation also included an assessment of the effectiveness

of six different symbol surround shapes and colors. Symbols which were the

most effective, according to the suggested criteria, were those which depicted

both the person and the hazard or protective gear, and which were more representational, rather than highly abstract. Based upon this research, a set of

40 symbols was suggested for further graphic refinement, additional evaluation,

and eventual use. In the third phase, these symbols were assessed in an inmlne evaluation at 2 sites. This evaluation indicated that the symbol signs

were generally well understood and conspicuous, with no problems of durability,

or poor contrast arising during the three-month evaluation. A Handbook for

using symbol signs in mines concludes the report.

Key words: communication; hazard; mining; plctogram; safety; signs; standards;

symbols; visual alerting; warnings.

iii
FOREWOEID

This report Is one of a series documenting National Bureau of Standards research

and analysis efforts In support of the Bureau of Mines (BoM)/ National Bureau of

Standards (NBS) Hazard Plctorlal/Saf ety Symbol Evaluation Program, This report

Is a deliverable product under BoM Contract Number JOl 13020 entitled, "Use of

Plctorlals/Symbols In the Minerals Industry,".

It was administered under the direction of Twin Cities Mining Research Center,

Minneapolis, Minnesota with Guy Johnson acting as the Technical Project Officer.

Phil Silas was the contract administrator for the Bureau of Mines. This report

summarizes the research completed as part of the contract during the period of

January 1981-January 1983.

ACKNOWLEDGEMENTS

The author wishes to acknowledge the help of the many people who were essential

to the completion of this report. The cooperation of the many miners who participated so willingly Is deeply appreciated, along with the mining companies who

allowed the use of their personnel and facilities. In addition, the following

people furnished Invaluable support during the course of the project:

Guy Johnson, Bob Mattes, and Mike Sapko, of the Bureau of Mines, provided con- tinuing support and use of mine facilities; Dr. Nell Lerner contributed extensively to the research planning, code review and documentation, and statistical

analysis; Dr. Austin Adams also provided Invaluable assistance during the

statistical analysis; and Ms. Karen Lister, Mr. Albert Hattenburg, Dr. Mary

Natrella, and Mr. George Turner, of the National Bureau of Standards provided

Insightful and helpful comments on the document. Finally, I would like to

thank the Word Processing Unit for their competent Job In typing the many

versions of the final report.

Iv
EXECUTIVE SUMMARY

Extensive highway research has demonstrated that, when chosen appropriately,

symbols can communicate information more rapidly and often, more effectively,

the words. Greater use of symbols for safety and hazard warning messages,

however, requires that they be understandable to the intended audience. The

present project was designed to assess the effectiveness of safety symbols and

hazard pictorials for mine-safety communication.

In the first phase of a three-phase evaluation, requirements for safety signs

in mines were determined by a series of site visits which assessed existing

practice, a hazard analysis which reviewed mine accident and fatality statistics,

and a code review which tabulated symbol and sign requirements in existing

national and international codes. From this first stage, a set of 40 messages

(referents) applicable to mine safety signs was developed. At the same time, one to two symbols were selected for further evaluation for each message,

(based upon previous research and code recommendations).

In the second phase, the understandablllty of the selected symbols was assessed

with 267 miners at 10 different mine sites in the United States. Miners indicated their understanding of a symbol's meaning by completing a four-choice

multiple response form. At each site, miners were split into two groups so that the performance of more than one symbol for a message could be compared.

In addition, the degree of danger (perceived hazardousness) indicated by six

different surround shapes was determined by a ranking procedure for several

different Interior images. The results from the second phase indicated that

statistically significant differences in performance occurred between symbols

for 72 percent of the referents for which 2 symbols were studied. An analysis

of variance revealed significant site and age differences as well. For 34

referents, at least one symbol was identified correctly by 85 percent or more

of the miners participating. Symbols which performed below this level Included:

Laser, Radiation, General Warning, Flammable, Fire Alarm Call Point, and No

Exit. Many of these latter symbols are either highly abstract or represent

unfamiliar concepts. Correctly identified symbols can be characterized as more

pictorial, often depicting a person plus an action, or piece of gear, or hazard. Although problems emerged for some of the more abstract hazard-warning

symbols, symbols for personal protective gear, prohibited actions, and fire/

safety equipment were generally correctly identified. The results of the

rankings for the perceived hazardousness of surround shape indicated that the

diamond and octagon were seen as most hazardous and the square and circle as least hazardous. Red, yellow, and orange were ranked as the most appropriate

colors for hazard warning.

In the third phase, a subset of 20 symbols was selected for an in-mine

evaluation, based upon the results from the second phase. This evaluation,

which took place at 2 mine sites in the Eastern United States, included further

assessment of the understandablllty of the 40 "best" symbols, determination of

confusions within, and conspicuity of, the subset of Installed symbols, and

determination of physical parameters such as contrast and durability. Although

the in-mine evaluation revealed continuing problems with the Flammable symbol.

V
the overall performance of the symbol signs was generally good. The need for

additional word messages on some hazard-warning signs was Identified.

Based on the three evaluation phases, a handbook was written for using symbol

signs In mines. This handbook, which concludes the report, provides suggestions

for symbol sign configuration, location, and testing at mine sites. In summary,

the overall evaluation of safety symbols In mines Indicated that symbols are a generally effective means of communicating safety and hazard Information. A

set of some 25-30 symbols Is suggested, along with a handbook containing general

guidelines for the use of symbol signs In mines.

Vi

J
TABLE OF CONTENTS

Page

ABSTRACT iii

FOREWORD iv

ACKNOWLEDGEMENTS iv

EXECUTIVE SUMMARY v

1. INTRODUCTION 1

1.1 FRAMEWORK FOR THE STUDY OF SAFETY SYMBOLS AND HAZARD PICTORIALS 1 1.1.1 Background Research 2

1.1.2 Methods of Evaluation 3

1.2 WORKPLACE SAFETY SYMBOL RESEARCH 4

1.3 MINE SAFETY SYMBOL RESEARCH 5

1.4 CODE REVIEW 6

1.5 HAZARD ANALYSIS 10

1.5.1 Overview 10

1.5.2 Detailed Hazard Analysis 14

1.6 SITE VISITS 18

1.6.1 Hazard Information from Site Visits 18

1.6.2 Sign Usage 18

2. SELECTION OF REFERENT MESSAGES AND CANDIDATE SYMBOLS 25

2.1 SELECTION OF REFERENT MESSAGES 25

2.2 SYMBOL SELECTION PROCEDURES 25

2.2.1 Symbols Selected 25

2.2.2 Rationale for Specific Symbol Selection 27

2.2.3 Surround Shape Concerns 28

2.3 EXPERIMENTAL RATIONALE 29

2.3.1 Evaluation of Understandablllty 29

2.3.2 Perceived Hazardousness of Surround Shape 31

3. METHOD 32

3.1 PROCEDURE 32

3.2 PARTICIPANTS 32

3.3 STIMULUS MATERIAL 32

3.4 PROCEDURE 34

3.5 SCORING OF RESPOJSE SHEETS 35

4. RESULTS 36

4.1 ANALYSIS OF COMPREHENSION DATA 36

4.2 DEMOGRAPHIC DATA 38

4.3 PERFORMANCE OF INDIVIDUAL SYMBOLS 44

4.4 RESULTS AND DISCUSSION OF INDIVIDUAL SYMBOLS 48

4.4.1

Individual Symbol Data 48

4. 4. 1.1 Hazard Warning Symbols 50

4. 4. 1.2 Prohibition Symbols 70

vii
TABLE OF CONTENTS (Continued)

Page

4. 4. 1.3 Protective Gear Symbols 70

4. 4. 1.4 Safety Equipment and Fire Emergency Symbols .... 76

4. 4. 1.5 Egress Related Symbols 87

4.5 SURROUND SHAPE AND COLOR DATA 95

4.6 SITE DIFFERENCES 106

5. DISCUSSION 112

5.1 COMPARISON WITH PREVIOUS RESULTS 112

5.2 FACTORS WHICH APPEAR TO AFFECT SYMBOL EFFECTIVENESS 112

5.3 SURROUND SHAPE AND BACKGROUND COLOR DATA 117

5.4 DISCUSSION OF SITE DIFFERENCES 119

5.5 SELECTION OF A PRELIMINARY SYMBOL SET 120

6. IN-MINE SYMBOL SIGN EVALUATION 125

6.1 SELECTION OF SYMBOL SIGNS 125

6.2 EVALUATION OF SYMBOL SIGN EFFECTIVENESS 125

6.2.1 Evaluation Procedures 125

6.2.2 Evaluation of Understandablllty—Both Sites 127

6.3 SYMBOL SIGN INSTALLATION 129

6.3.1 Specific Signs at the LL Site 129

6.3.2 Specific Signs at the EM Site 133

6.4 SIGN EVALUATION 133

6.4.1 Evaluation of Physical Characteristics 133

6.4.2 Cn-Slte Evaluation Form—LL Site 136

6.4.3 Comments from the EM Evaluation 140

6.5 GENERAL CONCLUSIONS FROM THE ON-SITE EVALUATION 140

7. RECOMMENDATIONS 143

7.1 SUGGESTIONS FOR IMPROVEMENT IN SYMBOLS 143

7.2 SURROUND SHAPE AND COLOR 143

7.3 CRITERIA FOR EVALUATING SYMBOL EFFECTIVENESS 144

7.4 DEVELCPMENT OF A SET OF RECOMMENDED SYMBOLS 145

8. HANDBOOK FOR USING SYMBOLS SIGNS IN MINES 147

8.1 INTRODUCTION 147

8.2 CURRENT STANDARDS FOR SYMBOL SIGNS 147

8.3 SELECTION OF SYMBOL SIGNS 148

8.4 FABRICATION OF THE SYMBOL SIGNS 151

8.4.1 Color and Surround Shape 151

8.4.2 Sign Material 161

8.4.3 Size 161

vlll
TABLE OF CONTENTS

Page

8.5 SIGN PLACEMENT 162

8.5.1 Sign Location 162

8.5.2 Number of Signs 166

8.6 SYMBOL EVALUATION-SUGGESTED PROCEDURES 166

8.7 ADDITION OF WORD MESSAGES 168

8.8 GENERAL RECOMMENDATIONS 169

REFERENCES 171

APPENDIX 179

lx
LIST OF TABLES

Table 1. Mine Safety Messages from the Code of Federal Regulations .... 7

Table 2. Synthesis of International Safety Symbol Codes 9

Table 3. Coding Sign Practices from International and U.S. Safety

Sign Standards 11

Table 4. Site Visit Information 19

Table 5. Safety Sign Messages Observed at Eight Mine Sites 21

Table 6. Referent Messages for Mine Safety Symbols 26

Table 7. Data Collection Locations 33

Table 8. Overall Percentage of Correct Answers and Mean Confidence

Ratings for All Symbols 37

Table 9. Site Data Analyses 39

Table 10. Summary Age Data 40

Table 11. Occupation Categories and Frequencies from All Sites

Combined 41

Table 12. Statistical Analysis Data for All Symbols and Across Sites ... 45

Table 13. Comparison of Percentage Correct and Confidence Ratings

for Group 1 Symbols 46

Table 14. Comparison of Percentage Correct and Confidence Ratings

for Group 2 Symbols 47

Table 15. Ranking Data for Hazard Symbols - Totals for All Sites 96

Table 16. Ranking Data for Explosion - Totals for Each Site 97

Table 17. Ranking Data for Entanglement - Totals for Each Site 98

Table 18. Ranking Data for Poison - Totals for Each Site 99

Table 19 . Ranking Data for General Warning - Totals for Each Site 100

Table 20. Ranking Data for Surround Alone - Totals for Each Site 101

Table 21. Ranking Data for First Aid - Totals for Each Site 102

Table 22. Ranking Data for Hard Hat - Totals for Each Site 103

X
LIST OF TABLES (Continued)

Page

Table 23. Ranking Data for Safety Information Symbols - Totals for

All Sites 104

Table 24. Site Comparison Data 108

Table 25. Percentage of Correct Response for Each Site 110

Table 26. Mean Confidence Rating Data for Correct Answers for All

Subjects at Each Site Ill

Table 27. Comparison with Previous Symbol Research 113

Table 28. Image Content—Ordered According to Percentage Correct

Responses—Group 1 115

Table 29. Image Content—Ordered According to Percentage Correct

Responses—Group 2 116

Table 30. Preliminary Selection of Images 122

Table 31. Percentage Correct and Confidence Rating Data for Final

Symbol Set for Both Sites 128

Table 32. Ranking Data for Surround Shapes for Hazard Symbols - LL

Site 130

Table 33. Sign Location and Luminance Measurements — LL Site 131

Table 34 . Sign Location and Luminance Measurements — EM Site 132

Table 35. Confusion/Consplculty Data 138

Table 36 . Mine Safety Messages from the Code of Federal Regulations .... 149

Table 37 . Categories of Safety Messages Used In the Handbook 152

Table 38 . Minimum Sizes Suggested for Symbols by the Treasury Board

of Canada 163

Table 39 . Different Symbolic Information for a Single Hazard 165

Table 40. A Suggested Matching Procedure 167

Table 41. General Suggestions for Using Safety Symbols at Mine Sites ... 170

xi
LIST OF FIGURES

Figure 1. Fatal mine accidents—1980 estimates 12

Figure 2. Estimated Injury data—NFDL and NUL—1980 13

Figure 3 . ANSI sign format for hazard-warning signs 22

Figure 4. Distribution of age by site for four age groups 43

Figure 5 . Percentage of correct responses as a function of mean

confidence rating 49

Figure 6 . Flammable hazard 50

Figure 7 . Radiation and laser hazards 52

Figure 8. Explosion hazard 53

Figure 9 . Electrical hazard 54

Figure 10. Corrosion hazard 55

Figure 11. Poison hazard 57

Figure 12. Fork lift truck hazard 58

Figure 13 . Slip hazard 59

Figure 14. Fall from elevation hazard 60

Figure 15. Overhead hazard 61

Figure 16. General warning 62

Figure 17 . Trip hazard 63

Figure 18. Pinch point and hot surface hazards 65

Figure 19. Crush hazard 66

Figure 20. Sudden pressure release hazard 67

Figure 21. Sever/cut hazard 68

Figure 22. Entanglement hazard 69

Figure 23. Do not touch 71

xll
LIST OF FIGURES (Continued)

Page

Figure 24. No smoking 72

Figure 25 . No open flame 73

Figure 26. Head protection required 74

Figure 27 . Hearing protection required 75

Figure 28. Eye protection required 77

Figure 29 . Foot protection required 78

Figure 30. Hand protection required 79

Figure 31 . Respiratory protection required 80

Figure 32. First aid location 81

Figure 33. Safety shower location 83

Figure 34. Eyewash location 84

Figure 35 . Fire extinguisher and hose and reel location 85

Figure 36. Fire alarm call point 86

Figure 37 . Exit 88

Figure 38. Emergency exit 89

Figure 39 . No exit 90

Figure 40. Do not enter 92

Figure 41 . Keep door open 93

Figure 42. Keep door closed 94

Figure 43. Rated hazardousness of surround shape 105

Figure 44. Preferred background color for selected symbols 107

Figure 45. Symbols fabricated as signs for In-mlne evaluation 126

Figure 46. Photographs of symbol signs as Installed at the LL site 134

xiii
LIST OF FIGURES (Continued)

Figure 47. Photographs of symbol signs as installed at the EM site 135

Figure 48. On-site evaluation form 137

Figure 49. Photographs comparing symbol signs with adjacent word signs . 142

Figure 50. Symbols suggested for safety messages 153

Figure 51. Typical symbol configuration 157

Figure 52. Examples of symbol configuration for each category 159

xlv
1. INTRODUCTia\l

1.1 FRAMEWORK FOR THE STUDY OF SAFETY SYMBOLS AND HAZARD PICTORIALS

Traditionally, hazard warnings and safety instructions have been provided by

written English signs within the United States. Such signs are designed to call

the workers' attention to a hazard, inform them of the nature of the hazard, and

provide information for avoiding the hazard or for following specified safety

precautions. The importance of worker safety is underscored by the statistic

that 13,000 persons were killed in work accidents, with disabling injuries

numbering 2,200,000, at a cost of approximately $30.2 billion in 1981 (National

Safety Council, 1981). In mines alone, a total of 237 miners were killed in

1981 and 172 miners in 1982, (Mine Safety and Health Administration, 1981; 1982.)

A total of 23,990 accidents (nonfatal occurrences with lost workdays) were reported for coal, metal, non-metal, stone, and sand and gravel mines for 1981.

In all workplaces, injuries are most likely during the first month of the first

year on the job (National Safety Council, 1979; Bureau of Labor Statistics,

1979). The need to warn the new miner or worker, then, is particularly acute.

Written signs, while commonly used, may not be the best way of providing safety

or hazard information, however. The use of pictorial, or symbolic signs has

become increasingly common, because such signs can provide essential information more rapidly (Janda and Volk, 1934), more accurately (Walker, Nicolay and

Stearns, 1965), and at a greater distance (Smith and Weir, 1978) even under con- ditions of distraction or interference (King 1971, 1975; Ells and Dewar 1979).

Symbol signs also can be smaller than written signs, while encoding the same information, making them suitable for equipment as well as for environmental

signs (Forbes, Gervais, and Allen, 1963; Green 1979). Symbol signs also have

the advantage of providing information without the use of a particular written

language. In addition, they may be more effective in altering behavior (Forbes,

et al., 1963). The use of symbolic signs, often without accompanying word

legends, is now mandated by the Department of Transportation (DOT) for

interstate highways in the United States (DoT, 1979).

The advantages of developing a uniform system of hazard pictorials and safety

symbols for mining applications are numerous. The mechanization of modern

mining has sparked the need for safety messages which are readily detectable

and understandable by a moving operator. In addition, there is a need to communicate information to those who are not fully literate or whose native language is not English. Estimates of illiteracy vary widely from about 2 to 64

million adult Americans (Kirsch and Guthrie, 1977-1978), while the Bureau of

the Census reported (Washington Post, 1979) that five million of the eight

million people in the U.S. whose native language was not English claimed to

have difficulty in speaking or understanding English. For these people, symbols could be the only visual warning for preventing accidents. These facts,

when combined with the data which indicate that symbols can be more effective

than word signs, reinforce the need to develop a workable system of hazard

pictorials and safety symbols for mining applications.

Simply selecting a pictorial to convey a safety message from existing catalogues

such as Dreyfuss (1972) or Modley and Myers (1976) is not sufficient, however.

1
Symbols are more effective than word signs If, and only If, they communicate

their message to the Intended user. Although the designer of a symbol may

understand Its message perfectly. It does not necessarily follow that others

will. Collins and Lerner (1982) found that several Internationally proposed

life-safety symbols communicated messages that were opposite to their Intended

message to a large number of people. Before symbols are selected for mining

applications, their effectiveness In communicating the Intended message to

members of a mining population must be evaluated. A symbol which does not

have good understandability will fail to communicate necessary safety

information.

1.1.1 Background Research

Numerous evaluations of symbol effectiveness have been performed. These are reviewed In detail elsewhere (Collins, 1982) but a brief overview Is provided

as a framework for the evaluation of mine-safety symbols and hazard pictorials.

Experimental assessments of symbol effectiveness have concentrated upon symbols

for highways, vehicles, machinery, and public Information. The bulk of the

research has focused on highway applications, beginning with a study by Janda

and Volk (1934) who determined that subjects responded faster to symbol signs

than to word signs. Walker, Nlcolay, and Stearns (1965) determined that symbol

signs were Identified more accurately than word signs. King (1975) found that

subjects Identified symbols more accurately when their response was delayed

and an Interference task Included. This experiment attempted to simulate an actual driving condition In which the Interval between viewing a sign and

acting upon It Is occupied with a driving task — a condition similar to many

mining operations during which a miner must see and act upon a sign's message

while continuing to perform a customary mining operation. In another experiment on highway symbols, Dewar, Ells, and Mundy (1976) found that reaction

time was always shorter for symbols under both normal and degraded viewing

conditions. In a laboratory study, Johnston, Cole, Jacobs and Gibson (1976)

determined that selected symbols were visible at a greater distance than their

word-sign counterparts.

Other experiments have concentrated upon assessing the meaningfulness of

individual highway symbols (Bralnard, Campbell, and Elkins, 1961; Griffith and

Actklnson 1978). Still another series of experiments assessed the effectiveness of selected symbols In actually changing behavior. Forbes, Gervals, and

Allen (1963) determined that a red "x" was most effective In controlling traffic lane use. In a series of lab and field studies. This symbol, demonstrably

superior to a comparable word sign In changing behavior, also could be smaller

and more flexibly positioned - another Important consideration for mining

applications. Dewar and Swanson (1972) also translated laboratory research

into effective highway signage, by demonstrating that positive, rather than

prohibitory symbols were more effective In altering driving behavior.

Many of the studies of automotive and machine symbols concentrated on measuring

the understandability of a specific set of symbols. In an evaluation of farm

and industrial machine symbols, Cahill (1975, 1976) found wide variability in

the performance of individual symbols, although experience and context improved

2
performance somewhat. She noted that more graphic, pictorial representations of

the intended message were better understood, while symbols denoting continuing

activities such as "Engage" or "Hours Running" were poorly understood. Such

"conceptual" messages appear to have poor initial understandability even to

experienced users. Wiegand and Glumm (1979), in an evaluation of automotive

control symbols, concurred with Cahill's results, noting that knowledge of the

understandability of a set of symbols can be used to indicate where graphic

redesign or additional education is necessary.

Other studies of automotive symbols assessed symbol performance by having

subjects touch the appropriate controls (Heard, 1974) or having them indicate

familiarity with and appropriateness of a set of proposed symbols (Green and

Pew, 1978). Green (1979) suggested that a valuable way to develop specific

symbols for a message is to have the user draw them - a technique known as the

production method. This technique is especially valuable in situations where

common symbols do not exist for a particular message.

Evaluation of public information symbols (Easterby and Zwaga, 1976; Freedman

and Berkowitz, 1977; Freedman, Berkowltz and Gallagher, 1976; Mackett-Stout

and Dewar, 1981; Zwaga and Boersema, 1981), also indicated a wide range of

comprehension among selected symbols, with pictorial symbols being more understandable than abstract ones. Studies of safety symbols have concentrated

upon symbols for consumer products (Easterby and Hakiel, 1977, a, b, c; 1981)

fire safety (Collins and Lerner, 1982; Lerner and Collins, 1980a), and industrial safety (Lerner and Collins, 1980b; Collins, Lerner and Pierman, 1982).

Easterby and Hakiel (1981) determined that the color Red was preferred for

flammable hazard signs while Black was selected for poison. Their data also

indicated that subjects preferred symbols which described the hazard to those

which prohibited the action or prescribed a particular action (to avoid the

hazard). In addition, symbols which were more visually complex (perhaps, more

representational) performed better than more abstract, graphically simpler

signs. They concluded that the content of the image, rather than the color,

primarily determines sign comprehension. Their data also indicated that subjects older than 55 performed consistently more poorly than all other age

groups, a finding confirmed by Lerner and Collins (1980) and Hulbert, Beers,

and Fowler (1979). For fire safety signs, Lerner and Collins (1980) found

that certain Important symbols for egress were not only not understood, they

also received a significant number of critical confusions (opposite-to-correct

answers). Again, these poorly performing images were among the most abstract

studied.

1.1.2 Methods of Evaluation

Understandability or meaningfulness has been assessed by numerous methods. One

of the most common methods is simply to ask people to write down a brief definition of the meaning of a sign (Brainard et al., 1961; Walker et al., 1965;

Cahill, 1975; Easterby and Zwaga, 1976; Collins and Lerner, 1982). In addition

to indicating the understandability of the symbol, wrong answers from the

definition procedure provide insight into the kinds of confusions and misunderstanding associated with a particular symbol. Another commonly used method is

a matching procedure in which people select the answer from a list of answers

3
which best "matches" the symbol's meaning (Bralnard et al., 1961; Griffith and

Actkinson, 1978; Wlegand and Glumm, 1979). Hulbert, Beers, and Fowler (1979)

used a multiple choice procedure with Immediate knowledge of results In an assessment of highway signs. Other researchers asked subjects to guide themselves along a highway or through a building relying upon symbolic Information

(Freedman et al; 1976; Forbes et al; 1963; Dewar and Swanson, 1972); or touch

the appropriate control (Heard, 1974). Still others asked for assessments of

rated meaningfulness or preference (Green and Pew, 1978; Collins, Lerner, and

Pierman, 1982; Easterby and Haklel, 1981). Mackett-Stout and Dewar (1981) suggested the use of an "efficiency index" derived from data on legibility distance,

comprehension, and preference, for a more comprehensive evaluation. In addition,

measures such as speed of detection or recognition have been obtained with and

without the addition of distracting tasks.

This orief overview indicates that the performance of symbols can be assessed

along several dimensions by a variety of methods. The performance dimensions

include understandabillty or comprehension (what does it mean?), detectability

(can it be seen?), discrimination (is it confused with other symbols, particularly in the same set?), conspicuity (does it attract attention?), and behavior

(do people perform the correct action in response to the sign?). Because

symbols are used primarily to replace or supplement written signs, it is

essential that they be understood - that they communicate their intended message. Once a symbol's understandabillty has been determined, its performance

on the other evaluation dimensions should then be assessed. For mining operations, both detectability and conspicuity (or salience) are also critical, particularly for mobile equipment operators. The focus of the present report,

however, is on understandabillty - or the determination of the relative

meaningfulness of two sets of symbols for a series of safety messages.

1.2 WORKPLACE SAFETY SYMBOL RESEARCH

A previous study conducted by the National Bureau of Standards (Collins, Lerner

and Pierman, 1982; Lerner and Collins, 1980b) examined the relative understandability of different safety symbols for a set of 33 referents. A total of 89

candidate images were studied. In the study by Collins et al. (1982), 222

employees from industrial sites at four different geographical locations provided short, written definitions of the meaning of one image for each referent.

In the second portion of the study, participants were shown all the candidate

images for a given referent, and asked to choose the one that best conveyed the

intended meaning to them. They also indicated the reasons for their choice.

In addition, 75 participants who were naive to the worksplace also participated

in a pilot study.

The understandabillty of the symbols, in terms of percentages of correct and

incorrect definition answers, varied widely for the thiry-three referents, as well as for the candidate images studied for each referent. Despite standardized use for many years, symbols for Radiation, Laser, and Biohazard were frequently misidentif ied . On the other hand, symbols for Protective Gear, First

Aid, and Emergency Equipment were generally correctly defined. The different

candidate images for the various hazard referents, showed the greatest

range in terms of percentage of correct definition, with responses to each of

4
the three Images for Entanglement, Electricity, Corrosion, and Overhead Hazard

being quite different. Referent messages for which all candidate Images

received less than 85 percent correct responses Included Radiation, Laser,

Biohazard, General Warning, Poslon, Combustible, Eyewash, Exit, No Exit, and

No Entrance. The first four referents were particularly poorly understood.

Generally, the preference data supported the understandablllty data, with the

Image receiving the highest percentage of correct answers also being the most

preferred. Participants also typically expressed strong preferences for one of

the candidate choices with significant differences occurring In all but two cases (Eyewash and General Warning). They also provided Insightful comments

about the reasons for their choices. Including Ideas about the visibility,

pictorial nature, and probable effectiveness of the various Images proposed for

each referent.

Although the study by Collins et al. (1982) assessed the relative

understandablllty of a number of workplace safety symbols. It did not assess stereotypes or perceived hazards associated with either symbol color or sur- round shape. Nor did It assess many of the hazards associated with mining and

mining equipment, or use members of a mining population. Rather, it provided an initial assessment with Industrial personnel of the understandablllty of graphic images for 33 referents - as these Images appeared in sign catalogues and

standards. These data do provide a basis for comparing the performance of

industrial and mining personnel, since many of the referents and symbols studied

are common to the two studies. A comparison of the two sets of data will be

given in Section 5.1.

1 .3 MINE SAFETY SYMBOL RESEARCH

Throughout the preceding section, the focus has been on research into the

effectiveness of symbolic messages. Generally, reseachers began their Investigations with an existing set of symbols suggested for a particular application.

For example, Freedman et al. (1976) evaluated a set of symbols proposed by the

American Institute of Graphic Arts (AIGA, 1974) for use in transportation

facilities, while Heard (1974) evaluated three sets of symbols proposed by the

International Organization for Standardization (ISO) for automotive displays.

In the case of safety symbols, however, no one set of symbols has been

recommended for use within the United States.

As a result, the assessment of symbolic images for mining environments required

a determination of the most important and most prevalent safety and hazard

warning messages used in mines. This determination involved first an assessment, given in Section 1.4, of existing international, national, and industrial

standards for safety symbols, particularly for mines. Secondly, it included

a hazards analysis, given in Section 1.5, to determine the nature and frequency

of mining accidents. Thirdly, it involved site visits, given in Section 1.6,

to a number of mines and discussions with mining personnel. Finally, it

included inputs from voluntary standards writing groups within the United

States such as the American National Standards Institute (ANSI) Z535 Committee

on Safety Signs and Colors, the Construction Industry Manufacturers Association

(CIMA) , and the Society of Automotive Engineers (SAE). A list of important

5
afaty massagat and aymbola waa developed from theae aourcea. The aelectlon

of aafety meaaagea and aymbola la deacrlbed In aectlon 2, along with the

experimental rationale • In sections 3, 4, and 5 an evaluation of the

understandablllty of symbols for each of 40 messages with miners from 10 mine

sites Is presented. An analysis of the perceived hazardousness of surround

shape and color Is also presented in these sections. Section 6 presents results

from an in-mine evaluation of a subset of the recommended symbols while section

7 provides recommendations based upon all phases of testing. Section 8 presents

a handbook for guidance In using symbol signs in an actual mine.

1.4 CODE REVIEW

Both national and international codes containing Information about sign and

symbol messages related to safety information and hazard warnings were reviewed.

The code applicable to mining operations, The Code of Federal Regulations,

Title 30, makes no provision for the specific use of symbols but does list the

situations for which signs are required. Table 1 presents the general messages

required and the relevant citations for sign requirements in mines from Title

30, Mineral Resources, of the Code of Federal Regulations (July 1, 1980 revision). Parts 55, 56, 57, 75 and 77 all concern mine safety standards. The

paragraphs cited include all references to the use of safety-related signs

and labels. Communications, which were not considered. Include references to

alarms, diagrams and maps, control panels, and communication and signaling

devices.

Parts 55 (Health and Safety Standards - Metal and Nonmetallic Open Pit Mines),

56 (Health and Safety Standards - Sand, Gravel, and Crushed Stone Operations),

and 57 (Health and Safety Standards - Metal and Nonmetallic Underground Mines),

comprise Subchapter N - Metal and Nonmetallic Mine Safety of the Code of Federal

Regulations, Title 30. The three parts are parallel in construction and similar

in content. The paragraphs of each part that refer to sign use are presented

in table 1. This table indicates all relevant paragraphs, and indicates which

of the three parts include that paragraph. For Part 57 , some paragraphs refer

to surface operations only or to underground operations only; where the requirement is so restricted, it is noted in the table. Subchapter 0 - Coal Mine

Health and Safety contains two relevant parts: Part 75 "Mandatory Safety Standards - Underground Coal Mines,” and Part 77, "Mandatory Safety Standards,

Surface Coal Mines and Surface Work Areas of Underground Coal Mines."

Other codes reviewed included the European Economic Commission (EEC) proposed \ directive for "Safety Signs at Work in Coal Mines" (1979) which contains

| specific recommended symbols for mining applications. Other safety codes and I standards reviewed are aimed at more general industrial applications, rather

than mines specifically. Nevertheless, many of the messages included are similar to those found in the Code of Federal Regulations and the EEC Directive

and so are included here. These include the EEC Directive for Safety Signs at \ Places of Work (771576) (1977), and various ISO (International Organization for

Standardization) proposed standards—DIS 3864.3 (1978); ISO 3461 (1980a); and

DP 6309 (1978).) The Canadian Standards Association (1977) provides referents

with suggested image content, but no specific imagery, while the Treasury Board

6
Table 1. Mine Safety Messages from the Code of Federal Regulations

GENERAL MESSAGE RELEVANT CITATIONS

No Entry,

Restricted Entry

55.3-

5, 55.6-103, 56.3-5, 57.6-103

57.3-

5, 57.5-28, 56.6-103, 57.20-20,

57.21-43, 75.303, 75.1711-3, 77.1303(g)

Hazard, Danger

(general)

55.20-11, 56.20, 57.20-11, 75.303

No Smoking 55.4-2, 55.6-110, 55.8-5, 56.4-2,

56.6-110, 56.8-5, 57.4-2, 57.6-110,

57.8-5, 77.1102

No Open Flame 55.4-2, 55.8-5, 56.4-2, 56.8-5, 57.4-2,

57.8-5, 77.1102

Explosive

55.6-

20(1), 55.6-43, 55.6-159(b),

56.6-

20(1), 56.6-43, 56.6-159(b),

57.6-

20(1), 57.6-29, 57.6-43, 57.6-159(b),

77.1301(c)(9), 77.1301(e), 77.1302(c)

Blasting Switch,

Safety Switch

77.1303(hh)

Burn Rate of Fuse 77.1303(v)

Flammable Liquid 77.1103(a)

Compressed Gas 75.1106-3

Hazardous Material 55.16-4, 56.16-4, 57.16-4, 77.208(c)

Toxic Material 55.20-12, 56.20-12, 57.20-12

Location of Flre-Flghtlng

Equipment

55.4-23, 56.4-23, 57.4-23

Location of Self-Rescuer 75.1712-2(f), 75.1714-2(g) (2)

Electrical Danger 55.12.21, 56.12-21, 57.12-21, 77.511

Electricity Lock-Out

55.12-

16, 55.12-17, 56.12-16, 56.12-17,

57.12-

16, 57.12-17, 75.511, 77.501

Electricity Disconnect 75.601, 75.809, 75.904, 77.600

Traffic Control 55.971, 56.971, 57.971, 77.1600(b)

7
Table 1. (Continued)

GENERAL MESSAGE RELEVANT CITATIONS

Traffic Control 55.971, 56.971, 57.971, 77.1600(b)

Train Crossing 55.9-59, 56.9-59, 57.9-59

Parked Vehicle Hazard 55.9-68, 56.9-68, 57.9-68, 77.1607(o)

Projection from Vehicle 55.9-49, 56.9-49, 57.9-49, 77.1607(t)

Men Working (In shaft)

55.19-

107, 56.19-107, 57.19-107,

55.19-

108, 56.19-108, 57.19-108

Emergency Stop (hoist) 55.19-13, 56.19-13, 57.19-13

Speed (hoist) 77.1908(k)

Maximum Load (hoist) 77.1402-2

Unsafe Equipment 55.9-73, 56.9-73, 57.9-73

Fall Hazard 55.11-12, 56.11-12, 57.11-12

Obstruction 57.9-104

Egress 57.11-51(b), 75.1704, 77. 1101(c)

Keep Door Open/Closed 55.21-57, 56.21-57, 57.21-57

Shelter Hole 57.9-111

Reduced Clearance 55.9-83, 56.9-83, 57.9-83, 75. 1403-8(b)

,

77.1600(c), 77.1605(h)

Reduced Overhead Clearance 55.9-60, 56.9-60, 57.9-60, 55.11-10,

56.11-10, 57.11-10, 75.1403-10(c),

77.1600(c)

8
Table 2. Synthesis of International Safety Symbol Codes

Referent Message Suggested Image Content

Flammable

Laser

Radiation

Electrical

Corrosion

Explosion

Poison

Forklift Truck

Overhead Hazard

Moving Machinery

General Warning

Hard Hat

Eye protection

Ear protection

Respiratory protection

Hand protection

Foot protection

First aid

No smoking

No open flame

Exit

No Exit

No Entrance

Not drinking water

Do not extinguish with water

Sound your hooter

Locomotive in area

Flames from horizontal surface

Sunburst with radiating line

Three blades around circle

Zig-zag or lightning bolt with arrow

Test tubes dripping acid on hand, bar

Exploding object with radiating particles

Skull and Crossbones

Person in forklift truck

Crane load breaking

Two rotating gears

Exclamation point

Front view of head with hard hat

Front view of head with safety glasses

Front view of head with ear protectors

Front view of head with respirator

Two hands with gloves

Side view of safety boot or shoe

Cross

Circle, slash, lighted cigarette

Circle, slash, lighted match

Variations of person moving, door, arrow

Person moving, door, circle, slash

Person walking, circle, slash

Circle, slash, faucet, water, cup

Circle, slash, bucket, water flames

Horn

Picture of locomotive

9
of Canada (1980) provides actual symbolic Imagery. Table 2 presents referents

and Image content as suggested by these codes.

As noted In the review of CFR, Title 30, applicable U.S. standards do not

usually address the use of symbols. In addition to the codes for mines, these

Include the ANSI Z35.1 (1972) and Z53.1 (1979) standards for Safety Signs, and

for Safety Colors, respectively; the Occupational Safety and Health Administration ( OSHA) standards (CFR, 1981) from which reference to symbols was deleted;

and the National Fire Protection Association (NFPA) life safety code (for exit

signs) (Sharry, 1978).

The NFPA Standard on Symbols for Fire Fighting operations (1980) provides

symbols for 10 fire messages, while two DoT-sponsored publications by the

American Institute of Graphic Arts (AIGA) (1974; 1979) provide extensive

symbology directed toward public Information signs. Similarly the DoT Manual

on Uniform Traffic Control Devices (DoT, 1979) provides both Informational and

warning symbols for highway applications.

An industry standard, SAE (1979), provides for the use of the hazard alert

triangle, while two industry publications, FMC (1978) and Westinghouse (1981),

provide both symbol and sign layout information. Table 3 provides documentation of some current International and U.S. conventions for color coding and

sign type.

1.5 HAZARD ANALYSIS

1.5.1 Overview

The MSHA Mine Injuries and Worktime Quarterly (1980; 1982) was reviewed to

determine the kinds of Injuries and fatalities occurring In mines. Percentage

occurrence of both fatalities and injuries (non-fatal days lost [NFDL] and no

days lost [NDL] were combined) were computed for all mines. These data are presented in figures 1 and 2. These figures allow both fatality and injury

percentages to be compared with each other for all mines and for each mine type.

As is common in accident data, fatalities and injuries do not appear to occur with equal frequencies in the same situations. The majority of injuries are

in the areas of material handling, hand tools, slips and falls, machinery, and

powered haulage (in that order), while the majority of fatalities are in powered

haulage, roof falls, machinery, electricity, falling materials, and explosions.

Furthermore, the percentage of fatalities seems to vary more between mine types

than does that for injuries, although this variability might be reduced by

weighting the data with an hours-worked measure, such as MSHA uses in its more

detailed annual injury reports for each mine type. It is also interesting to

note that the percentage of injuries occurring in mills and processing plants

is quite high. While this category only accounted for 6.8 percent of the coal

injuries, it accounts for 28.2 percent of the metal injuries, 56.6 percent of

the nonmetal injuries, and 36.5 percent of the stone injuries (MSHA, 1980)

(Preliminary 1982 figures indicate 6.2 percent injuries for coal, 15.5 for

metal, 13.4 for nonmetal and 10.9 for stone. Sand and gravel injury data were

not broken down into location.) Use of more effective signing techniques is

10
Table 3. Coding Practices from International and U.S. Safety Sign Standards

ISO/EEC CANADIAN U.S.

Red

Shape

Prohibition

0

Prohibition

Danger

O A

• Danger

• Stop

• Fire & Emergency

Orange • Dangerous Machine

• Energized Equipment

• Warning • Proposed

Yellow Warning

A

Caution

A

• Caution

- Storage for

Flammables

• Containers for

Explosives,

or Unstable

Materials

•Radiation

Green Information Emergency

Information

• Safety Information

• First Aid &

Safety Equip.

Blue Mandatory Action

O

Miscellaneous • information

• Bulletin Boards

• Railroad

Black Mandatory Action

O

11
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Suva ‘sdns

AMaNIHOVM

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asvinvH

daMOd

sividaivM

SNnONVH

aovj

jonva

l¥ldaiVN

SNmva

NOISOldXa

ivcNdioaia

12

Figure

1.

Fatal

niine

accidents

—

1980

estiaates
S€ 0€ K 02 fil 01 S 0

vaHiO

MM 1 mm

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nvj t dns

kmmym

NOllVQNnNNI

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13

Figure

2.

Estimated

injury

data

-

NFDL

and

NDL

-

1980

Total

N

=

38,

145
particularly feasible In milling and processing plants, since the operational

area does not change location on a continuous basis.

Examination of the accident data for coal mines (MSHA, 1979) reinforces the

need to provide safety messages and symbols related to cuts/ punctures,

contuslons/brulses , and stralns/spralns , both In terms of hazard warnings and

reminders to wear personal protective gear. (A potential accident-producing

situation may be Indicated by warning of the hazard, by requiring protective

gear, or by prohibiting a particular action.) In addition, Sheplch, Schllck,

and Thlrumalal (1978) point out the need to warn Inexperienced miners In

particular, due to their high rate of Injuries. These authors noted that In

1978, over 30 percent of the miner population (160,000 miners) were either

new entrants or relocated and untrained miners. Furthermore, over one-third

of the fatal injuries Involved miners with less than 1 year’s job experience.

1.5.2 Detailed Hazard Analysis

Nineteen "Yellow Jackets", or In-depth studies of specific types of mine

accidents, produced by the Health and Safety Analysis Center (HSAC) of MSHA, were

also reviewed In detail. (See the reference section for the list of titles.)

These studies examined the kinds of accidents, the causes, the personnel Involved , and trends over several years . The present review concentrated upon

determining those situations for which Improved hazard pictorials and signage

could be appropriate In warning personnel of a hazardous situation. These

situations will be discussed; situations requiring equipment modification,

specialized training or changes In practices are outside the scope of this

report.

The common factors listed as occurring for many "Mantrip" accidents and Injuries

for all mine types for 1978 and 1979 included poor separation of vehicles and

non-posted, non-enforced speed limits. Factors listed for haulage-related

fatalities and injuries for surface metal and non-metal mining included failure

to heed warning signs, excessive speed, unmarked railroad crossings and failure

to yield right of way. Powered haulage accounted for 41 percent of the injuries

in surface mining for metal, non-metal and sand and gravel in 1978-79, as well

as 18.5 percent of the fatalities in surface coal mines from 1973-76 and 29 percent of the fatalities in metal/non-metal mining for 1972-75. For this latter

category, job Inexperience was a contributory factor with 44 percent of the coal

fatalities and 34 percent of the metal/non-metal (M/NM) fatalities occurring

among those with less than 1 year of on-the-job experience and 72 percent of

coal fatalities occurring among those with less than 5 years. In all these

cases, clear and consistent signage indicating road conditions and speed limit

information would be appropriate. Signs related to safe operating practices

such as seat belt usage, do not leave running equipment unattended, setting

brakes, blocking vehicles, lowering blades, and no riding on buckets, blades,

etc,, are appropriate for both haulage and machinery accidents. Warning signs

of unsafe, unstable ground, berms, low or insufficient clearance and similar

hazardous (and often temporary) conditions are another important category of

potential signage related to mobile equipment.

14
Other accident/ injury categories covered by the "Yellow Jackets" treat moving

machinery including conveyors, front end loaders, bulldozers, draglines,

crushers, scrapers, lifts, cranes and drills. Front end loaders and conveyors

accounted for 49.5 percent and 18 percent respectively of the 138 machinery

fatalities in M/NM surface mining from 1972 to 1975. These fatalities could

again be related to job inexperience (34 percent with less than 1 year experience and 66 percent with less than 5 years). Failure to de-energize conveyors

accounted for 14 percent of these injuries and working under elevated equipment

for 5 percent.

Need for signs related to lock-out procedures recurred throughout the "Yellow

Jackets" reviewed. Another set of contributing causes for M/NM fatalities

included failure to wear protective eyeglasses, protective gear for falling

objects, safety lines, life jackets, safety harness, and safety gloves. Symbolic reminders of the need to wear personnel protective gear are appropriate

for all mine types.

An analysis of injuries in all types of M/NM mining for 1975 and 1976 noted

failure to wear proper safety gear and failure to shut off or lock-out machinery

as major injury factors. Gear Included both eye and foot protection. Again,

the group experiencing the most injuries (34 percent) were those with less than

1 year job experience. (The authors note that the total number of persons and

staff hours representing various experience categories are not available for

calculating an overall frequency rate.) Recommendations appropriate for signage include: warning to stay clear of suspended loads, wear hard hats, wear

suitable footgear, wear face shields/goggles/glasses, wear protective gloves,

and wear seat belts. Other recommendations include posting speed limits, and

repairing and maintaining equipment only when power is off or machinery blocked.

Appropriate signs would include those for entanglement, protective gear, as well

as reminders to shut-off /lock-out moving equipment, load equipment properly,

and use safe operating modes.

Conveyor injuries were studied in a separate analysis of M/NM mines for

1975-76. Routine maintenance and repairs accounted for 59 percent and 23 percent of the injuries, respectively. Generally, the injury related to catching

fingers, hands, arms, and upper extremities in a moving belt. While guards are used during normal operations, they may often be circumvented during maintenance.

Symbolic reminders of entanglement, pinch, crush, and sever hazards would be

appropriate for curbing conveyor Injuries. Reminders to wear hard hats also

would be appropriate since 18 percent of the injuries were the result of rocks

falling from the conveyor. Finally, a lock-out symbol to warn against energizing a belt during repair is needed, since both fatalities and injuries occurred

during conveyor repair.

Under slusher injuries, failure to wear safety equipment accounted for about 10

percent of the injuries. Again, about half the injuries occurred to those with

less than 1 year of job experience. Recommendations for reducing slusher

injuries which would be translated into signage included the need to secure

the slusher properly, the need to avoid working in the same area as the slusher,

and to wear proper protective gear. Because about one third of the Injuries

15
occurred Co chose wlch more Chan five years experience, addlclonal Cralnlng and

reminders of safe working pracClces may also be In order.

ElecCrlcal accldenCs accounCed for a noClceable percenCage of mining faCallCles

and Injuries. For coal, 2854 elecCrlcal Injuries occurred beCween 1974 and 1979

and some 50 faCallCles In M/NM mining beCween January 1972 and AugusC 1977.

Injuries Cyplcally occurred while working on various elecCrlcal sysCems and

juncClon boxes wlCh a lesser number occurring for energized clrculCs on mining

and haulage equlpmenC. Hands and eyes were mosC frequenCly Injured due Co

arcing near hands and face. Slgnage-relaCed recommendaClons Include Che use of

proCecClve gloves or cable handling devices, and Che need Co IdenClfy lock ouC,

nip polnC, and dlsconnecC swlCches. For M/NM mines abouC 60 percenC of Che

faCallCles occurred Co Chose wlCh less Chan 3 years job experience. MosC of

Che faCallCles occurred Co malnCenance personnel (78 percenC). A general con- clusion was ChaC faCallCles are caused by unsafe acClons In Che vlclnlcy of

leChal volcages or by Improper repalr/connecClon of elecCrlcal wires or by

working on a clrculC believed Co be de-energlzed. Because many of Che faCallCles Involve persons noC Cralned as elecCrlclans , Chere Is a greac need for

signs Co IndlcaCe hazards and correcC precauClons for avoiding hazards. These

could Include symbols for danger of elecCrlc shock, elecCrocuClon, gloves,

proper handling equlpmenC, and lock-ouC.

An analysis of pinch polnC Injuries for M/NM mines In 1978-79 IndlcaCed ChaC

vlcClms were caughC by conveyors, belCs, rollers, pulleys, gears, eCc., wlch

conveyors, V-belCs, and pulleys accounClng for abouC 60 percenC of Che Injuries.

AcClvlCles Cyplcally Included cleaning In and around equlpmenC (30 percenC),

using hand Cools around moving machinery (16 percenC), working on V-belCs (13

percenC), energizing equlpmenC wlChouC warning (12 percenC), and caCchlng handCools In equlpmenC (16 percenC). OccupaClons Included mlll/planC operaCor (26

percenC), uClllCy/laborer (24 percenC), mechanic/ repair (20 percenC) and supervisors (7 percenC). The following conclusions relevanC Co signage were reached:

vlcClms reached behind guard, failed Co block unlC agalnsC movemenC, failed Co

follow proper lock-ouC procedures (so ChaC equlpmenC could be energized by

persons oCher chan vlcClm) , and used handCools around moving machinery wlch

exposed plnch-polnCs . Conclusions reached In a sCudy of handCool Injuries In

M/NM mining from 1977-79 Included Che need Co remind personnel Co wear safeCy

glasses, face and dusC masks, Co InsCrucC on Che safe use of handCools, and Che

need noC Co drop Cools on fellow employees. CuCs, laceraClons and puncCures

accounCed for 33 percenC of Che Injuries, sCralns and sprains for 23 percenC,

conCuslons and bruises for 19 percenC, and dusC/meCal In Che eyes for 10 percenC.

MalnCalnlng equlpmenC In good condlClon was noCed as anoCher problem.

AnoCher class of Injuries sCudled was ChaC of back Injuries, occurring primarily

during handling and llfclng maCerlals such as cables/hoses, Clmbers/posCs , and

conCalners. An analysis of such Injuries In coal mining for 1978-79 and In

M/NM mining for 1977-79 noCed ChaC Cralnlng on proper llfclng procedures had

noC reduced back Injuries appreciably, since 82 percenC of Chose suffering

Injuries claimed ChaC Chey had followed correcC llfclng procedures. RecommendaClons for reducing back Injuries Included relocaClng maCerlal closer Co use

polnC, reducing large quanClCles of maCerlal Co smaller amounCs, using longer

shovels, Congs, eCc., and providing more InsCrucClon on correcC llfclng

16
procedures. Sjnnbol signage reminding people to follow proper procedures might

also be effective.

Another related category of injuries studied for M/NM mines was that of slips

and falls. Some 5800 injuries due to slips and falls occurred during 1977-78,

with falls from machinery being the most common type of injury at a work site.

Falls from stationary elevations such as ladders, platforms, scaffolds and catwalks accounted for about 10 percent of the injuries (with half of those being

from ladders). Slipping and falling during walking accounted for about 12 percent of the injuries at the worksite and fully 50 percent of those injuries

occurring away from the worksite were due to ice and water on walking surfaces

and falls on stairs or ramps. Causal factors Included improper mounting/

dismounting from machinery, jumping from machinery, and oil, ice, grease, etc. on ladders and other working surfaces. Signage possibilities include reminders

of proper mounting/dismounting techniques, use of safety belts where appropriate, and marking of openings in ground or floor with warning signs.

Comparison of injury rates for different coal seam heights indicated greater

likelihood of disabling injury for low coal (seam height less than 36 in.).

This may be due to poorer lighting and decreased visibility for low coal,

uncomfortable or cramped working positions leading to more disabling injuries,

low clearance, increasing difficulty of handling materials, problems associated

with low coal conditions including fewer canopied coverings on equipment, and

tendency for low coal mines to be smaller and perhaps to have less fully developed safety programs. Recommendations did not include anything relevant to

signage, although Increased attention to signage used in low coal might prove

worthwhile. Similarly, the analysis of falls of ribs, roof, and face accidents

for coal did not indicate many opportunities for improved signage, as these

accidents tend to occur at or near the face area, often where supports are not

installed and where permanent signage is impractical. Safety signs could be

profitably used at the entrance to a coal mine, in processing areas, or in

changing facilities, however.

Thus, review of the "Yellow Jackets" underlined the need for signs for personal

protective gear, hazard warning, such as electrical and entanglement, unsafe

practices (especially lock-out indications) and traffic signage.

Because the Department of Transportation (1979) already provides a system of

symbols for highway signage which is readily adaptable to the mine environment,

this need will not be considered further here. For the other hazards, referents or meanings not considered in the various codes which should be considered

include: lock-out indicators, life lines/jackets and similar protective gear,

do not jump from machinery/plat f orms , cut, sever, crush, and hole or open pit

hazards (slip, trip and fall).

The Code of Federal Regulations Title 30 ( 1980) requires signs for the following

messages for which symbols currently exist: No Entry/Restricted Entry, General

Hazard, No Smoking, No Open Flame, Explosives, Location of Fire Fighting Equipment, Electrical Danger, Fall Hazard, and Exit. Other CFR Messages which should

be considered for symbolization Include: Electricity lock out, limited horizontal

clearance, keep door open/ closed, shelter hole, and reduced vertical clearance.

17
1.6 SITE VISITS

1.6.1 Hazard Information from Site Visits

Visits to eight different mine sites also provided information about perceived

common hazards and necessary safety Information from the perspective of the

individual site safety and mining personnel. Safety personnel universally

mentioned injuries related to slipping, tripping, and falling, lifting and

straining, conveyors and entanglements, lock-out/ tagout procedures, as well

as explosion, fire, and potential electrical hazards. Problems related to

chemical processing such as corrosion, poison, and chemical burns, cropped up

in those mines with mills and processing plants attached. Signage tended to

be related to the major. Infrequently occurring hazards rather than the more minor, but ubiquitous hazards such as slip, trips, and falls, or pinching,

crushing, and severing. Because the latter can occur anywhere, they are much

more difficult to warn against. Nevertheless, there was a wide range of

different potential hazards in the eight sites visited.

Safety personnel also expressed interest in pictorial signage as a way of

communicating information rapidly and getting the miners' attention. Table 4

presents information from these visits, including the mine type, approximate

size, perceived hazards, and general sign use (as observed). This is by no means an exhaustive survey of current mine hazards and sign practices, but

combined with the MSHA hazards data, it provides some indication of the

various sorts of situations that could require symbol signs.

1 .6 .2 Sign Usage

As noted in 1,6.1, site visits were made to eight different mine sites to

determine the types of signs currently used, obvious hazards, and perceived

signage needs. These mines included two sand and gravel operations, two openpit copper, one underground molybdenum, one underground coal, one open-pit coal,

and two oil shale facilities. At several sites, the milling operations as well

as the mines were visited.

The site visits revealed extensive use of word signs with very few symbol or symbol plus word signs. (This is encouraging in that miners will not have to

"unlearn" a set of symbols which differs from any recommended sets.) The

symbols* actually observed at the sites included; ISO Radiation, ISO Electrical, cross for First Aid, hand for Stop, man with circle and slash (at woman's

dressing room), arrows for Direction, and circle, slash, and cigarette for No

Smoking, Sign messages typically referred to hazards, prohibited actions,

protective gear, and exit. Table 5 presents frequently observed messages from

the mine site visits related to hazard or safety information. Signs related to

traffic control — both rail and self-propelled were also observed, along

with informational signs such as women's and men's restrooms /changing areas.

See figures in section 4 for the appropriate imagery.

18
Table A. Site Visit Information

Type of Mine Approximate Size Typical Hazards Observed Sign Usage

Sand and Gravel 85 miners Dust few signs used

Mine & Mill some Illiterate conveyor belt, pinch, crush. word format - homemade

some Spanish speaking sever noise

high voltage

slips & falls

mobile equipment

Increased hazards during

maintenance

legibility problems due to dust & dirt

dim lighting levels inside

mill & packaging area

S3nnbols : none

Open Pit Copper AOO miners Explosion ANSI word signs - purchased

Mine & Mill some Spanish speaking fire

slips & falls

overhead hazards

mobile equipment

chemical - corrosion

poison

primarily "danger" category

extensive use of signs to mark every possible hazard

mine - mud & dirt a problem

mill - problems of durability

due to corrosion - frequent

sign replacement

problems of "red" fading

outside

Symbols: radiation; DoT

highway symbols on haulogy

roads

Underground 1500 (3 shifts) Fire Including vehicle Illumination (cap lamp)

Molybdenum about 15 percent explosion metal halide lighting In mine & shops Spanish speaking

no real literacy problem

underground fueling

mobile equipment

shops & control facilities

generally young roof falls

pinch point, crushing

dust/noise

slips & falls

ANSI word sign format

signs 10 - 10 ft off floor

because of dust spraying

extensive signage, perhaps

some visual clutter

Symbols: "hand" for stop,

"no men" at woman's changing

room

Open Pit Copper 3000 miners Slips & falls from equipment Sign use concentrated In experienced work force blasting/explosives repair/maintenance shops

mine & mill high voltage & concentrator/ crusher

& moving equipment areas

shops flying particles

entanglement , crushing

noise

respirable dust

chemical bums

radiation

overhead hazards

strains, sprains

Word signs - handmade

Some dust & weathering

problems

S3^bol: radiation symbol In conveyor belt area

19
Table 4. (Continued)

Type of Mine Approximate Size Typical Hazards Observed Sign Usage

Induatrlal Sand 75 mlnera Slips & falls ANSI word signs

Mine & Mill 3 shifts conveyor belt Inquiries Many signs, generally located

no literacy problem dust

noise

explosives

some chemicals

fire, burns

lockout failure

on or near hazard

Protective gear at entrance

to site

Some rust & dirt but

generally legible signs

Symbol: ISO lighting zig-zag

Underground 400 miners Fall of roof & rib, objects relatively few signs used

Coal Mine no literacy problem slips & falls underground

& Mill young workforce entanglement, pinching,

crushing (conveyor belts)

electrical

fire

explosion

Improper lifting

mobile equipment

high voltage most frequent

sign

signs - homemade

problems of poor contrast

due to dust & poor color

choice

escapeway signs In yellow & white

Illumination by cap or vehicle light

Symbols : none

Open Pit 100 miners Mobile equipment protective gear sign at Coal young workforce

some literacy problems

falls from equipment entrance to mine

relatively few word signs

Symbols i none

Underground 100 total Electrical hazards ANSI word format generally

Oil Shale young workforce explosion hazards

flammable materials

Used limited signage under

ground

demonstration slips & falls Hazard warning signs

mine construction hazards

chemical - corrosion

generally located on or near hazard

mine

construction

site

- poison Protective gear - entrance to site or hazard area Few legibility problems

Symbol: electrical zlg zag

20
Table 5. Safety Sign Messages Observed at Eight Mine Sites

Hazard

High Voltage, Electrical

Radiation

Hazardous Area

Combustible, Flammable

Explosive, Blasting

Slip

Corrosion

Oxidizers In Use

Poison

Overhead Crane In Operation

Falling Material

Keep Clear Of Pit

Stay Clear Of Moving Machinery

Protective Gear

Wear Hard Hat

Wear Safety Glasses

Wear Safety Shoes

Respirator Required

Self Rescuer Required

Ear Protection Required

Life Jackets Required

Prohibition

No Smoking

No Open Flame

Do Not Start

Do Not Operate Past This Point

Egress

Exit

Escapeway

Stop

Automatic Fire Door

Restricted Area

Authorized Personnel Only

Safety

Eyewash

Fire Extinguisher Location

Fire Hose

First Aid

Shelter Area

21
DANGER - BLACK & WHITE

- RED OVAL

- signal word panel

- red oval

- message panel

CAUTION - BLACK & YELLOW

- signal word

- message panel

EXAMPLE

XANTHATE-ORGAN1C

IRRITANT - DO NOT

APPLY HEAT - DO

NOT MIX WITH AGIO

red background

white letters

white background

black letters

Figure 3. ANSI sign format for hazard-warning signs

22
The only consistently observed sign format was the ANSI Danger and Caution

word signs. These were used fairly extensively, often with quite long messages

manufacturers except where the safety personnel felt auxiliary protective

equipment or "no smoking" signs might be necessary. In other mines, however,

the signs were clearly homemade, using idiosyncratic colors and formating.

For example, in one mine, the escapeway signage was presented in yellow and

white with poor legibility.

Problems of sign legibility were abundant. In one operation, the signs were so badly corroded as to be almost illegible, while other signs (including a radiation sign) were obscured by dust. Since mining operations typically involve

moving and crushing large quantities of material, as well as chemical processing, problems of dust, dirt, corrosion, and weathering are not surprising.

They do suggest, however, that signs may need careful monitoring, cleaning,

and frequent replacement. In underground operations, additional problems arise

because of the low lighting levels. Where cap lamps are used, signs are visible only if the miner turns the lamp toward them. As a result, the signs should

be in an area typically Illuminated within the normal sweep of a cap lamp.

Placement at the celling or the floor would appear to be ineffective. Retroreflective and/or fluorescent materials should be considered for critical signs.

Where general mine lighting was used, light levels varying widely from about

1-150 fc were observed. Positioning of the sign with respect to the lighting

also varied widely. As a result, observations of low contrast - resulting in

less likelihood of detection - were common. Light sources Included fluorescent,

mercury, tungsten, and high pressure sodium, with most mines using a variety of

sources depending on the location. In addition, signs were located anywhere -

2 ft off the ground, on an inaccessible area of a piece of equipment, or 10 -

15 ft above the ground. For example, spraying to reduce dust requires that

signs be placed high above the floor. Lower placement increases the likelihood

of sign obscuration by the dust- reducing agent. In addition, the likelihood

that miners may be moving rapidly in motorized vehicles past a sign Increases

the need for legible signs.

The amount and extent of signage varied widely from mine to mine. In one mine,

very few signs were used and these related primarily to escapeways, voltage

dangers, and rail traffic Indicators. In another, every conceivable hazard was marked, sometimes with more than one sign. The latter approach can result in

visual clutter and confusions. The miner does not know what is the most critical message to attend first. In such over-signed installations, the attentiongetting value of the individual sign is lost. On the other hand, the danger

of under-signing is that an important safety message is left unsaid. Another

issue is the repetition of a message - at what intervals do signs need to be

placed to warn of recurring hazards, such as entanglement in a conveyor belt?

Still another is that of multiple hazards - a refueling area must be marked to

warn of flammable and explosive hazards as well as no smoking and no open flame.

Similarly, certain chemicals may be explosive, flammable, corrosive, and poisonous at the same time. Although ANSI standards exist for labeling chemicals,

there are no comparable guidelines for signing a mine or a mill. Determining

the most dangerous hazard in terms of potential Injury and economic cost would

appear to be a viable starting point - particularly if signs for this hazard

would tend to keep people away from it. Anecdotal evidence suggests, for

23
example, that more attention Is paid to a "danger - blasting" sign than to a "danger-keep out" sign.

Another set of concerns relates to the durability of a sign. Problems related

to dust and dirt could be solved by cleaning on a regular basis, although In some dusty sites that might prove burdensome. On the other hand, corrosion

and weathering will eventually require replacement of the sign, sometimes on a monthly basis. Obviously the material composition of the sign Is Important.

Consideration of the relative performance of vinyl, plastic, and metal signs

needs to be made. Vandalism Is yet another problem. In one mine, the safety

officer noted that signs present a challenge In terms of how quickly they

could be defaced or destroyed. Pictorial signs could present a new outlet for

creative, artistic vandalism.

Although a previous study of Industrial signs (Collins et al., 1982) Indicated

widespread use of color coding to indicate areas for personal protective gear,

fire equipment, and selected production facilities, such coding was infrequently

observed for mine operations. One site did code the location of fire extinguishers with a patch of yellow located above them, however.

In summary, there appears to be some consistency across mine sites of the sign

messages observed (due most likely to the commonality of hazards) but not In

formating, positioning, amount, or color coding. Development of a suggested

set of pictorial signs could Increase consistency between sites. In addition,

mine safety personnel expressed Interest In a set of pictorials and symbolic

signs for mine safety. They mentioned the desirability of being able to purchase signs related to their needs from existing sign catalogues. This could

decrease reliance upon homemade signs of dubious design, durability, and legibility. As a result, the development of a set of pictorials and symbols for

mine hazards appears to have potential acceptance from the mine safety community.

24
2. SELECTION OF REFERENT MESSAGES AND CANDIDATE SYMBOLS

2.1 SELECTION OF REFERENT MESSAGES

After reviewing the wide range of symbols and referents (messages) collected

from sign and symbol standards, sign catalogues, sign manufacturers, mine

hazard analysis, mine site visits and previous research, forty referents were

selected for further experimental study. The study was intended to determine

those symbols that were understandable and that could be effective with a mining population. The 40 referents, presented in table 6, represent safety

situations and hazards which appear to be frequently occurring and dangerous.

The referents are given in intentionally general form (e.g., "danger - Entanglement Hazard.") At some point, further discrimination among the possible messages for a particular safety referent may be required (e.g., "danger

of entanglement in a conveyor belt", or "a continuous miner", or "a shuttle

car"). Some of these messages were also studied in an earlier experiment on safety symbols (Collins et al., 1982), although additional hazard warning

messages were Included to represent a broader selection of possible mining

hazards. Data from the present experiment will be compared with the previous

study wherever common symbols were studied. This will allow the responses of

different workplace samples to be compared.

Referents from five different categories of safety messages are included.

Hazard warning messages are Intended to warn of a particular hazard or danger.

The hazard messages selected represent the major kinds of injuries reported in

section 1.3, or are among the messages given in the various international/

national standards. The prohibition referents indicate various prohibited

actions. "Do not touch", an addition to the various international standards,

appears useful as a general cautionary/ prohibitory message. Personal protective

gear referents indicate the need to wear various types of safety equipment typically found in mining and milling. Egress-related messages refer to "exit" and

"no exit", including "keep door open/closed" . Finally, the safety instruction

messages refer to both first aid and fire emergency information.

2.2 SYMBOL SELECTION PROCEDURES

2.2.1 Symbols Selected

A total of 72 symbols were tested for the forty referents. These symbols are presented in section 4—Results, along with the data for each message. Two

symbols was tested for each referent, except where symbols were already standardized or no alternative symbol for a concept was located. One symbol per

referent was studied for each group of miners to avoid confusions between

symbols. Symbols were selected to represent a range of symbolic approaches,

such as hazard alone/hazard with person; abstract/representative; detailed/

simple; black and white/colored, because these factors are thought to affect

overall symbol understandablllty.

Symbols were obtained from a variety of sources including national and

international standards, sign/ symbol catalogues, and product manufacturers.

Several symbols were modified or redrawn from their original sources, usually to

simplify an otherwise graphically complicated image.

25
Table 6. Referent Messages for Mine Safety Symbols

HAZARD WARNINGS

Danger - Explosion Hazard

Electrical Hazard

Corrosion Hazard

Flammable Hazard

Overhead Hazard

Poison Hazard

Fork Lift Hazard

Entanglement Hazard

Slip Hazard

Trip Hazard

Fall from Elevation

Sudden Pressure Release

Crush

Sever

Pinch

Hot Surface

Laser

Radiation

General Warning

Prohibited Action - No Open Flame

No Smoking

Do Not Touch

Protective Gear - Wear Hard Hat

Wear Eye Protection

Wear Ear Protection

Wear Respiratory Protection

Wear Safety Shoes

Wear Safety Gloves

Egress - Exit

Emergency Exit

No Exit

No Entrance

Keep Door Open

Keep Door Closed

Emergency - Safety

First Aid

Safety Shower

Eyewash

Fire Extinguisher

Fire hose and reel

Fire Alarm

26
2.2.2 Rationale for Specific Symbol Selection

About 60 percent of the 72 symbols studied in the present experiment were also

evaluated in the earlier workplace symbols experiment. In that study, the

number of symbols located for a given referent varied from two to well over 40 or 50, since there was no standard set of safety symbols in the United States.

As a result, selecting a symbol for evaluation necessarily required decreasing

the number of symbols to a smaller, more manageable set, if further research

with a large number of subjects was to be practical. A ranking procedure was used to reduce the large set of symbols to a more manageable set for further

study. In a ranking procedure, subjects order a set of Images according to

how well they believe that each image conveys the intended meaning of the

referent. Use of this procedure allows an ordered selection of a limited set

of symbols for more detailed research. It also suggests that the set of Images

tested will be at least somewhat meaningful. As a result, ISO TC-145-SC1 recommended rank-ordering as the best procedure for reducing the size of a set of

Images. Easterby and Zwaga (1976) followed this procedure with small groups

of subjects in two countries to select three sets of public information symbols.

Similarly, Heard (1974) and Green (1979) had subjects rank-order images for

automotive displays and controls according to meaningfulness, before proceeding

with further symbol evaluation.

For the workplace symbol study (Collins et al., 1982) the ranking procedure was used to select the final set of Images to be evaluated for each referent. About

30 representatives of the safety and graphic design communities rank-ordered

images in terms of their appropriateness for each referent. Participants rankordered only the five best Images for each graphic concept, although in some cases as many as 20-30 Images were presented. They then rank-ordered the

graphic concepts to determine which concept best conveyed the referent. Thus, a two-stage process of ranking both symbolic images and graphic concepts was used

to select one to five images for each referent.

The set of images selected by the rank order procedure for further experimental

study represented a range of concepts. Images that participants ranked as the

best representation for each referent were generally Included. These selections

were modified by the following factors: the need to include those safety

symbols suggested by the International Organization for Standardization (ISO) in

the final testing, and the desire to select as graphically diverse a set of

images as possible. In addition, only one image was selected for further testing for six referents because these Images were already widely standardized.

These referents included Laser, No Smoking, Biohazard, Radiation, Fire

Extinguisher, and Hose and Reel connection.

In the present experiment, the initial selection of Images was based on the

results from the Collins et al., (1982) study. Where common referents existed,

two images which were either well understood or preferred were selected for

further study with the mining population. In a number of cases, however, the

data from this earlier research indicated that only one of the images tested

was reasonably successful. This was particularly true for Overhead Hazard,

Poison, Slip, Trip, and Emergency Exit. In these cases, a second image was selected for study based on comments given by the industrial subjects, the

27
•arllar ranking data, and auggaatlon by tha ANSI and CIMA aymbol aubcommlttaas*

In addition, tha aubcommlttaaa auggeatad the naad for tha following rafarantai

Sudden Praaaure Relaaae, Cruah, Sever, Pinch, and Hot Surfaca# Symbola for

theae referenta were also supplied by these subcommittees! Additional Exit

symbols were selected based upon preliminary results from an NBS experiment on

exit symbol visibility (Collins and Lerner, 1983) • The CFR review also suggested the need for symbols for Keep Door Open/Closed. In the case of Personal

Protective Gear symbols, almost all the symbols studied In the earlier experiment were well understood, although those symbols showing the gear on a person

seemed to be slightly more preferred and better understood* Because the ISO

symbols using this approach (which were used In the earlier experiment) are somewhat outmoded, a newer set developed by the Treasury Board of Canada (1980) was selected Instead*

The final set of Images selected represented the following sorts of general

concepts: hazard (abstract or representational); hazard consequences; prohibited actions; protective gear (by Itself, or on a human form); and safety

devices* The Images also varied along the following dimensions: complexity - simplicity; abstraction - representation; presence - absence of human flgure(s);

and activity - Inactivity* The use of color and surround shape also varied,

and was determined by currently existing standards* This meant that the hazard

symbols were generally presented as a black figure on a triangular yellow background; the prohibition symbols as a black figure on a circular white surround

with a red circle and slash; personal protection as a white figure on a solid

blue disk; safety information as a white Image on a square green background;

and fire Information as a white Image on a square red background* Egress

symbols varied In color between green and white, black and white, red and white,

and red, white and black* In addition, some of the hazard symbols were presented as black figures on a square white background, or as white figures on a red background* In general, however, the majority of the symbols followed the

coding conventions given by ISO TC 80 (1979)*

2.2.3 Surround Shape Concerns

The various international standards typically use an auxiliary coding system to

Indicate the category to which the symbolic message belongs. Generally, the

following system Is used Internationally (ISO, 1979; EEC, 1977; 1979):

o hazard - black figure, yellow background, black triangular surround,

o protective gear (mandatory action) - white figure, solid blue circular disk

o prohibition - black figure, white surround, red circle and slash

o egress & safety - white figure, square green surround

o fire - white figure, square red surround

The Canadian Standards Association (1977) uses color for the hazard category to

Indicate the level of hazard. Red Indicates danger and yellow, caution. A

black disk, rather than a blue disk. Is used for protective gear. A standard

by the Standards Association of Australia (1980) recommends the use of a diamond

surround to Indicate the presence of a hazard, as does the U.S. DoT (1979)

for highway caution signs.

28
The use of surround shape and color appears to be a viable means of indicating

additional, complimentary information about the symbolic image. In the case of

hazard symbols, however, at least four different surround shape coding strategies have been used in the United States. There is the internationally used

triangle, the diamond used by the Department of Transportation (DoT, 1979),

the square used by the FMC Corporation (1978), and the circle occasionally used

by the Nutheme Corporation (1975). In addition, DoT (1974), in conjunction

with the United Nations (UN), places the hazard warning symbol in the upper half

of a diamond. Thus, the user in the U.S. is potentionally exposed to at least

four, if not five, different coding strategies.

The triangle has been criticized because it can limit the size of the interior

image. As a result, the square has been suggested (FMC, 1978). Yet, several

researchers (Cochran, Riley and Douglas, 1981) have suggested that angular

"pointy" shapes convey the idea of danger of hazard better than rounder, less

angular shapes.

Few researchers, however, have actually determined whether the prospective user

is aware of the Intended message behind all the coding systems. Do triangles,

squares, diamonds, circles, and the like convey any information about the likelihood of danger or hazard? Has the American user become aware of the coding

systems used in the highways - (the symbol system probably viewed by the largest

number of persons) - or have American users become familiar with international

practice - or do the various surround shapes make little, if any, difference?

Consequently, as a supplement to the main study on the relative understandability of safety symbols, a study on the perceived hazardousness of surround

shape was conducted. The six surround shapes most frequently used in both

safety and highway symbol sign systems were selected. These were the circle,

square, triangle, diamond, octagon, and Inverted triangle. Because these

shapes are usually presented with an interior image, which may influence perceived hazardousness, the effect of different Interior Images was also studied.

Thus, the six shapes were presented both alone and with four different interior

hazard images. These four Images were those for explosion, poison, entanglement, and general warning, which represented a range of direct personal involvement, hazard severity, abstraction, and probable consequences. Two additional

safety images were presented: the cross for first aid and the hard hat.

2.3 EXPERIMENTAL RATIONALE

2.3.1 Evaluation of Understandabllity

To be effective, a symbol must be understood; it must communicate the desired

meaning to those who encounter it. While understandabillty is a critically

important criterion by which to evaluate a symbol, it is not the only one. A

symbol should also be detectable at a given distance under specific light

levels. A symbol should be discriminable , or distinguishable from other symbols

within a particular set. A symbol should be recognizable, or be remembered and

identified under different circumstances. A symbol should be graphically

satisfactory and command attention. Finally, a symbol should alter behavior in

the intended direction and facilitate conformance with the message. A fully

29
effective symbol performs well in each of these areas. Understandability

,

however, is the key which unlocks the whole process of communicating safety

messages. As a result, the priority for the research on safety symbols presented in the present report is the determination of the relative understandability of several images selected for each referent. In this way, the most

understandable image could be recommended for a given referent.

Understandability or comprehension has been assessed by a number of different

procedures. Perhaps the most commonly used is simply to ask a person to give

a short definition of the meaning of a symbol (definition procedure). Other

techniques have involved asking a person to match a symbol to a definition (or

vice versa) (matching procedure) or to select the correct definition from a set of alternative choices (multiple-choice procedure). While the definition

procedure has been widely used, it poses numerous problems. These include difficulties in scoring or determining exactly what subjects meant by their answers

and the assumption that subjects are verbally facile enough to be able to write

down a reasonable (and readable) answer. The latter problem emerged as significant at several of the workplace sites studied; there was no reason to assume

that miners might have less trouble with a definition procedure than Industrial

personnel. Answers obtained with a multiple choice procedure with confidence

ratings (to be discussed later) were shown to correlate highly with answers obtained from a definition procedure in an earlier NBS study (Lerner and

Collins, 1980a). Use of a multiple choice procedure for determining "understandability" was therefore used for the study of mine hazard pictorials and

safety symbols. This procedure was used with some confidence because it used

as incorrect choice alternatives those "wrong" and "partially correct" answers given in the earlier workplace symbols project. These answers, which are tabulated in the report by Collins et al. (1982), formed the source of the choice

alternatives used in the multiple choice response form. A major attempt was made to include serious confusions among the choice alternatives for each

referent, because previous NBS research indicated that some symbols communicate

messages which are opposite to the intended one. In particular, where appropriate, a "critical confusion" or an opposlte-to-correct choice was deliberately

included

.

The multiple choice procedure was combined with a confidence rating procedure

in which subjects provided a rating of their confidence in the correctness of

each choice alternative for a given symbol. This procedure, which was previously shown to provide an index of guessing and confusions, provides

additional information about the effectiveness of a given symbol.

Thus, the relative understandability of two symbols was compared for 32

referents. (Eight symbols were assessed individually). The comparison is made

in terms of the percentage of correct answers for each symbol, as well as of

the confidence ratings for the four alternative choices. Various other statistical analyses are also made for the various types of data. These results are discussed in section 4.

30
2.3.2 Perceived Hazardousness of Surround Shape

Although symbol surround shape and color were not shown to affect symbol

understandability in any consistent manner in the earlier workplace symbol

research (Collins et al., 1982), they may influence the perceived hazardousness

of a symbol, and provide additional safety coding information.

In the second portion of the mine-safety symbol experiment, participants were

given an opportunity to rate the perceived hazardousness of the different sur- round shapes commonly used for safety messages. These shapes included triangle,

square, circle, octagon, diamond, and inverted triangle. Each of the six shapes was presented for a single image. Six different Images were used—four Hazard,

one Personal Protective Gear, and one Safety Instruction. In addition, the sur- round shapes alone were also presented. Participants were asked to rank order

the six images according to the degree of hazard or danger indicated by the

symbol. They were also asked to select the background color (red, green, blue,

yellow, orange, and black) that best conveyed the symbol message. Part II was

thus designed to assess whether specific surround shapes and colors were asso- ciated with different types of safety messages and hazard warnings. (See

Appendix for samples of the ranking sheets.)

Data obtained from the present study are designed to provide information on miners' comprehension of selected safety symbols, confusions related to specific symbol messages, and the coding value of surround shape and color. They

will be compared with applicable data on industrial safety symbols, to provide

an indication of safety symbol effectiveness for different types of industrial

and mining populations.

31
3 . METHOD 3.1

PROCEDURE

The experimental study consisted of two parts, one on symbol understandablllty

(part 1) and one on perceived hazardousness of surround shape (part 2). In the

first part, participants selected a multiple choice answer from a set of four

alternatives, and rated their confidence In the correctness of each of the four

alternative choices. Part 1 was designed to assess the relative understandablllty of the two candidate symbols for each message. In the second part,

participants rank-ordered each of six surround shapes In terms of perceived

hazardousness. Participants also Indicated the most appropriate background

color for the most "hazardous" surround shape. Part 2 was designed to test

the hypothesis that all surround shapes are perceived as equally dangerous.

3.2 PARTICIPANTS

A total of 271 people participated In the experiment Including 16 females.

These people came from eight different testing locations. Involved In both sur- face and underground mining. The locations Included two coal mines (BC and EM), one open-pit copper (BT), one Industrial sand (WED), two oil shale (OS), one

oil shale mine construction site (CO), and one college mine-safety class (MT).

(Data from the three oil shale sites and mine-safety class will be analyzed

statistically as one site (OS).) Table 7 presents Information on the data col- ' lection locations. The various sites were chosen to represent a broad range I of different mining occupations In a wide geographical distribution, although

no attempt was made to get a random sample (due to the difficulty of gaining

access to different sites). Participants were typically miners or personnel

^ likely to be working at a mine site and hence subject to possible mining hazards.

[ Testing sessions were generally held as part of a safety training meeting.

Although color deflclences occur In 8 to 10 percent of Caucasian males (Rubin | and Walls, 1969), color vision of the participants was not measured, because It

j was not believed to be essential for understanding a symbol’s message. Color

is, nevertheless, believed to play an Important role in facilitating sign

^ detectability, discriminability and conspicuity (Glass et al., 1983). i

With the exception of the various oil shale and mine safety class sites, both

groups of symbols were administered at each site. One hundred thirty-five

miners saw symbols from group 1, while 136 viewed symbols from Group II. Data

from 4 miners were excluded from part 1 due to scoring problems, making the | total number of participants for part 1 to be 267. No miner saw both group 1 and group 2 symbols. Eight symbols were, however, common to the two groups.

| Since part 2 followed directly after part 1, a total of 271 people were potential participants. The number (N) of actual participants was lower due to |j statistical restrictions which will be discussed in 4.5.

3.3 STIMULUS MATERIAL

For part 1, each symbol was initially silk-screened Into a 30 cm x 30 cm (12 in

X 12 in) placard. Color slides were then photographed individually from each > placard. Symbols were tested using the color and surround shape given in the

I
Table 7. Data Collection Locations

Site Location Mine Type Number of Pa

BCl* Kentucky Coal 26

BC2** Kentucky Coal 24

EMI Pennsylvania Coal 10

EM2 Pennsylvania Coal 16

BTl Montana Open-pit Copper 36

BT2 Montana Open-pit Copper 35

WEDl Illinois Sand & Gravel 24

WED2 Illinois Sand & Gravel 20

OSl Colorado Oil Shale 24

0S2 Colorado Oil Shale 6

MTl*** (OSl) Montana College Mine Safety Class 20

C02*** (0S2) Colorado Oil Shale Construction 30

TOTAL 271

1 refers to Group 1 symbols

2 refers to Group 2 symbols

MTl was combined with OSl and and C02 with 0S2 for statistical comparisons

due to the smallness of the 0S2 site. OSl and 0S2 were used for subsequent

statistical comparisons.

33
original source. A total of 72 symbols were shown in part 1. (See figures

6-42 for a representation of each symbol studied.)

In part 2, the six surround shapes were drawn to a constant size using ISO

guidelines (1980a ). The interior images were then placed within each of the

six surrounds. Participants were given a random set of seven sheets. On each

sheet, all of the six surround shapes were used, in random order, to surround

one interior image. Che sheet showing only the surround shapes alone was included as well. The seven sheets were drawn in black and white and then

photocopied

.

3 .4 PROCEDURE

Each experimental session consisted of the following sets of events:

a) participants read and signed the Research Participant Agreement and the

Privacy Act Advisory Statement (see Appendix for example); b) instructions

for the use of the multiple choice form in part 1 were given and a practice

example worked; c) participants completed the 40 item multiple choice sheet,

for part 1 of the study; d) instructions for part 2, (perceived hazardousness of surround shape and color), were given; e) participants rated surround

shapes and color; f) participants were debriefed as to the meaning of each

symbol, and given a chance to comment and provide suggestions for Improvement.

The entire session including a break between parts 1 and 2 required about

1 to 1 1/2 hours.

Observers participated in groups of 4-30 people at locations chosen by the

safety office. The testing session typically occurred during a safety-training

session, to minimize disruptions to production. Typically, 2-4 testing sessions

were held at each site so that an equal number of participants could view the

two sets of symbols. Each set of symbols was presented In a different random

order to minimize order effects. In part 1, symbols were presented at a rather slow rate (about 30 sec per symbol - or when everyone had finished

responding). Participants were instructed to circle the correct choice alternative for each symbol and then rate their confidence on a scale of one to

five in the correctness of each of the four answers. They were also instructed

that the session was a test of the sjnnbols, not of them, but that all forms were

to be completed Individually. (Participants were informed that their participation was voluntary and that they were free to terminate the test at any time.)

After part 1 was completed, participants were given part 2. They were instructed to rank order each symbol according to how much danger, or hazardousness, the symbol indicated to them using a scale from one to six (with one being

most and six being least hazardous). They were also asked to circle the background color that was most appropriate for the shape ranked as number one. Participants were also asked to indicate their age, sex, job title, and years of

mining experience.

34
3.3 SCORING OF RESPONSE SHEETS

The number of correct, Incorrect, and no responses were tabulated for each

symbol. The confidence ratings given for each of the four answers were also

tabulated In part 1. These tabulations were then computerized for further

summary and analysis. In part 2, rankings given for each surround shape were

tabulated, along with the frequency of each color selection. Statistical

analyses will be described In detail In section 4.

35
4. RESULTS

4.1 ANALYSIS OF CCMPREHENSION DATA

The data on symbol understandabllity were analyzed using the SPSS [1973] set of

statistical programs on the NBS UNIVAC 1100/82 to test for statistical significance. The percentage of correct responses for each symbol was calculated

across sites for both group 1 and group 2. In addition, the distribution of

responses across the four choice alternatives was tabulated for each of the 72

symbols studied. Similarly, the distribution of confidence ratings was also

tabulated for the four answers, and a mean confidence rating calculated for each

choice alternative. Table 8 presents the percentage of correct answers and the

mean confidence rating for the correct answer for both version 1 and 2 of each

symbol. A mean confidence rating for the correct choice was also calculated

for only the correct participants. This measure is termed "CCONF". Individual

results for each symbol will be discussed in detail in section 4.4.

Statistical comparisons were made for several measures of overall performance.

These included one-way analyses of variance (ANOVA) which were calculated to assess the effects of age and site on both percentage correct and confidence

ratings (CCONF).

Although data were collected in at least eight separate location, for the

purposes of statistical comparisons, several groups of participants were com- bined into a larger groups. Thus, a new site group, OSl , was created which

contained OS and MT. Similarly, 0S2 contained CO and OS. The OSl and 0S2 site

groups are unique in that everyone was not from the same mine site, but rather were from 4 geographic locations in Western Colorado and Montana. Nevertheless,

for purposes of comparison they will be referred to as the OS sites. Furthermore, some participants in both OS site groups were somewhat less familiar with

mining per se, as they contained some mine construction workers (CO), and minesafety students (MT). Neither group, however, can really be considered naive

to mining, as they either worked at a mine site or had received training in

mine safety. (Thus, the statistical analysis focused on sites EMI and 2, BTl

and 2, BCl and 2, WEDl and 2, and OSl and 2.)

Three statistical analyses were made for the overall data. These were an analysis of variance (ANOVA) for the number of correct responses, and mean CCCKJF, as a function of site, and of the number of correct responses as a function of

age. The overall number of correct responses and mean correct confidence rating (CCONF) were calculated for each site. The ANOVA for each revealed a significant site difference, attributable to the BC site. Personnel in the

four other sites typically identified about 32 of the 40 symbols correctly.

For the BC group, however, the mean number of correct responses was closer to

28. Similarly, the mean confidence rating given by correct subjects for the

correct answer at the BC site was about 3.10, in comparison with a range of

3.8 to 4.2 for the other sites.

The analysis of variance of the number of correct responses as a function of

age also was statistically significant. Two age categories stand out in this

analysis; the older subjects (aged 50-61) whose mean number of correct responses

36
Table 8. Overall Percentage of Correct Answers and Mean Confidence Ratings for

All Symbols

Version Version 2^

Number Symbol Percentage* Mean Confidence Rating Percentage Mean Confidence Rating

1 Flammable 57.5 3.68 64.1 3.91

2 Laser 30.4 2.70 — — 3 Radiation 37.7 3.10 — — 4 Explosion 91.7 4.56 92.3 4.49

5 Electrical 96.2 4.77 51.6 3.64

6 Corrosion 86.4 4.75 71.3 4.15

7 Poison 90.0 4.67 81.5 4.17

8 Fork Lift Truck 95.3 4.71 94.5 4.72

9 Slip 83.6 4.39 99.2 4.77

10 Fall 95.3 4.67 91.5 4.40

11 Overhead Hazard 70.7 4.21 97.7 4.67

12 General Warning 59.4 2.98 — — 13 Trip 97.0 4.78 80.8 4.16

14 Pinch 88.2 4.34 — — 15 Hot Surface 91.8 4.43 — — 16 Crush 74.2 4.05 90.6 4.28

17 Sudden Pressure

Release 89.2 4.22 31.0 2.71

18 Sever/ Cut 82.9 4.11 89.2 4.42

19 Keep Door Open 89.7 4.23 96.8 4.38

20 Do Not Touch 95.5 4.59 89.6 4.32

21 Keep Door Closed 83.1 3.98 71.1 3.89

22 Head Protection 96.9 4.68 97.7 4.65

23 Hearing Protection 96.2 4.75 96.1 4.69

24 Eye Protection 96.9 4.70 96.2 4.61

25 Foot Protection 88.8 4.15 97.7 4.70

26 Hand Protection 92.2 4.49 95.3 4.58

27 No Smoking 95.8 4.89 — — 28 No Open Flame 95.4 4.85 94.5 4.69

29 First Aid 84.2 4.52 95.9 4.59

30 Safety Shower 65.6 3.91 86.9 4.41

31 Eye Wash 91.3 4.32 68.5 3.90

32 Exit 72.1 3.78 91.5 4.35

33 Emergency Exit 89.3 4.18 55.7 3.30

34 No Exit 81.1 4.29 69.5 4.00

35 Do Not Enter 93.8 4.43 80.5 3.89

36 Fire Extinguisher 96.2 4.86 — — 37 Hose & Reel 92.3 4.62 . — — 38 Alaram Call Point 56.0 3.60 64.3 3.82

39 Entanglement 80.3 4.01 92.3 4.48

40 Respiratory

Protection 70.6 4.13 83.2 4.49

For correct alternative only

^ Number of participants for version 1 • 136

2 Number of participants for version 2 • 131

37
was 28.9, and those people who failed to report their age. Their mean number

of correct responses was 28.1, as compared with an overall mean of about 32

correct responses for the other age categories. See table 9 for comparisons.

4.2 DEMOGRAPHIC DATA

Demographic data on age, sex, and job title were obtained for miners at each

of the eight locations studied. These locations Included two coal mines (BC

and EM), one copper (BT), one industrial sand (WED), two oil shale (OS), one

oil shale mine construction site (CO), and one college mine-safety class (MT).

The summary age data for all locations are given in table 10. The summary data

include mean age, N, (number of participants reporting age) median age, modal

age, and age range. These data are presented for group 1, group 2, and combined

groups for all locations. A total of 256 participants reported their age.

Fifteen participants, about 5.5 percent of the whole sample, failed to report

their age or sex. This Included six people from group 1 and nine from group

2, primarily from the EM, WED, and BT locations.

The mean age of all participants studied was 34.76 years. For those

participants who received group 1 slides, it was 34.79; for those receiving

group 2 slides, it was 34.34. The age range was 20-61, while the median age was 32.2. Only 16 females participated out of a total group of 256. Their

mean age was 27.8 as opposed to the mean male age of 35.3. There were several

differences in mean age between locations, with BT participants being noticeably

older with a mean age of 42.4, and MT being younger with a mean age of 24.5. BC

and CO were also somewhat younger than the overall mean, with mean ages of 30.6

and 30.5 respectively. There were no age differences greater than 1.5 years

between groups 1 and 2 at any given location, except the oil shale locations.

Table 10 presents the overall age distribution of participants from each of the

locations as well as from the total sample. Figure 4 presents the age data

grouped into four age categories: 20-30, 30-40, 40-50, and 50-61, for all participants and then for the individual locations. This figure demonstrates

clearly that the majority of the participants (70.1 percent) were under 40, but

that the distribution varied widely from location to location for each age

group. These variations were most marked for the youngest group which contained

1.5 percent of the BT participants and 90 percent of the MT participants. The

BT participants, as noted earlier, had a greater concentration in the two older

categories (40-50, 50-61) than the other locations, while BC tended to have a lesser concentration (and MT had none) in these categories.

The number of female participants, 16 or 5.9 percent of the total sample, is

too small to make any statement about sex-related differences. The women were

also concentrated in two locations which might reasonably be expected to be

less familiar with mine safety messages (MT and CO — a safety class and a mine construction firm).

Table 11 presents a summary of 57 job title/occupation categories as reported

by the participants. A total of 265 participants reported their job title,

although two of these were too illegible to decipher or categorize. About 61

38
Table 9. Site Data Analyses

SCORE DATA

SITE MEAN SCORE STD. DEV. N

BCl 27.62 8.36 26

BC2 28.71 4.16 24

BTl 23.36 5.24 36

BT2 31.60 6.92 35

EMI 32.70 3.16 10

EM2 33.25 3.80 16

OSl 31.57 7.35 44

OS2 32.92 3.14 36

WEDl 31.50 5.19 20

WED2 33.05 4.12 20

Total 31.47 5.93 267

ANOVA - F - 2.639 slg. .01 level

CCONF DATA

Mean Confidence Rating - Correct Answer

Correct Subjects Only

SITE MEAN SCORE STD. DEV. N

BCl 3.09 1.31 26

BC2 3.10 1.17 24

BTl 4.08 .89 36

BT2 3.77 1.06 35

EMI 3.94 .64 10

EM2 4.07 .46 16

OSl 3.94 .91 44

OS2 4.13 .64 36

WEDl 4.22 1.06 20

WED2 4.11 .78 20

Total 3.85 1.005 267

ANOVA - F - 4.77 slg. .05 level

AGE DATA

AGE MEAN SCORE STD DEV. N

0 28.07 8.12 15

20-29 31.91 5.48 90

30-39 31.89 5.80 91

40-49 32.48 3.37 44

50-61 28.82 8.30 27

Total 31.47 5.93 267

ANOVA - F - 3.26 slg. .05 level

39
Table 10. Summary Age Data

Location 4

Age

Mean

Age

Range Mode Median Total N**

Group I EM 10 34.8 24-50 50 34.5 10

BT 35 42.5 30-60 48 41 36

BC 25 31.3 21-54 31 31 26

WED 20 30.8 20-58 22 26 24

OS 24 36.0 24-60 24

MT 20 24.6 21-32 23 24 20

STD. DEV. 10.22

MEAN 34.79 21-61 24 32.5 136

Total ^s 130

Group II

EM 12 36.2 28-47 32 35 16

BT 31 42.2 27-58 - 36 35

BC 24 29.8 20-54 24 28 24

WED 20 34.2 22-58 22 32.5 20

OS 6 40.0 26-55 - 40 6

CO 29 30.5 21-60 - 29 30

STD. DEV. 10.01

Mean 34.34 20-60 26 32.36 131

Total S^s 122

TOTAL

EM 22 35.6 24-50 32 34.5 26

BT 66 42.4 27-61 40; 48 41 71

BC 49 30.6 20-54 30 31 50

WED 40 33.6 20-58 22 32 44

OS 30 36.8 24-60 30

MT 20 24.6 21-32 23 24 20

CO 29 30.5 21-60 — 29 30

ALL 256 34.76 271

Male 240 35.3

Female 16 27.8

*

N

Number of subjects reporting age

Number of subjects participating

40
Table 11. Occupation Categories and Frequencies from

All Sites Combined

Category Number

Miner

Foreman

Safety/Training

Student

Mechanic

Electrician

Steelworker

Engineer

Mobile Equipment Operator

Machinist

Van/bus driver

Supervis or/manager

Beltman

Teamster

Roof-bolter

Maintenance

Boilermaker

Motorman

Warehouse/ Supplies

Laborer

Utility

Millpacker

Cost-survey & engineering

Construction

20

17

16

13

13

11

11

11 (mining, environ., structural, field, boiler-room)

9 (underground)

9

9

9

8

8

6

5

5

4

4

4

4

4

4

3

Deadwork 3

Miner helper 3

Screen utlllty,tester ,brusher 3

Sandbagger 3

Mill, crusher operator 3

Flotation operator 3

Welder 2

Surface truck operator 2

Welghmaster, weigher 2

Clean-up, car cleaner 2

Tireman 2

Carpenter 2

Geological technician 2

Rigging draftsman 1 Medic 1 Rodman 1 Power plant trainee ’ 1 Scale loader 1 Coal passer 1 Crane operator 1 Footman 1

41
Table 11. (Continued)

Category Number

Grinding floor operator 1 Dredge operator 1 Mason 1 Processing 1 Surveyor 1 Serviceman 1 Floating man 1 Logger 1 Woodworker 1 Secretary 1 Computer technician 1 Industrial hygienist 1 Dental hygienist 1 Industrial Technician 1 P.R. 1 Photographer 1

TOTAL 263

Two were too illegible to categorize

42
GEZ

[HI

(HE

E

EE

ix'‘'

I

latL. rw

i X.

EE

CE

EZ

rTTT

0<«

CEE

rrnr 9

E"- ffe

8 S 3 8 8

Q. u q: u u z H a u o.att»-MUH4Q.cczi-(A

43

Figure

4.

Distribution

of

age

by

site

for

four

age

groups
percent of the total sample could be categorized into thirteen categories,

including the general "miners" category, which comprised anywhere from 8-20

people. The other categories, while quite diverse, do not contain a large

number of participants. It is, of course, difficult to determine whether different terms for similar occupations were used at different sites. Furthermore,

some of the students were classified in occupations such as dental hygenlst,

carpenter, and woodworker, rather than student, although both classifications

are equally applicable. The occupations reported represent a reasonably wide

variety of mine site activities, with the possible exception of the mine safety

students. This latter category might well be more representative of the new

miner, however.

Although differences between jobs probably determine symbol comprehension, at

least to a limited extent, no one Job title in the present sample contains

enough participants to make statistically meaningful Inferences. Consequently,

general analysis of the data concentrated on age and site differences.

4.3 PERFORMANCE FOR INDIVIDUAL SYMBOLS

The performance of the individual symbols will be discussed in terms of several

measures - overall percentages of correct responses, mean confidence rating for

the correct choice by all subjects, and by subjects giving correct answers only

(CCONF), most frequently chosen and highest rated alternatives, chi square (x^)

analysis of the difference in choice frequencies for the correct choice, and

t-test analysis of the difference in mean confidence ratings for the correct

choice from all subjects.

Based upon the above analyses the difference in performance between the two

candidate images selected for the 32 referents was statistically significant (at

or beyond the .05 level) for 23 referents. These referents include the following 23 messages: Electrical, Corrosion, Poison, Slip, Trip, Fall, Overhead

Hazard, Crush, Sudden Pressure Release, Do Not Touch, Door Closed, Foot Protection, No Open Flame, First Aid, Safety Shower, Exit, Emergency Exit, No Exit,

Do Not Enter, Door Open, Entanglement, Eyewash, and Respirator. In nine cases,

no significant differences between candidate images emerged, while for eight

referents only one image was assessed. See table 12 for the chi square and

t-test data.

Tables 13 and 14 present the symbol referents ordered in terms of percentage

correct and confidence ratings. The two tables demonstrate that as the percentage correct response Increases so does the mean confidence rating. Thus symbols

receiving 90 percent correct responses had mean confidence ratings of 4.5 or more, while symbols with only 30-70 percent correct had much lower confidence

ratings - (generally below 3.5 to 4.0). As a result confidence ratings above

4.5 can be considered "high", while confidence ratings below 3.5 can be

considered "low".

The data in tables 13 and 14 can be examined to see those instances where a confidence rating was noticeably different from that for symbols with a similar

percentage of correct identification. In group 1, symbols for which the

confidence ratings were noticeably lower Included: Laser, Entanglement, Exit,

44
Table 12. Statistical Analysis Data for All Symbols Across Sites

Referent

Flammable

Explosion

Electricity

Corrosion

Poison

Forklift

Slip

Fall

Overhead

Trip

Crush

Sud. Pres. Rel.

Cut

Open Door

No Touch

Close Door

Head Protection

Ear Prot.

Eye Prot.

Foot Prot.

Hand Prot.

No Open Flame

First Aid

Safety Shower

Eyewash

Exit

Emergency Exit

No Exit

No Entrance

Alarm

Entanglement

Respirator

t-test Sig.

-1.43 .155

.73 .465

8.80 .000

5.45 .000

4.52 .000 - .13 .900

-3.81 .000

2.63 .009

-4.08 .000

6.02 .000

-1.64 .102

9.22 .000

-1.81 .071

-1.05 .296

2.20 .028

.55 .586

.31 .759

.77 .444

1.00 .320

-4.64 .000 - .83 .407

2.04 .043 - .62 .535

-3.57 .000

2.74 .007

-3.69 .000

4.78 .000

1.85 .066

3.82 .000

-1.34 .180

-3.44 .001

-2.92 .004

X-test sig.

.861 .3533

.001 .9709

64.108 .0000

7.749 .0054

3.142 .0763

.000 .9885

18.419 .0000

.975 .3236

32.627 .0000

15.666 .0001

10.785 .0010

88.550 .0000

1.611 .2043

3.862 .0494

2.416 .1201

4.593 .0321

.000 .9917

.081 .7753

.000 .9907

6.564 .0104

.600 .4387

.001 .9771

8.265 .0040

14.829 .0001

19.438 .0000

15.200 .0001

34.545 .0000

3.987 .0458

9.035 .0026

1.468 .2256

6.868 .0088

4.891 .0270

45
Table 13. Comparison of Percentage Correct and Confidence Ratings

for Group 1 Symbols

Mean

Referent Z Correct Confidence Rating

Laser (2)* 30.4 2.70

Radiation (3) 37.7 3.10

Alarm Call Pt. (38) 56.0 3.60

Flammable (1) 57.5 3.68

General Warning (12) 59.4 2.98

Shower (30) 65.9 3.91

Respirator (40) 70.6 4.13

Overhead (11) 70.7 4.21

Exit (32) 72.1 3.78

Crush (16) 74.2 4.05

Entanglement (39) 80.3 4.01

No Exit (34) 81.1 4.29

Cut/Sever (18) 82.9 4.11

Door Closed (21) 83.1 3.98

Slip (9) 83.6 4.52

First Aid (29) 84.2 4.52

Corrosion (6) 86.4 4.75

Pinch (14) 88.2 4.34

Foot (25) 88.8 4.15

Sud. Pres. Rel (17) 89.2 4.22

Emergency Exit (33) 89.3 4.18

Door Open (19) 89.7 4.23

Poison (7) 90.0 4.67

Eyewash (31) 91.3 4.32

Explosion (4) 91.7 4.56

Hot Surface (15) 91.8 4.43

Hand (26) 92.2 4.49

Hose (37) 92.3 4.62

No Entrance (35) 93.8 4.43

Fall (10) 95.3 4.67

Forklift (8) 95.3 4.71

No Open Flame (28) 95.4 4.85

Do Not Touch (20) 95.5 4.59

No Smoking (27) 95.8 4.89

Electrical (5) 96.2 4.77

Ear (23) 96.2 4.75

Extinguisher (36) 96.2 4.86

Head (22) 96.9 4.68

Eye (24) 96.9 4.70

Trip (13) 97.0 4.78

* Symbol number

46
Table 14. Comparison of Percentage Correct and Confidence Rating Data

for Group 2 Symbols

Mean

Referent X Correct Confidence Rating

Laser (2)* 30.4 2.70

Sud . Pres . Rel (17) 31.0 2.71

Radiation (3) 37.7 3.10

Electricity (5) 51.6 3.64

Emergency Exit (33) 44.7 3.30

General Warning (12) 49.4 2.98

Flammable (1) 64.1 3.91

Alarm Call Pt. (38) 64.3 3.82

Eyewash (31) 68.5 3.90

No Exit (34) 69.5 4.00

Door Closed (21) 71.1 3.89

Corrosion (6) 71.3 4.15

No Entrance (35) 80.5 3.89

Trip (13) 80.8 4.16

Poison (7) 81.5 4.17 ’

Respirator (40) 83.2 4.49

Shower (30) 86.9 4.41

Pinch (14) 88.2 4.34

Cut/ Sever (18) 89.2 4.42

Do Not Touch (20) 89.6 4.32

Crush (16) 90.6 4.28

Exit (32) 91.5 4.35

Fall (10) 91.5 4.40

Hot Surface (15) 91.8 4.43

Explosion (4) 92.3 4.55

Entanglement (39) 92.3 4.48

Hose (37) 92.3 4.62

Forklift (8) 94.5 4.72

No Open Flame (28) 94.5 4.69

Hand (26) 95.3 4.58

No Smoking (27) 95.8 4.89

First Aid (29) 95.9 4.59

Ear (23) 96.1 4.69

Extinguisher (36) 96.2 4.86

Eye (24) 96.2 4.61

Door Open (19) 96.8 4.38

Foot (25) 97.7 4.70

Head (22) 97.7 4.68

Overhead (11) 97.7 4.67

Slip (9) 99.2 4.77

* Symbol nimber

47
Eyawtfh and Do Not Touch. In group 2, almllar aymbola Included: Laaar, Sudden

Preseure Release, Fire Alarm Call Point, No Entrance, Cruah, Exit, and Keep

Door Open. Theae aymbola can be considered to be ones for which the participants were leaa sura of the correct meaning and for which some guessing may

have occurred.

Other symbols are noteworthy In that the confidence ratings were higher than

those for symbols with similar percentages of correct Identifications. For

group 1, these symbols Included: Flammable, Alarm Call Point, Overhead, Slip,

First Aid, Corrosion, Poison, Hose and Reel, No Open Flame, Extinguisher, and

No Smoking. For group 2 the symbols Included: Electricity, Corrosion, Respirator, No Smoking, and Extinguisher. It appears that those people who Identified these particular symbols correctly tended to be very certain of their

response. While these distinctions are arbitrary and dependent upon the symbols

tested, they do Indicate situations where either guessing may have occurred or where some participants were very certain of their answers.

A correlation coefficient of 0.92 was found between the percentage of correct

responses and mean confidence ratings for group 1 symbols, and of 0.96 for

group 2 symbols. Figure 5 plots the mean confidence rating as a function of

the percentage correct for each symbol. (Each symbol Is Identified by an arbitrary number given In table 8.) These data demonstrate further that symbols

which receive high percentages of correct responses also typically receive high

mean confidence ratings (confidence ratings could range from 1 to 5). Symbols

for which low confidence ratings are given for high percentages of correct

responses Indicate Instances where participants were somewhat unsure of the

correct response or when another alternative appeared plausible. In addition,

selection of an Incorrect choice alternative Is another Indication of confusion

about a symbol's meaning. Such choices will be termed confusions. When the

choice Is an opposlte-to-correct one. It will be termed a critical confusion.

These Instances will be discussed In detail for each symbol.

4.4 RESULTS AND DISCUSSION FOR INDIVIDUAL SYMBOLS

4.4.1 Individual Symbol Data

Each figure for a given referent reports the test data in terms of percentage

of correct answers, mean confidence rating for correct answers for all subjects,

and for subjects who selected the correct answers (CCCWF) , and frequency of

selection and mean confidence rating from all participants each choice alternative. The figures also present the choice alternatives given to all participants, as well as a black and white reproduction of each symbol. (Symbols were generally tested in the appropriate Z53 safety color. The color for each symbol as tested is given in the figures). Each figure also presents statistical

data when the performance of two symbols was compared, in terms of significance

levels (p < .05, .01, or .001, and NS = not significant. The text also indicates

if a symbol were suggested by ISO TC80, by terming the symbol as the "ISO

symbol .

48
Imipl

PERCENTAGE CORRECT

Gnup2

Figure 5. Percentage of correct responses as a function

of mean confidence rating

49
4. 4. 1.1 Hazard Warning Symbols

Data for the first referent to be reported, Flanunable, figure 6, Indicate that

neither symbol was well understood. Even the ISO candidate Image, //2, was correctly Identified by only 64 percent of those responding. It received a relatively low confidence rating, 3.9, as well. Performance for Image 1 was even poorer, with 57.5 percent correct Identification, and a mean confidence

rating of 3.68. In fact, alternative C, "fire permitted," emerges as a critical

confusion (or opposlte-to-correct response) for both symbols. This answer was chosen by 20.8 percent for Image 1, and by 20.3 percent for Image 2. Choice

"a" , "excessive heat area" was also selected by a high percentage of people for

both Images 1 and 2.

Data for both lUidlatlon and Laser, figure 7, Indicate that these two symbols

continue to be poorly understood with correct Identifications of 38 percent and

30 percent, respectively. Mean confidence ratings for the correct answer for

both symbols were among the lowest given for any symbol — around 3.0. The

Radiation symbol. In fact, received more answers (47.5 percent) for rotating

fan blades than for radiation, with a similar mean confidence rating (also of

3.0). In addition, 14 percent Identified the radiation symbol as "fallout

shelter" - a critical confusion. Laser similarly received more answers related

to solar power (47.6 percent) with higher confidence ratings (3.23) than for

"laser hazard". There was also a high percentage of answers (19.8) related to

radiation hazard as well as to flying particles (11 percent). Clearly, neither

of these two symbols successfully communicated the Intended message. This poor

performance may be somewhat attributable to the Infrequent or localized occurrence of these two hazards In mining operations as well as to the abstract

graphic representation of the 2 symbols. Nevertheless, the data suggest that

training and/or word messages should accompany any use of these symbols to

communicate hazard warnings, since their Initial comprehension Is so poor.

In contrast, both candidate symbols for Explosion, figure 8, had a high

percentage of correct answers (above 90 percent) and reasonably high confidence

ratings. Symbol 1 obtained only 6 percent responses related to fire, while

symbol 2 received 4 percent responses related to bomb shelter location.

A statistically significant difference emerged between candidates 1 and 2 for

Electrical Hazard, figure 9, for both the percentage correct and confidence

rating data. Image 1, showing a whole body being electrocuted, received 96.2

percent correct answers, in contrast to 51.6 percent for image 2, the ISO

lightning bolt. Image 1 received a mean confidence rating of 4.77 and Image 2, a mean rating of 3.36. This latter symbol also received 46.8 percent answers

for "lightning strike likely," (compared with 0.7 percent for Image 1) and a mean confidence rating of 3.32, (compared with 1.8 for Image 1).

For Corrosion, figure 10, the ISO Image (1) (showing both a hand and a bar

being corroded) received a higher percentage of correct responses, 86.4 percent, compared with 71.3 percent for the more stylized Image of 2. Image 1

also received a significantly higher confidence rating of 4.75 compared with

Image 2, with a mean confidence rating of 4.15. Confusions for both symbols were with the choice "emergency hand wash location," with 10 to 20 percent

50
Figure 6

Flaannable Hezerd

Percentage 57.5 64.1

Chi square Not significant (MS)

Mean Conf • Rat

3.68 3.91

t-test NS

CCONF Mean* 4.14 4.48

CCOMF Median 4.5 4.69

Color Black^ on White^ Black on Yellow

Answers

e. Excessive heat area

b. Danger of explosion likely in this area

c. Fire permitted in this area

d. Danger of fire starting in this area

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 22 2.9 2.85 a 19 2.76 2.75

b 4 2.1 1.69 b 1 2.01 1.78 c 25 2.64 2.43 c 26 2.52 2.15

d 69 3.68 3.92 d 82 3.92 4.27

n - 120 n - 128

missing « 16 missing 3

* Correct eubjecte, correct eaewers only

1 image color

2 background color

51
Figure 7

Radiation Hazard Later Hazard

1 2

Percentage 37.7 30.4

Chi square

Mean Conf . Rat

.

3.10 2.70

t-test NS

CCONF Mean 4.61 3.57

CCONF Median

Color Black on Yellow Black on Yellow

Ansv/ers

a. Danger from rotating fan blades a • Laser hazard present

b. Fallout shelter location b e Solar power source

c. Radiation hazard present c • Danger from flying particles

d. Noise hazard present d • Radiation hazard present

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 122 3.04 3.15 a 75 2.69 2.55

b 36 2.46 2.08 b 108 3.23 3.29

c 97 3.09 3.29 c 18 1.65 1.24

d 2 1.54 1.25 d 46 2.44 2.15

n - 257 n - 247

missing 10 missing 20

52
Figure 8

Explosion Hazard

1 2

Percentage 91.7 92.3

Chi square NS

Mean Con£« Rat. 4.56 4.49

t-test NS

CC(X<F Mean 4.62 4.55

CCONF Median 4.78 4.74

Color Red on White Black on Yellow

Answers

a. Danger of explosion likely

b. Bomb shelter location

c. Broken glass In area

d. Danger of fire starting In area

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 121 4.56 4.76 a 120 4.49 4.71

b 3 1.86 1.46 b 5 2.52 2.42

c 0 1.19 1.08 c 4 1.54 1.27

d 8 2.22 1.98 d 1 1.60 1.25

n - 132 n - 130

missing - 4 missing 1

53
Flgur* 9

BlactrlcAl lUsard

1 2

Percentage 96.2 51.6

Chi square significant beyond .001 level

Mean Conf. Rat. 4.77 3.64

t-teet sig. .0001

CCONF Mean 4.81 4.36

CCONF Median 4.91 4.62

Color Black on White Black on Yellow

Anawert

a* Electrical hazard preeent

b. Floors may be slippery

c. Ligbning strike likely

d. Danger of fire starting in this area

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 125 4.77 4.90 a 65 3.64 3.84

b 2 1.18 1.09 b 2 1.18 1.10

c 1 1.61 1.30 c 59 3.32 3.56

d 2

n - 130

iseing 6

1.35 1.13 d 0

n - 126

aiesing 5

1.73 1.36

54
Figure 10

Corrosion Hasard

1 2

Percentage 86.4 71.3

Chi square sig. .01

Mean Conf* Rat. 4.75 4.15

t-test sig. .0001

CCONF Mean 4.82 4.58

CCONF Median 4.89 4.72

Color Black on Yellow White on Red

Answers

a. finergency hand wash location

b. Corrosive hazard may cause chemical bums

c. First aid location here

d. Hazardous machinery used here

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 13 2.27 1.94 a 27 2.78 2.74

b 108 4.75 4.85 b 92 4.15 4.47 c 2 1.64 1.34 c 6 1.81 1.41

d 2 1.37 1.14 d 4 1.32 1.12

n - 125 n - 129

missing 11 sdssing 2

55
selecting this answer. This choice also received a mean confidence rating of

2.27 from group 1 participants and 2.78 from group 2.

Statistically significant differences for both percentage correct and mean

confidence rating emerged between images 1 and 2 for Poison, figure 11. The

familiar skull and crossbones was correctly identified by 90 percent of the

participants, while image 2 was Identified by only 81.5 percent. Similarly

image 1 received a mean confidence rating of 4.67 while 2 received one of 4.17.

About 19 percent of those responding indicated that image 2 meant "nuclear

hazard present". This answer also received a mean confidence rating of 2.52.

There were no significant differences between the two images studied for Fork

Lift Truck, figure 12, with both images receiving about 95 percent correct

responses and mean confidence ratings of 4.7. No real confusion emerged for

either image, although answer "d" , "warehouse storage location" received mean

confidence ratings of around 2.1. Both Images communicated the message

successfully, however.

Image 2 for Slip, figure 13, received 99.2 percent correct answers, compared

with 83.6 percent for image 1. Image 2 showed the whole body slipping and

falling, while image 1 showed only the feet. Image 2 also received a higher

mean confidence rating, 4.77 vs. 4.39. Both measures were significantly

different according to the chi square and t-test statistics. For image 1,

14.8 percent picked "keep area clean", while giving it a mean confidence rating

of 2.47. Although no one chose this answer for image 2, it did receive a somewhat higher confidence rating of 1.89. No other answers received very

high confidence ratings.

Image 1 for Fall From Elevation, figure 14, received a slightly higher

percentage of correct answers (95.3 vs 91.5) and also had a significantly

higher confidence rating of 4.67 compared with 4.40. No real confusions

emerged for either image, however.

Larger and significant differences in percentage correct were elicited for the

two images for Overhead Hazard - 97.7 percent for image 2, and 70.7 percent for

image 1, figure 15. Mean confidence ratings were also significantly different

for the two images - 4.67 versus 4.21. Image 1 received 8.9 percent answers

for "loading zone" and 17.9 percent for "check gear before hoisting". These

two choices were given mean confidence ratings of 2.56 and 2.14 respectively.

Only one image was studied for General Warning, figure 16. It, however,

received a low percentage of correct answers, 59.4 percent, and a corre- spondingly low mean confidence rating, 2.98. In addition, 16.6 percent of the

total participants, failed to respond to this symbol. The answer, "yield ahead"

was selected by 24 percent of the participants and received a mean confidence

rating of 2.27. "Danger from falling objects" was selected by about 12 percent

of the participants and received a mean confidence ratings of 1.78. Performance

was almost as poor for this symbol as for laser and radiation.

Statistically significant differences occurred for the two Images for Trip,

Figure 17. Image 1, showing a person tripping over an object, was correctly

56

I
Figure 11

Poison Hazard

1 2

Percentage 90.0 81.5

Chi square NS

Mean Conf. Rat. 4.67 4.17

t-test sig. .001 level

CCONF Mean 4.79 4.30

CCONF Median 4.90 4.60

Color Black on Yellow Black on White

Answers

a. Poison hazard present

b. Watch out for safety hazards

c. Yield to elderly pedestrians

d. Nuclear hazard present

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 117 4.67 4.86 a 101 4.17 4.48

b 8 1.89 1.39 b 0 1.57 1.29 c 2 1.22 1.06 c 0 1.11 1.03

d 3 1.79 1.36 d 24 2.52 2.30

n - 130 n 125

issing 6 issing “ 6

57
Figure 12

Fork Lift Truck Hazard

1 2

Percentage 95.3 94.5

Chi square MS

Mean Conf • Rat

.

4.71 4.72

t-test NS

CCONF Mean 4.77 4.76

CCONF Median 4.89 4.88

Color Black on Yellow Black on Yellow

Answers

a. Do not lift by forklift

b. Forklift truck operating In this area

c. Do not lift by hand

d. Warehouse storage location

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 5 2.03 1.44 a 0 1.52 1.27

b 123 4.71 4.87 b 121 4.72 4.86

c 1 1.71 1.38 c 4 1.94 1.50

d 0 2.07 1.88 d 3 2.13 1.94

n - 129 n - 128

missing 7 missing 3
Figure 13

Slip Hazard

1 2

Percentage 83.6 99.2

Chi square significant beyond .05 level

Mean Conf. Rat. 4.39 4.77

t-test slg. .0001

CCONF Mean 4.67 4.77

CCONF Median 4.81 4.88

Color Black on White Black on Yellow

Answers

a. Keep area clean

b. Wear boots In area

c. Danger of poisonous snakes In area

d. Slippery floors In area

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 19 2.47 2.28 a 0 1.89 1.62 j b 0 1.40 1.17 b 1 1.44 1.22 c 2 1.28 1.10 c 0 1.08 1.04

d 107 4.39 4.71 d 130 4.77 4.88

n 128 n - 131

missing 8 Isslng • 0
Figure 14

Fell From Elevation Hazard

I

I

I

I

I

Percentage 95.3 91.5

Chi square NS

Mean Conf . Rat

.

4.67 4.40

t-test slg .01

CCONF Mean 4.69 4.50

CCONF Median 4.83 4.74

Color Black on White Black on White

Answers

a. W^r safety shoes

b. Jump clear at this location

c. Men working In area

d. Danger of falling from height

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 2 1.34 1.07 a 2 1.30 1.10

b 4 1.50 1.23 b 6 1.78 1.43

c 0 1.41 1.22 c 3 1.66 1.30

d 123 4.67 4.82 d 119 4.40 4.71

n - 129 n - 130

•isslng 7 isslng 1

60

i
1

Figure 15

Overhead Hazard

Percentage 70.7 97.7

Chi square significant .001 level

Mean Conf. Rat. A. 21 4.67

t-test slg .0001

CCONF Mean 4.62 4.68

CCONF Median 4.78 4.86

Color Black on Yellow Black on Yellow

Answers

a. Loading zone

b. Equipment repair area

c. Check gear before hoisting

d. Danger from overhead objects

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 11 2.56 2.28 a 1 1.24 1.12

b 3 1.52 1.24 b 2 1.48 1.19

c 22 3.14 3.29 c 0 1.60 1.30

d 87 4.21 4.55 d 125 4.67 4.85

n 123 n 128

lasing 13 Isslng 3

61
Flgurt 16

General Warning

Percentage

Chi square

Mean Conf. Rat.

t-test

CCONF Mean

CCONF Median

Color

59.4

2.98

3.71

Black on Yellow

Answers

a. Danger from falling objects

b. Dangerous crossing ahead

c. Watch out for safety hazards

d. Yield ahead

Choice Conf Mean Median

a 28 1.78 1.27

b 9 1.65 1.28

c 136 2.98 2.99

d 56 2.21 1.60

n - 229

missing 38

62
Figure 17

Trip Hazard

1 2

Percentage 97.0 80.8

Chi square significant .0001

Mean Conf. Rat. 4.78 4.16

t-test slg .0001

CCONF Mean 4.81 4.32

CCOMF Median 4.90 4.60

Color siack on White Black on Yellow

Answers

a. Wear safety shoes

b. Slippery floors in area

c. Danger of tripping over object

d. Men working In area

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 1 2.56 1.30 a 11 2.22 2.00

b 2 1.52 1.41 b 12 2.26 2.00

c 128 3.14 4.89 c 101 4.16 4.45

d 1 4.21 1.09 d 1 1.24 1.09

n - 132 n - 125

missing “ 4 missing - 6

63
Identified by 97 percent of the participants, but Image 2 was Identified

correctly by only 80.8 percent. The mean confidence ratings, of 4.78 and 4.16,

also were significantly different. Confusions for Image 2 were related to

"wear safety shoes" and "slippery floors" (about 9 percent), with mean confidence ratings of around 2.2.

The only Image studied for Pinch, figure 18, was Identified correctly by 88.2

percent of the participants. It also received a mean confidence rating of

4.34. Some confusion arose with the choice, "wear protective gloves", which

was selected by 9 percent of the participants. Hot surface, figure 18, also

received a high percentage of correct answers (91.8 percent) and a confidence

rating of 4.43. Answer c, "danger from sharp objects on surface" was selected

by about 8 percent of those responding. No other answer emerged as plausible,

judging by the low confidence ratings.

The two Images for Crush, figure 19, received significantly different

percentages of correct answers, with Image 1 receiving 74.2 percent correct

answers and Image 2, 90.6 percent. A small difference occurred In the mean

confidence ratings, 4.05 versus 4.28. Twenty-four percent selected "pinch

point" for Image 1 and gave It a confidence rating of 3.27. Only two percent

selected this answer for Image 2. "Danger from flying particles" appeared to

be a reasonable choice for Image 2 to eight percent of the participants.

Image 1 for Sudden Pressure Release, figure 20, performed slgnflcantly better,

than Image 2. It was Identified correctly by 89.2 percent, but received a relatively low confidence rating of 4.22. Serious confusions arose for Image 2,

which received a higher percentage of choices (64.3) for "danger from bright

lights," than for the correct answer (31.0), and a much higher mean confidence

rating (3.57 vs 2.71). Differences In response between the two Images were statistically significant, but the fairly low confidence rating for Image 1 suggests that even this graphic rendition was not particularly well understood.

In contrast, image 2 for Cut or Sever, figure 21, was identified correctly by

89.2 percent of the participants and received a mean confidence rating of 4.42.

A small percentage of people (10 percent) identified this image as "pinch

point". Image 1 was identified correctly by 82.9 percent of the participants

and received a mean confidence rating of 4.11. About 14.6 percent identified

this image as meaning Pinch Point . This answer also received a mean confidence

rating of 2.69. It is interesting to note that the single change from a hand

to a foot being severed decreased the percentage of correct answers, lowered

the mean confidence rating, and increased the number of confusions.

Similarly, for Entanglement, figure 22, inclusion of a hand in the gears, image

2, Increased performance on all three measures. This Image was Identified

correctly by 92.3 percent, received a mean confidence rating of 4.48, and had a low percentage (6.2) of wrong answers (and this for the answer, "protective

gear required"). Image 1, which performed significantly more poorly, depicted

the gears alone. Only 80.3 percent identified this image correctly and gave it

a low mean confidence rating of 4.01. About ten percent selected "wear protective gear" for image 1 while another 5.4 percent selected "oil gears while

64
Figure 18

Pinch Hazard Hot Surface Hazard

t

j Percentage 88.2 80.8

1 Chi square

Mean Conf. Rat. 4.34 4.43

t-test

CCONF Mean 4.50 4.54

CCONF Median

Color Black on White Black on White

Ansvrers

a. Pinch point hazard a. Do not wear gloves

b. Equipment repair area b. Hot surface may burn you

c. Keep machinery In operation c. Danger from sharp objects on

d. Wear protective gloves surface

d. Place hand here

1 Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 225 4.34 4.73 a 1 1.23 1.09

b 2 1.39 1.17 b 235 4.43 4.72

c 7 1.28 1.09 c 20 2.05 1.52

d 21 2.03 1.57 d 0 1.26 1.10

1 n - 225 n - 256

missing • 12 missing * 11

65
Figure 19

Crush Haserd

Percentage 74.2 90.6

Chi square slg .001 level

Mean Conf . Rat

.

4.05 4.28

t-test NS

CCONF Mean 4.42 4.34

CCONF Median 4.71 4.67

Color Black on White Black on White

Answers

a. Equipment repair area

b. Danger; material can crush you

c. Pinch point danger

d. Danger, flying particles

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 1 1.25 1.09 a 1 1.34 1.13

b 95 4.05 4.50 b 115 4.28 4.62

c 31 3.27 3.32 c 2 1.91 1.61

d 1 1.44 1.19 d 10 1.82 1.35

n - 128 n - 128

Isslng 8 isslng 3

66
Figure 20

Sudden Pressure Release Hazard

1 2

Percentage 89.2 31.0

Chi square significant beyond .0001

Mean Conf. Rat. 4.22 2.71

t-test 0.001

CCONF Mean 4.36 4.05

CCOMF Median 4.58 4.08

Color Black on White Black on White

Answers

a. Danger of sudden pressure release

b. Fire may start here

c. Hazardous nuclear material

d. Danger from bright lights

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 116 4.22 4.52 a 39 2.71 2.81

b 5 1.93 1.57 b 2 1.60 1.35 c 4 1.77 1.35 c 4 1.94 1.59

d 5 1.51 1.20 d 81 3.57 3.98

n - 130 n - 126

missing 6 missing " 5

67
flgur* 21

8«v«r HAiard

1 2

Parctntagt 82.9 89.2

Chi square NS

Maan Goaf* Rat. 4.11 4.42

t-tast NS

CCONF Mean 4.43 4.56

CCONF Median 4.73 4.79

Color Black on White Black on White

Answers

a. Danger of cuts from sharp objects { b. Repair machinery while In operation

c. Danger from corrosive liquids

d. Pinch point danger I !

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median |

a 102 4.11 4.61 a 116 4.42 4.73

b 2 1.26 1.09 b 1 1.21 1.06

c 1 1.13 1.06 c 0 1.17 1.08

d 18 2.69 2.59 d 13 2.50 2.42

n - 123

1 n 130

missing 13 missing 1 1

68
Figure 22

Entanglement Hazard

1 2

Percentage 80.3 92.3

Chi square significant .001

Mean Conf. Rat. 4.01 4.48

t-test slg. .001

CCONF Mean 4.18 4.59

CCONF Median 4.57 4.79

Color White on Red Black on White

Answers

a. Protective gear required

b. Oil gears while machinery Is running

c. Machinery repair area

d. Keep clear of moving machinery

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 12 1.78 1.31 a 8 2.10 1.77

b 7 1.59 1.28 b 2 1.25 1.09 c 6 2.05 1.77 c 0 1.69 1.33

d 102 4.01 4.40 d 120 4.48 4.76

n - 127 n - 130

Isslng 9 missing « 1
machinery is running" , Addition of the hand to the gear graphic appears to

have a noticeable, positive effect upon the effectiveness of this message.

4. 4. 1.2 Prohibition Symbols

For the first of the prohibition referents, Do Not Touch, figure 23, both

candidate images were identified correctly by about 90 percent or more of

those participating. Image 1 showing the whole hand received a significantly

higher mean confidence rating (4.59 versus 4.32) and a higher percentage of

correct answers. Confusions for both images arose primarily for the answer,

"do not lift objects manually," with a higher percentage (6.4) occurring for

image 2. Although both Images communicate their message well, use of the

whole hand, rather than just a finger, appears to be more effective.

The circle, slash, and cigarette Imagery for No Smoking, figure 24, was correctly identified by 95.8 percent of the participants. This image also

received one of the highest mean confidence ratings - 4.89. Confusions, 2

percent, did arise for "smoking permitted"; however, this answer received a very low confidence rating (1.18). This low rating suggests that the confusions may have been due to misreading the choices.

Similarly, the use of a circle, slash, and flame or match, resulted in high

percentages of correct answers for No Open Flame, figure 25. No statistically

significant differences emerged between the two images. Image 1 received

95.4 percent correct responses, and a mean confidence rating of 4.85, while

image 2 received a slightly lower percentage of correct answers, 94.5 percent,

and lower mean confidence rating, 4.69. Only a few confusions arose for "no

danger of fire" for image 2 (3 percent), and for "fires permitted in this area"

for image 1 (2 percent). Both images thus appeared quite successful in terms

of the three performance measures used.

4. 4. 1.3 Protective Gear Symbols

In general, all images for personal protective gear performed well, perhaps

because miners are all required to wear such gear and because the Images

studied are highly representational.

For Head Protection Required, figure 26, both images received high percentages

of correct answers—96.9 percent for image 1, and 97.7 percent for image 2.

Mean confidence ratings were also high—4.68 for image 1 and 4.65 for image

2. Wrong answers were elicited from only 1-2 percent of those responding. The

answer, "Construction workers in the area," received mean ratings of 2.11 and

2.21 for images 1 and 2. Some miners commented that neither image showed the

attachment for a cap lamp common to mining hard hats. Nevertheless, both

images performed quite well on the three measures.

Similarly, both images for Hearing Protection, figure 27, performed well.

Image 1 was identified correctly by 96.2 percent and received a mean confidence

rating of 4.75, while image 2 was selected by 96.1 percent and received a con- fidence rating of 4.69. Minimal confusions (3.0 and 1.6 percent) were elicited

70
Figure 23

Do Not Touch

1 2

Percentage 80.3 89.6

Chi square NS

Mean Conf. Rat. 4.59 4.32

t-test Big. .05

CCONF Mean 4.62 4.47

CCONF Median 4.82 4.77

Color Black » White, Red Black, White, Red

Answers

a. Do not touch

b. Do not lift objects manually

c. Wear protective shoes

d. First aid location

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 126 4.59 4.81 a 112 4.32 4.73

b 4 1.58 1.20 b 8 1.47 1.19 c 2 1.20 1.07 c 3 1.20 1.08

d 0 1.20 1.07 d 2 1.54 1.22

n - 132 n - 125

lasing " 4 Isslng 6

71
Figure 24

No Smoking

1

Percentage 95.8

Chi square

Mean Conf. Rat. 4.89

t-test

CCONF Mean 4.94

CCONF Median

Color Black, White , Red

Answers

a. Smoking permitted

b. Do not discard cigarettes

c. Smoke only cigars

d. No smoking allowed

here

Choice Freq Conf Mean Median

a 6 1.18 1.05

b 3 1.98 1.54

c 2 1.20 1.07

d 249 4.89 4.97

n - 260

missing 7

•

72
Figure 25

No Open Flame

1 2

Percentage 95.4 94.5

Chi square NS

Mean Conf • Rat

4.85 4.69

t-test NS

CCONF Mean 4.88 4.73

CCONF Median 4.96 4.87

Color Black, White, Red

Answers

a. No danger of fire

b. Use lighters here

c. No open flame permitted

d. Fires permitted In this area

Choice Freq. Conf Mean Median

; Choice Freq. Conf Mean Median

a 2 1.35 1.09 a 4 1.47 1.21

b 1 1.21 1.10 b 1 1.28 1.09 c 124 4.85 4.95 c 121 4.69 4.85

d 3 1.23 1.06 d 2 1.24 1.07

n - 130 n - 128

missing 6 missing 3
I

Figure 26

Head Protection Required

1 2

Percentage 96.9

ki 97.7 1 Chi square NS 1 Mean Conf. Rat. 4.68 4.65 ( t-teat NS 1 CCONF Mean 4.68 4.67

CCONF Median 4.88 4.84

Color White on Blue White on Blue I

Axiswera i

a. Do not wear hard hat

b. Hard hat required

c. Locker room location ; d. Construction workers in area

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median 1

a 2 1.32 1.09

1 a 1 1.20 1.07

b 125 4.68 4.88 b 127 4.65 4.83

c 0 1.30 1.13 c 1 1.21 1.10

d 2 2.11 1.96 d 1 2.21 2.00

n - 129 n - 130

missing 7 missing • 1

74

I
Figure 27

Hearing Protection Required

Percentage 96.2 96.1

Chi square NS

Mean Conf. Rat. 4.75 4.69

1 t-test MS

CCONF Mean 4.77 4.73

CCONF Median 4.89 4.88

Color White on Blue White on Blue

Answers

a. Wear ear protection

b. Communication by headset only

c. Alarm location

d. Quiet, broadcast on air

1

1

1 Choice Freq.; Conf Mean Median Choice Freq. Conf Mean Median

a 127 4.75 4.89 a 124 4.69 4.87

b 4 2.25 2.14 b 2 2.29 2.12 c 1 1.34 1.13 c 1 1.26 1.11

d 0 1.58 1.30 d 2 1.64 1.29

n - 132 n - 129

missing “ 4 missing 2

75
by answer 2 "communications by headset only" which also received mean confidence

ratings of about 2.2.

For Eye Protection, figure 28, both images were generally identified correctly

with 96.9 percent correct responses for image 1 and 96.2 percent for image 2.

Mean confidence ratings were also high—4.70 for image 1 and 4.61 for image 2.

The frequency of wrong answers was small, with only four incorrect answers for

image 1 and five for image 2. Image 2 did receive higher confidence ratings

for all incorrect answers than did image 1.

For Safety Shoes Required, figure 29, image 2 performed significantly better

with 97.7 percent correct responses and a mean confidence rating of 4.70, com- pared with 88.8 percent correct and 4.15 for image 1. Image 2 also received

only three incorrect answers. Image 1 received about 5 percent responses for

the answers, "rubber boots required", and "leave shoes here." The incorrect

alternatives for image 1 all received higher mean confidence ratings, as well.

Again several miners commented that image 2 was a more realistic depiction of

safety footgear. Certainly, it received a significantly higher percentage of

correct answers.

For Hand Protection Required, figure 30, both images received a high percentage

of correct answers (92.2 percent for image 1 and 95.3 percent for image 2) and

high confidence ratings (4.49 for image 1 and 4.58 for 2). In addition, image

1, showing one glove alone, received 7 percent responses for answer d, "stop

here" and a mean confidence rating of 2.04—the highest for any of the choice

alternatives. Similar confusions were reported for the image of one glove

alone in Collins et al. (1982).

Images for Respirator, figure 31, did not perform as well as those for the other

protective gear messages. Image 2 received 83.2 percent correct responses, and

a mean confidence rating of 4.49, while image 1 received 70.6 percent correct

responses, and a confidence rating of 4.13. A significant difference between

the images occurred for both the t-test measures. Confusions arose for

both images for the answer "face mask required," which was chosen by 27.8 percent and 15.2 percent of the participants, and received mean confidence ratings

of 3.59 and 3.74. Although an apparently plausible alternative, this answer

does not indicate the need for respiratory or breathing protection.

4. 4. 1.4 Safety Equipment and Fire Emergency Symbols

Images for both safety equipment location and fire emergency messages were studied. With the exception of Safety Shower and Fire Alarm Call Point, all

images were generally identified correctly.

A significant difference in the percentage of correct responses emerged between

images 1 and 2 for First Aid, figure 32. Image 2 received 95.9 percent correct

responses, while image 1 received only 84.2 percent. The mean confidence ratings, 4.59 and 4.52 respectively, were about the same for both, however. Confusions arose for image 1 with the answer "safety training location" (10.5

percent response and mean confidence rating of 2.41.) Although the frequency

of selecting this answer was much lower for image 2 (1.6 percent), the mean

76
I

Figure 28

Eye Protection Required

Percentage 96.9 96.2

Chi square NS

Mean Conf. Rat. 4.70 4.61

t-test NS

CCONF Mean 4.72 4.63

CCONF Median 4.87 4.84

Color V/hlte on Blue Blue on White

Answers

a. Do not wear glasses

b. Read Instructions before using

c. Wear safety glasses

d. Wear sunglasses

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 0 1.18 1.06 a 2 1.56 1.21

b 2 1.39 1.16 b 1 1.96 1.64 c 127 4.70 4.86 c 125 4.61 4.83

d 2 1.83 1.41 d 2 2.31 2.24

n 131 n 130

missing « 5 missing 1

77
Figure 29

Foot Protection Required

1 2

Percentage 88.8 97.7

Chi square significant beyond .01

Mean Conf . Rat

.

4.15 4.70

t-test sig .0001

CCONF Mean 4.30 4.70

CCONF Median 4.67 4.84

Color White on Blue White on Blue

Answers

a. Safety shoes required

b. Shoe store location

c. Rubber boots required

d. Leave shoes here

Choice Freq. • Conf Mean Median Choice Freq. Conf Mean Median

a 111 4.15 4.59 a 125 4.70 4.84

b 2 1.89 1.41 b 1 1.85 1.48

c 6 2.31 2.17 c 0 2.10 1.85

d 6 1.82 1.38 d 2 1.63 1.33

n - 125 n * 130

missing » 11 missing * 1

78
Figure 30

Hand Protectioa Required

i

I 1 2

f

1

i Perceatage 92.2 95.3

Chi square NS

Mean Goaf. Rat. 4.49 4.58

j t-test NS

CCONP Mean 4.62 4.59

CCONF Median 4.82 4.79

Color White on Blue

Answers

a. Turn this way

b. Safety gloves required

c. Wash hands here

d. Stop here

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 0 1.26 1.08 a 2 1.13 1.05

b 119 4.49 4.79 b 123 4.58 4.78

c 1 1.53 1.31 c 4 1.55 1.32

d 9 2.04 1.62 d 0 1.24 1.09

n - 129 n - 129

missing - 7 missing - 2

79
Figure 31

Respiratory Protection Required

1 2

Percentage 70.6 83.2

Chi square significant .05

Mean Conf. Rat. 4.13 4.49

t-test slg .01

CCONF Mean 4.50 4.59

CCONF Median 4.72 4.79

Color White on Blue White on Blue

Answers

a. Underwater activity required

b. Safety glasses required

c. Face mask required

d. Respirator required

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 1 1.26 1.08 a 2 1.38 1.13

b 1 4.49 4.79 b 0 1.37 1.13

c 35 1.53 1.31 c 19 3.59 3.83

d 89 2.04 1.62 d 104 4.49 4.72

n - 126 n 125

missing “ 10 missing “ 6
Figure 32

First Aid Location

Percentage 84.2 95.9

Chi square significant .005 level

Mean Conf. Rat. 4.52 4.59

t-test

CCONF Mean 4.78 4.59

CCONF Median 4.89 4.81

Color Green on White White on Green

Answers

a. First aid located here

b. Give blood here

c. Safety training location

d. Crossroad ahead

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 112 1.26 1.08 a 117 4.59 4.81

b 2 4.49 4.79 b 1 1.41 1.21 c 14 1.53 1.31 c 2 1.93 1.50

d 5 2.04 1.62 d 2 1.16 1.04

n - 133 n - 122

lasing 3 issing > 9

81
confidence rating was somewhat similar (1.93). Because the white cross and

green background is frequently used at mines to indicate the safety office and

its activities, a few miners commented that the color of the first aid sign

should perhaps be red. On the other hand, this color might lead to confusions

with the "Red Cross" society (as opposed to the green cross of the National

Safety Council).

Image 2 for Safety Shower, figure 33, was more successful than image 1 in terms

of the measures used. Image 2 was identified correctly by 86.9 percent, while

image 1 was only identified by 65.6 percent of those participating. This

difference was significant. While the confidence rating for image 2 was higher

(A. 32 versus A. 00), this still was relatively low. Image 1 received a fairly

high percentage (18.8) of choices for answer d, "sprinkler system control"

while image 2 received only 9.3 percent for this choice. Mean confidence

ratings for "d" were 3.11 and 1.33 respectively. In addition, seven percent

of the participants selected "watch out for falling objects" for image 1 and

"locker room location" for image 2. The somewhat poor performance of these

symbols may be attributable to the relative infrequency of safety showers

within mines themselves, as opposed to mills or chemical processing areas.

Similar comments may be made for Eyewash, figure 3A , although the two images

for this referent performed somewhat better. Image 1 was correctly Identified

by 91.3 percent while image 2, a more abstract version, was identified correctly

by only 68.5 percent. This difference was significant. The rather low mean confidence ratings, A. 32 and 3.90 respectively, may indicate the miners' relative unfamiliarity with this concept. Image 2 received a number of answers

(23.8 percent) for "eye irritant," which also had a mean confidence rating of

2.5A. Only 2. A percent selected this answer for image 1. About 5-6 percent of

the miners indicated that both images meant "wear eye protection". Again, eyewashes are more common in processing areas rather than mining/production areas.

Both Fire Extinguisher, and Fire Hose and Reel, figure 35, received high

percentages of correct answers (96.2 percent and 92.3 percent) as well as reasonably high confidence ratings (A. 86 and A. 62). Fire extinguisher received

2.6 percent choices for "gasoline pump location," although this answer also

received a low confidence rating (1.35) suggesting that the majority of miners

did not consider this to be a reasonable alternative. For "fire hose and reel"

confusions were related to "hot radiator located here" (A. 2 percent) and "high

pressure area" (2.3 percent). Both images, however, performed well in terms of

the three performance measures.

Fire Alarm Call Point, figure 36, however, appears to be both an unclear and

unnecessary referent for mining applications. Neither image was well understood, with image 1 being correctly identified by 56 percent of the miners and

image 2 by 6A.3 percent. Both images received low confidence ratings also,

3.60 and 3.82. These two images work almost as well for "noise hazard" (answer

c) with image 1 receiving 29.6 percent responses for this choice, and image 2

receiving 33.3 percent. Mean confidence ratings for noise hazard were 2.86 and

3.05 respectively. The images appear to communicate the idea of noise but not

the message of "call point". In conversations with miners and safety personnel.

82
il

Figure 33

Safety Shower Location

1 2

Percentage 65.6 86.9

Chi square significant .0001

Mean Conf. Rat. 2.91 4.41

t-test slg .0001

CCONF Mean 4.31 4.52

CCONF Median 4.67 4.79

Color White on Green White on Green

Answers

a. Watch out for falling objects

b. Safety shower located here

c. Locker room location

d. Sprinkler system control

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 9 1.61 1.24 a 1 1.07 1.03

b 80 3.91 4.21 b 113 4.41 4.74

c 4 2.02 1.78 c 9 2.21 1.98

d 28 3.15 3.11 d 7 1.65 1.33

n - 121 n - 130

Isslng 15 missing » 1

83

i
Figure 34

Eyewash Location

Percentage 91.3 68.5

Chi square significant .Opi

Mean Conf . Rat

.

4.32 3.90

t-test slg .01

CCONF Mean 4.40 4.38

CCONF Median 4.70 4.71

Color White on Green White on Green

Answers

a. Eye irritant located here

b. Eyewash location

c. Intense light source in area

d. Wear eye protection

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 3 1.79 1.34 a 31 2.54 2.21

b 116 4.32 4.69 b 89 3.90 4.35

c 2 1.22 1.08 c 1 1.37 1.20

d 6 1.66 1.30 d 9 1.82 1.35

n - 127 n - 130

isslng 9 missing * 1

84
Figure 35

Fire Extinguisher

Location

Fire Hose and tael

Location

Percentage

Chi square

Mean Conf. Rat.

t-test

CCONF Mean

CCONF Median

Color

96.2

4.86

4.90

White on Red

92.3

4.62

4.78

White on Red

Answers

a. Fire hazard area

b. Gasoline pump located here

c. Do not extinguish fire here

d. Fire extinguisher located here

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Medial

a 3 2.12 1.74 a 11 1.40 1.11

b 7 1.35 1.13 b 6 1.61 1.29

c 0 1.18 1.08 c 3 1.89 1.61

d 251 4.86 4.95 d 241 4.62 4.88

a. Hot radiator located here

b. High pressure area

c. Use hose to clean area

d. Fire hose and reel

n - 261

•lasing * 6

n - 261

lasing 6

85
Figure 36

Fire Alarm Call Point

1 2

Percentage 56.0 64.3

Chi square NS

Mean Conf. Rat. 4.60 3.82

t-test NS

CCONF Mean 4.04 4.30

CCONF Median 4.32 4.65

Color White on Red White on

Answers

a. School zone ahead

b. Emergency shelter

c. Noise hazard

d. Fire alarm call point

Choice Freq. Conf Mean Median Choice Fre^^ Conf Mean Median

a 12 1.79 1.27 a 1 1.12 1.03

b 6 1.52 1.23 b 2 1.37 1.18

c 37 2.86 2.74 c 42 3.05 3.09

d 70 3.60 3.68 d 81 3.82 4.12

n 125 n 126

lasing 11 lasing “ 5

86
this referent did not appear to be as necessary as one for "alarm location" - a message for which the two images tested are not really appropriate.

4 . 4 . 1 . 5 Egress Related Symbols

All mines are required by MSHA to have "exit ways" clearly marked. At this

point, only word signs are required, so that there would be no need to "unlearn"

a set of symbol signs. The possibility thus exists for researching the feasibility of different symbol signs for egressways and selecting the one that performs best. As a result, four images were studied for the referents Exit and

Emergency Exit, with the implicit assumption that both messages could indicate

an exit way from the mine to the outside.

For the referent Exit, figure 37, there was a large and significant difference

between the two Images studied. Image 1 was correctly identified by 72.1 percent and received a mean confidence rating of only 3.78. Image 2, however was identified by 91.5 percent of those participating and received a confidence

rating of 4.35. Image 1 also received 27.1 percent responses for "no passageway, dead end" - an opposite meaning. This answer also got a mean confidence

rating of 2.49. This critical confusion suggests that image 1 should not

receive further consideration as an "exit" marker. Image 2 received only 4.6

percent responses for this wrong answer with a mean confidence rating of 1.38.

The two images studied for Emergency Exit, figure 38, also elicited similar

differences, with image 1 performing significantly better than image 2. Image

1, a privately copyrighted symbol (Yanone, 1979), was identified correctly by

89.3 percent of those participating, and given a relatively low confidence

rating of 4.13. Image 2, however, received an even lower confidence rating

(3.34) and a low percentage of correct responses (55.7 percent). Both images

received a number of responses for "do not run" (9.2 percent for image 1, and

19.7 percent for image 2, with confidence ratings of 1.72 and 2.20 respectively). A sizable number of people (20.5 percent) also selected answer d, "no

way out" as their choice for image 2. This critical confusion received a mean

confidence rating of 2.13. Image 2 clearly does not convey the message of

"emergency exit" successfully to those people who participated in this study.

Furthermore, of the four exit images studied, image 2 of Figure 37 appears to

be the most successful. It received the highest percentage of correct answers,

highest confidence rating, and lowest number of confusions.

In addition, a version very similar to this has been proposed to ISO for

consideration as an "exit - emergency exit" symbol by the Japanese (1980).

The two images studied for No Exit, figure 39, were not particularly successful

in terms of percentage correct and mean confidence rating, with image 1 receiving 81.1 percent correct resposes and a mean confidence rating of 4.29, and

image 2 receiving 69.5 percent and a rating of 4.00. Neither symbol thus was particularly effective in communicating the message of No Way Out or No Exit.

Confusions for image 1 arose primarily for answer b, "keep door closed" (13.4

percent, mean rating 2.48) while those for image 2 were related primarily to

answer d, "no running", (21.9 percent, and 2.43). The relatively poor

performance of symbols for this message, also seen in other NBS studies, may

87
Figure 37

Exit

1 2

Percentage 72.1 91.5

Chi square significant .0001

Mean Conf . Rat

.

3.75 4.35

t-test slg .001

CCONF Mean A. 18 4.44

CCONF Median 4.65 4.74

Color White on Green Green on White

Answers

a. Exit

b. Mo passageway, dead end

c. Men's room location

d. No walking allowed

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 93 3.78 4. 24 a 119 4.36 4.71

b 35 2.49 2.08 b 6 1.38 1.15

c 1 1.33 1.16 c 3 1.43 1.22

d 0 1.26 1.12 d 2 1.37 1.14

n - 129 n - 130

isslng * 7 isslng « 1

88
Figure 38

Emergency Exit

Percentage 89.3 55.7

Chi square significant .0001

Mean Conf. Rat. A. 18 3.30

t-test .001

CCONF Mean A. 40 A. 16

CCONF Median A.67 A.6A

Color Red. Black, White Black and White

Answers

a. Emergency Exit

b. Restroom located here

c. Do not run

- d. No way out '

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 116 A. 18 A.58 a 68 3.30 3.82

b 1 1.19 1.07 b 5 1.A6 1.16

c 12 1.72 1.2A c 2A 2.19 1.80

d 2 1.3A 1.11 d 25 2.13 1.A8

n - 131 n - 122

missing “ 5 missing 9

89
Figure 39

Mo Exit

1 2

Percentage 81.1 69.5

Chi square slg .05

Mean Conf. Rat. 4.29 4.00

t-test

CCONF Mean 4.46 4.48

CCONF Median 4.71 4.75

Color White on Red White, Black, Red

Answers

a. Exit this way

b. Keep door closed

c. Not a way out

d. No running

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 7 1.43 1.12 a 5 1.48 1.14

b 17 2.48 2.19 b 6 1.58 1.29

c 103 4.29 4.65 c 89 4.00 4.57

d 0 1.28 1.09 d 28 2.43 2.04

n - 127 n - 128

isslng - 9 Isslng “ 3

90
well indicate a situation in which the positive message Exit is more appropriate

and communicative than the negative. Of course, Exit signs are also a far more

common occurrence in buildings and facilities than No Exit signs. Whatever

the reason, NBS has been unsuccessful in locating a graphic image for No Exit

that is understood by more than 70-80 percent of those responding.

On the other hand, the two images for Do Not Enter, figure AO, were more

successful. Image 1 was identified correctly by 93.8 percent of the miners and

received a mean confidence rating of 4.43. Image 2, which was significantly

different from image 1, received only 80.5 percent correct responses and a mean

confidence rating of 3.89. This image also received 16.3 percent responses for

"wear protective gloves". In contrast to "no exit", "no entrance, keep out,

restricted area" is a common message in industrial and mining situations. The

better performance of this message may reflect a greater familiarity with the

idea of "do not enter."

The two remaining referents. Keep Door Open, figure 41, and Keep Door Closed,

figure 42, were intended to symbolize a common mining situation of opening and

closing off segments of the mine after passing through them. These messages

are also required by the CFR (Title 30, 1980). The symbol for Keep Door Open

received higher percentages of correct answers than "keep door closed". For

both referents, however, the blue and white version performed significantly

better than the red and white version, according to the statistics. Image

1 for "door open" which consisted of a red door on a white background received

89.7 percent correct responses and a confidence rating of 4.23. Image 2, con- sisting of a blue door on a white background, was identified correctly by 96.8

percent and received a mean confidence rating of 4.38. Both images received

about 2-4 percent responses for "not an exit", although the mean confidence

ratings were low for this choice. Both versions, differing only in color,

appeared to communicate the intended message, although the confidence ratings

were relatively low compared with the high percentages of correct responses.

Similar differences in performance were found for the two images for Keep Door

Closed, which again differed in color, although the overall percentage of

correct responses was lower than for Keep Door Open, Image 1 , a white door on

a blue background, was identified correctly by 83.1 percent of the participants,

and received a (low) confidence rating of 3.98. Image 2, however, showing a white door on a red surround, received only 71.1 percent correct responses, and

a mean confidence rating of 3.89. This image had a large number (15.6 percent)

of choices for the answer Emergency Exit and for the answer Keep Door Open

(12.8 percent). These two choices also received mean confidence ratings of

2.44 and 1.86. The percentage of selection for these two choices and mean

for the answer Emergency Exit and for the answer Keep Door Open (12.8 percent).

These two choices also received mean confidence ratings of 2.44 and 1.86. The

percentage of selection for these two choices and mean confidence ratings was lower for image 1. The reasons for the differences in performance are not

clear. It may be that some participants saw the arrows as pointing to the

opening - indicating a direction of travel - with the red indicating emergency.

Whatever the reason, these confusions occur much less frequently with a blue

background. Neither of these two referents appeared particularly successful.

91
Figure AO

Do Not Enter

1 2

Percentage 93.8 80.5

Chi square significant .005

Mean Conf. Rat. 4.43 3.89

t-test slg .001

CCONF Mean 4.51 4.05

CCONF Median 4.76 4.42

Color Black, White, Red White on Red

Answers

a. No running

b. Exit this way

c. No entrance, restricted area

d. Wear protective gloves

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 6 1.58 1.16 a 4 1.81 1.45

b 1 1.38 1.13 b 0 1.14 1.06

c 122 4.43 4.72 c 99 3.89 4.21

d 1 1.17 1.04 d 20 1.83 1.31

n 130 n - 123

Isslng - 6 aisslng 8
Figure 41

Keep Door Open

Percentage 89.7 96.8

Chi square slg .05 level

Mean Conf. Rat. 4.23 4.38

t-test NS

CCONF Mean 4.40 4.43

CCONF Median 4.75 4.73

Color Red on White Blue on White

Answers

a. Not an exit

b. Keep door closed

c. Lock door behind you

d. Keep door open

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 5 1.82 1.33 a 3 1.48 1.22

b 3 1.64 1.27 b 1 1.18 1.06

c 4 1.56 1.23 c 0 1.37 1.15

d 105 4.23 4.69 d 122 4.38 4.71

n - 117 n 126

missing “ 19 missing - 5

93
Figure 42

Keep Door Closed

Percentage 83.1 71.1

Chi square sig .05 level

Mean Conf. Rat. 3.98 3.89

t-test NS

CCONF Mean 4.37 4.71

CCONF Median 4.69 4.49

Color White on Blue White on Red

Answers

a. Emergency exit

b. Keep door closed

c. Keep door unlocked

d. Keep door open

Choice Freq. Conf Mean Median Choice Freq. Conf Mean Median

a 12 2.06 1.46 a 20 2.42 2.18

b 108 3.98 4.54 b 91 3.89 4.41

c 1 1.62 1.35 c 1 1.86 1.47

d 9 1.54 1.18 d 16 1.86 1.28

n “ 130 n - 128

missing “ 6 missing - 3

94
as miners often indicated puzzlement at the imagery. On an actual door, however

they might be much more successful.

4.5 SURROUND SHAPE AND COLOR DATA

Data on the perceived hazardousness of surround shape were collected from 268

miners. Data were excluded from the final statistical analysis where a miner

failed to follow directions and rate each surround differently - e.g., by

giving one or more shapes the same rating. About 30-50 miners failed to rate

each surround differently, leaving about 214-228 people with statistically

usable data. (The typical "incorrect" response was to give two or three shapes

the same ranking, but not to give all 6 shapes the same rank.) Data were also

collected on the most appropriate background color for the shape ranked as number one

The rankings of 1-6 given for each surround shape were summed for each interior

image for each sites. Table 15 presents the overall rank sums for each of the

surround shapes for all referents (or interior images). The same data are presented graphically in figure 43. This figure also presents the overall ordering of surround shapes in terms of perceived hazardousness, with 1 representing

most hazardous and 6 representing least hazardous. Tables 16-20 present the

individual rank sum totals for each site as well as the overall rank sum total

and mean rank. Table 16 presents site data for Explosion; table 17 for Entangle

ment; table 18 for Poison; table 19 for General Warning; and table 20 for

Surround Alone.

Data were also collected on the perceived safety of surround shapes associated

with two images for safety - First Aid and Hard Hat. These data are presented

in tables 21, 22 and 23, and are included in figure 43. It is not clear, however, whether the miners followed the instructions to rate these shapes according to safety, or continued to rate them for hazardousness. These two shapes

were always presented last, while the hazard shapes were presented first, but

in differing orders. (The only limitation was that the surround alone was never presented first).

The data on the perceived hazardousness of surround shape were analyzed for

statistical significance using Kendall's coefficient of concordance for all

data obtained for each interior image (General Warning, Poison, Entanglement,

Explosion, surround alone. Hard Hat and First aid) for all subjects. A similar

analysis was performed for a subset of about 50 subjects from the various oil

shale sites. This analysis revealed that differences in the ranks for the

surround shape were statistically significant (beyond the .05 level for the oil

shale personnel and beyond the .001 level for the whole sample.)

Figure 43 demonstrates clearly that for the hazard warning symbols, the diamond

is ranked lowest (is perceived as most hazardous for all images except sur- round alone). The octagon is a very close second, while the circle is consistently ranked sixth (as least hazardous in all cases). Generally the triangle

is ranked third, the inverted triangle fourth, and the square fifth. Furthermore, there is a clear difference between the two shapes ranked as first and

second (most hazardous) and the remaining shapes—with a very large difference

95
Table 15. Ranking Data for Hazard Symbols - Totals for All Sites

Referent o o A o V N

General Warning 561 887 573 739 979 755 214

Poison 569 928 598 831 947 852 225

Entanglement 573 861 590 796 981 861 222

Explosion 580 883 628 843 927 927 228

Surround 631 991 534 775 998 775 224

Sum 2914 4550 2923 3984 4832 4170 1113

Mean Rank 2.62 4.09 2.63 3.58 4.34 3.75

Rank Order 1 5 2 3 6 4

96
Table 16. Ranking Data for Explosion - Totals for Each Site

Surround

Shape O O A o V N

BC 89 97 62 128 101 132 29

BT 138 235 202 229 280 239 63

WED no 165 99 148 147 150 39

EM 48 80 52 89 82 90 21

OS 195 306 213 249 317 316 76

Sum 580 883 628 843 927 927 228

Mean Rank 2.54 3.87 2.75 3.70 4.07 4.07

Rank Order 1 4 2 3 6 6

97
Table 17 . Ranking Data for Entanglement - Totals for Each Site

Surround

Shape O n O A o V N

BC 62 97 66 96 93 111 25

BT 117 217 158 233 282 232 59

WED 112 165 101 141 164 136 39

EM 53 79 55 72 101 81 21

OS 229 303 210 254 341 301 78

Sum 573 861 590 796 981 861 222

Mean Rank 2.58 3.88 2.66 3.59 4.42 3.88

Rank Order 1 5 2 3 6 4

98
Table 18. Ranking Data for Poison - Totals for Each Site

Surround

Shape o o" A o V N

BC 78 102 62 109 100 116 27

BT 135 231 174 236 249 214 59

WED 115 179 99 159 164 145 41

EM 39 76 51 82 92 80 20

OS 202 340 212 245 342 297 78

Sum 569 928 598 831 947 852 225

Mean Rank 2.53 4.12 2.66 3.69 4.21 3.79

Rank Order 1 5 2

1 _1_J

6 4
Table 19. Ranking Data for General Warning - Totals for Each Site

Surround

Shape o o A o V N

BC 80 122 79 108 122 119 30

BT 121 216 145 204 269 200 55

WED 115 165 107 153 178 143 41

EM 59 75 49 64 92 81 20

OS 186 309 193 210 318 212 68

Sum 561 887 573 739 979 755 214

Mean Rank 2.62 4.1A 2.68 3.45 4.57 3.53

Rank Order 1 5 2 3 6 4

100
Table 20. Ranking Data for Surround Alone - Totals for Each Site

Surround

Shape o O A o V N

BC 84 120 58 116 121 no 29

BT 151 247 138 223 260 199 58

WED 119 183 100 142 164 132 40

EM 56 90 42 72 103 78 21

OS 221 351 196 222 350 256 76

Sum 631 991 534 775 998 775 224

Mean Rank 2.82 4.42 2.38 3.46 4.46 3.46

Rank Order 2 5 1 4 6 4

101
Table 21. Ranking Data for First Aid - Totals for Each Site

Surround

Shape O O A o V N

BC 76 89 69 114 99 120 27

BT 192 185 180 241 296 266 60

WED 165 103 166 130 130 146 40

EM 51 62 56 93 70 88 20

OS 253 217 292 325 231 299 77

Sum 737 656 763 903 726 919 224

Mean Rank 3.29 2.93 3.41 4.03 3.24 4.10

Rank Order 3 1 4 5 2 6
Table 22. Ranking Data for Hard Hat - Totals for Each Site

Surround

Shape o O A o V N

BC 75 91 53 98 98 110 25

BT 169 204 216 238 234 241 62

WED 140 144 155 113 138 150 40

EM 59 74 64 83 71 90 21

OS 224 253 260 282 272 305 76

Sum 667 766 748 814 813 896 224

Mean Rank 2.98 3.42 3.34 3.63 3.63 4.0

Rank Order 1 3 2 5 5 6

103
Table 23. Ranking Data for Safety Information Symbols - Totals for All Sites

Surround

Shape o O A o V N

Hard Hat Sum 667 766 748 814 813 896 224

First Aid Sum 737 656 763 903 726 919 224

Sum 1404 1422 1511 1717 1539 1815 448

Mean Rank 3.13 3.17 3.37 3.83 3.43 4.05

Rank Order 1 2 3 5 4 6

104
Hazard

Warnings

Safety

Messages

Mean

Ranks

Mean

Ranks

T

1 1 r

5 oSa

® s ^ e«i r*> m ^ c*

c*> ^ m C4 CD

«> <•> C4 m m CD

OD &<3 ^

8 % O O

gCM OO

O g<l CO

CD

O M %

I I

I I- CD lO

W^ 5i e « €» =

> E S

</>

CO »

s

s

S9NIXNVM

cn ^ m CD

CM ^ ^ in CD

*- CM <*» m (D

V- CM CO « m CD

^ CM CO « m CD

^ CM CO ^ m CD

O o 4 o o

MaOM XNVH llVHaAO

Figure 43. Rated hazardousness of surround shape

105
between the shapes ranked as first and sixth. The rank ordering of surround

shapes for hazard warning is reasonably consistent from interior image to

interior image. ,

The data on surround shape for the two safety messages are less clear cut. The

rankings are clustered more closely together—but with rather different patterns

for the two interior images. Thus the diamond is ranked number one for Hard

Hat while the square is ranked first for First Aid. Use of the Kendall coefficient of concordance indicated that the differences in ranks are significant,

however.

In addition, the colors selected as most appropriate for the background color

were tabulated. This tabulation appears as a set of histograms in figure 44,

and indicates that red was selected as the most appropriate color by the majority of miners for poison, explosion, entanglement, and surround alone. Yellow

was selected as the first choice for general warning and was second for all

other messages, except poison for which black was the second most frequent

choice. Orange was selected by the third largest number of miners for all

hazards except poison, where white was the third choice. Except for the poison

image, black, white, blue, and green were selected for hazard-warning symbols

by almost equally small numbers of participants. The color choice data, then,

tend to reinforce the common workplace stereotypes of red, yellow, and orange

as appropriate colors for hazard warning symbols.

As with surround shape, color stereotypes for the two safety Images are less

clear cut. For hard hat in particular, the percentages are fairly evenly

divided across colors with black, orange, and white seen as slightly less appropriate, and green, yellow, red, and blue somewhat more. For first aid, however,

the preference is split between red and green as most appropriate, with a much

lower percentage choice for the other colors.

Since the cross for first aid tends to be presented in red for "red cross" or green for "safety", these preferences seem to follow existing use of colors.

Conversely, the lack of a similar stereotype for "wear hard hat," may well

reflect the absence of standardized symbolic messages for personal protective

gear.

4.6 SITE DIFFERENCES

Table 24 presents overall information for the five different sites. Generally

performance was quite similar, with mean age and score being about the same with a few notable exceptions. As noted earlier the ANOVA for score, (reflecting the mean number correct out of a possible forty) indicated that the two BC

sites were significantly different with a mean score of 27-28 compared with

the overall mean of 31-32. These two sites tended to be younger while the

BT sites tended to be older. The data will be examined in some detailed to see which symbols, if any, caused problems for specific sites.

A chi square analysis of the frequency of correct response for each referent

for each testing site indicated about 11 to 12 symbols where significant differences between testing site occurred. For group 1 and 2 these symbols Included;

106
33I0H3 a9VlN33)i3d

Figure 44, Preferred background color for selected symbols

107

POISON

EXPLOSION

GENERAL

ENTANGLEMENT

SURROUND

HARD

HAT

RRST

AM)

WARNING

ALONE
Table 24. Site Comparison Data

EASTERN GOAL

EMI EM2

SC ORE*32.9 SCORE s 33.7

AGE 34.8 AGE = 36.2

N 10 N = 16

BCl BC2

SCORE = 27.7 SCORE = 28.6

AGE 31.3 AGE = 29.8

N 26 N = 24

OPEN PIT COPPER

BTl BT2

SCORE = 33.5 SCORE s 31.5

AGE 34.9 AGE = 42.2

N 36 N = 35

SAND & GRAVEL

WEDl WED2

SCORE = 32.8 SCORE = 33.2

AGE 34.2 AGE s 30.8

N 20 N = 20

OIL SHALE

OSl OS2

SCORE = 32.3 SCORE 33.1

AGE 30.8 AGE = 31.9

N 44 N 8 36

OVERALL

TOTAL TOTAL

SCORE = 31.3 SCORE at 31.7

AGE 34.2 AGE as 34.9

N 136 N 8 131

Mean number correct for a total of 40 symbols Thus

represents a perfect "score".

108
Flammable, Laser, Radiation, Pinch, Keep Door Closed, Emergency Exit, and No

Exit. In group 1, additional S3rmbols for which statistically significant site

differences occurred included; Corrosion, Poison, Shower, Exit and Respirator.

For group 2, differences occurred for Cut, Eyewash, No Entrance and Entanglement.

Table 25 presents the percentages of correct response for each symbol for each

site. Table 26 presents the mean confidence rating data for each symbol for

each site. As can be seen from these tables, the differences between sites are

often, but not always attributable to the poorer performance of the BC site.

A chi square analysis indicated significant (at or beyond the .05 level) site

differences in frequency of correct response for the following Group 1 symbols:

Flammable, Corrosion, Poison, Keep Door Closed, Safety Shower, Exit, Emergency

Exit, No Exit, and Respirator. Similar significant differences were also calculated for the following Group 2 symbols: Flammable, Laser, Cut, Keep Door

Closed, Eyewash, Emergency Exit, No Exit, No Entrance, and Entanglement. Significant site differences (at or beyond the .05 level) occurred for Laser,

Radiation and Pinchpoint, which were seen by all participants.

Site differences can be examined in greater detail in table 25. Performance in

terms of percentage of correct response for the group 1 symbols will be discussed first. In six cases, poorer performance is generally attributable to

the BC site, with percentages of correct response as much as 20-50 percent

lower. This included symbols for: Flammable, Radiation, Eyewash, No Exit,

Poison, Pinch, and Close Door. (Percentages for these last three were also

lower at the WED site). Other group 1 symbols for which individual site performance was markedly poorer included Exit (EM). On the other hand, for Laser,

WED and OS performed about 30 percent better; for Corrosion OS alone received

a perfect score; for Safety Shower, BT and OS were some 20-50 percent better;

and for Exit and Respirator, WED was 20-30 percent better than the other sites.

In no case however, was the performance of the BC group noticeably above the

group mean.

Similar differences occurred for group 2 symbols. The BC site performance was poorer for Pinch, Laser, Keep Door Closed, Eyewash, Exit, No Exit, and Entanglement while the WED performance was poorer for Cut. The EM site performance

was better for Flammable and Laser, while the OS performance was better for

Flammable, Radiation, No Exit, and No Entrance. In several cases BC performance

was above the group mean. (Forklift, Do Not Touch, Foot Protection) Performance of the BT site was distinguished in that it was rarely above or below the

group mean, for both sets of symbols.

109
Table 25. Percentage of Correct Response for Each Site

Group 1 Group 2

Number of Sc

Site

N=10

EMI

N=26

BCl

N=36

BTl

N=44

OSl

N=20

WEDl

N=16

EM2

N=24

BC2

N=35

BT2

N=36

0S2

N=20

WED2

Symbol

Flammable 0.80 0.18 0.63 0.68 0.45 0.81 0.54 0.56 0.82 0.63

Laser 0.00 0.09 0.19 0.42 0.44 0.81 0.13 0.40 0.36 0.10

Radiation 0.50 0.08 0.32 0.56 0.42 0.47 0.17 0.37 0.54 0.20

Explosion 0.80 0.81 0.91 0.98 1.00 0.81 0.91 0.91 1.00 0.90

Electrical 1.00 0.80 1.00 1.00 1.00 0.60 0.29 0.59 0.45 0.70

Corrosion 0.80 0.73 0.80 1.00 0.89 0.81 0.54 0.79 0.74 0.65

Poison 1.00 0.77 0.97 0.93 0.82 0.73 0.86 0.74 0.85 0.90

Fork Lift 1.00 0.84 0.97 0.98 1.00 0.94 1.00 0.88 0.94 1.00

Slip 0.80 0.75 0.91 0.88 0.74 1.00 1.00 0.97 1.00 1.00

Fall 1.00 0.85 1.00 1.00 0.89 1.00 0.79 0.91 0.97 0.90

Overhead 0.90 0.64 0.63 0.65 0.95 1.00 0.96 0.97 1.00 0.95

Gen. Warning 0.63 0.52 0.38 0.60 0.60 0.78 0.50 0.71 0.66 0.75

Trip 1.00 0.88 1.00 1.00 0.95 0.93 0.71 0.71 0.85 0.95

Pinch Point 1.00 0.67 0.91 1.00 0.83 0.88 0.45 0.91 1.00 0.95

Hot Surface 0.89 0.85 0.80 0.92 0.89 1.00 0.96 0.91 1.00 1.00

Crush 0.70 0.88 0.71 0.72 0.72 0.94 0.91 0.82 0.94 0.95

Sud .Pres .Release 0.90 0.77 0.94 0.95 0.85 0.33 0.36 0.47 0.17 0.20

Cut/ Sever 0.80 0.76 0.94 0.84 0.71 0.94 0.96 0.94 1.00 0.50

Door Open 1.00 0.80 0.97 1.00 0.68 1.00 0.96 0.94 1.00 0.95

Do Not Touch 0.90 0.84 0.97 1.00 1.00 0.87 0.96 0.81 0.91 0.95

Door Closed 1.00 0.73 0.91 0.90 0.58 0.86 0.42 0.76 0.67 0.95

Hard Hat 1.00 0.88 0.97 1.00 1.00 0.94 0.96 0.97 1.00 1.00

Ear Protect. 1.00 0.85 1.00 1.00 0.95 1.00 0.92 0.94 1.00 0.90

Eye Protect. 1.00 0.92 0.97 1.00 0.95 1.00 0.96 0.89 1.00 1.00

Foot Protect. 0.78 0.92 0.86 0.86 1.00 1.00 1.00 0.97 0.97 0.95

Hand Protect

.

1.00 0.88 0.91 0.92 0.95 1.00 0.96 0.91 0.97 0.95

No Smoking 1.00 0.84 0.94 1.00 0.95 1.00 0.96 0.91 1.00 1.00

No Open Flame 1.00 0.81 0.97 1.00 1.00 0.93 0.96 0.91 0.97 0.95

First Aid 0.80 0.76 0.86 0.88 0.90 0.93 0.95 0.97 1.00 0.95

Safety Shower 0.44 0.33 0.79 0.83 0.58 0.75 0.78 0.89 0.97 0.85

Eyewash 1.00 0.68 0.94 1.00 0.95 0.94 0.42 0.66 0.71 0.85

Exit 0.30 0.63 0.78 0.72 0.95 1.00 0.78 0.91 0.94 0.95

Emerg. Exit 1.00 0.92 0.94 1.00 0.95 0.77 0.40 0.50 0.40 0.39

No Exit 1.00 0.50 0.83 0.89 0.95 0.69 0.46 0.68 0.94 0.65

No Entrance 1.00 0.83 0.97 1.00 0.85 0.87 0.70 0.67 0.97 0.85

Extinguisher 1.00 0.88 1.00 0.95 0.95 0.94 1.00 0.94 1.00 0.95

Hose & Reel 0.90 0.80 0.94 0.97 0.95 1.00 0.88 0.91 0.97 0.85

Alarm Call Pt. 0.50 0.54 0.57 0.69 0.33 0.67 0.43 0.68 0.71 0.70

Entanglement 0.90 0.65 0.79 0.84 0.89 1.00 0.75 0.94 0.97 0.95

Respirator 0.56 0.76 0.50 0.76 0.95 0.71 0.75 0.85 0.82 1.00

110
Table 26. Mean Confidence Rating Data for Correct Answers for

All Subjects at Each Site

Group 1 Group 2

Site EMI BCl BTl OSl WEDl EM2 BC2 BT2 0S2 WED2

Symbol

Flammable 4.10 2.93 3.97 3.29 3.39 4.25 3.42 4.00 4.22 4.37

Laser 1.89 2.92 2.52 2.62 3.17 2.50 1.81 3.67 2.80 2.33

Radiation 3.00 2.29 3.00 3.48 3.17 3.27 2.28 3.58 3.43 2.27

Explosion 4.33 4.38 4.60 4.57 4.79 4.00 4.29 4.44 4.77 4.72

Electrical 4.60 4.48 4.91 4.78 4.89 3.75 3.14 3.93 3.38 4.17

Corrosion 4.67 4.65 4.78 4.76 4.84 4.25 3.44 4.21 4.31 4.38

Poison 4.70 4.17 4.94 4.67 4.78 3.69 4.10 4.00 4.29 4.72

Fork Lift 4.70 4.47 4.75 4.67 4.95 4.69 4.57 4.71 4.71 4.90

Slip 4.00 4.15 4.73 4.31 4.44 4.69 4.65 4.91 4.74 4.80

Fall 4.60 4.57 4.82 4.56 4.79 4.47 4.05 4.34 4.47 4.67

Overhead 4.56 4.19 4.22 3.85 4.84 4.81 4.35 4.91 4.47 4.85

Gen. Warning 1.80 2.76 3.10 2.18 3.89 3.18 2.82 3.37 3.00 3.89

Trip 4.50 4.59 4.94 4.79 4.84 4.07 3.53 4.26 4.34 4.42

Pinch Point 4.80 3.70 4.54 4.46 4.68 4.19 3.06 4.30 4.57 4.79

Hot Surface 4.12 4.50 4.33 4.05 4.56 4.56 4.47 4.44 4.66 4.70

Crush 3.30 3.77 4.29 3.90 4.71 4.50 3.65 4.19 4.39 4.68

Sud .Pres .Release 3.80 3.95 4.54 4.12 4.42 2.75 2.61 3.26 2.65 2.00

Cut/ Sever 4.10 4.37 4.46 3.78 4.33 4.62 4.29 4.64 4.47 3.82

Door Open 4.50 4.20 4.47 3.97 4.10 4.57 4.05 4.44 4.54 4.20

Do Not Touch 4.50 4.68 4.69 4.36 4.89 4.13 4.45 4.50 3.97 4.68

Door Closed 3.80 4.00 4.38 3.90 3.53 4.00 3.05 4.14 3.77 4.50

Hard Hat 4.50 4.25 4.79 4.68 5.00 4.44 4.67 4o84 4,53 4.68

Ear Protect. 4.40 4.38 4.94 4.76 5.00 4.81 4.25 4.65 4.83 4.95

Eye Protect. 4.50 4.57 4.76 4.68 4.89 4.56 4.33 4.76 4.56 4.80

Foot Protect. 3.20 4.78 4.06 3.75 4.89 4.75 4.57 4.70 4.69 4.84

Hand Protect4.30 4.68 4.67 4.15 4.79 4.56 4.32 4.75 4.50 4.74

No Smoking 5.00 4.75 4.82 5.00 4.79 5.00 4.76 4.93 4.85 5.00

No Open Flame 4.90 4.54 4.97 4.82 5.00 4.75 4.67 4.68 4.61 4.84

First Aid 3.89 4.64 4.58 4.49 4.63 4.71 4.41 4.64 4.39 4.95

Safety Shower 3.60 3.35 3.70 4.24 4.23 4.44 3.45 4.77 4.42 4.79

Eyewash 3.67 3.58 4.67 4.29 4.84 4.25 3.11 4.14 3.74 4.26

Exit 2.80 3.87 4.09 3.29 4.68 4.06 4.00 4.58 4.31 4.83

Emerg. Exit 4.10 4.04 4.57 4.34 4.68 3.29 2.81 3.58 2.68 3.22

No Exit 4.00 4.20 4.48 4.08 4.63 1.67 3.33 4.25 4.37 4.00

No Entrance 3.90 4.20 4.64 4.46 4.53 4.29 3.18 3.77 3.94 4.33

Extinguisher 4.90 4.76 4.97 4.77 5.00 4.75 4.80 4.90 4.86 4.95

Hose & Reel 4.30 4.05 4.70 4.85 4.74 4.80 4.60 4.68 4.66 4.40

Alarm Call Pt. 3.30 3.21 3.85 3.60 3.72 3.60 2.95 4.03 3.94 4.32

Entanglement 3.30 3.85 4.42 3.55 4.84 4.50 3.94 4.61 4.61 4.47

Respirator 4.10 4.45 3.84 4.12 4.33 4.38 4.09 4.67 4.56 4.63

111

L
5. DISCUSSION

5.1 COMPARISON WITH PREVIOUS RESULTS

At least fifty-five of the symbols studied with miners were also assessed with

both industrial personnel and naive participants by Collins et al . , (1982). As

noted earlier, the industrial study utilized both a definition procedure and

preference choices. Table 27 presents a comoarison of the results from the two

studies. This table identifies the symbol, provides the percentage of correct

responses for both industrial and naive personnel from the earlier study, the

percentage preference for these two groups of participants, the percentage

correct responses from the miners, and their mean confidence ratings. Correlation coefficients were determined for data from industrial -naive participants

(0.73), mining-naive participants (0.72), and industrial-mining participants

(0.81). These coefficients exclude data for No Exit and Fire Alarm Call Point

for which severe scoring problems emerged with the definition data from the

earlier experiment. When data for hazard warning symbols only are considered,

the correlation coefficient between industrial and mining personnel jumps to

0.87.

Despite changes in response procedure, there was thus reasonably good agreement

in the percentage of correct responses for common symbols from the two studies.

It is particularly interesting to note that the correlation coefficient for

both miners and industrial personnel with the naive data were so similar. This

suggests that differences in the data between miners and industrial personnel

may be due more to population differences than to methodological differences

between the two studies. (The naive people and the industrial personnel used

the definition style response form; the miners used the multiple-choice form).

Generally, however, symbols which were correctly identified by miners were also

correctly identified by industrial personnel. Differences in performance

exceeded 10 percent in 13 cases with miners performing better in 7 cases and

worse in 6 cases. The most noticeable discrepancy occurred for the Radiation

symbol with which the industrial personnel appeared to be more familiar.

5.2 FACTORS WHICH APPEAR TO AFFECT SYMBOL EFFECTIVENESS

Review of the data obtained from both the mine and industrial personnel suggest

some factors which appear to affect symbol effectiveness, as measured by the

various understandability assessment procedures. In both studies, the very

abstract symbols performed poorly. They received low percentages of correct

responses, large percentages of critical confusions, low confidence ratings, and

were rarely selected as the "preferred" symbol. Schiff (1980) confirms that

very abstract symbols are poor communicators of information. Examples of

abstract symbols in the present study include Radiation, Laser, General Warning,

and the arrow and open box for Exit. Of course, one reason for the existence

of these abstract symbols is that these concepts do not readily lend themselves

to pictographic representations. Since these symbols do not have good initial

understandability, they appear to require further training and/or an auxiliary

word message. The data suggest further, that existing informal training for

the Radiation and Laser symbols has not been particularly effective. For

example, the Radiation symbol was one of the few symbols actually observed

112
r

Symbol

Table 27 . Comparison with

Industrial^

% Correct Preference

Previous Symbol Research

Naive

X Correct Preference X Correct Miners

Mean Conf

1 Flammable ISO 65.2 50.9 65.2 44.9 64.1 3.91 Laser ISO 25.0 25.9 30.4 2.70

Radiation ISO 65.9 30.2 37.7 3.10

Explosion ISO 82.5 56.1 90.2 57.7 92.3 4.49

1 FMC 88.3 38.3 88.7 39.7 91.7 4.56

1 Electrical ISO 63.9 9.0 37.7 6.4 51.6 3.64

! FMC hand 96.5 79.3 95.1 89.8 96.5

FMC Body 96.5 4.77

Corrosion ISO 90.9 78.2 92.6 64.1 86.5 4.75

PICTOG 80.8 17.8 83.0 32.0 71.3 4.15

1 Poison ISO 76.1 94.1 81.5 79.5 90.2 4.67

i Forklift ISO 96.8 59.7 92.5 57.7 95.3 4.70

; w/o driver 93.0 8.3 88.5 7.7 94.5 4.71

i Slip ISO 90.4 52.7 96.2 56.4 99.2 4.77 FMC 94.2 37.8 90.8 33.3 83.6 4.39

Fall FMC-bkw 92.0 25.2 51.8 38.5 95.3 4.67

Overhead Crane 59.5 69.6 73.6 52.6 70.7 4.21

Entanglement FMC 94.3 81.8 94.5 88.5 92.3 4.48

Gears Alone 82.9 11.5 90.6 10.2 80.3 4.01

General Warning ISO 56.4 40.1 79.3 44.9 59.4 2.98

j 30Z no pref.

1 Trip Boot in hole 90.7 20.3 91.8 14.3 80.8 4.16

1 No Open Flame Match 93.5 45.7 98.1 45.5 95.4 4.85

1 Flame 90.7 42.6 93.5 50.6 94.5 4.69

No Smoking Dot 96.5 55.4 98.4 71.8 95.8 4.89

: Hard Hat AF 97.9 46.6 98.0 25.6 96.9 4.68 CAN 97.7 4.65

ISO 95.5 23.4 90.8 19.2 Hearing AF 81.8 17.1 59.2 12.8 96.1 4.69 CAN 96.2 4.75

1 ISO 90.7 16.7 60.7 6.4

1 Eye Protection AF 89.7 10.6 87.1 6.4 96.2 4.61

! CAN 96.9 4.70

ISO 100.0 38.3 91.8 33.3

Shoes ISO 96.5 14.4 79.6 22.5 88.8 4.15 CAN 95.7 22.5 90.6 14.1 97.6 4.70

Hand ISO 90.8 16.7 100.0 5.1 95.3 4.58

CAN 90.7 17.1 64.0 5.1 92.2 4.49

Respirator ISO 73.2 61.9 92.5 50.0 20.6 4.13 NEW 83.2 4.49

First Aid Cross 87.1 59.0 94.4 46.8 95.9 4.59

Hand & Cross 91.9 39.6 93.5 53.2 84.2 4.52

Shower Head & Drops 76.6 1.4 66.0 1.3 65.9 3.91 Man & Shower 98.9 83.8 99.9 75.6 86.9 4.41

Eyewash Eye & Drops 64.9 32.4 46.3 27.6 68.5 3.99

Head & Drops 67.0 31.3 56.6 17.9 91.3 4.32

Fire Extinguisher 98.8 96.7 96.2 4.86 Hose & Reel 95.4 92.6 92.3 4.78

Alarm Bell Sounder & 10.2* 12.6 48.1* 46.8 56.0 3.60 Hammer 4.6* 15.4 42.6* 43.6 64.3 3.82

j Exit * (arrow) 59.1 12.8 83.3 9.0 72.1 3.78

Japanese 91.5 4.35

1 Emergency Exit Y 93.0 23.9 82.0 19.2 89.3 4.18

i ISO 72.7 21.6 83.3 19.2

No Exit ISO 38.4* 39.3 39.3* 37.7 69.5 4.00

MAN, DO(» 59.1* 64.9 35.2* 57.7 81.1 4.29

j No Entry MAN 76.7 47.1 78.7 33.3 93.8 4.43

I MAN, BIG HAND 85.0 38.3 92.4 38.5 80.5 3.89

* Scoring problems with definition data arose here.

^ N ° about 86 to 94 participants

^ N » about 53 to 61 participants

^ N • about 131 to 135 participants

Rat

113
during the site visits. Yet, it had very poor identification performance.

On the other hand, the informal training for First Aid, another abstract, but

widely used symbol, has been reasonably effective - suggesting that abstract

symbols can be learned, if presented frequently and appropriately enough.

Tables 28 and 29 present the image content for the symbols, ordered according

to the percentage of correct responses (lowest to highest). It can be seen from these tables that although several of the very abstract symbols were among

the poorest performing symbols, several pictorial or representational symbols

did equally poorly. In particular, version 2 of Sudden Pressure Release performed as badly as Radiation and Laser. Other poorly performing examples

included version 2 for Exit, Poison, and Trip which, although representational

in nature, do not appear to communicate their messages as effectively as the

group 1 image. For group 1, poorly understood, but representational Images

included Overhead Hazard, Crush, Cut, and Entanglement. These differences suggest that the pictorial image should relate to ideas and messages with which

the intended audience is familiar. Thus, version 2 of the Sudden Pressure

Release image appears to depict bright light or welding hazard, judging by the

number of miners who selected this answer. Similarly the Overhead Hazard image

which shows a hammer and stone falling is a more common occurrence for many

mines than a crane load breaking and falling. (Yet, this latter image could be

appropriate in a processing plant where overhead loads are common.) Likewise

the Crush image showing the whole body being crushed may depict roof fall or low clearance to miners accustomed to working underground.

Differences in performance among the various representational or pictorial

versions of a referent reinforce the need to assess each image with the

intended audience. Simply drawing a picture is not sufficient to ensure that

it will communicate its message to the user as well as it does to the designer.

Nevertheless, symbols which proved to be effective in terms of initial

understandability in the present study generally included those symbols showing

a person with a hazard or a piece of gear. The more representational symbols

usually received a high percentage of correct responses and higher mean confidence ratings. Examples in which the more representational image performed

better than the more abstract one, include Safety Shower (2)* Exit (2), Entangle

ment (2), Slip (2), Emergency Exit (1), Eyewash (1), Posion (1), Electricity

(1), and Trip (1).

Familiarity with the underlying concept also appears to affect performance.

The most obvious examples of lack of familiarity include: Safety Shower, Eyewash, Laser, General Warning, and Fire Alarm Call Point. Examples of signs

relating to these messages were rarely observed during the site visits. On

the other hand, the data suggest that a number of the ISO hazard warning symbols, also used on the DoT-UN hazardous materials transport placards, are some- what familiar to the miners. For Poison, Corrosion, Flammable and Explosion,

the ISO image received a higher percentage of correct answers and a generally

* The number in parentheses refers to the image number as given in figures 6

to 42

.

114
Table 28. Image Content—Ordered According to Percentage Correct Responses

Referent

Laser

Radiation

Alarm Call

Flammable

General Warning

Shower

Respirator

Overhead

Exit

Crush

Entanglement

No Exit

Cut /Sever

Door Closed

Slip

First Aid

Corrosion

Pinch

Foot

Sud . Pres . Rel

Emergency Exit

Door Open

Poison

Eyewash

Explosion

Hot Surface

Hand

Hose

No Entrance

Fall

Fork Lift

No Open Flame

Do Not Touch

No Smoking

Electrical

Ear

Extinguisher

Head

Eye

Trip

Group 1

Content Surround Shape

Abstract—resembles sun beam A

Abstract—3 blades A

Bell Ringing D

Picture of Flame ^

Abstract—I A

Shower Head & Drops

Head y Gas mask 0

Hook, crane load, broken strap A

Arrow, broken rectangle

Mangled hand, rectangle, arrow

Gears alone 0

Man, door, x, 0

Severed hand, pointed object

Open door , wall , arrows 0

Foot & Squiggle

Hand, bandage, cross

Pictures of test tubes, bar,

hand being eaten away A

Hand, rollers

Two shoes 0

Upper body, steam

Man, arrow, flame 0

Open door , wall , arrows 0

Skull and crossbones A

Head, drops toward eye

Abstract Exp.

Hand, radiating surface

One glove 0

Coiled hose, knob

Standing man 0

Man, falling back, ledge

Man and truck A

Circle, slash, lit match 0

Hand, surface 0

Circle, slash, lit cigarette 0

man, wire, lightning bolt

Ear protectors, head 0

Extinguisher—Pictorial 0

Hat Alone 0

Goggles, head 0

Man, falling forward, object

115
Table 29. Image Content —Ordered According to Percentage Correct Responses

Group 2

Referent Content Surround Shape

Laser Abstract A

Sud . Pres . Rel Head—Explosion Toward Eye

Radiation Abstract A

Electricity Abstract Lightning Bolt A

Emerg. Exit Bicolor person, door

General Warning Abstract ! A

Flammable Picture of flame A

Alarm C.P. Alarm ringing, hammer

Eyewash Eye, drops

No Exit Person, open door

Door Closed Open door, arrows toward wall 0

Corrosion Drops, hand eaten away A

No Entrance Person w/big hand 0

Trip Boot in hole 0

Poison Person, clouds, lungs, starry eyes

Respirator Head, new respirator 0

Shower Man pulling shower chain, drops a

Pinch Hand rollers

Cut Pointed object, foot

No Touch Finger, surface 0

Crush Rectangle, +, falling man

Exit Person, open door, wall

Fall Person, diving forward, surface

Hot Surface Hand, radiating surface

Explosion Object being blown apart A

Entanglement Hand in gears

Hose Coiled hose

Fork Lift Truck alone A

No Open Flame Circle, slash, flame 0

Hand Two gloves 0

No Smoking Lit cigarette 0

First aid Cross

Ear Ear protection alone 0

Extinguisher Pictorial extinguisher

Eye Eye glasses alone 0

Door Open Open door, arrows, away from wall 0

Foot One shoe w/laceholes 0

Head Hat , head 0

Overhead Hammer, rock, downward motion A

Slip Person falling, level surface

116
higher mean confidence rating. The only ISO image for which this statement

does not hold is the one for Electrical where the more representational

picture, including a person and the hazard, performed better.

Another instance of probable familiarity includes the use of the circle and

slash for prohibition. Early research by Brainard et al. (1961) indicated that

their subjects were unfamiliar with this concept. Use of this approach in

highway signing over the last 20 years, however, has clearly improved the

effectiveness of the prohibition symbolization. All the prohibition symbols

except one (no exit, version 2) were correctly identified by 90 percent or more

of the miners responding. Similar results were found for industrial personnel.

It remains, however, a graphic convention which must be learned. Dewar (1976)

also pointed out that the prohibitory slash may obscure the symbol underneath,

particularly if this symbol has a large amount of graphic detail. The prohibition symbols studied in the present experiment were relatively simple images

such as No Smoking, Do Not Touch, Do Not Enter, representing noncomplicated

messages.

As noted in previous NBS reports (Lerner and Collins, 1980a; Collins et al.,

1982), messages related to egress appear to be difficult to symbolize effectively. Although one image for Emergency Exit and Exit each was identified

correctly by more than 89 percent of the participants, the confidence rating

for each image was relatively low (4.18 and 4.35). Both symbols for No Exit

were identified correctly by only 75-77 percent of those responding. The

better performance data for the Exit symbols suggest that it may be possible

to use the Exit symbol as the basis for the No Exit symbol, and thus improve

performance. This message, however, does not appear to be as familiar as the

exit message.

5.3 SURROUND SHAPE AND BACKGROUND COLOR DATA

Contrary to expectations, variations in surround shape do affect the perceived

hazardousness of a safety symbol. Although it was hypothesized that the six

different surround shapes might well be ranked the same during part II of the

present experiment, clear, statistically significant differences (using the

Kendall coefficient of concordance) emerged between the six shapes. Furthermore, variations in interior image had little effect upon the overall ranks.

Thus, regardless of whether a poison, explosion, entanglement, or general warning image were presented, the diamond and octagon were ranked as most hazardous

and the square and circle as least.

The consistency in the rank orders is perhaps even more surprising since the

miners had already participated in part I. In this portion of the experiment,

hazard warning images were presented within triangles, squares, or once, a circle. The diamond and octagon were never presented as surround shapes in

any portion of part I. The persistence, then, of the diamond and octagon as the most "hazardous" shapes suggests that the widespread use of these shapes

for highway signs has been "learned" by the miners. These two shapes were

ranked as more indicative of hazard, despite immediately prior familiarization

with the triangle or square as hazard surround shapes.

117
Based upon these data, the diamond can be recommended as a good surround shape

for hazard warnings. It was most often ranked as most hazardous, is in conformance with existing U.S. highway practice for warning signs, and does not limit

interior image area as does the ISO triangle. It is also used in the DoT-UN

hazardous materials transport signs. The octagon may be best reserved by DOT

to indicate "stop", along with the inverted triangle for "yield". The latter

does not appear to indicate hazard as forcefully as the diamond, and again

limits the interior image size. The circle clearly indicated hazardousness

least of the six shapes studied, although the square was a close second. The

square does allow more room for the interior image, particularly in comparison

with the 2 triangular shapes, but the consistently high (non-hazardous) rankings

suggest that this shape is not the most effective to warn of the presence of a hazard.

A study by Cochran, Riley and Douglass (1981), confirms that the diamond and

octagon, as well as the inverted triangle are among the most effective warning

shapes. These authors examined nineteen different geometric shapes for warning

labels using the method of paired comparisons. Black and white shapes were viewed without interior images. Sixty-six subjects were asked to chose which

sign of a pair best depicted "warning". The shapes that best represented warning were the inverted triangle, diamond, octagon, and triangle. "In general,

shapes with corners with sharper appearing points apparently are more frequently

recognized as warning shapes" (p. 397). Shapes which were less preferred for

warning are "more simple looking, less irregular, and resting on a solid base,

giving them the appearance of being in equilibrium" (p. 397). The authors point

out that the influence of traffic signs can be seen in the results, with the

shapes for the following (traffic) signs predominating - inverted triangle,

octagon, hexagon, and diamond.

Although Cochran et al. (1981) comment that the invented triangle performed

best, it was not significantly different from the diamond, octagon, or hexagon,

nor was it preferred to these shapes. These four shapes thus appear to be

about equally successful in Indicating hazard warning. In conjunction with

the present study, then, these data support the contention that neither the

circle nor the square indicate hazard warning information as successfully as the other shapes studied.

The color data obtained in the present study also tend to reinforce existing

warning sign practice. The primary colors selected by the miners for hazard

warning - red and yellow - are currently widely used for industrial and highway

warning signs (ANSI Z53.1, 1979; DoT, 1979). All of the hazard warning symbols

studied in Part I of the present experiment were presented with yellow, white,

or red background colors. Although red was less frequently presented as the

background color, it was selected by the majority of the miners for 4 of the 5

warning images studied in Part II. Only once, for general warning, was yellow

selected more frequently. These data suggest that the existing ANSI practice

of using red for "danger" and yellow for "caution" (a lesser degree of hazard)

continues to be appropriate. Miners, at least, appear to recognize these sterotypes. Collins et al. (1982) also noted comments from industrial personnel

about the need to use red and yellow colors with various hazard symbols. They

118
also noted that color does not appear to affect understandability but may

contribute to the overall effectiveness of the symbol.

Along these lines, another study examined the attention-getting properties of

color, surround shape, and word legend for four traffic signs. Adams and Hsu

(1981) were concerned with the extent to which changes could be made to the

coding details without these changes being detectable. Each sign was presented

to fifty subjects in its original form, and with either the color, shape, or legend changed - for a total of sixteen signs, under degraded viewing conditions.

The results indicated that color appeared to be the most salient dimension,

followed by shape, and then by word legend. The word legend did not appear to

be particularly noticeable for the exposure conditions of this experiment.

The authors concluded that both color and shape can contribute to more rapid

sign recognition.

The two studies reviewed above, plus the data from the present study suggest

strongly that surround shape and color can communicate additional useful

information about the presence of a hazard to a potential user. These cues can reinforce the information given by the interior image. Although the effect

of such cues was not studied for a word sign, they appear useful for purely

symbolic signs - the focus of the present investigation.

5.4 DISCUSSION OF SITE DIFFERENCES

Reasons for the site differences in performance are not particularly clear.

The site with the poorest performance, the BC site, was an eastern U.S. coal

mine, but so was the EM site which was characterized by much better performance.

Miners at the BC site appeared to have much more difficulty with the testing

situation, however. Their data sheets were characterized by greater failure

to do the confidence rating portion of the experiment. They also appeared to

be less familiar with some of the symbols related to chemical processing—safety

shower, eyewash, corrosion, and poison—as well as the equipment-hazard symbols

pinch, cut, and entanglement. The abstract symbols for radiation and laser

also appeared to be unfamiliar. Many of these concepts may not have been necessary for their site. Both the OS 2 and EM 2 groups contained several safety

professionals which may have improved their overall performance. The BT site, was characterized by older, but very experienced personnel, two opposing factors which might both decrease and increase performance. The BC site was characterized by much younger personnel with less mining experience—factors

which might also lead to poorer symbol recognition.

The symbols for which significant performance differences emerged are primarily

the hazard and egress symbols. Failure to comprehend these symbols could lead

to greater likelihood of an accident and injury. The personal protective gear

symbols, on the other hand, appeared to elicit relatively similar performance

from all groups. For those concepts for which problems seem to occur, (particularly the common hazards of flammable, corrosion, poison, entanglement,

pinch, and cut), additional training and supplementary word signs may be

required. Again, focus on the young inexperienced miner appears appropriate.

119
5.5 SELECTION OF A PRELIMINARY SYMBOL SET

The data on symbol understandability obtained in both the present experiment and

the previous industrial symbols experiment (Collins et al. 1982) were used to

select a set of symbols which best conveyed the intended referent. A series of

decision rules was generated for making this initial selection. While these

rules are somewhat arbitrary, they seem to represent the best approach based

upon the available data. These rules were used for selecting the interior graphic image. These images were then combined with the appropriate background/

surround shape as determined from part 2 of the present research.

A reasonable minimum selection criterion is that a symbol be understandable.

ISO has suggested an understandability criterion of at least 85 percent correct

responses, using a definition procedure, and no more then five percent critical

confusions. The good correlation between data obtained with the definition

procedure and with the multiple choice procedure suggests that an 85 percent

cut-off figure can also be appropriate for the data obtained in the present

experiment. A more stringent criterion could, of course, be used to exclude

more symbols from consideration. In this experiment, however, a selection was made for all referents. The seven symbols which do not meet the understandability criterion are identified with an asterisk. These particular symbols

require further training and/ or accompanying word legends to ensure comprehension. It should be noted the majority of these symbols also performed poorly

in the industrial symbols project.

If both images met the minimum understandability criterion, then the image

which performed better statistically was selected. This performance was measured by either the chi square test for the frequency of correct responses

or the t-test for confidence ratings. If the two s3rmbols could not be

discriminated by these two statistical measures, then the image with the

higher percentage of correct responses was selected. A minimum difference

between percentages correct was required to avoid basing the choice on spurious

differences. A minimum difference of five percent was required, since this

corresponds to approximately plus or minus two standard errors^ of the mean,

or an approximate 95 percent confidence interval.

If the two images still could not be discriminated, the next decision rule

involved correspondence with existing symbol standards. Conformance with these

standards appears useful once the understandability criteria are met. In particular, the ISO set (DIS 5864.3, 1978), which is also used for the DoT/UN

hazardous materials transport placards, appears to be a useful guide for hazardwarning symbols. These symbols already appear upon containers and trucks which

serve mining facilities. As a result, many miners are incidentally exposed to

them. Similar weight is given to the DoT (1979) set and the Treasury Board

^ The standard error for the percentage correct measure can be estimated by

using the normal approximation to the binomial curve. Based upon this relationship

,

the standard error of the proportion of items correct is estimated

by /NPQ/N (where N is the number of subjects per group, P is the proportion

of correct answers, and Q is the proportion of incorrect answers).

120
of Canada Federal Identity Program (1980) as miners may again be more likely to

be exposed to these symbols. The goal of an understandable set of symbols is

likely to be defeated if numerous different symbols are used for the same message. Consequently, if a symbol from existing standards meets the

understandability criterion, then extensive graphic redesign appears unwise.

Nevertheless, the graphics approach embodied in the DoT (AIGA, 1974, 1979)

symbols, an approach similar to that used by FMC (1978) and the Canadian

Treasury Board standard (1980) is finding wide use in the United States. As a result, weight was also given to this approach, particularly as its simplicity

may also come closer to meeting eventual legibility criteria.

The various decision rules used in selecting each symbol, its image content,

and referent message are given in table 30. Illustrations of the symbols

selected for each message are given in section 8 (Handbook).

Thus, the decision rules utilized are the following:

1) The symbol should meet the understandability criterion of 85 percent

correct identification and 5 percent or fewer critical confusions (oppositeto-correct answers).

2) There should be statistically significant differences between symbols - for frequency of correct answers, t-test for mean confidence rating for

correct answers, and the standard error of the mean as a supplement for

percentage correct.

3) There should be conformance with ISO (DoT/UN), Canadian or DoT S3nnbol

standards, with more weight given to ISO for hazard warning and more weight

given to the Canadian for personal protective gear.

4) There should be fewer than five percent critical confusions with an incorrect choice alternative.

5) There should be overall conformance of graphic imagery with other members

of the same set.

In six cases, the recommended image content differs from that given in Collins

et al., (1982). Because the Canadian set of symbols had not been issued at the

time this earlier study was done, its Personal Protective gear symbols consequently were not studied. The image content of the Canadian set is very similar

to the ISO set, except that the graphic approach is simpler and more in line

with the DoT (AICA, 1979) series of symbols. Similarly for Overhead Hazard,

Exit /Emergency Exit, and Trip, new symbols were included in the present study.

They were chosen to be: more relevant to mining in the first case; to include

symbols from a laboratory legibility study in the second case; and to depict

triping over an object in the third case. In each case, the "new" symbol performed better according to the decision rules outlined above. In two other

cases. Explosion and No Entry, results from the two studies did not coincide.

For Explosion, although miners performed better for both images, their

performance was markedly better (10 percent) for the ISO version - lending

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Table 30. Preliminary Selection of Images

Message Image Content Decision Rule

Hazard Warning

Flammable flame - ISO Binomial—does not meet criterion; ISO selected

Radiation 3 blades Does not meet criterion ISO standard; DoT/UN

Laser sunburst with streamer Does not meet criterion ISO standard; DoT/UN

Explosion exploding object Both symbols above criterion, no statistical

difference; hence, DoT/UN/ISO standard used

Electricity cord, person, zigzag X^, t both significant

Corrosion test tubes, drops in hand, bar t-test, binomial, significant

Poison skull and crossbones t-test significant

Forklift person and forklift truck both symbols above criterion, no statistical

difference, here use ISO symbol

Slip person falling backwards, surface X^, t-test significant

Fall person falling backwards, ledge t-test significant

Trip person falling forwards, object t-test, x^ significant

Overhead hammer, rock falling X^, t-test significant

Pinch hand and rollers above criterion

Hot Surface hand and radiating surface above criterion

Entanglement hand and gears X^ and t significant

Cut/Sever hand and sharp object binomial slgnflcant

Crush person and overhead object, arrow X^ significant

General warning exclamation point does not meet criterion

Sudden pressure release human torso, steam X^, t significant

Prohibition

No smoking circle, slash, lit cigarette exceeds criterion

No open flame circle, slash, lit match both meet criterion, no standard here

conforms with DoT

Do not touch circle, slash, hand X^ significant

Safety & Fire

Emergency

First aid cross alone X^ significant

Safety shower person in shower; simpler version needed for X^ and t-test significant

legibility

Eyewash head, drops and basin X^ significant

Fire Extinguisher fire extinguisher meets criterion; NFPA 178 Hose & Reel Connection hose and reel meets criterion; NFPA 178 Fire alarm call point no selection made neither meet criterion nor seem appropriate

Personal Protective Gear

Head hard hat on head both meet criterion, Canadian approach used

Eye glasses/goggles on head both meet criterion, Canadian approach used

Ear ear protection on head both meet criterion, Canadian approach used

Hand 2 gloves both meet criterion, ISO approach used because

of confusion with stop for 1 glove alone

Foot 1 shoe with laces X^, t significant

Respirator respirator on head X^, t significant

Egress Related

Emergency exit person running , open door X^, t significant

No exit person running, open door, circle, slash neither meets criterion; confusion w/exlsting

standards

No entrance person standing, circle, slash X^, t significant

Keep door open blue and white, open door, arrows away from wall X^ significant

Keep door closed blue and white, open door, arrows toward wall X^ significant

* Does not meet understandability criteria.

122
support to the idea that miners may well be more familar with explosive and

blasting hazards. For No Entry the miners also gave a higher percentage of

correct responses (93.8 vs 76.7 percent) to the "circle, slash, standing man"

approach. Furthermore, during the actual study, presentation of the "man with

big hand" image was often greeted with snickers and laughter—suggesting that

this image might not be taken seriously.

As noted earlier, several symbols which had not performed well with industrial

personnel continued to do poorly with miners. In particular, these included

Flammable, Radiation, Laser, General Warning, Fire Alarm Call Point, and No

Exit. The performance of Sudden Pressure Release imagery, which was not used

in the earlier study, could be improved perhaps by the inclusion of a bursting

hose. Corrosion, which barely met the criterion, appears to be a concept with

which some miners are unfamiliar. Various images for Flammable succeed in

communicating messages of fire successfully, but often with the idea that

"fire is permitted" or "is actually present." This may be an instance where

surround shape plays a role - people have become accustomed to seeing a circle

and slash for prohibition. When it is not present, they assume that no prohibition exists—hence, "fires permitted," an incorrect (double-negative) answer selected by 20 percent of the participants. Use of a specified surround shape

for hazard warning, such as the diamond, might lessen these confusions. Also,

a "permissive" surround shape, such as the green circle used in some Canadian

provinces (Dewar, 1976), might be appropriate in cases where an action is

permitted. For example, DoT (AIGA, 1979) recommends a circle with a cigarette,

but no slash, in those places where smoking is permitted. Whatever the reason,

the flammable hazard idea appears to be difficult to convey with existing

imagery.

In every study of safety S3nnbols conducted to date at the National Bureau of

Standards, symbols proposed for No Exit were poorly understood. The present

study is no exception. This appears to be a difficult message to communicate

with either words or symbols. The best approach might be to select a symbol

for Exit and combine it with the circle and slash - and then restrict its use

to those situations where a user might legitimately confuse an interior door

with an exit. Problems of the circle and slash obscuring the message, or simply being ignored, have also been noted by Dewar (1976) who recommended

using the positive approach whenever possible. It appears more useful to present users with positive information — go this way, this way out, exit here —

to guide their path, particularly during an emergency. Hence, development of an effective, legible Exit symbol might well be the best approach.

Finally, Fire Alarm Call Point is simply an unclear referent. In neither study

were symbols for this message at all effective. This referent, which is

intended to mean the place where an alarm is turned in, seems to be confused

with the alarm (or noise) itself. Since various combinations of the approaches - call point alone, sounder alone, and call point plus sounder - can be used, it

may be best to develop warning systems, procedures, and accompanying symbols,

on an individual mine basis. Certainly miners and industrial personnel do not

appear to discriminate between the various intended messages and do not

separate the idea of "call point" from that of "alarm".

123
In this section a set of symbols was recommended for use in mining applications.

To determine the effectiveness of these symbols an in-mine evaluation of symbol

signs at 2 mines was conducted. This evaluation will be presented in section

6. Suggestions for further graphic refinement aad additional research on legibility and conspicuity are given in sectiom 7 . A Handbook for using symbol

signs in mines is given in section 8.

124
6. IN-MINE SYMBOL SIGN EVALUATION

6.1 SELECTION OF SYMBOL SIGNS

The effectiveness of a subset of the "effective" symbols recommended in section

5.5 was evaluated during a 3-month in-mine evaluation at two sites in the

Eastern United States. One facility (LL) was an underground limestone mine,

currently undergoing renovation, while the other (EM) was an underground coal

mine and preparation plant. This latter site had participated in the initial

evaluation, (See section 4.)

Based on the results of the understandability and perceived hazardousness

evaluations, and discussions with the mine safety personnel, a set of 20 symbols

was selected for the in-mine evaluation. This set included messages for the

following categories: Hazard Warning, Personal Protective Gear, First Aid,

Fire Equipment Location, and Egress. Several sets of 19 12-in. by 12-in. signs

were then fabricated of impact-resistant plastic material with three holes in

the top and in the bottom, to facilitate ease of mounting.

Figure 45 presents the 20 symbol signs as fabricated, (The Exit symbol was fabricated in 2 directions of travel.) Only one symbol which was poorly

understood in the initial study was included in the in-mine evaluation. This

symbol. Flammable Hazard, was needed to indicate the location of certain com- bustible materials. The No Smoking symbol does not adequately convey this

message, although it effectively conveys the idea of no smoking.

Symbol surround shape and color were used to code the different message

categories. The hazard warning symbols were all shown within the diamond,

rather than the triangle currently suggested by the ISO TC 80 draft standard

(ISO, 1978), The diamond, in addition to being perceived in the initial study

as "most hazardous", also allows a greater area for the interior image, and is

consistent with the DoT (1979) practice. Otherwise, the surround shapes were

in accordance with the ISO recommendations. The recommendations of the ISO

draft (1978) and the ANSI Z53.1 (1979) standard were followed for the color

specifications. As a result, the hazard warning signs consisted of a black

image on a yellow surround, within a black diamond. Symbols for personal

protective gear were fabricated as white images on a solid blue disc. Safety

and exit messages consisted of white images on a solid green square, while

fire equipment messages consisted of white images on a solid red square.

Prohibition messages consisted of a black image on a white background with a red circle and diagonal slash. It should be noted that the symbols tested in

the initial study followed these guidelines, with the exception of the diamond

for hazard warning.

6.2 EVALUATION OF SYMBOL SIGN EFFECTIVENESS

6.2.1 Evaluation Procedures

Several different evaluations were performed at the two facilities to determine

the overall effectiveness of the symbols when installed as signs. This

evaluation included selection of relevant messages and symbols, determination

125
HAZARD WARMING SYMBOLS

Cnish Explosion Fall Electrical

PERSONAL PROTECTIVE GEAR

Hard Hat Safety Glasses Ear Protection Safety Shoes

SAPETY AND EGRESS

First Aid Fire Extinguisher

m

Exit Arrow (with Exit)

Mo Open Flaae Ho Saoklng No Admittance (Mo Entry)

Figure 45 . Symbols fabricated as signs for in-mine evaluation

126
of appropriate location, and assessment of visibility, durability, contrast,

vandalism, and theft. It also included further assessment of the understandability of the final set of 40 symbols recommended in section 5.5 at both

sites. In addition, an evaluation of the confusions between members of the

S3rmbol subset and the conspicuity of the symbols actually installed was made

for the LL site.

6.2.2 Evaluation of Understandability—Both Sites

A total of 99 people at the two sites participated in an evaluation of the

understandability of the final set of symbols. This set included some hazard

warning symbols within a diamond surround (see figure 45). This evaluation

was intended to determine if unexpected changes in understandability had

occurred for the final symbol set. The same multiple choice response form

used in the initial study was used, so that the results would be comparable

(see Appendix for form.)

At the LL site, 11 participants were shown the final set of 40 symbols. All

groups of participants at the LL site also completed the evaluation of the

perceived hazardousness of the set of six surround shapes for different interior images. This evaluation simply replicated the procedures from the initial

study, and was designed to determine whether any unexpected differences in

rated hazardousness arose at the LL site. (See section 4 for a full description of the procedure and rationale.)

Data from the initial evaluation for the EM site were presented in section 4.

The additional in-mine testing consisted of an evaluation of the final symbol

set, as tested at the LL site, using the multiple-choice procedure with 88

participants during weekly training sessions. The symbol signs had been

installed at the site during these sessions so that the miners should have

been familiarized with some of the symbol signs.

The data on symbol understandability are presented in table 31 . The percentage

of correct answers for each symbol is presented, along with mean confidence

rating data for the correct choice alternative from the multiple choice procedure. Visual inspection of the data in table 31 indicates that the majority

of S 3nnbols were well understood, with most symbols being correctly identified

by more than 90 percent of those participating.

Inspection of the percentage correct data revealed that only six symbols were

correctly identified by fewer than 80 percent of the participants. These

included: Flammable, Radiation, General Warning, Laser, Safety Shower, and

Fire Alarm Call Point. The most marked difference from the data collected in

the initial study was that the percentage correct for the final symbol set was higher for 23 of the 40 symbols studied, with perfect scores in 9 cases. The

confidence ratings were generally lower, however. The performance of only

one symbol — Flammable — was noticeably poorer (greater than 10 percent

lower) than in the initial study. Others which performed somewhat more poorly

(between 5 and 10 percent) included the redrawn Explosion symbol. General

Warning, Sever, Hearing Protection, and Safety Shower. The poorer performance

of the Explosion symbol was most likely attributable to its new configuration.

127
Table 31. Percentage Correct and Confidence Rating Data for Final

Symbol Set for Both Sites

Mean

Confidence

Rating

Correct

Symbol Correct N Response N % Correct Answer

Flammable 44 94 ** 46.8 3.58

Radiation 37 92 40.2 2.83

*Laser 23 74 31.1 2.24

*Explosion 71 83 ** 85.5 3.23

Electrical 99 99 100.0 4.72

Corrosion 91 99 91.9 4.69

Poison 96 98 97.9 4.75

Fork Lift Truck 98 98 100.0 4.83

Slip 98 99 ** 98.9 4.54

Fall 98 99 98.9 4.42

Overhead Hazard 99 99 100.0 4.58

*General Warning 36 68 ** 52.9 2.09

Trip 99 99 100.0 4.72

Pinch 99 99 100.0 4.49

Hot Surface 88 96 91.7 4.05

Crush 94 98 95.9 4.17

Sudden Pressure

Release 90 95 94.7 3.88

Sever 82 99 ** 82.8 4.32

Entanglement 84 95 ** 88.4 3.99

Do Not Touch 94 96 97.9 4.04

No Smoking 98 99 98.9 4.97

No Open Flame 99 99 100.0 4.89

Head Protection 96 98 97.9 4.48

Hearing Protection 89 97 ** 91.8 4.39

Eye Protection 95 98 96.9 4.57

Foot Protection 90 96 ** 93.8 4.21

Hand Protection 97 97 100.0 4.32

Respiratory

Protection 77 95 ** 81.0 3.93

First Aid 93 97 95.9 4.46

Safety Shower 78 99 ** 78.8 4.30

Eye Wash 83 91 91.2 3.65

Fire Extinguisher 99 99 100.0 4.83

Hose & Reel 98 99 98.9 4.77

Fire Alarm 53 98 60.2 3.18

Exit 96 96 100.0 4.20

Emergency Exit 79 94 ** 84.0 3.76

No Exit 85 97 87.6 3.95

Do Not Enter 93 94 98.9 4.10

Keep Door Open 82 89 ** 92.1 3.46

Keep Door Closed 85 93 91.4 3.66

* Symbols characterized by 10 or more participants failing to respond to any

choice alternative.

Symbols receiving a lower percentage of correct responses than in the

initial study.

128
Its increased similarity to the Laser symbol will be discussed in detail in

6.4.1. The poor performance for the Safety Shower symbol may have occurred

because such showers are rarely used at either site, so that this symbol was interpreted as indicating the location of the changing room. Although the

Flammable symbol was not well understood during the initial study, its even

poorer performance here is of concern. The only change in the configuration

from the initial study was the use of a diamond surround shape, rather than a triangle. This change did not decrease performance for the other hazard warning symbols, however. Some of the participants did suggest that this symbol

should be red to indicate emergency. Whatever the reason, the Flammable

Hazard symbol continues to be poorly understood, with many miners Interpreting

it as indicating that fire is permitted or present.

Nevertheless, the data given in table 31 confirm that the majority of the

symbol set was correctly identified. Because the symbol signs had been

installed at both sites during the understandability evaluation, this may have

resulted in slightly better performance than that obtained during the initial

study. In addition, the performance of the EM site had been somewhat above

the group mean for the initial testing, so that the Improvement in performance

seen for the final symbol set might represent the generally better performance

of this site, and not be applicable to all miners.

The data on the perceived hazardousness of surround shape were in general

agreement with those from the Phase I study. Table 32 presents these data. It

demonstrates that the diamond was always ranked as "most hazardous", while the

circle was generally ranked as the least hazardous. The data also indicate that

the triangle or the octagon was generally ranked as second-most hazardous.

These data confirm that the diamond is viewed as indicating the highest degree

of hazard for the various sites studied.

6.3 SYMBOL SIGN INSTALLATION

The majority of the symbol signs were installed by mine personnel during

September 1982. Tables 33 and 34 present the signs installed at that time and

their location at the two sites. Signs were generally mounted about 4-6 feet

( l-2m) above the ground, or directly above exit doors or entry ways. Where an equipment hazard was marked, such as Electrical or Entanglement, the sign was mounted as close to the hazard as possible, again preferably at eye level or within the normal line of sight.

6.3.1 Specific Signs at the LL Site

A number of unexpected problems arose during the mounting process at the LL

site. The rib walls generally proved to be both too crumbly and brittle to

mount the signs directly, so that they were mounted on nearby constructed

areas. This procedure was followed for the signs within the bulkhead rooms,

gas mixing stub area, fueling areas, fan-door entry-way, and in the shop. The

Exit signs, arrows, and No Entry (to the quarry area), however had to be sus- pended from the wire mesh located just below the roof by long wires. This

allowed them to be placed about 4-6 feet above the ground, while keeping them

out of the way of traffic within the facility. Unfortunately, they were not

129
Table 32. Ranking Data for Surround Shapes for Hazard Symbols - LL Site

Surround

Shape O o A o V N*

General Warning 14 15 15 17 24 20 5

Poison 32 51 45 49 68 49 14

Entanglement 36 49 47 36 59 49 13

Explosion 30 47 50 52 55 60 14

Surround 27 55 46 41 62 42 13

Sum 139 217 203 195 268 220 59

Mean Rank 2.36 3.68 3.44 3.30 4.34 3.73

Rank Order 1 4 3 2 6 5

* N represents the number of people who responded to each individual item
Table 33. Sign Location and Luminance Measurements — LL Site

Message Location Luminance-B Luminance-D Contrast Contrast (Lab)

First Aid^ Shop 27.8 fL 3.7 fL 0.87 0.86

Electrical^ Shop 14.1 0.9 0.94 0.90

Eye Prot.3 Shop/Grinder 25.0 3.7 0.85 0.90

Fire Exting^ Shop 27.7 7.0 0.75 0.76

Exitl In Mine 17.1 2.2 0.87* 0.84

Arrow! In Mine 13.8 0.9 0.93* 0.84

No Admit.

In Mine 15.4 5.5 0.64* 0.77

No Smoking^ Gas Stub B drift 16.3 3.5 0.78 0.76

Flammable^ Same 9.7 1.4 0.86 0.93

No Admit.

Ventilator 10.1 2.9 0.71* 0.77

Entanglement^ Air Tugger D 16.4 1.1 0.93 0.92

Extinguisher^ Bulkhead Rm D 3.0 1.0 0.67 0.76

First Aid! Same 17.8 2.1 0.88 0.86

No Smoking^ Outside fueling 56.1 13.7 0.76 0.76

Hard Hat^ Gate 43.7 5.2 0.88 0.90

Eye Prot.3 Gate 39.2 5.0 0.87 0.90

Safety Shoe^ Gate 39.1 4.4 0.89 0.87

These measurements were made by cap lamp and flashlight, and represent approximations

only, due to the difficulty in holding both light source and meter steady.

^ - White and Green - Colors apply to both table 33 and 34

^ - Yellow and Black

^ - White and Blue

^ - White and Red

^ - White, Red, and Black

131
Table 34. Sign Location and Luminance Measurements — EM Site

Message Location Luminancc-B Luminance -D Contrast Contrast

Exitl Training room 36.2 fL 8.4 fL 0.77 0.84

Arrowl Training room 60.7 14.9 0.75 0.84

Fire Ext ^ Interior room 14.4 3.3 0.77 0.76

Fire Ext.^ Entranceway 35.2 8.6 0.76 0.76

Eye Prot.3 Over grinder 37.1 5.0 0.87 0.90

Slip2 Over greaser 38.0 5.0 0.89 0.90

No Admit.Outside Warehouse 41.1 9.4 (13.9)** 0.77 (0.66) 0.77*

Flammable^ Outside Warehouse 33.5 2.7 0.92 0.93

No Smoking^ Outside Warehouse 56.8 12.2 0.78 0.76*

Hard Hat^ Outside Warehouse 58.7 10.1 0.83 0.90

Trip2 Inside Warehouse 17.8 2.5 (3.5)** 0.86 (0.80)** 0.92

No Admit.

5

Outside Warehouse 40.3 9.1 0.77 0.77*

Safety Shoes^ Prep Plant 7.4 1.6 0.78 0.87

Hard Hat^ Prep Plant 7.4 1.6 (4.6)** 0.78 (0.36) 0.90

Trip2 Prep Plant 3.7 0.3 0.92 0.92

Overhead^ Prep Plant 2.5 0.5 0.8 0.92

Overhead^ Outside P. Plant 59.5 15.4 0.74 0.92

Overhead^ Near Loading Area 37.4 7.8 (16.8)** 0.79 (0.55) 0.92

No Open Flame

5

Main Shaft Entry 3.8 0.8 0.79 0.76*

No Smoking^ Main Shaft Entry 4.8 1.1 0.77 0.76*

Contrast between white surface wd red circle and slash measured.

Contrast between image and dirty area of surface measured.

1 - White and Green - Colors apply to both table 33 and 34

2 - Yellow and Black

^ - White and Blue

^ - White and Red

5 - White, Red, and Black

132
as stationary as desirable. In the shop areas, signs were placed above the

location of the safety equipment to be marked, again just at eye level. Signs

for Personal Protective gear (Hard Hat, Safety Shoes, and Safety Glasses) were

secured with wire to the front gate at the entrance to the facility. A No

Smoking sign was placed just below the fuel tanks in an outside location with a Flammable Hazard sign to be added later. At the time of installation, all signs were clearly visible under cap illumination or daylight (exterior) illumination.

Figure 46 presents selected photographs of the various signs as installed.

6.3.2 Specific Signs at the EM Site

Signs were installed by the safety personnel in above-ground areas only. No

signs were installed underground because mine personnel felt that existing word

signs were adequate, and because relatively few signs were actually used there.

Symbol signs were mounted in the main shaft entrance area, training room, warehouse, heavy equipment repair area, processing plant, and refuse area. The

location of signs is given in table 34. Since all the signs were above ground,

these were no problems with mounting the signs to the mine walls or roof. Signs

were generally mounted directly to the room wall or surface about 4-6 feet above

the ground. Signs were also mounted directly above equipment hazards, as appropriate. See figure 47 which presents typical photographs of the signs after

installation. Unlike the LL site, the EM site had an existing word-sign system,

so that the symbol signs functioned as a supplement, to attract attention.

6.4 SIGN EVALUATION

The evaluation of the signs as installed used two different approaches. The

first approach was the visual and photographic inspection of the signs, discussions with safety personnel, and measurement of sign luminance for contrast

calculations. A short on-site test was also administered to personnel at the

LL site to assess any confusions between the symbols in the set and to

determine if the signs were conspicuous.

6.4.1 Evaluation of Physical Characteristics

At both sites, a number of procedures were used to evaluate the physical

performance of the signs during the 3-month installation period. These

included visual and photographic inspections of the signs, measurements of sign

luminance, calculations of sign contrast at the site and in the NBS laboratory,

and discussions with safety personnel.

The signs were inspected in October and December 1982. No problems of fading,

deterioration, or poor legibility were observed. In addition, no problems of

vandalism, theft or similar destruction were encountered. A few problems with

dust and dirt build-up were noted after 3 months, particularly in some areas

at the EM site, such as the preparation plant and refuse areas. Exterior

signs, which had been subjected to normal weathering and dust, appeared to be

in excellent shape, with no problems in legibility. Figure 47 reveals that

these signs were still legible at that time. Build-up of a static electric

charge on the plastic material of the signs may have caused fine dust particles

133
134
Figure 47 . Photographs of symbol signs as installed at the EM site

135
to adhere to the sign surface. The surface was easily cleanable , however. No

problems of fading, rust, or corrosion were encountered at either site, for

either exterior or interior signs.

During the December visit, a series of luminance measures was taken, from which

the contrast for each sign was calculated. These calculations and measurements

are also given in tables 33 and 34, along with comparison calculations from laboratory measurements at NBS on clean signs under fluorescent lighting. (Light sources at the mines included daylight, fluorescent, incandescent, and high

pressure sodium.) The calculations generally confirm that little or no reduction in contrast occurred during the testing period, except where coal dust had

accumulated on some of the EM signs. These signs were still legible, however.

It should be noted that some of the underground measurements at the LL site were only approximations due to the difficulty of making luminance measurements

by cap lamp, which is both unsteady and creates large specular reflections.

Cap illumination appeared to be an adequate illuminant for viewing underground

signs —although it did not provide general illumination to the space. Consequently, use of retroref lective materials would be advisable to maximize the

conspicuity of a sign (particularly as the cap lamp is moved around a space).

Discussions with mine personnel uncovered few problems. They did note, however,

the need for a mirror-image exit symbol for locations where the direction of

travel goes from left to right, as well as the right to left direction shown in

figure 46. Such signs were subsequently installed at the LL site. Safety personnel also noted the problem of dust build-up, which they attributed to static

electricity on the signs. In addition, they felt that underground signs should

be self-luminous or retroreflective to maximize detection. Personnel at the EM

site strongly felt that symbol-plus-word signs would be the most effective

approach for safety signs.

6.4.2 On-Site Evaluation Form—LL Site

The on-site evaluation test used at the LL site is presented in figure 48.

This form consisted of two portions — a confusion evaluation, and a conspicuity

evaluation. Twenty-two symbols which seemed most applicable to mining operations were depicted on this form, along with a list of short definitions (more

definitions than symbols were provided.) In the confusion portion, people

matched each symbol with a short definition. In the conspicuity portion, people

indicated if they had seen each of the 22 symbols, by rating them on a scale

of 1 to 5, where 1 meant that they had seen the S3rmbol and 5 that they had not.

The 22 symbols shown on the form deliberately included a number of symbols not

installed at the site, to see if people would claim to have seen them. Administered after the initial installation of symbol signs, the on-site evaluation

form provided an additional check on the effectiveness of the symbols in

communicating the desired message.

Table 35 presents confusion and conspicuity data for the 22 symbols including

the 12 actually installed at the time of testing at the LL site. Table 35

presents the confusion data first, in terms of the percentages of correct and

incorrect matches; and the conspicuity data second, in terms of mean rating

and standard deviation. For example, the symbol. Flammable , was correctly

136
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137

Figure

48.

On-site

evaluation

form
Table 35. Conf usion/Conspicuity Data

Confusion Consplculty

Message % Correct % Incorrect Mean Rating ST. Dev. N

A*-Corrosion** 37 78.4 M=10.8;I,T,C,X-2.7 4.15*** 1.46 20

B-Crush** 36 88.9 C=8.3;Z-2.8 4.21 1.28 19

C-Fall** 37 86.5 Z=8.1;J=5.4 4.16 1.31 19

D-Polson** 36 100 .0 3.58 1.76 19

E-Slip** 36 94.4 C,F-2.8 3.79 1.51 19

F-Ear Prot.** 37 86.5 G=10.8;E-2.7 3.16 1.69 19

G-Eye Prot. 37 100.0 2.40 1.77 20

H-Electrical 35 91.4 T=5.7;0=*2.8 3.58 1.73 19

I- Exit 37 89.2 V=8.1;U»2.7 2.84 1.74 19

J-Entangle 34 91.2 A=8.8 3.78 1.65 18

K-Explosion** 37 56.8 I^35.1;H=^5.4;Z-2.7 3.88 1.49 17

0-Flammable 36 88.9 *K=5.6;A,W»=2.8 2.74 1.62 19

Q-First Aid 36 91.7 I=5.6;T=2.8 1.94 1.35 17

R-Extinguisher 37 97.3 M=2.7 2.10 1.68 19

S-Head Prot. 36 97.2 (>»2.8 2.60 1.71 20

U-No Entry 37 89.2 V=ll.l 2.84 1.66 19

V-No Exit** 36 58.3 U=lb^7;Z,J»=8.3;T,R.b»2.8 4.33 1.10 18

W-No Flame 36 86.1 0,K-5.6;S=2.8 2.56 1.54 18

X-No Smoking 36 97.2 U=2.8 2.68 1.56 19

Y-Radiation** 34 88.2 T=5.9;P,Q»2.9 3.84 1.66 19

Z-Trip** 36 80.6 E=8.3;1^5.8;C,B»2.9 4.05 1.32 19

AA-Foot Prot. 34 91.2 E=5.9;B,L=2.9 2.57 1.73 21

P=Fire Extinguisher

T=Laser Hazard

M=Eyewash location

* Letter refers to letters which identified the symbol message on the matching form,

and which are given in the first colunn of this table.

** Refers to symbol signs not ii^stalled at the tioe of testing.

*** The rating scale used 1 to indicate that the sign bad bean seen; 5 that it had

not. Thus, a low rating means that the sign was probably seen.

refers to the number of people who completed each answer.

138
matched with definition "0" by 88.9 percent (of the 36 people who made the

match). It was incorrectly matched with "K" , Explosion, by 5.6 percent, and

with both "A", Corrosion, and "W”, No Open Flame, by 2.8 percent. Flammable

also received a mean rating of 2.74 with a standard deviation of 1.62, from the

19 people who completed the conspicuity portion.

Thirty-seven people completed the confusion portion of on-site evaluation form.

Their data indicated that the Explosion symbol was identified correctly by only

53 percent of those responding with major confusions arising with the message.

Laser. The high number of confusions seen for the Explosion symbol, not seen

in the initial understandabllity data is most likely due to an unintentional

change in the graphic configuration of this symbol during the sign fabrication

process. Figure 46 demonstrates that the reconfigured symbol now has a strong

horizontal directional component, not unlike the common Laser symbol. Furthermore, No Exit was identified correctly by only 58 percent of the participants

with major confusions arising with symbols for No Entry, Trip, and Entanglement.

Some of these confusions may have arisen because the extreme graphic complexity

of the No Exit symbol resulted in the loss of critical detail on the photocopied

test form. Such loss of detail could also occur as the result of dust or smoke

for an installed sign, and suggests that this symbol should be redrawn and

simplified. Confusion of No Exit with No Entry also arose in the initial data,

probably due to the graphic similarity of these two symbols (see section 4).

Furthermore, the No Exit concept does not appear to be a familiar one (Collins

and Lerner, 1982). The Corrosion symbol was identified correctly by only 78

percent of the participants, with confusions arising with Eyewash. Here subjects may have been indicating the action to take after encountering a corrosive

chemical.

The data on the conspicuity of the symbols , also contained in table 35 were somewhat less clear-cut. Only 19 people attempted to complete this form, with

many people indicating that they had not been underground or had not been in a position to see the signs. The conspicuity data indicated that the 12 signs

actually installed at the site received generally low numerical ratings, indicating that they had, in fact, been seen. (The rating scale instructions

called for the use of a 1 if the sign had been seen, 5 if it had not. Signs

actually installed at the site generally received mean ratings below 3.) In

particular, signs located in heavily traveled areas such as the main gate, the

shop and the underground entry typically received lower numerical ratings

(indicating that the signs were conspicuous.) Only the Entanglement and Electrical symbols, located in underground bulkhead rooms, received somewhat high

ratings. The Poison symbol, which was not installed at the site, received a high rating, despite its perfect score on the confusion portion of the form.

Although the limited number of people responding to this portion of the form

makes it difficult to draw firm statistical conclusions, the data do suggest

that those signs that were installed were seen and remembered.

In summary, the data suggest that the original Explosion symbol should be used,

rather than the modified version, and that the No Exit symbol should not be

used where it could be interpreted as No Entry. Despite the confusions for a few symbols, the data indicate strongly that the majority of the symbols were

well understood, and not confused with other symbols within the set of symbols

139
selected for the LL facility. In particular, symbols for Protective Gear,

General Safety, Exit, and Fire Equipment were well understood, as were most of

the Hazard Warning symbols. The conspicuity data further suggest that the

symbols were successful in attracting attention. In summary, the data given in

table 35 indicate that symbol signs installed at the LL site were generally

well understood and successful in attracting attention, thus fulfilling their

intended purpose.

6.4.3 Comments from the EM Evaluation

Comments during the evaluation of sign understandability at the EM site

(see 6.2) included a number of suggestions by the miners participating in the

testing. There was a feeling that some signs should be red to reflect danger

or high levels of hazard, but that the yellow sucessfully indicated caution.

Some miners felt that the First Aid and Exit signs should be red rather than

green because these represent emergency conditions. (Note that some code

recommendations are in conflict over the use of red and green for these situa-*

tions, as well). The miners generally felt that the prohibition circle and

slash were quite effective. As far as specific symbols were concerned, they

did not think the redrawn Explosion symbol was at all effective, along with the

General Warning symbol. They suggested that the Hard Hat should be redrawn to

resemble a miner's hard hat (with a cap-lamp connection) and not look like an "upside-down soup kettle". The Fire Alarm symbol was not considered to be

effective, nor was the alternate Exit symbol showing an arrow (see figure 37).

Many of the miners expressed a liking for the No Smoking and Entanglement

symbols, however. Some miners also suggested that a few carefully chosen words

could Increase the effectiveness of the symbol signs, an opinion shared by

their safety and training personnel.

6.5 GENERAL CONCLUSIONS FROM THE ON-SITE EVALUATION

In general, the overall good understandability of the symbol signs demonstrated

by the different evaluation procedures suggests that the symbols signs Installed

communicate reasonably effectively. The data suggest that the symbol signs were

generally well understood and conspicuous enough to be seen and remembered even

by visitors on tours through a site. These data indicate that the symbol signs

were effective in communicating Information and attracting attention. They were also effective in terms of physical parameters such as contrast, durability,

and general visibility.

Although the problems which occurred for individual symbols, such as Flammable

and Explosion, have already been discussed, two additional points can be made.

The first is that the rather small change made in the graphic configuration of

the Explosion symbol had a large effect upon its understandability. This

suggests that any new symbol introduced to a site, or any change to an existing

symbol should be evaluated with the miners at that site. Secondly, the problems

with the Flammable symbol might be lessened by the use of a surround shape

(such as diamond), which can indicate "hazard" as well as the circle and slash

indicate "prohibition". Use of a red background color to indicate danger,

emergency, or stop might also lessen confusions with "fire permitted".

140
Other problems occurred where the message was too complex for a single symbol

to represent it. This is particularly true for situations which vary over

time, represent more than one hazard or require both a prohibition and a hazard

message. Examples of such signs would include: Blasting in Progress, Flammable/

Explosive Area, or Blasting, No Admittance. Discussions with mine personnel

indicated that they felt that some combined word/symbol signs would be advisable, either as a training aid (while people learned the meaning of the symbols)

or as supplementary Information. In this format, the symbol would be used to

transmit information about the presence of a hazard, and to attract the user's

attention, while the word message would provide additional information. Such

signs have the potential of being very cluttered, which might obscure the

intended message, however. As a result, such signs require an evaluation of

the legibility of the overall sign layout to determine if the symbol is still

conspicuous and if the addition of words has cluttered the message beyond

recognition.

While the mounting problems have already been addressed, it should be noted

that simply affixing a sign to a mine wall is sometimes easier said than done.

Signs suspended by wires from the roof are subject to movement from ventilation

air or passing equipment. Yet, the signs could not be attached to the walls

because they crumbled. A stationary pole-mounted sign may be the best solution

if it can be kept out of the way of mobile equipment. Other problems occurred

when the space was not big enough for the sign, forcing it to be mounted below

or beside the hazard. Clearly, having signs in a variety of sizes is desirable,

as well as in a format with an adhesive backing for marking equipment hazards.

One side benefit of the symbol signs is that where word and symbol signs of

comparable size were displayed together, the symbol sign was visible at a greater distance (see figure 49 which shows this effect for the Personal Protective Gear and No Open Flame/No Smoking signs.) In this respect, the symbol

signs are more conspicuous than their word counterparts, and hence have the

possibility of receiving greater attention.

Thus, the testing program indicated that when chosen appropriately, symbol

signs are an effective means of communicating safety and hazard information.

Symbols for personal protective gear, safety equipment, fire equipment, prohibition and egress appear to be adequate in their present format. These symbols

are well understood and appear to be both legible and conspicuous. Thus, the

recommendations for supplementary word signs are most applicable to the hazardwarning signs. It is this class of messages for which changing conditions,

restrictions, and supplementary information may be needed on the sign. With

these exceptions, the symbol signs emerged as generally effective during the

on-site testing at both mine sites.

1

i 141
Figure 49. Photographs comparing symbol signs with adjacent word signs

142
7. RECOMMENDATIONS

7.1 SUGGESTIONS FOR IMPROVEMENT IN SYMBOLS

A number of recommendations can be made for improving symbol sign effectiveness,

based on data from the initial testing and the in-mlne evaluation. A major

needed Improvement to the set of symbols selected in 5.5 is the need for a consistent graphic style in both image content and surround shape. The latter

will be discussed in 7.2. Both the AIGA (1979) and Follls and Hammer (1979)

emphasized the need for an integrated, internally consistent graphic style

within a particular set of symbols. Needless to say, the symbols presented in , and Handbook were drawn from a variety of sources which depicted no single,

consistent graphic style. As a result the final selections require graphic

redesign and refinement to bring the set to a more consistent format. Even

the symbols used in the in-mlne testing require some graphic modification for

consistency and legibility (see Figure 45).

Based upon all the research to date, the following changes in image content can

be suggested. These changes also include suggestions given by individual miners

during the debriefing following part 1 of the present study (see appendix).

1) Where possible, follow the ISO/DoT/UN format for Hazard Warning symbols, but

simplify the imagery using fewer details and bolder graphics. 2) Try to include

a person with the hazard where possible. Where the hazard is more likely to be

initiated by only a part of the body, showing the hand with the hazard appears

effective. For this reason, the Electrical Hazard symbol might show the wire

with the hand rather than the whole body. However, for Slip, Trip and Fall,

the whole body is immediately affected, and hence is depicted. 3) For Sudden

Pressure Release, a hose or connection should be shown rupturing. 4) Both the

Safety Shower and Eyewash Images require some refinement. For safety shower,

the image should be greatly simplified with a more universal person. The handbook presents an initial attempt at simplification and reduced detail. For

Eyewash, the drops should be shown approaching the eye rather than the nose.

5) For Eye Protection, it might be more effective to show glasses rather than

an eye mask. The Respirator symbol also should use the same head as the other

symbols. 6) The Exit and No Exit symbols should be redrawn to provide consistency between the two without unnecessary detail. 7) The Keep Door Open/Closed

symbols should be made more massive, to resemble mine doors rather than ordinary

doors. 8) The original explosion symbol, showing an object blowing apart,

should be used. Other suggestions include increasing the legibility and graphic

consistency of the whole set.

7.2 SURROUND SHAPE AND COLOR

The results of part 2 of the present experiment indicate that the diamond

should be seriously considered as a plausible surround shape for hazard warnings. Therefore the hazard warning symbols should be redrawn with the diamond.

Use of the diamond is consistent with the MUTCD (DoT, 1979) and created no problems during the in-mlne testing. (The diamond is, however, inconsistent

with ISO and EEC recommendations.) Other results Indicate that the circle and

slash are reasonably well understood for prohibition. This convention appears

to be effective, provided that the interior image is not overly detailed. The

143
use of a square for safety and circle for protective gear did not elicit comment*

These shapes were Judged as less hazardous and therefore appear more appropriate

for safety Information as opposed to hazard warning messages. Furthermore,

unlike the diamond for hazard warning, there appears to be no reason not to follow existing ISO/Canadlan practice for the surround shape for the safety and

egress messages.

As far as color Is concerned, there appears to be agreement among miners that

red and yellow Indicate hazard. This Is In line with current ANSI Z35.1 (1979)

recommendations In which red Is used for danger and yellow for caution. As a result. It appears reasonable that color coding be used to Indicate the level

of hazard—with red reserved for those situations where there Is a high probability of personal Injury or death as well as extensive property damage, and

yellow used for those situations where a lesser degree of Injury or property

damage might result. Again, because existing color conventions do not appear

contradictory for the other categories of safety symbols, the ISO recommendations appear valid. These Include: solid green background and white Image for

safety Information, Including egress; red circle and slash, white background,

and black Image for prohibition; solid blue background and white Image for

personal protective gear; and solid red background with white Image for fire

fighting equipment. Color should not be used as the sole Indicator of a hazard/safety message due to the prevalence of red-green color deficiencies,

however.

7.3 CRITERIA FOR EVALUATING SYMBOL EFFECTIVENESS

Schlff (1980) commented that use of symbols that "naturally suggest their

referents or connotatlves correspond to their referents are Important considerations" (p. 340). Thus, a symbol Is likely to be more effective If It begins

with a reasonable degree of understanding or meaningfulness to the Intended

audience. As a result, throughout the present report, the major criterion for

determining the effectiveness of a symbol has been understandablllty. Understandablllty was arbitrarily defined as a certain percentage of correct answers

on a multiple choice response form. Clearly, this Is not the only criterion by

which effectiveness may be measured. Understandablllty Itself may be affected

by a number of factors. Context Is one of the most Important. Something that one expects to see is likely to be more understandable than an unexpected

object. Testing a symbol in context, as on a piece of machinery or near a potential hazard would certainly be expected to Increase its apparent understandability (Cahill, 1975). In some respects, testing a symbol out of context

can be considered a "worst case" approach. Symbols which perform well under

these conditions should continue to be effective when appropriately located.

Although use of a multiple choice procedure will Itself provide some context

through the various choice alternatives, performance could also be Impaired

because a miner did not understand, or agree with, the choices given for a symbol. Yet, numerous problems are encountered in scoring a definition-style

approach for assessing symbol comprehension. These were discussed by Collins

et al. (1982) and Lerner and Collins (1980a). This latter approach also assumes a certain verbal dexterity on the part of the participants. Finally,

It should be remembered that correct Identification of a symbol does not

necessarily mean that safe behavior will follow.

144
In addition to understandablllty , however, other criteria for assessing the

effectiveness of a given set of symbols should also be considered. First and

foremost is that of legibility. Mining is typically a dirty, dusty operation

in which low light levels and poor visibility can occur. As a result, any set

of safety symbols should be evaluated for legibility under degraded viewing

conditions, to maximize the likelihood of being seen under field conditions.

Other criteria include discriminability (or minimizing confusion between symbols

within a set), and behavior (or determining that the symbolic message results

in the appropriate actions). Determining the correct size of a symbol for both

good legibility and conspicuity is also critical.

Throughout the preceding paragraphs, understandablllty was treated as though it

were a clearly defined entity. Because it is not, a criterion of 85 percent

correct responses was set as an arbitrary cut-off value below which a symbol

could be said not to communicate. Similarly, a criterion of 5 percent critical

confusions was also suggested to eliminate those symbols for which substantial

misconceptions and inversions exist. These values were adopted from recommendations by standards groups and previous studies. Although they appear reasonable, the criteria are by necessity arbitrary and subject to discussion. For

example, adoption of more lenient or stringent criteria is certainly possible.

Conceivably, the level of hazard or potential danger to the user could also be

used as an index by which to set a criterion for selection. Symbols for more

dangerous situations could require a higher percentage correct, for example,

before they are used as the sole hazard-warning message. More lenient criteria

could be selected if training were provided, or additional verbal materieil

added, or if workers were familiarized with the symbols and the possible hazards.

Selection of an acceptable criterion cut-off appears to depend on the criticality of the message, as well as on opportunities for training or providing

additional verbal material.

Certainly for those symbols which do not meet the 85 percent correct criterion,

additional information for the user appears necessary. In addition, perhaps

the graphic rendition of such symbols should be changed, in the hopes that a more effective design might emerge. (Four of the seven symbols which did not

meet the understandablllty criterion are incorporated in existing standards

which could make any graphic change more difficult.)

7.4 DEVELOPMENT OF A SET OF RECCMMENDED SYMBOLS

One problem in the development of a set of symbolic safety messages is the size

and extent of the message set. The 40 messages studied in the present experiment represent common mining hazards and safety messages. Generic symbols

which depicted a class of potential hazards on safety messages were selected

for study. Many others exist, however. Furthermore, subsets of messages

exist within a single referent. For entanglement, for example, the symbol

could depict the most vulnerable body part (finger, hand, foot, leg, etc.) as well as different equipment types. While it appears more efficient to use a single symbol to communicate a generic hazard , instances may arise where more

specificity is desirable. However, the use of many, very specific images

depicting a set of limited messages may potentially confuse the user, who is

forced to distinguish between very similar Images. The end concern must always

145
be for the users and the effectiveness of the symbolic message In communicating

with them. A set of guidelines for the graphic development and user evaluation

of a proposed symbol at a given site might well be a good solution. Determining the effectiveness of every proposed message/ symbol combination was clearly

beyond the scope of the present study. Instead, the messages that appeared to

be most critical from the sources given earlier were studied In the hope that

this Information, albeit limited, would prove useful to those concerned with

mine safety symbols.

Despite the many problems In developing and evaluating a set of safety symbols

noted In earlier portions of this report, the present study successfully

Identified symbols for 34 safety messages which meet the understandablllty

criteria. The generally good agreement with the data obtained by Collins et

al, (1982) In their study of Industrial safety symbols suggests that a set of

symbols has been Identified which can successfully communicate safety

Information to a wide variety of Industrial and mining personnel.

The task Is not yet complete. Decisions remain about selecting the best

surround shape and color for hazard warning symbols, because of conflicts with

existing national and International standards. Some Images also require graphic modification as well as Integration Into a consistent set. The final set

should then be evaluated with an appropriate mining audience to ensure that

unexpected confusions do not arise, and that legibility problems are minimized. The Issue of legibility raises the Issue of size for symbols. Because

all guidelines for symbol size appear to be derived from letter legibility (see

section 8), a measure such as minimum critical detail or strokewldth should be

developed for specifying symbol size. Once these and other Issues have been

settled, then the overall effectiveness of the symbol within a word sign format,

such as the one recommended by ANSI Z35.1 (1972), should also be assessed to

determine overall consplculty and legibility. In addition, a study similar to

the one conducted by Laner and Sell (1960) which demonstrated that safety

posters effectively Increased safe behavior, should be conducted, A critical

research Issue In workplace signage Is that of determining If people notice and

follow the recommendations given by safety signs and symbols.

Nevertheless, the evaluation given In the preceedlng pages appears to allow the

selection of a reasonably effective set of hazard pictorials and safety Information symbols. The conclusions are still based on a limited sample of subjects,

but the good correlations with the earlier study, with a different group of

participants, provides at least some assurance that the symbols selected should

be reasonably understandable. The data obtained In the present study suggest

that the symbols discussed In section 5 can be used as the basis for developing

a final set of safety symbols not only for mines but for other Industrial

applications as well.

146
8. HANDBOOK FOR USING SYMBOL SIGNS IN MINES

8 . 1 INTRODUCTION

Because symbol signs can be perceived more rapidly and accurately than word

signs, the U.S. Department of Transportation (1979) uses them on the highways.

Symbols often require less space on a sign than a comparable word message, so that symbol signs can be larger, command more attention, and be more legible

under poor viewing conditions (Forbes, Gervais and Allen, 1963; King, 1975).

Finally, of course, symbols communicate information without the use of words,

a desirable attribute if the audience does not read English well. Because

symbols can communicate essential information rapidly and accurately, without

the use of words, they have many advantages for use in modern, mechanized

mining operations.

As a result, the National Bureau of Standards (NBS) undertook an evaluation of

the effectiveness of symbol signs in mines, under a contract supported by the

U.S. Bureau of Mines (JOll-3020). This research was designed to determine if

safety symbols were understood by miners and were effective as mine safety signs.

In this research, two sets of symbols for mine-safety and hazard-warning messages were evaluated with miners at 8 different mines in the United States.

Based on this evaluation, a set of mine safety symbols was developed. This

set of symbols was further evaluated for understandability during an in-mine

testing program at two mine sites in the Eastern United States. This testing

program evaluated confusions among the symbols and determined if the symbols

installed in the mine were seen and remembered. The In-mine testing program

also evaluated the physical parameters of the signs such as durability and

contrast, in addition to determining the opinions of mine-safety personnel

about symbol sign effectiveness.

Based upon the various evaluations of mine safety symbols, a number of

suggestions can be made for using symbol signs in mines. These suggestions are Intended to be helpful to the mine safety officer who is confronted with symbol

signs for the first time, and must decide when and how to use them. Because

not all aspects of sign use were evaluated by NBS, many of the suggestions are drawn from sign design handbooks, voluntary standards (both national and international), and the Manual of Uniform Traffic Control Devices (MUTCD) , of the

Department of Transportation (DoT, 1979). These suggestions are only guidelines, and are, in no sense, regulations or standards. Rather, they are Intended to serve as a framework for helping anyone who wishes to institute a symbol sign system at a mine site. They are intended to supplement the individual safety officer's own experience, when using a relatively new type of

sign at a mine site.

8.2 CURRENT STANDARDS FOR SYMBOL SIGNS

There is no standard, voluntary or regulatory, for using safety symbols in

workplaces or on products in the United States. The American National Standards Institute (ANSI) has a (voluntary) standard for word signs, the Z35.1

(1972) "Specifications for Accident Prevention Signs", and another for safety

colors, the Z53.1 (1979), "Safety Color Code for Marking Physical Hazards".

147
Both standards are now being revised by the Z535 committee on Safety Colors and

Signs. This committee is also drafting a standard for safety symbols. The

Occupational Safety and Health Administration regulation section 1910 (CFR 29,

1981) now specifies only the symbol for slow moving vehicles, having deleted

specific reference to the radiation and biohazard symbols. It does specify the

radiation symbol for use at construction sites in section 1926 (1981), however.

It also specifies the meaning of safety colors in line with the ANSI Z53 recom- mendations. The Mine Safety and Health Administration (HSHA) in CFR 30 (1980)

provides no specific recommendations for the use of symbols or safety colors,

although it does list situations which require signs.

As a result, because safety symbol signs are an innovative means of

communicating safety and hazard information, the following suggestions are given for their use at mine sites. Before providing specific suggestions for

using symbol signs at a mine site, it should be noted that the MUTCD (DoT, 1979)

is probably the best guidebook to use for signing mine haulageways and roads.

The MUTCD provides guidance on symbol signs, word signs, placement, size (as

a function of roadway speed), color, mounting procedures, and general information about road signs. These guidelines represent one of the best compilations

of traffic sign information, and are applicable for road signs on mine sites.

The suggestions given in the present Handbook apply to other, non-roadway,

areas on a site such as the main facilities, preparation plants, shops and

maintenance/repair areas, and permanent underground Installations.

The philosophy expressed by DoT in the MUTCD about the properties of effective

traffic control devices and signs is applicable to any system of safety signs.

The MUTCD notes that signs should meet the following five requirements:

Fulfill a definite need.

Command attention.

Communicate a clear and simply stated meaning.

Command the user's respect.

Provide adequate response time.

To meet these requirements, attention should be paid to factors such as: sign

design, placement, maintenance, and uniformity. In the following pages,

suggestions for using these factors are given as guidance for developing and

installing an in-mine safety symbol sign system.

8.3 SELECTION OF SYMBOL SIGNS

The initial decision about which situations require safety signs should be

based on the MSHA (1980) code requirements. Table 36 presents a list of MSHA

sign messages. Although MSHA does not require symbol signs for any of these

messages, the data obtained by the NBS-BoM symbol research suggests that at

least 11 of the messages could be effectively communicated by symbols. These

messages are marked in table 36 with an asterisk. In addition, the symbol

research suggested an additional 20-25 safety and hazard warning messages for

which symbol signs could also be used.

148
Table 36. Mine Safety Messages from the Code of Federal Regulations

General Message Relevant Citations

*No Entry,

Restricted Entry

55.3-

5, 55.6-103, 56.3-5, 57.6-103

57.3-

5, 57.5-28, 56.6-103, 57.20-20,

57.21-43, 75.303, 75.1711-3, 77.1303(g)

Hazard , Danger

(general)

55.20-11, 56.20, 57.20-11, 75.303

*No Smoking 55.4-2, 55.6-110, 55.8-5, 56.4-2,

56.6-110, 56.8-5, 57.4-2, 57.6-110,

57.8-5, 77.1102

*No Open Flame 55.4-2, 55.8-5, 56.4-2, 56.8-5, 57.4-2,

57.8-5, 77.1102

*Exploslve

55.6-

20(1), 55.6-43, 55.6-159(b),

56.6-

20(1), 56.6-43, 56.6-159(b),

57.6-

20(1), 57.6-29, 57.6-43, 57.6-159(b),

77.1301(c)(9), 77.1301(e), 77.1302(c)

Blasting Switch,

Safety Switch

77.1303(hh)

Burn Rate of Fuse 77.1303(v)

*Flammable Liquid 77.1103(a)

Compressed Gas 75.1106-3

Hazardous Material 55.16-4, 56.16-4, 57.16-4, 77.208(c)

*Toxlc Material 55.20-12, 56.20-12, 57.20-12

*Locatlon of Flre-Flghtlng

Equipment

55.4-23, 56.4-23, 57.4-23

Location of Self-Rescuer 75.1712-2(f), 75.1714-2(g) (2)

*Electrlcal Danger 55.12.21, 56.12-21, 57.12-21, 77.511

Electricity Lock-Out

55.12-

16, 55.12-17, 56.12-16, 56.12-17,

57.12-

16, 57.12-17, 75.511, 77.501

Electricity Disconnect 75.601, 75.809, 75.904, 77.600

Traffic Control 55.971, 56.971, 57.971, 77.1600(b)

* Symbols exist for these messages

149
Table 36. (Continued)

GENERAL MESSAGE RELEVANT CITATIONS

Traffic Control 55.971, 56.971, 57.971, 77.1600(b)

Train Crossing 55.9-59, 56.9-59, 57.9-59

Parked Vehicle Hazard 55.9-68, 56.9-68, 57.9-68, 77.1607(o)

Projection from Vehicle 55.9-49, 56.9-49, 57.9-49, 77.1607(t)

Men Working (In shaft)

55.19-

107, 56.19-107, 57.19-107,

55.19-

108, 56.19-108, 57.19-108

Emergency Stop (hoist) 55.19-13, 56.19-13, 57.19-13

Speed (hoist) 77.1908(k)

Maximum Load (hoist) 77.1402-2

Unsafe Equipment 55.9-73, 56.9-73, 57.9-73

*Fall Hazard 55.11-12, 56.11-12, 57.11-12

Obstruction 57.9-104

*Egress 57.11-51(b), 75.1704, 77.1101(c)

*Keep Door Open/Closed 55.21-57, 56.21-57, 57.21-57

Shelter Hole 57.9-111

Reduced Clearance 55.9-83, 56.9-83, 57.9-83, 75.1403-8(b)

,

77.1600(c), 77.1605(h)

Reduced Overhead Clearance 55.9-60, 56.9-60, 57.9-60, 55.11-10,

56.11-10, 57.11-10, 75.1403-10(c),

77.1600(c)

150
T

Table 37 categorizes these safety messages in 5 different categories: Hazard

Warning, Mandatory Action, Prohibition, Egress location, and Safety and Fire

: Equipment Location. These categories are typically communicated by the use of

both color and surround shape. These provide additional information about the

message. (For the handbook. Keep Door Open/ Closed is categorized as mandatory

action, as this message appears to be more a required action than egress-related.)

Hazard warning messages are used to warn of the presence of a hazard, and, if

possible, to indicate the consequences of encountering the hazard. This category Includes both danger and caution messages, such as "Danger, blasting in

progress", or "Caution, slippery floor ahead".

Mandatory action messages are used to indicate required actions. This category

primarily includes protective gear messages, such as "Wear Hard Hat", but could

also include other required actions, (such as "Keep door open/closed").

Prohibition messages indicate forbidden or prohibited actions, in other words,

something that must NOT be done. This category includes messages such as "No

Smoking in this area"

.

The egress category Includes messages related to Exit or passage through a door

or exitway. This category also Includes some prohibitory messages related to

exit, such as No Exit.

Safety and Fire Location messages indicate the location of safety and emergency

equipment. For example, a typical safety message might be "Eyewash located

here", while a fire equipment message might be "Fire extinguisher location".

Figure 50 presents a series of symbols suggested for messages within each of

these categories. (These symbols were found to be understood by a large number

of miners during the NBS research on mine safety symbols.)

8.4 FABRICATION OF THE SYMBOL SIGNS

The following suggestions for symbol sign configuration, color, and size are given for fabricating the signs. These suggestions assume that the sjmbols

have been determined to be effective with the miners at the site, through use

of an evaluation procedure such as that given in Section 8.5. A symbol con- sists of an interior image plus a surround shape. The images shown should be

in accordance, as closely as possible, with the images shown in figure 50. A

typical example is given in figure 51.

8.4.1 Color and Surround Shape

The following suggestions are given for using surround shape and color with

each of the message categories. The physical specifications for the symbol

sign colors should be those specified by ANSI Z53.1 (1979). This standard

provides the specifications for each color, in a format familiar to most sign

manufacturers, and is a good way to ensure that "red" is the correct "red".

The colors have been specified to yield the best possible color discrimination

for all people, including those with color vision deficiencies.

151
Table 37 . Categories of Safety Messages

Used in the Handbook

Forklift

Entanglement

Pinch, Cut/Sever

Overhead

Crush

Hot Surface

Hard Hat

Ear Protection

Keep Door Open/Closed

Do Not Touch

No Open Flame

SAFETY AND FIRE EQUIPMENT LOCATION

First Aid Safety Shower

Eye Wash Extinguisher

Fire Hose & Reel

EGRESS LOCATION

Exit No Entrance

No Exit

HAZARD WARNING

Corrosion

Poison

Explosion

Electrical

Slip, Trip, Fall

Sudden Pressure Release

MANDATORY ACTION

Safety Shoes

Safety Glasses

Hand Protection

PROHIBITION

No Smoking

152
HAZARD WARNING SYMBOLS

ELECTRICAL EXPLOSION FLAMMABLE

ENTANGLEMENT CRUSH POISON

Figure 50. Symbols suggested for safety messages

153
ADDITIONAL HAZARD WARNING SYMBOLS

CORROSION HOT SURFACE PINCH POINT




CUT/ SEVER

RADIATION

TO BE USED ONLY AFTER TRAINING OR WITH

SUPPLEMENTARY WORD MESSAGES

LASER

Figure 50. (continued)

154
PROHIBITION

NO SMOKING

KEEP DOOR OPEN

NO OPEN FLAME

EGRESS-LOCATION

DIRECTIONAL ARROW

NO ENTRY

KEEP DOOR CLOSED

DO NOT TOUCH
(MANDATORY ACTION)

EYE PROTECTION

SAFETY GLOVES

HARO HAT EAR PROTECTION

SAFETY SHOES

i

KEEP DOOR OPEN

SAFETY AND FIRE EQUIPMENT LOCATION

FIRST AID

FIRE EXTINGUISHER

EYEWASH SAFETY SHOWER

FIRE HOSE AND REEL

Figure 50. (continued)

156
Figure 51. Typical symbol configuration

157
The Z53 standard also provides the following meanings for safety colors. Red

means Danger or Stop; Yellow means Caution; Green means Safety and Location of

First Aid and Safety Equipment; Blue means Information; and Orange designates

dangerous parts of machines or energized equipment. Specifications are also

given for white, black, grey, purple, and brown, although these colors are not

given specific safety meanings.

If a safety officer Is relying on color to communicate a sense of urgency or danger, he/ she should be aware that this message can be lost under certain

energy-efficient light sources (which have become very popular due to their low

maintenance costs.) Under high Intensity discharge lights such as low pressure

sodium (LPS) high pressure sodium (HPS) , or clear mercury, red colors often

appear brown, thus eliminating color as a coding dimension. To avoid this

problem, the sign should be self-lllumlnated, the sign color should be modified,

or the lighting system should be changed. Using fluorescent colors which are correctly Identified under most light sources. Including LPS and HPS Is one way of modifying the color (Jerome, 1977; Glass, Howett, Lister, and Collins,

1983).

Four types of surround shape are suggested. The diamond Is suggested for

hazard-warning symbols. In accordance with the MUTCD recommendations. A square

(or rectangle) Is suggested for safety and fire equipment location symbols. A

circle Is suggested for mandatory or required actions, while a circle and slash

are suggested for prohibited actions. (These suggestions are In line with the

ISO (1978) recommendations for safety symbols, except for hazard-warning, which

Is In accordance with the MUTCD.)

Hazard warning symbols should be centered within a diamond shape. (If, for some reason, the symbols are used on equipment to be shipped outside the U.S.,

the hazard warning symbol should be shown within a triangular shape for

conformance with the 1977 EEC Directive).

Two background colors are suggested for use on hazard warning signs In

accordance with the recommendations of the ANSI Z35 standard (and suggestions

made by miners during the In-mine symbol evaluation) . The current ANSI standard Identifies two levels of hazard: Danger and Caution. Danger Is used when

the hazard is likely to result In death or severe Injury. Caution Is used If

the hazard Is likely to result In Injury or damage of a less serious nature.

If the hazard Is In the Danger category, a red backgound color should be used,

with a white Image and a thin white border around the background. See figure

52. If the hazard Is less serious, It Is In the Caution category. A yellow

background should be used with a black Image and thin black border. The use

of yellow as a cautionary color is widely recognized, and is recommended by

Dot (1979).

Prohibition symbols should consist of black Images on a white background,

centered within a red circle and slash. The slash should go from upper left to

lower right at a 45 degree angle (DoT, 1979). See figure 52.

158
HAZARD WARNING

DANGER

RED BORDER

WHITE BACKGROUND

WHITE AND RED IMAGE

CAUTION

PROHIBITION

Figure 52. Examples of symbol configuration for each category

159
MANDATORY

SOLID BLUE BACKGROUND

WHITE IMAGE

WHITE BORDER (OPTIONAL)

EGRESS

SOLID GREEN BACKGROUND

WHITE IMAGE (OR GREEN IMAGE ON WHITE

DOORWAY)

WHITE BORDER (OPTIONAL)

Note: No Exit should follow

requirements for Prohibition

SAFETY INFORMATION

FIRE INFORMATION

SOLID GREEN BACKGROUND

WHITE IMAGE

—WHITE BORDER (OPTIONAL)

SOLID RED BACKGROUND

_WHITE IMAGE —WHITE BORDER (OPTIONAL)

Figure 52. (Continued)

160
Mandatory action symbols should consist of white Images centered on a solid

blue circle or disc (ISO TC 80, 1978). See figure 52. (The Keep Door Open

symbol should reverse the colors.)

The Exit symbol should consist of a white Image on a square green background

similar to the general safety messages (AIGA, 1979). See figure 52. The No

Exit and No Entry symbols should follow the recommendations for the prohibition category, with a black Image on a white background surrounded by a red

circle and slash.

Symbols for safety equipment location should consist of a white Image centered

on a square green background. Thus, the First Aid cross should be a white

cross on a green square. (This avoids confusions with the "green cross for

safety" theme of the National Safety Council, or the "red cross" for the Red

Cross Society.) Symbols for fire emergency equipment should consist of a white image on a red background. See figure 52.

8.4.2 Sign Material

Sign material should be durable and easily cleaned. A variety of materials is

availible from sign manufacturers including steel, aluminum, porcelain, and

various plastics. Choice of sign material will depend on the environment in

which the sign will be located, and the desired sign life. In preparation and

processing plants, corrosion and rust become a significant factor, while in

other areas, dust and dirt must be considered (so that the sign must be easy to

clean). Some colors will also fade after exposure to the weather or corrosive

chemicals. Consultation with a sign manufacturer about the best material for a particular location is suggested.

The MUTCD recommends the use of reflectorized or illuminated signs so that the same colors and shape are seen by both day and night. Retroreflective materials

are also available from sign manufacturers. These materials reflect light on

the sign from headlights or cap lamps. They should be used underground or where night operations are in progress, because they increase the visibility of

the sign at night and under low lighting levels.

In addition, a schedule of periodic inspection and maintenance is necessary.

For the signs to be effective in getting people's attention and reminding them

of safe behaviors, the signs must be legible. Equipment should not be parked

or positioned so that it obscures any safety sign. Build-up of layers of dust

will also eliminate any benefit from using signs. In areas where corrosive

chemicals are used, signs may require frequent replacement, while signs in

dusty areas will require periodic cleaning. The purpose of the signs is to

get the miner's attention and communicate information; they must be clean and

in reasonable repair to do this

.

8.4.3 Size

The recommendations for sign legibility which are given in the MUTCD and ISO

standards were developed from, and apply primarily to, the visibility of letters

in words. They are designed to ensure that a letter or word be recognizable.

161
No similar research appears to exist for symbols, probably because of the

difficulty In specifying the critical detail (comparable to letter height or strokewldth) for symbols. As a result, It Is difficult to specify how large a symbol must be to be seen and be effective.

The MUTCD (DoT, 1979) was consulted for recommendations for highway symbols.

The MUTCD guidelines for symbol size assume a given sign size, typically a square, 18, 24, 30, or 36 Inches high. The longest dimension of the symbol Is

then specified as being 83.3 percent (Brooks, personal communication) of the

sign height. For a 24-ln. sign, the dimension would be 20-ln; and for a 30-ln.

sign, the dimension would be 25-ln. Using DoT's rule of thumb of 1-ln. of

letter height visible at 50 feet, the 18-ln. sign as a whole should be visible

at 900 feet. Assuming that the visibility of a symbol Is somewhat equivalent

to that of a letter of the same height, the 15-ln. symbol should be recognizable

at 700-750 feet and should be highly visible. Safety signs available from three

catalogues came In a range of 10 In. by 12 In.; 8 In. by 12 In.; 8 In. by 8 In.;

as well as 20 In. by 24 In.; 24 In. by 24 In.; 30 In. by 30 In. and larger.

Symbol signs tested In the In-mlne evaluation were 12 In. by 12 In. signs, a size which seemed to provide more- than- adequate legibility for the relatively

short viewing distances used. Unless a relatively small area Is Involved, the

sign should probably not be smaller than 8 In. square.

If the symbol Is used to Indicate a general hazard, then It must command

attention, and should probably be bigger than the minimum visibility requirements for letters would suggest. Suggestions for minimum symbol size developed

by the Treasury Board of Canada (1980), In agreement with Smith's (1979) recom- mendations, and ISO suggestions (1980b; 1982), are presented In table 38. It

should be noted that the suggestions given In those sources are based on research on letter, rather than symbol, visibility. In practice, the best

procedure may be to determine, simply by looking at the sign, that It Is legible at all reasonable viewing distances. Nevertheless, Smith (1979) suggests

that for good legibility, a letter should be about 0.84-ln. high to be viewed

at 10 feet and 2. 1-ln. high at 25 feet. The use of the DoT recommendations of

1-in. for every 50 feet of viewing distance (a recommendation within Smith's

values for 90 percent, but not 100 percent legibility) would result in even smaller letters. These various recommendations are Intended to ensure that a letter or word be recognizable 90 to 100 percent of the time. Certainly, the

symbol should never be smaller than these recommendations for letters, regardless of the application. The smaller details of many of the symbols will be

lost, however, even if these recommendations are followed. Again, the safety

officer's best Judgement is needed. He/she must first determine the distance

at which the sign will typically be seen, and size the symbol so that it is

clearly legible at this distance.

8.5 SIGN PLACEMENT

8.5.1 Sign Location

General recommendations call for symbols to be placed within the normal line

of sight with a variation of +/- 15 degrees (ISO, 1982). Thus a sign located

10 m (32.8 ft) from a viewer could be about 2.5 m (8.2 ft) above or below the

162
Table 38. Minimum Sizes Suggested for Symbols

by the Treasury Board of Canada*

Viewing Symbol

Distance Size

3-6 m 40 mm

6-9 m 60 mm

9-12 m 80 mm

12-15 m 100 mm

15-18 m 120 mm

18-24 m 160 mm

24-30 m 200 mm

30-36 m 240 mm

36-48 m 320 mm

48-60 m 400 mm

60-72 m 480 mm

72-90 m 600 mm

Note: The values are based on viewing under good light conditions and

viewing angles which do not exceed 10 degrees.

* The values are given by the Treasury Board of Canada standard ( 1980) , and

are not based on research performed by NBS. They are given only as a guide

for absolute minimum symbol size.

163
normal line of sight. The line of sight depends, of course, on whether the

person is seated or standing, in a mine-haulage truck or shuttle car. Signs

located more than 30 degrees above the line of sight are very unlikely to be seen (Follis and Hammer, 1979). The recommendations mean that a sign should

probably be located about 5 to 7 feet from the ground, unless extremes of

haulage vehicles are operating in the area. In addition, these suggestions do

not apply if the area is sprayed with chemicals to reduce dust. Signs should

then be mounted above the sprayed area so that they can remain legible.

Any sign such as the Exit symbol which shows obvious directional characteristics

should be mounted so that its direction is appropriate. The Exit symbol should

generally be used with an arrow, to reinforce the direction of travel.

The location of the sign in relation to the hazard or safety action is also

critical. The nature of the message on the safety sign should determine its

placement. The DoT MUTCD recommends placing prohibition or mandatory action

signs at the place where the recommended action is to occur. Hazard warning

signs, however, should be placed some distance before the hazard to warn users

that they are approaching a hazardous situation so that they can take appropriate action (Treasury Board of Canada, 1980). The DoT manual suggests distances of 250 feet for low-speed zones, and 1500 feet for high-speed highways.

While these distances are probably too long for many mining applications,

particularly those within buildings, placing of the sign some distance before

the hazard is encountered appears wise. This would allow the user time to

avoid the hazard and take proper precautions.

Thus for most mining situations, the sign should be visible before the hazard

is encountered to allow people to react properly. Equipment hazards, however,

should probably be indicated on the equipment itself. (Most equipment is cur- rently shipped by the manufacturer with warning labels already in place.) A

number of guidelines for labels and symbols for product safety have been

published, including the FMC (1978) and Westinghouse (1981) handbooks. Their

recommendations are quite useful for marking or labeling possible hazards on equipment which does not already have warning labels.

Signs for prohibited actions, such as No Smoking, should be carefully placed

only in the areas for which the prohibition applies. Similarly, mandatory

action signs, such as Hard Hat Required, should be used only where the restriction applies. Thus, ear protectors are typically required only in certain

designated high noise areas, not a whole site (unlike safety shoes).

A number of different approaches may be selected to mark a hazardous situation.

Table 39 presents signs that could be used to indicate the presence of a corrosive chemical. The sign may warn of a hazard, indicate the consequences of the

hazard, require protective gear, prohibit touching the hazard, or indicate

first aid measures. The safety officer should determine which sign approach

best fits the particular situation. More than one symbol/sign may be used

depending on the desired safe behavior.

164
Table 39. Different Symbolic Information for a Single Hazard

HAZARDiCORROSION

DESCRIPTIVE

CONSEQUENCES

PROHIBITION

165
8.5.2 Number of Signs

It is Important that the safety officer exercise his/her best Judgement In

using signs. Overslgnlng can be as harmful as undersigning, because the Important messages may be lost In general visual clutter. Thus, the MUTCD (DoT,

1979, p. 2, A. 3) noted that "care should be taken not to Install too many signs.

A conservative use of regulatory and warning signs Is recommended as these

signs. If used to excess, tend to lose their effectiveness." The Treasury

Board of Canada (1980) commented that "the number of symbols placed in any one facility should be strictly limited to those that are absolutely necessary.

This principle increases the effectiveness of the symbols displayed and prevents visual confusion" (p. 18). These cautionary statements are intended to

warn against a common tendency to mark everything in sight and thus lose the

attention-getting value of the safety sign. The safety officer should only

use signs for situations where the likelihood of injury, particularly serious

injury, is great, or where certain behaviors must or must not occur.

8.6 SYMBOL EVALUATION—SUGGESTED PROCEDURES

The symbols presented in figure 50 were evaluated for understandablllty with

as many as 360 miners from 11 different sites in the U.S. While this represents a reasonably large number of people, it certainly does not represent all

possible miners. Since many of these symbols are new, they may be unfamiliar

to at least some miners at a site. As a result, it is suggested that the

understandablllty of the symbols be determined for miners at a site, before

symbol signs are used there. A good mechanism for determining symbol

understandablllty could be a short test given during the safety or training

session.

While there are many ways of determining the understandablllty of a set of

symbols, two testing procedures can be suggested. In the first procedure,

miners are asked to define the meaning of the symbols. In the definition

procedure, the miners are shown slides or reproductions of the symbols. Each

Individual miner is asked to write down a short definition of no more than 10

words of the meaning of the symbol. (This procedure should take no more than

one-half hour for the symbols shown in figure 50.) After collecting all the

answer sheets, the safety/ training officer should then discuss the meaning of

each symbol, and note any problems that seem to arise. The officer should

then score the answers as right or wrong. If more than 15 percent of the

miners get the answer wrong for a particular symbol, then the meaning of the

symbol should be discussed further at the next meeting. If this symbol is used

on a sign, it should be accompanied by a short, clear explanatory word message.

The second procedure is suggested as an alternative method, if the time for

scoring the definitions is likely to be a problem. (Scoring problems can arise

because of difficulties in reading handwriting, and in being certain of what a person meant by a particular answer. Yet, the definition procedure allows the

identification of many possible wrong answers that might arise for a particular

symbol. As such, it provides more information than the matching procedure,

although is more time-consuming.) In the matching procedure, a form such as that given in table 40 could be used. This form contains all the symbols

166
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167
given In figure 50. The miners are asked to match each symbol with one (and

only one) of the short definitions given at the right. There are more definitions than symbols so that the process of elimination cannot be used to make

matches. The definitions deliberately Include some common confusions that have

arisen In previous testing, such as Fire Permitted for the Flammable Hazard

symbol (as well as the correct answer).

Again, the miners are asked to complete the form Individually, without talking

to each other, and hand It In. As In the first method, the correct answers for

each symbol are then discussed, and any problems noted. If more than 15 percent of the answers for a particular symbol are wrong, then further training

and the use of supplementary word signs are Indicated. Periodic retesting Is

a good Idea, particularly If there Is large turnover In the workforce. If a miner cannot read or write English, these various evaluation procedures are Inappropriate. The training officer might conduct oral evaluation sessions, by

asking each miner. Individually, to explain what each symbol means. Additional

training or multl-llngual signs may also be Indicated.

8.7 ADDITION OF WORD MESSAGES

Symbol signs can be used to attract attention and communicate Information

rapidly. There are some situations, particularly hazard situations, for which

word signs may be more appropriate, or for which both symbol and word signs

should be used. Additional word messages may be particularly useful In providing Information about actions to take In response to specific hazards or In

defining the extent of the hazard. The In-mlne symbol sign evaluation suggested that the other categories of symbols—prohibited action, mandatory

action, safety and fire equipment location, and egress—may be somewhat less

likely to require additional explanatory Information.

If word messages are used, they should be short and to the point. Follls and

Hammer (1979) suggest that word messages should be as short as possible so that

they can be read quickly and mean the same thing to all viewers. Thus the word

"Stop" Is used for highways, rather than "All drivers must come to a full stop,

before proceeding through the upcoming Intersection" , or some similarly lengthy

statement. The word message should communicate Information such as the probable consequences of the hazard, how to avoid the hazard, or the duration of a restriction. Examples might Include; the Flammable symbol with the phrase

"combustible materials In area"; the Entanglement symbol with the phrase "keep

fingers away from moving parts"; the Ear Protection symbol with the phrase "ear

protection required for exposures greater than 1 hour". The symbol Is used to

get the user's attention and communicate the kind of hazard or action, while

the word phrase explains what to do or what happens If the hazard Is Ignored.

In addition, word messages should be used for symbol signs which are poorly

understood by miners at the site. Examples of likely candidates Include:

Radiation, Laser, and Flammable. The MUTCD, for example, recommends the use of

supplementary word messages for symbols which are not well understood for a period of at least three years after Initial Installation. When symbols are Initially used at a site, use of an accompanying word message to facilitate

learning the symbols may also be a valid recommendation.

168
It is Important, however, to avoid lengthy word messages. The American Hospital

Association (1979) recommends no more than 26 characters per line, and no more

than 16 words on a sign. The FMC manual (1978) recommends a format in which

only 19 characters are used per line. It suggests further that messages be

limited to no more than 3 to 5 lines of type. Although such recommendations

have not been researched for their impact on legibility, they do represent the

best judgement of a number of sign designers. Long messages simply cannot be

read in the time necessary to react to the sign and avoid the hazard or perform

the required action.

8.8 GENERAL RECOMMENDATIONS

Table 41 summarizes a number of the general suggestions presented in this

Handbook for using symbol signs at mine sites. These suggestions are intended

to be helpful to the safety officer who wishes to use symbols and signs to

communicate safety information. They provide general guidelines for selecting

and locating safety symbol signs when combined with the symbols given in

figure 50.

In conclusion, the Department of Transportation uses symbols on the highways

because they communicate rapidly and accurately. Words are used only as a supplementary, training device or to provide directional guidance. The same approach appears valid for mines sites, because, when chosen appropriately,

symbols can communicate safety and hazard Information effectively. The

preceedlng sections have presented three phases of research on symbol signs

which demonstrate the general feasibility of using symbol signs at mine sites.

The handbook has presented some general considerations and guidelines for

actually installing these symbol signs.

169
Table 41. General Suggestions for Using Safety Symbols at Mine Sites

Use DoT "Manual of Uniform Traffic Control Devices" for mine road signs.

Use symbol signs to attract attention and communicate Information rapidly.

Avoid overslgnlng—use signs to Indicate the Important safety messages.

Be sure that background color and surround shape correspond to message

category:

Hazard Warning—Danger—Red—Diamond Surround

Caution—Yellow—Diamond Surround

Mandatory Action—Blue—Circle (Disk) Surround

Prohibition—Red—Circle and Slash Surround

Egress—Green—Square (Rectangle) Surround

Equipment Location—Safety—Green—Square (Rectangle) Surround

Fire—Red—Square (Rectangle) Surround

Use reflective materials for underground and night operations.

Locate warning signs before the hazard and all other signs as close to

the desired action as possible.

Be sure that signs are legible at Intended viewing distances.

Place signs within normal llne-of-slght.

Be sure that directional signs agree with actual direction of travel.

Institute regular sign maintenance and replacement program.

Evaluate symbol understandablllty with miners—Provide supplemental training

or word messages If necessary.

Keep word messages short and to the point.
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171
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!

i
57. Laner, S. and Sell, R. G., An Experiment on the Effect of Specially

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175
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Report #28, July 1981.
Yellow Jackets* Reviewed

1. Mantrip accldent/injuries - January 1978 - January 1979

2. Electrical Injuries in coal - 1974-79

3. Electrical fatalities at M/NM mines - 1972 - August 1977

4. Back injuries M/NM 1977-1970

6. Pinch point Injuries M/NM 1978 - June 1979

7. Handtool injuries M/NM - 1977-1979

8. Conveyor injuries M/NM - 1975-1976

9. Slusher accidents M/NM 1975-1977

10. Machinery accidents M/NM 1975 - September 1976

11. Near fatal accidents M/NM 1975-1976

12. Forecasts of fatality rates, conditional totals 1981-1985

13. Surface fatalities M/NM 1972-1975

14. Injury comparison - surface mlne/NM, S & G 1978 - November 1979

15. Truck haulage related fatalities surface coal - 1978-1976

16. Injury hazard comparison in different coal seam heights

17. Surface coal mine Injury experience - key to accident prevention

18. Fall or rib, roof, face accidents - underground coal

19. Criteria for selecting mines for special attention

* Publications of the HSAC Branch of MSHA

177
APPENDIX A. MINERS' COMMENTS DURING SYMBOL DEBRIEFING

Forklif t"perf«r th« ona showing the men In the forklift*~-forkllf t with men

•howe operetlonel unlt‘»the other could meen perk forklift here

Safety Shower—-men In shower Is better; more realistic; more abstract symbol

Is no good; looks like a sprinkler system

Corrosion—more abstract symbol Is not good; ISO symbol shows two things

(hand and metal); ISO symbol shows corrosion to metals as well

as hand

Exit—Arrows and squares take too long to figure out; requires thought; It

looks like a dead end; could mean "creep that way"; looks like a football field

Flammable—-confusion: because circle, slash end flame mean "no fire",

therefore flame alone must mean "fire"; could mean fire permitted;

need for a symbol to Indicate permission; perhaps use person and

flames to Indicate fire hazard

No Smoking—like the use of circle end slash to meen "no"

Fire alarm—sounder or horn better for fire alarm; bell no good; both look

like "noise hazard"

Ear protection—protectors on head better; more defined; protectors by

themselves require you to stop and think; look like an arch without

the head

Entanglement—hand In gears good—many groans when slide shown

Electricity—ISO symbol means lighting strike here; man and electricity good

Sudden pressure release—head with explosion (image 2) looks like welding;

like and arc; guy looks like he's wearing a welding mask; image 1 looks like flash burns, boiling water, may indicate steam release;

really needs pipe or hose to show rupture and steam escaping

Hard hat—hat by itself doesn't look like hard hat, looks like turtle, or upside-down soup kettle; hat on head looks like military hat—perhaps

show attachment for cap lamp

Cut/ Sever—foot image perhaps too drastic for the message "cut"

Door open—do not like

Overhead load—rocks and hammer better for underground mines or shop or construction—hammer gives idea of falling—crane means hoisting

Safety gloves—gloves with cuffs can cause problems in underground mines

178
Hot Surface—plate and flames should be red—need to indicate radiant, not

direct heat; need to show hand with flat palm (looks like guy is

something up)

Pinch Point—graphic—get attention

No Exit—"X" over door is not good as "X" is the word "exit"—the other

symbol is vague and unclear

Fall from elevation—backward fall provides idea of height

Crush—hand crush shows damage; whole body can also indicate low clearance

No open flame—don't set fires; match better, more universal, flame looks

like campfire

Safety glasses—glasses on man look like both safety glasses and goggles

General Warning—do not like—seems dumb—baseball field ahead—does not

make sense—poor

Respirator—ISO image perhaps better for chemical processing—image 2 better,

looks more like what is worn—is not a whole face piece—perhaps make

smaller

Poison—skull and crossbones better; more familiar—has been used for years

the other is better for bad or polluted atmosphere;

Explosion—ISO image—like fragments—idea that something has blown-up perhaps

need bomb with fuse—the other explosion symbol is better

Slip—legs alone looks like debris, upset can of oil

First Aid—green cross for safety—red for red cross

Trip—could be confused with running—perhaps show hard hat falling off—man

and object better, indicates message—perhaps show foot being caught

Fire Extinguisher—change nozzle

Emergency Exit—man and flame—run fast from fire—two tone man—disappearing

man, theft. Integrated schools

Do Not Touch—make slash over finger narrower—looks like electrical emergency

button or high pressure valve; circle and slash works well

Eyewash—head and drops is better—perhaps add drops on face

Safety shoes—ISO (two shoes) image is too delicate, need laces to look like

boots, dumb, like dress boots or rubber boots; Canadian symbol—like

eyelets, but show safety, steel toe

179
U.l. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (Sm Inetruetlone)

T PUBLICATION OR'

REPORT NO.

NBSIR 83-2732

2. Parformlng Organ. Raport No. 1. Publication Data

June 1983

4. TITLE AND SUBTITLE

Use of Hazard Pictorials /Symbols In the Minerals Industry

5. AUTHOR(S)

Belinda Lowenhaupt Collins

6. PERFORMING ORGANIZATION (If Joint or other than NflS, eee Inetruetlone)

NATIONAL BUREAU OP STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No. J0113020

9.

SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESi (itraat. City, State, HlP)

U.S. Bureau of Mines

Columbia Plaza

2401 E Street, N.W.

Washington, D.C. 20241

I. T/pa of Raport & Parlod Covarad

10. NBSIR 1/81—1/83

SUPPLEMENTARY NOTES

Documant daicribaa a computar protram; SF»I85, FIPS Softwara Summary, la attachad.

11.

ABSTRACT (A 200-word or leei factual eummary of molt elgnlfleant Information. If document Includei a elgnlflcant

bibliography or literature eurvey, mention It here)

This report documents a roultl^phase research effort on the evaluation of the effectiveness of safety symbols and hazard pictorials for use In mining and milling

operations. In the first phase, applicable codes and standards were reviewed, along

with documentation of typical mining hazards, to determine relevant safety messages.

In the second phase, site visits were made to eight mine sites to document existing

sign practice and common mining hazards. In the third phase, the effectiveness of

two sets of symbols for 40 different safety messages was evaluated with 267 miners

from ten sites at disparate geographical locations. This evaluation also Included an assessment of the effectiveness of six different symbol surround shapes and colors.

Symbols which were most effective were those which depicted both the person and the

hazard or protective gear, and which were more representational rather than highly

abstract. Use of a diamond to Indicate hazard-warning Is also recommended. Based

upon this research, a set of 40 symbols are suggested for further graphic refinement,

additional evaluation, and eventtaal use. A subject of 20 of these symbols was selected for in-mine evaluation at two mine sites. This evaluation determined that

the symbol signs were generally well-understood, conspicuous, durable, and legible.

A handbook which provides suggestions for using symbol signs at mine sites concludes

the report.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons)

communication; hazard; mining; pictogram; safety; signs; standards; symbols; visual

alerting; warnings

13. AVAILABILITY

Unlimited For Official Distribution. Do Not Release to NTIS

I I Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

20402.

[^3] Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

/fJ

1$. Price

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