NAT'L INST. OF STAND & TECH

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»IR 83-2675

«ii (Evaluation of Exit Symbol

Visibility

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Washington, DC 20234

April 1983

Final Report

U S DEPARTMENT OF COMMERCE

NATIONA, BUREAU OF STANDARDS

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NBSIR 83-2675

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'4.'<r to/\y 2 1983

AN EVALUATION OF EXIT SYMBOL

VISIBILITY

Belinda L. Collins

Neil D. Lerner

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Washington, DC 20234

April 1983

Final Report

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

NATIONAL BUREAU OF STANDARDS. Ernest Ambler. Director
*-
ABSTRACT

The performance of exit symbols was assessed in a laboratory experiment using

viewing conditions degraded to resemble smoke. Research participants were presented with color slides showing symbol signs designed to be used in

buildings. For each slide the participant indicated if the symbol conveyed

the message of "exit". A total of 108 symbol slides were used, of which 18 were exit symbols. Each of the 42 participants were familiarized with a random

set of 9 of the 18 exit symbols, prior to data collection. During the experiment, the symbol slides were presented under three levels of viewing difficulty.

In general, errors increased as the viewing conditions became more degraded

but the increase in errors became much more severe for some symbols than others.

Fewer errors were made for some of the symbols that had been familiarized. The

data suggested that increased errors under degraded viewing conditions were related to graphic features of the symbols. A number of specific symbol features that influence exit symbol effectiveness were identified along with

features of non-exit symbols that produce confusions. Finally, recommendations

for exit symbol design are presented that may lessen egress-related confusions

during emergency evacuation.

iii
TABLE OF CONTENTS

Page

1. INTRODUCTION 1

1.1 Understandability Considerations 1 1.2 Visibility Considerations 4

1.3 Visibility: Methodological Concerns 5

2. EXPERIMENTAL APPROACH 8

3. METHOD 11

3.1 Subjects 11

3.2 Symbols 11

3.3 Symbol Lists 11

3.4 Apparatus 11

3.5 Sequences of Lists and Viewing Conditions 13

3.6 Procedure 13

4. RESULTS AND DISCUSSION 15

4.1 Exit Symbol Data - Overview 15

4.2 Viewing Conditions 15

4.3 Familiarity 19

4.4 Features of Exit Symbols Related to Performance 21

4.4.1 Filled Versus Outline Figures 21

4.4.2 Direction of Figure-Ground Contrast 21

4.4.3 Color 22

4.4.4 Surround Shape 22

4.4.5 Relationship of Elements and Figure-Ground

Contrast 22

4.4.6 Specific Pictorial Elements 23

4.5 Foil Symbols 24

4.5.1 Intended Messages 24

4.5.2 Features of Foil Symbols Related to Exit Message

Confusions 29

4.6 Summary - Symbol Features Related to the Successful

Exit Message 32

4.7 Comparison with Other Symbol Understandability Evaluations ... 32

5. CONCLUSIONS 35

6. REFERENCES 38

APPENDICES

A - Foil Symbols 41

B - Instructions to Subjects 47

iv
LIST OF FIGURES

Page

Figure 1. Exit symbols proposed for use 2

Figure 2. Exit symbols tested in the present experiment 12

% Figure 3. Percentage of errors as a function of viewing condition .... 17&18

Figure 4. Japanese exit symbols in use 36

LIST OF TABLES

Page

Table 1. Correlation of Symbol Performance Under Multiple Viewing

Conditions 7

Table 2. Percentage of Errors for Each Exit Symbol and Viewing

Condition 16

Table 3. Percentage of Times Each Foil Symbol is Incorrectly

Identified as Exit 25

Table 4. Foil Symbols with More Than 10 Percent Errors 26

Table 5. Percent Errors (Difficult Viewing Condition) for Symbols

with Different Surround Shapes 30

Table 6. Supplementary Data on the Understandability of Selected

Exit Symbols 33

v

1. INTRODUCTION

Systems of pictorial signs are increasingly used to replace or supplement

traditional written messages. These pictorial signs have a number of advantages in addition to the obvious virtue of communicating to the foreign speaking or functionally illiterate (Collins, 1982). In many public, industrial,

and transportation facilities, messages related to egress such as "exit” and

"no exit" provide the most fundamental information for public safety. Nonetheless, there is little agreement on how information regarding exits should be

graphically portrayed or symbolized. Many symbolic versions of the "exit"

message have been developed, including efforts by various international and

national standards groups and government agencies. Yet in only a few cases has there been a formal evaluation of the effectiveness of various individual

symbols. Furthermore, the increasingly wide variety of images used to convey

information symbolically also contributes to confusion. Figure 1 shows a few

proposed exit symbols; some further examples may be found in Lerner (1981).

The diversity of graphic approaches illustrates the lack of common agreement

on imagery for depicting exit (see Lerner and Collins, 1980) as well as the

need to evaluate the effectiveness of different images for the exit message.

Two factors are critical in evaluating a pictogram for "exit." One factor is

how well the symbol is understood by those who encounter it. This factor

has been emphasized in several previous NBS publications (Collins and Pierman,

1979; Lerner and Collins, 1980; Collins, Lerner, and Pierman, 1982). The

second factor is how visible * the symbol remains under potential emergency

conditions where viewing may occur under degraded conditions involving smoke,

reduced illumination, and so forth. A limited body of research has compared

different graphic images for understandability under good viewing conditions

while another, smaller, body has compared their visibility under degraded

viewing. The present research focuses on the intersection of the understandability and visibility problems: that is, how effectively do various symbols

communicate the message of "exit" when viewing conditions are seriously

degraded?

1.1 UNDERSTANDABILITY CONSIDERATIONS

Several studies conducted at the National Bureau of Standards have

evaluated the understandability of safety symbols, including some providing

egress-related messages. While detailed results are discussed in the original

reports (Collins and Pierman, 1979; Lerner and Collins, 1980; Lerner, 1981;

Collins, Lerner, and Pierman, 1982; Collins, 1982), several important conclusions regarding egress messages are summarized below.

* Visibility is defined by the Illuminating Engineering Society (IES) (1972,

p. 1-21) as, "The quality or state of being perceivable by the eye...." "In

indoor applications it is usually defined in terms of the contrast or size

of a standard test object observed under standardized viewing conditions,

having the same threshold as the given object."

1
Figure 1. Exit symbols proposed for use

2
In an initial evaluation of exit symbols proposed by the International

Organization for Standardization, (ISO) TC21 (1978), Collins and Pierman (1979)

determined that the originally proposed "exit" symbol was correctly defined by

only 25 percent of the participants, while the percentage of correct definitions

for the "no exit" symbol was even lower (3 percent). This latter symbol also

elicited answers related to exit or safe haven from some 35 percent of those

tested. Figure 1 includes the symbols studied in the research summarized in

section 1.1.

In an experimental assessment of different evaluation methodologies, Lerner and

Collins (1980) included three "exit" and two "no exit" symbols. The proposed

ISO image, showing a person and an open door was correctly understood by some 70-85 percent of those studied (as compared with 22-60 percent for the original

ISO "exit”). The third "exit" symbol, showing a figure, arrow and fire, was correctly identified by 85-95 percent. The two "no exit" symbols, ISO original

and ISO proposed, were correctly identified by only 7-30 percent, and 33-70

percent, respectively. (Subjects received no special training on exit symbols

in these studies.) These data indicate a wide range in the comprehension of

different graphic approaches for symbolizing egress messages. Two other experiments, Collins, Lerner, and Pierman (1982) and Collins (in preparation) also

determined that the understandability of additional images for "exit" and "no

exit" differed substantially in terms of percentage correct identification.

While the results varied somewhat, depending on the procedure and population

studied, the poorest symbols were understood by fewer than 25 percent of the

participants, while the best approached 100 percent understandability.

Lerner and Collins (1980) also determined that no strong stereotypical image

existed for the major egress concepts. When people were given an opportunity

to sketch their own ideas for an "exit" symbol, many subjects had difficulty

in producing any image at all, with little agreement among those images produced. These data suggest that the level of consensus that exists on the

essential graphic elements for messages such as "fire extinguisher" and "no

smoking," does not exist for the message "exit.”

The NBS studies on symbol comprehension also revealed that a number of ambiguous

symbols not only failed to communicate their intended meaning but also elicited

critical confusions in meaning. For example, somewhat abstract symbols indicating firefighting equipment or direction were interpreted as indicating egress

by substantial numbers of participants. More importantly, some symbols designed

to indicate "not an exit” were given the opposite interpretation. Such critical

confusions could easily lead a sign user in a totally inappropriate direction

during a building emergency.

The large percentages of incorrect responses to some exit symbols, the lack of

a common image stereotype for exit messages, and the number of critical

confusions elicited by some exit and no exit symbols, underscore the need to

evaluate the effectiveness of egress symbols. Despite the problems noted for

egress symbols, symbols, in general, have been shown to be an effective means

of communicating information. When compared with word signs, selected symbols

have been demonstrated to be perceived more rapidly (Janda and Volk, 1934),

3
more accurately (Walker, Nicolay, and Stearns, 1965), and at a greater distance

(Smith and Weir, 1978), even under distracting conditions.

Such advantages are clearly desirable for egress symbols, where emergency

conditions could reinforce the need for rapid and accurate understanding of

information on signs. As a result, the present investigation was undertaken

to assess the relative effectiveness of 18 egress symbols under adverse viewing

conditions similar to those which might occur during a fire or similar building

emergency.

1.2 VISIBILITY CONSIDERATIONS

As noted earlier the success of an egress symbol depends not only upon good

understandability , but also upon clear legibility, particularly during emergency

conditions. Smoke poses a major threat to life during fires, since problems of

perception in smoke which disrupt escape usually precede the thermal and toxic

effects of the fire (Gross, Loftus, and Robertson, 1966). The disorienting

effects of smoke, fear, lachrymation, and possibly even confusion due to interference with the central nervous system by some noxious smoke products (Phillips,

1978) can further compound the problem of seeing the correct way out of a smokefilled building. This potential disruption emphasizes the importance of egress

signage during emergencies. In addition, smoke obscuration can cause special

problems for viewing signs: since smoke density increases with distance above

the floor, obscuration may be greater at the typical location of such signs

(such as above a door) than toward the floor (Demaree, 1979). Automatic sprinkler systems can drastically influence the pattern of smoke as well. Tests of

simulated hospital room fires reveal that the initiation of sprinklers can divert the flow of gases from a burning room to a corridor from hot gases

passing through the top of the doorway to cooler gases passing through the

bottom of the doorway (O'Neill, Hayes, and Zile, 1980). This rapidly results

in a relatively uniform ceiling-to-f loor obscuration in the adjacent corridor.

Thus, while sprinklers may be an effective means of fire containment, they may

also augment visibility problems. The increased use of automatic sprinkler

systems therefore should not lead to less concern with exit sign visibility.

Although the visibility of signs in smoke has been researched, the focus of

interest has generally been either on smoke parameters, such as composition

and density, or on hardware parameters, such as illumination source and intensity or reflectivity (Demaree, 1979; Bono and Breed, 1965; Jin, 1970). Almost

no research has focused specifically on the visibility of symbolic imagery on signs in building environments. Some reports have compared the visibility of

symbols with word signs for highway applications (Jacobs, Johnston, and Cole,

1975; Dewar and Ells, 1974; Dewar and Swanson, 1972). Although the symbols

generally were more visible than the written messages, these experiments used

distances much too long and presentation times too brief to represent realistic

conditions for people in buildings, however appropriate for highway users.

One study which did compare exit symbols in smoke (Japanese proposal, 1980)

found a 35 percent difference in the range at which the symbols were visible.

Unfortunately, the translated discussion of this Japanese research does not

provide any methodological detail.

4
An additional complication in considering visibility and understandability is

that these factors may not be independent. In general, the exit symbols found

to be most understandable tended to be literal depictions of walking or running

figures, doors, and flames in various degrees of realism and detail. At the

other extreme, highly abstract, simple images were much less well understood.

Although understandability and visibility data for the same set of exit symbols

are not available, it can be hypothesized that the detailed, well-understood

symbols will in general be less visible than the bold and simple, but more ambiguous, symbols. This hypothesis underscores the importance of considering

both understandability and visibility in designing and testing exit symbols.

Using only one criterion could produce a symbol which is deficient on the

other factor.

1.3 VISIBILITY: METHODOLOGICAL CONCERNS

In evaluating how well a symbol communicates when visibility is reduced, two

methodological factors demand special consideration. These are: the response

required of the viewer; and the means of manipulating the viewing conditions to

degrade visibility.

Most research that has compared the visibility of various symbols (usually for

highway applications) has used a limited set of symbols, in which the subject

indicates which of a known set of images has been presented on a given trial.

A primary problem with this procedure is that it may be described as a discrimination experiment, in which the participant must decide which of several known

images is presented. Thus, the findings may reflect how well symbols within a known set can be discriminated from one another, rather than how well any individual symbol can be identified when encountered alone in the environment. To

determine which stimulus of a specific set was presented, the participant may

rely on minor irrelevant cues which effectively distinguish one symbol in the

set from another one. These cues may be unrelated to the features which are actually used to recognize a symbol encountered in a real environment. For

example, Zwaga (1979) compared two methods for determining the legibility of

public information symbols proposed by ISO. In one procedure, participants were

familiarized with the set of symbols, and on each trial indicated which symbol

of this set was presented. In the other procedure, participants were unfamiliar

with what they were to see, and their task was to describe what was presented.

Very different results were obtained with the two methods. The same symbol was

not necessarily best under both procedures, and the procedure in which participants were familiar with the symbols consistently yielded much higher visibility

estimates. Perhaps most critically, Zwaga reported that for "familiar" participants, legibility was related to the uniqueness of subsets of symbol features.

Thus, the flaws in this general procedure are that "visibility" is strongly

determined by exhaustive knowledge of all the symbols included in the evaluation. Furthermore, the subject’s perceptual task may not be a good

approximation to the real-life situation.

The alternative of using a totally unfamiliar set of symbols, with no prior

exposure, has its own disadvantages. First, visibility is confounded with

understandability. It would be difficult to determine whether a subject

indicated that a symbol was not visible because he/she could not see it or

5
simply because he/she did not know what it meant. Secondly, if a limited set

of symbols is tested, the symbols will become more familiar with repeated presentations; thus, familiarity may change through the course of an experimental

session, and the previously identified problem of reliance on a subset of cues can arise.

Presenting each symbol only once may overcome this problem but may be so inefficient a procedure as to be impractical. Thus, whether the subject

identifies a particular symbol from a known set or attempts to interpret an unfamiliar symbol can have a major effect on the results, and neither method

may be entirely appropriate. The resolution of this methodological problem for

the present experiment is discussed in section 2.

The other major methodological concern is the way in which viewing conditions

are degraded. Experiments evaluating symbols (usually for highway applications)

have manipulated perceptability in a number of ways: by severely constraining

viewing time (Markowitz, Dietrich, Lees, and Farman, 1968); reducing brightness

contrast (Smith and Weir, 1978); restricting the visual angle subtended by

reducing size or increasing distance (Mackett-Stout and Dewar, 1981); blurring

the stimulus image (Smith and Weir, 1978); introducing smoke (Japanese proposal,

1980) ; or stressing subjects by demands for speed or performance of additional

tasks (Testin and Dewar, 1981). If these various manipulations produced equivalent results, choosing one method would simply be a matter of methodological

convenience. However, there is evidence that the relative visibility of two

symbols may vary depending on the specific viewing conditions.

Although explicit experimental comparisions are not common, results from

different experimental approaches can be compared. Thus, where two viewing

conditions are employed in an experiment, the correlation coefficient for the

response measures under the two conditions can be calculated. If the relative

visibility of the symbols in a set is similar under both conditions, the corre- lation will be high. Table 1 presents the correlation coefficients, as presented by the authors or as calculated from published data, for six experiments.

The comparison viewing conditions are listed as well. Table I indicates that

the correlations tend to be only moderate. Two values are presented for the

experiment described in the Japanese proposal (1980); because the obtained

value of r=0.83 is due to one extreme data point. With this point omitted,

the correlation is essentially zero. The relatively low correlations given

in table 1 may reflect changes in procedure confounded with changes in the

visibility condition, or a relatively large error variance relative to the

difference between symbols. In addition, there may be interactions with the

response measure. These findings suggest that any discussion of symbol

visibility must include reference to the actual physical and response parameters

varied.

These findings raise two important points. First, any assessment of symbol

visibility should provide a reasonable simulation of the actual viewing

conditions of interest, since results may not generalize well. Secondly, any

theories or empirical generalizations attempting to explain or predict relative

visibility must be able to account for the effect of the specific method for

degrading perception. More extensive empirical data would certainly be useful

6
in indicating the extent to which a theory of symbol visibility must include

specific viewing conditions.

Table 1. Correlation of Symbol Performance Under Multiple Viewing Conditions

Experiment Viewing Conditions Correlation

Mackett-Stout and Dewar (1981) Distance vs. duration r = 0.25

Smith and Weir (1978) Blur vs. glare r = 0.49

Jacobs et al. (1975) Maximal blur vs. no blur r = 0.53

Testin and Dewar (1981) Distance vs. various

loading tasks

r's from

0.34 to 0.73

Ells and Dewar (1979) Glare, darkness vs. good viewing

r = 0.82

Japanese proposal (1980) Smoke vs. no smoke r = 0.83

(r = -0.11 if

symbol 1* is

omitted)

7
2. EXPERIMENTAL APPROACH

In the present experiment, the performance of various exit symbols was studied

under conditions intended to simulate emergency viewing under reduced

visibility. The physical parameters of the viewing condition were designed to

simulate the problems of reduced illuminance and increased light scatter typical

of smokefilled environments. The response conditions were designed to model

the problem of determining whether a given symbol does, in fact, indicate "exit"

or a different message. The graphic features of exit symbols were varied to

determine their relative visibility under different viewing conditions.

The effects of smoke reduce visibility by lowering target luminance, and

increasing scattered light, which reduces overall contrast (Middleton, 1952).

In the present experiment, these effects were simulated, according to the

method employed by Lerner (1981), by using neutral density filters to reduce

target luminance and by adding a veiling luminance to reduce contrast.

Choice of an appropriate response task involved consideration of both the

effects of familiarity noted in section 1.3 and the need to simulate decision

problems faced by persons during a fire. In a fire a person's main objective

is to locate and use the nearest exit. An individual is confronted with the

problem of deciding whether each sign encountered is presenting exit information or not. Under these circumstances, a person would not normally have

detailed knowledge of the entire set of signs present in the building, and

certainly could not be expected to have explicit experience in discriminating

them. Thus, the task becomes one of encountering a sign, familiar or unfamiliar, and determining whether it might be an exit sign. While a person might

have some preconceived ideas about what such signs might look like, he/she

could not assume that a specific exit image is present, particularly given the

present lack of standardization.

In an attempt to simulate such considerations for the present experiment, the

subject's response task was to view a large set of symbol signs and decide

whether each sign was or was not an exit sign. These symbol signs portrayed a variety of messages typically encountered in buildings and workplaces. Only

one-third of the symbols were actually intended to mean "exit". The subject

responded "yes" if he/she thought the symbol was an "exit" message and "no" if

not. Adequate viewing time was provided to avoid producing spurious effects

of temporal factors.

The other parameter of special note is viewing distance (or correspondingly,

image size). Several studies have determined visibility by obtaining the distance at which symbols are recognized under "good" or "normal" viewing conditions; a number of these experiments specifically addressed symbols for building

use. While the authors typically emphasized the differences between symbols,

perhaps the overlooked finding is that visibility under good viewing conditions

may not be a critical concern. Virtually all the symbols tested may be adequate

under these conditions. To determine typical reported viewing distances, the

results of the experiments on building symbols were transformed, using the

relationship, tangent visual angle = size/distance, to determine at what

distance a 12 in (30.5 cm) sign could be recognized. Jin's (Japanese proposal,

8
1980) results for exit signs indicate distances of about 48 to 92 m (about 150

to 300 ft). Mackett-Stout and Dewar's data (1981) for public information signs

indicate distances of about 60 to 150 m (about 200 to 500 ft). Zwaga's (1979)

recognition data for public information symbols indicate a distance of at least

105 m (about 345 ft). These distances are all large relative to most building

spaces, especially given code requirements for distances to exits. For example,

Sharry (1978, p. Ill) has summarized the maximum permissible distance to exits

(for new construction) prescribed in the Life Safety Code. For public and

industrial settings, these range from 75 to 150 ft (22.9 to 45.7 m) for various

unsprinklered occupancies, and from 75 to 200 ft (22.9 to 61.0 m) for sprinklered occupancies (greater distances are permitted in certain low risk storage

and business occupancies). Because symbols appear to be detectable at a greater

distance than that required for travel to an exit, they will generally be adequately visible under ideal viewing conditions. But given the often poor

correspondence between relative visibility measures obtained under different

and degraded viewing conditions, it may be unwarranted to generalize the relative performance under normal building conditions to poor visibility conditions.

The present experiment therefore attempted to use a realistic visual angle for

the stimulus, and more representative visual conditions. The subtended visual

angle of 1.3° is equivalent to viewing a 30 cm (12 in) sign at 13.4 m (44 ft),

while the stimulus presentation procedure simulated emergency lighting and

smoke.

In addition, to deal with the problem of familiarity, each subject was familiarized with a randomly selected subset of 9 of the 18 exit symbols prior

to beginning the experiment. This provided a general familiarity with the

kind of symbol signs that might be encountered. However, since neither the

full set of exit symbols, nor any of the non-exit symbols, were viewed in

advance, subjects were not able to learn a subset of graphic cues that could

be used to discriminate exit symbols from other messages. Thus, during the

experiment they presumably had to rely on interpreting each symbol, rather

than simply locating some known graphic feature.

The performance measure obtained for a given symbol is determined both by how

effectively its imagery conveys the message of "exit", and by how conspicuous

its elements remain when viewing conditions are degraded. Poor performance

could reflect either poor understandability or poor visibility. The prefamiliarization of a set of exit symbols for each subject allowed these two

factors to be discriminated to some extent. A large difference in performance

between those subjects familiarized with a symbol and those not familiarized

with it indicates that low understandability is contributing to poor performance. On the other hand, if familiarization has no effect on performance, the

symbol must be successfully communicating its message without prior familiarization. Similarly, a symbol which is correctly identified under "normal"

viewing conditions, but not under "poor" viewing conditions can be said to

have poor "visibility". In this way the effects of understandability and of

visibility can be somewhat separated.

Because subjects could also err by interpreting an unrelated message as "exit",

the present procedure provided additional information about egress-related

confusions through the use of foil or non-egress symbols. The sign features or

9
messages of the foil symbols which most often caused confusion with exits could

then be identified. These features could then be eliminated from exit symbols

so that possible serious errors under true emergencies would be anticipated,

and corrected.

The experiment had as its major goals the following:

(a) To compare proposed exit symbols for their effectiveness in communicating

the appropriate message under emergency conditions, particularly under

dim, smoke-filled circumstances.

(b) To identify the relative contributions of visibility and understandability

factors for particular exit symbols.

(c) To identify some general features of successful exit symbols.

(d) To identify features of non-exit symbols that might cause them to be

misinterpreted as exit indicators.

10
3 . METHOD

3.1

SUBJECTS

The subjects were 42 volunteers, 14 males and 28 females, ranging age from 18

to 53 years (mean age=27.3). They were recruited from the Gaithersburg, MD, area through local advertising and paid for their participation. All reported

normal or corrected-to-normal vision. Corrective lenses were worn by those

who normally wore them.

3 .

2

SYMBOLS

One-hundred-twenty-six different symbols were presented. Each symbol was originally drawn as a 30.4 cm x 30.4 cm (12 in x 12 in) placard, and then

photographed against a medium grey background for presentation in slide form.

Eighteen of the symbols were intended to convey the messages of "exit" or "emergency exit." The other 108 foil symbols depicted a wide range of other

messages, the only common feature being that all were messages that might be seen in or around buildings. The symbols were selected (with modifications in some instances) from adopted or proposed standards, commercially produced signs,

and symbols used for various public facilities or events. The 18 exit symbols,

and the sources from which they were taken, are shown in figure 2; the remaining

foil symbols are shown in appendix A.

Luminance measurements were taken for each of the various colors that appeared

in the slides, so that brightness contrasts for the various color combinations

occurring could be calculated. The approximate ratios of the luminances, averaged over several measurements, were: red/white: 1/8; green/white: 1/8;

blue/white: 1/11; black/yellow: 1/28; black/white: 1/35. An exception to

these measures was for exit symbols N through R, which had been drawn at a different time than the other symbols. These black and white slides had a brightness ratio of about 1/80. Thus, the contrast can be calculated as about

0.97 for the black and white slides; 0.91 for blue and white; 0.88 for red or green and white; and 0.96 for yellow and black.

3.3

SYMBOL LISTS

Three separate presentation lists of 54 symbols were constructed. Each list

consisted of 18 exit symbols, together with 36 non-exit, or "foil", symbols.

The 108 foil symbols were initially divided into 36 triads on the basis of

similarity of meaning and appearance; one member of each triad was then assigned

to each list. The order of the 54 slides in a list was randomized with the

following constraints: the first two and last two items of each list were

foils; exit symbols could not occur more than three times in succession (in

fact they never actually occurred more than twice in succession); foil stimuli

could not occur more than five times in succession.

3.4

APPARATUS

The stimulus slides were viewed through the binocular eyepiece of a three-channel

projection tachistoscope. One channel was always illuminated, so that a

11
mA u Green ft White

B

Green & White

BlD El

Green & White

E

Green 4 White

J K

Green & White Green & White

C

Green & White

F

Black & White

I

Black & White

L

Black & White

Green & White Black & White Black & White

P

Black & White

Q

Black & White

R

Black & White

Figure 2. Exit symbols tested in the present experiment

12
constant dim field was visible. This procedure provided a veiling illumination

when the stimulus slide was simultaneously presented, resulting in reduced

brightness contrast in the viewed symbol. The veiling field also served to

maintain a relatively constant luminance level, so that no significant change

in brightness occurred when the symbol slide was presented.

To create low luminance levels deliberately, all symbols were projected through

a neutral density filter. By inserting different filters, the luminance

(brightness) of the stimulus slide could be changed. Thus, the image viewed

by the subject was of a symbol first reduced in brightness by the filter and

then optically combined with a veiling light to reduce contrast. The resulting

image was a dim, "washed out" symbol, which simulated the light-attenuating

and scattering effects of smoke.

As presented during the experiment, the projected image of the symbol subtended

a visual angle of 1.3 degrees. The luminance of the veiling light was approximately 1.0 cd/m^. Since this value was roughly an order of magnitude greater

than the luminance of the symbol slide, the total luminance did not change substantially when the slide image was added to the veiling light. The symbol

slides were projected through one of three neutral density filters, which had

nominal values of 2.7, 3.0, and 3.3 log units. The resulting luminances, for

a white slide image as viewed through the eyepiece and measured with the

veiling channel turned off, were 0.085, 0.060, and 0.032 cd/m^, respectively.

This resulted in three viewing conditions (which represented a range of easy

to difficult task performance based on pilot research).

3.5 SEQUENCES OF LISTS AND VIEWING CONDITIONS

The three presentation lists were each shown in forward and reverse orders,

effectively yielding six sequences. Each participant viewed each sequence

once. The participant saw all three lists in one direction before being presented with any of the lists in the opposite direction (direction of first

lists counterbalanced across participants) . A given viewing condition remained

in effect for an entire list. Each viewing condition (determined by the choice

of the neutral density filter) occurred once during the first three lists and once during the final three lists.

Across subjects, each viewing condition occurred an equal number of times at

each of the six list positions. Each filter/list combination occurred an equal

number of times as well.

3.6 PROCEDURE

After reading instructions that outlined the general nature of the experiment

(appendix B), the participant was shown a random set of nine of the eighteen

exit symbols for familiarization. The symbols were in placard form, and the

participant was free to spend as much time as needed to become familiar with

them. Next, more detailed instructions (appendix B) were presented which

stressed the importance of making a best guess for every slide, even when the

decision was very difficult. After five minutes of visual adaptation to the

dim level of room illumination used during data collection, a sample slide was

13
shown, using the brightest of the three viewing conditions. This familiarized

the participant with the appearance of the stimuli and the operation of the

response key.

Presentation of the stimuli was controlled by the participant. When a telegraph

key located near the tachistoscope was pressed, a red dot appeared, which served

as a ready signal. After 1 second the ready signal terminated and the symbol

slide was presented for 4 seconds. The participant indicated "yes" or "no" on an answer sheet to indicate whether or not the symbol shown conveyed the message

of "exit". After recording an answer, the participant pressed the key to initiate a new trial with the next slide. After an entire list of 54 slides was completed, the subject had a brief rest period during which the experimenter

changed both the slide set and viewing condition. An entire experimental

session of six presentation lists took less than 90 minutes.

14
4. RESULTS AND DISCUSSION

4.1 EXIT SYMBOL DATA - OVERVIEW

Table 2 presents the percentage of errors, or failures to identify a symbol as an exit, for each of the 18 exit symbols. The data for each symbol are presented for each of three viewing conditions and for the average of the three

viewing conditions. Data for subjects familiarized and not familiarized with

each symbol are also presented in table 2. Each listed value is based on 21

subjects making two observations. A total of 126 observations were made per

symbol, across all three viewing conditions for each familiarity condition.

Figure 3 portrays the information from table 2 graphically. Open circles depict

data for unfamiliarized subjects while filled circles depict data for familiarized subjects. Line segments connect the values for the two groups of subjects.

Figure 3 also shows estimated standard error bands for various percentages of

incorrect responses. These standard error estimates are based on the normal

approximation to the binominal distribution, with the approximation

S e = /NPQ/N x 100 percent (where N = number of observations; P = proportion

of correct responses; Q = proportion of incorrect responses).

The data on the response to the symbols can be discussed in at least four

different ways. These include the responses to: the viewing condition;

familiarization; specific graphic characteristics of the symbols; and the

foil stimuli. While the different experimental manipulations can be identified

separately, it should be noted that their effects interact in many cases. Separating the effects of the different experimental manipulations is difficult,

due to the overall interaction between visibility and understandability

.

Nevertheless, the following general results are apparent.

First, increasing the difficulty of seeing by decreasing slide luminance

(increasing filter density) increases the number of errors, for both familiarized and unfamiliarized symbols. Secondly, providing initial familiarization

decreases the number of errors. Thirdly, the effects of viewing condition and

familiarity vary widely with the graphic features of the symbols studied. In

general, the symbols with a greater number of details (more graphic elements)

tend to have higher error rates for both familiar and unfamiliar conditions,

particularly for the poorest viewing conditions. The most abstract symbols

appeared to benefit most from familiarization. Fourthly, a number of the foil

symbols elicit exit-related confusions. Other results will be discussed in

detail in the following sections, including the graphic elements of foil

stimulus related to exit confusions.

4.2 VIEWING CONDITIONS

The overall effect of varying the viewing condition was to increase the

numbers of errors made under the poorest viewing condition, regardless of

familiarization. Under the most favorable viewing condition, all exit symbols

(which had been familiarized) produced error rates under ten percent, except

for symbol Q. Thus, with the exception of Q, the performance of viewers for

these symbols is not statistically discriminable . The high proportion of

15
Table 2. Percentage of Errors for Each Symbol and Viewing Condition

Visibility Condition (Neutral Density Filter Value, Log Units)

All

Exit Symbol 2 .

7

3.0 3.3 Conditions

Familiar Unfamiliar Familiar Unfamiliar Familiar Unfamiliar Familiar Unfamiliar

A 7.1 83.3 7.1 83.3 19.0 81.0 11.1 82.5

B 9.5 33.3 9.5 23.8 35.7 54.8 18.3 37.3

C 7.1 9.5 7.1 11.9 26.2 28.6 13.5 16.7

D 2.4 0.0 2.4 2.4 26.2 26.2 10.3 9.5

E 0.0 2.4 2.4 2.4 28.6 33.3 10.3 12.7

F 9.5 0.0 16.7 2.4 33.3 23.8 19.8 8.7

G 4.8 14.3 4.8 31.0 59.5 71.4 23.0 38.9

H 2.4 11.9 4.8 21.4 64.3 81.0 23.8 38.1

I 9.5 45.2 11.9 35.7 14.3 38.1 11.9 39.7

J 2.4 0.0 0.0 4.8 31.0 50.0 11.1 18.3

K 0.0 0.0 2.4 0.0 19.0 19.0 7.1 6.3

L 4.8 2.4 0.0 7.1 42.9 28.6 15.9 12.7

M 2.4 2.4 7.1 4.8 33.3 40.5 14.3 15.9

N 0.0 0.0 4.8 2.4 19.0 28.6 7.9 10.3

0 0.0 2.4 0.0 0.0 31.0 28.6 10.3 10.3

P 0.0 4.8 0.0 4.8 23.8 33.3 7.9 14.3

Q 16.7 11.9 33.3 26.2 90.5 88.1 46.8 42.1

R 2.4 4.8 16.7 14.3 81.0 88.1 33.3 35.7

16
PERCENT

ERROR

PERCENT

ERROR

100

90

80

70

60

50

40

30

20

10

0

100

90

80

70

60

50

40

30

20

10

0

viewing coNorrm a

< j> Each port = 42 obsowalMB [2 p* 9rtppect)

-

i >

-

< > -

- 9

# i

I I

6 9 1- - —

i ! —& e

* » e ? Y L ABCDEFGHli KLMNOPQR

SYMBOL

VIEWING CONDITION B

Each point = 42 observations

0

- Cj>

— J

c>

- M

® ® 16 ? 4 I I

I

A B C D E F G H I J SYMBOL

KLMNOPQR

Figure 3. Percentage of errors as a function of viewing condition

17
PERCENT

ERROR

PERCENT

ERROR

Figure 3. Percentage of errors as a function of viewing condition (continued)

18
correct responses, under the easiest viewing condition indicates that, when

familiar, the symbols were well comprehended. Thus, poor performance under

more difficult viewing conditions may be attributable to visibility decrements,

rather than to inherently poor understanding.

Under the intermediate viewing condition, performance decrements became

more pronounced. Fourteen of the 18 symbols still showed fewer than 10 percent errors when familiarized. However, the performance associated with symbols Q

and R (outline figures) deteriorated. Symbols G and H, (a person, fire and a door or an arrow) showed poorer performance for unfamiliarized, though not for

familiarized subjects. Symbol F (person and flames) was unusual in that the

familiar subjects made 14 percent more errors than unfamiliarized subjects. A

similar reversal, though smaller, also occurs for the other viewing conditions

for symbol F.

When viewing was most difficult, symbols Q and R (outline figures) were identified as "exit" at a very low rate, similar to that of the foil stimuli

(see table 3). These symbols thus, were the least visible. Symbols G and H

also resulted in poor performance with even familiarized subjects showing

about 60 percent errors. Symbol I showed the lowest error rate (14 percent)

for familiarized subjects, with symbols A, K, and N at 19 percent. Error rates

for the others were roughly in the 25-35 percent range (symbol L showed a higher

rate for familiarized subjects, but a lower rate for unfamiliarized subjects

suggests this may be spurious). Examination of the data in table 2 for familiar

subjects only reveals that degrading viewing conditions clearly increases the

percentage of errors. Of interest, though, is the fact that some symbols, such

as B, G, H, L, Q, and R, are affected to a greater extent by the degradation in

viewing. For other symbols, A, I, K, and N, the degradation is much less marked.

Across all viewing conditions, the data indicate symbol Q to be least visible,

followed by symbol R, and then symbols G and H. Performance is generally

better for the other symbols, with symbol K one of the most generally visible

symbols for all three viewing conditions studied.

4.3 FAMILIARITY

The overall effect of familiarity with the symbols was to decrease the number

of errors made under the best viewing condition. Nevertheless, for the majority

of exit symbols, error rates were quite similar regardless of whether or not

subjects had been familiarized with the specific symbol. Of course, since

there were similarities between many of the symbols, even subjects nominally

unfamiliar with a symbol may have benefitted from viewing related symbols. A

clear improvement in performance due to familiarization was observed for six

symbols: A, B, G, H, I, J. Before discussing these, some points regarding

the symbols not showing an effect of familiarization should be noted.

Symbols C, D, and E might have been expected to benefit from familiarization,

since previous research (Lerner and Collins, 1979; Collins, Lerner, and Pierraan,

1982) had shown these symbols to have ambiguous meaning. Since symbols D and E

were conceptually very similar, familiarization for one symbol could generalize

to increase familiarity with the related symbol. To assess this hypothesis,

19
data only from subjects unfamiliarized with both symbols D and E were examined.

The error rates (over all three viewing conditions) were slightly higher,

13.9 percent (10 of 72) for D and 16.7 percent (12 of 72) for E. However

since these data were obtained with only 12 subjects, interpretation is difficult, and in any case, any effect of familiarization for D and E is small, and

limited to the most difficult viewing condition. Similarly, the absence of an effect of familiarization for the arrow (symbol C) should not be attributed to

familiarization with the other symbols (D and E) having an arrow as a central

feature. Only five subjects were unfamiliarized with C, D, and E; but of 30

observations of symbol C by these subjects, only two were in error. Thus,

this finer analysis does not contradict the conclusion that no substantial

effect of familiarization exists for symbols C, D, and E.

The largest effect of familiarization was for symbol A, proposed by the

Department of Transportation (AIGA, 1979). Without the benefit of familiarization, the symbol simply was not recognized (over 80 percent errors regardless

of viewing condition). Another abstract symbol, B, once proposed by ISO, also

was poorly recognized when familiarization did not occur (37 percent errors).

While more representational, symbol I was frequently misinterpreted by unfamiliarized subjects (AO percent errors). Symbols A, B, and I not only showed the

largest overall effects of familiarization—they also were the only symbols to

show substantial familiarization effects even under the most favorable viewing

condition.

For other symbols, familiarization improved performance only under degraded

viewing conditions. Symbols G, H, and J showed pronounced effects of familiarization when viewing became more difficult, but were generally correctly identified under the most favorable viewing conditions. Symbols G and H were the

only exit symbols appearing in a circular, rather than square or rectangular,

surround. The circular surround may have contributed to confusion, especially

where viewing conditions made image details difficult to discriminate. For

example, those subjects who saw neither of the circular symbols during familiarization showed especially high error rates: for six subjects, 36 percent of

all observations were in error for both G and H; 75-83 percent of the most

difficult observations were in error. The red color in these symbols may also

have contributed to problems, since the inherent brightness contrast was lower

than with the black-and-white symbols. The effects of color contrast are discussed further in section 4.4.3.

Although symbols J and K resemble one another, their response to familiarization

is different for degraded viewing conditions. Despite the conceptual similarities between symbols J and K, the figure-ground relationship is more complex in

J. Symbol J shows not only a doorway, but a door, detached from the doorframe

and foreshortened to indicate depth. The running figure is superimposed on

this background. Familiarization with this symbol has a substantial effect

only when viewing condition is poorest. It appears likely that familiarization

does not so much clarify the meaning of this symbol, which is well-understood

under better viewing conditions, as it helps the subject to analyze the symbol

features under difficult viewing conditions. Further discussion of the

understandability of these symbols will be found in section 4.7.

20
The large effects of familiarization for some exit symbols must be taken into

account when the visibility of the various symbols is compared. Nevertheless

at least several symbols, including K, N, and P, performed reasonably well

whether familiarized or not, under all three viewing conditions. These data

thus suggest that the graphic features of these particular symbols contribute

to good visibility as well as good "understandability" . In the following

sections the graphic features of both the exit and foil symbols will be

discussed in detail.

4.4 FEATURES OF EXIT SYMBOLS RELATED TO PERFORMANCE

A comparison of subjects' performance for the various exit symbols permits a number of generalizations regarding specific graphic features. Since in most

cases these features were not explicitly varied in a controlled manner, a number of variables may be confounded; therefore these inferences must be

regarded as tentative.

4.4.1 Filled Versus Outline Figures

Symbols Q and R were identical to symbols 0 and P except that they were drawn

as outline, rather than solid figures. The outline figures were not only less

visible (or correctly identified less frequently under degraded viewing conditions) than their filled counterparts, they were the least visible of all exit

symbols tested. The use of solid figures has been recommended by researchers

(Easterby, 1970) and is in fact typically used. However, the ISO standard that

provides general principles for graphic symbol design (ISO, 1976) recommends

avoiding filled areas. A proposed revision (ISO, 1980) reverses this position

for public information symbols. The magnitude of the decrement in visibility

observed in the present experiment strongly suggests the use of filled rather

than outline figures.

4.4.2 Direction of Figure-Ground Contrast

Symbols 0 and Q were identical to symbols P and R except that the former

portrayed black figures on a white background, and the latter white figures on

a black background. Both directions of figure-ground contrast are commonly

used. While some guides have recommended one version as being more easily

perceived (DoT, 1974), experimental evaluations have shown small and variable

effects (Konz and Mohan, 1972; Lerner, 1981). In this experiment, there was

no observed difference between the performance for symbols 0 and P, while the

performance for symbol Q (black on white outline figure) was somewhat poorer

than that for symbol R. Across the entire set of symbols, A, B, C, H, J, L,

and M also portrayed white figures on darker backgrounds. Subjects' performance

for these symbols as a group was not noticeably different from that for the

remaining symbols, with a range of results for both types of symbols. In all,

the data do not reveal any substantial difference in performance with either

direction of figure-ground contrast.

21
4.4.3

Color

Under the viewing conditions of the experiment, chromatic information was limited and there was little subjective sense of color. The overall luminance

of about 1 cd/m^ probably resulted in mesopic rather than true scotopic vision,

however. The major effect of the various color combinations studied was presumably through differences in brightness contrast, with some combinations producing greater contrast than others. The physical contrast measurements

reported in the Method section suggest that black and white should be superior

to green and white or red and white. The differences in physical contrast may

not have been great enough to result in larger perceptual differences, however.

Although symbols H and G which contained red elements were among the least

visible symbols, color was confounded with shape and other features, making

interpretation difficult. There was no overall indication that the black and

white symbols were superior to the green and white symbols, however.

4.4.4 Surround Shape

Twelve of the eighteen exit symbols included a square symbol surround, three a rectangular surround, and two a circular surround. A final symbol (A), while

circular in shape, had no actual surround. Symbols with a rectangular surround

did not show any substantial effect of familiarization and were not distinguishable from the square-surround symbols. In contrast, the symbols with circular

surrounds showed substantial effects of familiarization, and poor visibility

even for familiarized subjects. The confounding of surround shape with color

makes interpretation difficult, but the case for an effect of surround shape

will be discussed in section 4.5.2. It seems likely that subjects have certain

expectancies regarding the surround shape of exit symbols, although it is also

possible that the familiarization portion of the experiment may have contributed to such stereotypes, since the majority of exit symbols presented were in

square or rectangular surrounds.

4.4.5 Relationship of Graphic Elements and Figure-Ground Contrast

Eleven of the exit symbols employ the concept of a human figure exiting

through a doorway. Literally, this concept implies an interaction, in three

dimensions, between a human figure and a doorway, which can be graphically complex. This problem has been approached in different graphic ways among the

symbols. For purposes of this discussion, symbols L, P, Q and R are not

explicitly discussed, since they are conceptually identical to symbols M or 0.

Three symbols (H, J, K) attempt to portray three-dimensionality; three (I, M, 0) are two-dimensional portrayals, with the figure displaced from the doorway; and

one (N) shows the interaction of figure and door in a more symbolic fashion, by

altering the figure color, for contrast, as it enters the doorway. Since symbols K, N, and 0 are among the most visible symbols, and did not show familiarization effects, all three approaches appear viable, and none is clearly favored

by these data. However, within a graphic approach, the individual symbols vary

considerably. Comparing symbol K with J and H suggests the advantage of simplifying the interacting elements and providing a simple background against which

the figure may be viewed. The poor performance of unfamiliarized subjects for

22
symbol I indicates further that the door, too, must be readily recognizable.

While the data do not favor one particular approach, these limited comparisons

do suggest simplifying both elements and minimizing the overlap of the graphic

details of the figures and doors.

The more complex the graphic image was , as indicated by a greater number of

features, the greater the number of errors occurring for the poorest viewing

condition. For example, symbols G, H, L, and M all contain three major features, consisting of a human figure, an arrow, a door, or flames. These

symbols have error rates among the highest, from 33 percent to 64 percent,

except for the outline symbols Q and R (discussed in 4.4.1). Symbols with

several major graphic elements may suffer from complexity itself or from the

reduced size of each element when several are combined.

4.4.6 Specific Pictorial Elements

Certain pictorial elements commonly occur in symbols for exits and emergency

exits (Lerner and Collins, 1980). These elements include human figures, flames,

arrows, and doorways. When Lerner and Collins had experimental subjects in a study on fire-safety symbols sketch a pictogram for "exit" or "fire exit," no consensus stereotype image occured, but these common pictorial elements often

emerged. None of these elements is in itself adequate to portray the exit

message unambiguously, but each may contribute importantly to the successful

graphic portrayal of the exit message. The data from the present experiment

were examined to see if any of these elements were consistently associated

with good performance for both familiarized and unfamiliarized subjects.

For the limited sample of symbols, no striking effect of figures, flame, or doors was observed: each of these elements occurred among all symbols, regardless of percentage of correct identification. Further indications of the role

of some of these factors are discussed below regarding foil stimuli. The most

interesting observation among the exit symbols was in how readily the arrow

(C), and the diagrammatic symbols incorporating the arrow (D and E) , were interpreted as "exit." Even unfamiliarized subjects had more than 90 percent

correct response under the most favorable viewing conditions. This finding

differs from other experiments (Lerner and Collins, 1979; Collins, 1982; Collins

et al., 1982) in which such symbols were less frequently interpreted as exit

indicators, even though the viewing condition was not degraded. Three other

symbols (G, L, M) incorporated smaller arrows into the pictogram. Of these,

symbol G had a somewhat higher error rate for unfamiliarized subjects, even under the easiest viewing condition. The arrow is discussed further when

errors for foil stimuli are presented (section 4.5).

The specific factors which appear to decrease the visibility (increase errors

in accurate identification under poor viewing conditions) of exit symbols

include the use of outline figures, larger number of graphic features, and use

of circular surround shapes. Factors which do not appear to degrade visibility

substantially are the direction of figure-ground contrast and differences in

color contrast between black and white and green and white.

23
4.5 FOIL SYMBOLS

Features which appear to influence the interpretation of a symbol as an "exit" symbol can be inferred from an analysis of those foil symbols falsely

identified as "exit". Table 3 presents the percentage of times each foil symbol

was incorrectly identified as "exit" under each of the three viewing conditions,

(2.7, 3.0, 3.3) as well as the average error rate (incorrect identifications)

across all conditions. (Note that table 3 presents data for 108 different

symbols, so that 34X is not the same symbol as 34Y or 34Z.) Error rates ranged

from zero to over 80 percent. Some foil symbols showed the highest error

rates under the easiest viewing condition, indicating the message as portrayed

was confusable with "exit". Errors occurred more frequently for most foil

symbols, however, as the viewing condition was made more difficult. (Foil

symbols are depicted in appendix A.)

Table 4 lists those symbols for which the highest overall error rates occurred

(greater than 10 percent), in the order of error rate. This include approximately one-third of the foil symbols. The table also lists certain graphic

features that frequently occurred in these symbols.

Two aspects of the data obtained for the foil symbols will be discussed. First,

the intended messages represented among the high-error symbols will be reviewed.

Secondly, generalizations regarding those symbol features that contribute to

confusion will be considered. In comparing symbols, two factors should be kept

in mind. First, since many features covary between symbols, interpretation of

differences between symbols is necessarily speculative. Secondly, the error variance of the proportion of errors for each symbol should be kept in mind.

The estimated standard error is about 4 percent when the error rate is 5 percent,

and ranges up to a maximum of about 9 percent for 50 percent errors.

4.5.1 Intended Messages

The symbol most frequently confused with exit was the directional arrow (Z28).

This arrow was intended by ISO TC 21 (1978) to indicate direction as a supplement

to a particular sign. Of course, half of the subjects had seen another arrow

(symbol C) familiarized as meaning "exit”; still, those not shown symbol C still

identified the directional arrow as "exit" at about the same rate (76 percent

overall). The problems arising from the confusion of exit symbols with directional indicators are detailed in Lerner (1981), along with suggestions for

reducing such problems.

Two versions of the message "use stairs not elevator, in case of fire" were included as foil stimuli. One, which did not show an elevator (X34), had substantial (60-77 percent) confusions at all viewing conditions. The other (X8),

showed a much lower overall rate (9.5 percent). However, since errors for this

latter symbol were greater (17.9 percent) under the most favorable viewing con- dition, the low overall rate may simply indicate that this symbol can not be

discriminated well enough to be confused with exit under poor viewing conditions. When it is seen well, the message is apparently confusable. Both of

these symbols are intended to be used on or near elevators. This context may

improve raeaningfulness in actual use - however, the danger that the elevator

24
Table 3. Percentage of Times Each Foil Symbol is Incorrectly Identified as Exit

(Percent Errors for Foil Stimuli Under Each Viewing Condition)

List X List Y List Z

2.7 3.0 3.3 Overall 2.7 3.0 3.3 Overall 2.7 3.0 3.3 Overall

1 0.0 7.1 14.3 7.1 7.1 3.6 3.6 4.8 3.6 7.1 14.3 8.3

2 3.6 10.7 14.3 9.5 0.0 0.0 3.6 1.2 3.6 3.6 7.1 4.8

3 7.1 17.9 10.7 11.9 0.0 7.1 10.7 6.0 0.0 3.6 10.7 4.8

4 14.3 14.3 10.7 13.1 3.6 3.6 3.6 3.6 3.6 7.1 10.7 7.1

5 0.0 7.1 14.3 7.1 0.0 0.0 7.1 2.4 3.6 0.0 0.0 1.2

6 0.0 3.6 10.7 4.8 3.6 0.0 0.0 1.2 3.6 7.1 14.3 8.3

7 60.7 78.6 60.7 66.7 21.4 28.6 21.4 23.8 0.0 0.0 10.7 3.6

8 17.9 7.1 3.6 9.5 10.7 7.1 17.9 11.9 3.6 17.9 21.4 14.3

9 0.0 0.0 7.1 3.6 9.5 10.7 7.1 4.8 3.6 0.0 10.7 4.8

10 0.0 0.0 14.3 4.8 0.0 7.1 10.7 6.0 0.0 0.0 3.6 1.2

11 0.0 0.0 7.1 2.4 0.0 3.6 10.7 4.8 0.0 7.1 7.1 4.8

12 3.6 0.0 17.9 7.1 7.1 7.1 7.1 7.1 0.0 0.0 0.0 0.0

13 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3.6 0.0 14.3 6.0

14 0.0 0.0 7.1 2.4 0.0 0.0 10.7 3.6 0.0 0.0 3.6 1.2

15 0.0 0.0 10.7 3.6 0.0 0.0 7.1 2.4 0.0 0.0 3.6 1.2

16 14.3 10.7 0.0 8.3 17.9 21.4 14.3 17.9 7.1 14.3 25.0 15.5

17 3.6 3.6 21 .4 9.5 10.7 28.6 14.3 17.9 7.1 0.0 14.3 7.1

18 3.6 14.3 35.7 17.9 21.4 42.9 17.9 27.4 0.0 10.7 21.4 10.7

19 3.6 7.1 28.6 13.1 7.1 17.9 14.3 13.1 10.7 21.4 10.7 14.3

20 0.0 3.6 14.3 6.0 0.0 0.0 7.1 2.4 7.1 7.1 17.9 10.7

21 3.6 0.0 14.3 6.0 10.7 39.3 25.0 10.7 10.7 10.7 10.7 10.7

22 0.0 0.0 10.7 3.6 3.6 3.6 3.6 3.6 7.1 3.6 7.1 7.1

23 0.0 7.1 25.0 10.7 7.1 3.6 10.7 7.1 7.1 3.6 21.4 10.7

24 0.0 3.6 7.1 3.6 3.6 10.7 0.0 4.8 7.1 32.1 17.9 17.9

25 10.7 17.0 7.1 11.9 0.0 0.0 7.1 2.4 0.0 3.6 10.7 4.8

26 0.0 3.6 0.0 1.2 0.0 3.6 10.7 4.8 32.1 35.7 35.7 34.5

27 14.3 14.3 25.0 17.9 3.6 3.6 3.6 3.6 3.6 7.1 17.9 9.5

28 0.0 3.6 14.3 6.0 0.0 0.0 3.6 1.2 85.7 85.7 39.3 70.2

29 10.7 7.1 10.7 9.5 7.1 17.9 10.7 11.9 14.3 39.3 46.4 33.3

30 3.6 17.9 7.1 9.5 3.6 14.3 10.7 9.5 25.0 14.3 10.7 16.7

31 3.6 3.6 14.3 7.1 3.6 7.1 14.3 8.3 3.6 7.1 10.7 7.1

32 3.6 7.1 7.1 6.0 0.0 10.7 0.0 3.6 0.0 3.6 3.6 2.4

33 3.6 21.4 7.1 10.7 14.3 3.6 3.6 7.1 0.0 3.6 7.1 14.3

34 82.1 60.7 21.4 54.8 39.3 14.3 14.3 22.6 3.6 14.3 25.0 14.3

35 0.0 3.6 7.1 3.6 0.0 0.0 10.7 3.6 0.0 7.1 3.6 3.6

36 0.0 0.0 17.9 6.0 21.4 17.9 14.3 17.9 7.1 7.1 17.9 10.7

25
Table 4. Foil Symbols with More Than 10 Percent Errors (34 of 108)

Symbol

Overall

Z Fig. Arrow Flame Door Door Propor

.

Stair Feet Surround

1 Z 28 70.2 Rect R ISO Arrow

2 X 7 66.7 / Square R No exit

3 X 34 54.8 / Square

B&W

(R) Use stair in fire

4 z 26 34.5 Square R Ladder

5 z 29 33.3 / Square R Standpipe

6 Y 18 27.4 / / Circle Blu Close fire door

7 Y 21 25.0 / / Square G Shower

8 Y 7 23.8 Circle R DOT

No entry

9 Y 34 22.6 / Triangle Y Old ISO

No exit

10 X 18 17.9 Circle B Mandatory Action

11 X 27 17.9 Square R FF equip.

12 Y 16 17.9 / Circle Blu

ISO Boots

13 Y 17 17.9 Circle Blu Glove

14 Y 36 17.9 / Square B&W Slip

15 Z 24 17.9 / Circle R Forklift

16 Z 30 16.7 / Square R Wall w/arrow

17 Z 16 15.5 Circle Blu Boot

18 Z 8 14.3 / / Square B ,W,R No exit

ISO

19 Z 19 14.3 / Square Blu Elec, shutoff

20 Z 34 14.3 / Square B&W Fall from ledge

21 X 4 13.1 / Triangle Y Slip

22 X 19 13.1 / Square Blu Elec, shutoff

23 Y 19 13.1 / / Square Blu Gas shutoff

24 X 3 11.9 Triangle Y Forklift

(with driver)

25 X 25 11.9 / Circle R Flammable

26 Y 8 11.9 / Circle R No exit

27 Y 29 11.9 Square R Standpipe

28 X 23 10.7 Square R Emerg. Phone

29 X 33 10.7 / Circle Y Trip

30 Z 18 10.7 (archway) Circle Blu Ear muff

31 Z 20 10.7 / Square G Eyewash

w. head

32 Z 21 10.7 Square G Shower drops

33 Z 23 10.7 Circle R

Explosion

AF

34 Z 36 10.7 Square B&W Falling objects

26
could be construed as an emergency exit facility during a fire raises concern

about the use of these symbols.

Symbols intended to warn explicitly that a route does not lead to safe egress - "no exit" - were interpreted as "exit" with alarming frequency. The majority of

subjects interpreted symbol X7 as exit under all conditions. While Y8 and Z8 were confused much less often, both showed about 20 percent confusions when

viewing was most difficult. The elements of these symbols (moving figure,

door) are common to many exit pictograms, and apparently the indication of

prohibition (slash, X, lock) is less effective when visibility is poor. Symbol

Y34 is based on a diagram, showing an arrow entering a closed rectangle. Previous experiments on symbol understandability (Collins and Pierman, 1979;

Lerner and Collins, 1980) under good viewing showed this to be a poorly understood image, with frequent egress-related misinterpretations. The present

results confirm this finding, with this image being confused with exit especially under the most favorable viewing condition (39.3 percent). The high

rate of confusions may partly reflect the intentional use of a procedure that

predisposed subjects to look for exit messages. Nevertheless, the data obtained

in the present experiment further support the inadequacy of symbols and messages

for "no exit." The inadequacy of the entire set of "not an exit" symbols

appears to be a critical problem in the design of symbols for life safety.

This message appears to be very difficult to symbolize effectively and may be

better conveyed by words (to those who are, literate).

Five "No Entry" symbols were evaluated. Three (X9, Y9 , Z9) were similar in

graphic concept, showing a human figure, overlaid with prohibitory circle and

slash. Error rates were low for these symbols, in contrast to the "no exit"

symbols. Similarly, symbol Z7 was infrequently interpreted as exit. In contrast, the abstract DoT "No Entry Symbol" (Y7) was misinterpreted as "exit" over

20 percent of the time under all viewing conditions. This poor performance

occurs despite the wide use of this symbol for highway signage, for transportation facilities, and for other public settings. In addition, understandability

data obtained by Collins et al., (1982) indicate that only 30-50 percent of

those tested identified this symbol correctly, further evidence of its ineffectiveness. Under building emergency conditions, this common symbol could send

people searching for a way out in an inappropriate direction.

The set of fire safety symbols proposed by ISO (1978) includes several to

indicate the location of firefighting equipment. Of these, "Ladder” (Z26) and

"Location of Equipment" (X27) showed confusions with "exit", confirming the

earlier findings by Lerner and Collins (1980). The fire hose and reel (Standpipe) symbol (Z29) was also frequently interpreted as exit in the present

experiment unlike previous experiments using good viewing conditions. This

probably occurred because the fine separation in the folds of the hose cause

the degraded image to appear as a rough rectangle with the proportions of a doorway. In contrast, two symbols (X29, Y29) , which incorporate a modified

version of the standpipe resulted in much lower error rates (about 10 percent

overall); however, the modification is confounded with other graphic

differences, so that straightforward interpretation is not possible.

27
One version (Y21) of the safety shower message was interpreted as "exit" one- fourth of the time. Although Collins et al., (1982) found this symbol to be

interpreted correctly under good viewing conditions, certain of its details

apparently contribute to confusion when viewing is degraded. In this symbol,

a human figure is shown standing under a shower pipe which is shaped and sized

as an archway. An arrow, though small, is also present. The other versions

of the safety shower message (X21, Z21) result in much lower error rates.

Four of the six symbols in the category of slip, trip, and fall resulted in

moderately high error rates (11-18 percent, overall) while two resulted in low

rates (4-7 percent). Interestingly, two symbols showing a falling figure (X4,

Z34) produced more confusions than a third image of a falling figure (Z4);

and two symbols (X33, Y36) showing a foot (or feet) produced more confusions

than a third showing the image of a foot (Y4). It is not apparent what factors

distinguish the more confusing images from the less confusing images.

The three symbols indicating the need for safety footwear are similar to some

of the slip/fall symbols in showing a boot as the primary image. Two (Y16, Z16)

of these symbols showed a substantial number of confusions with "exit" (17.8

and 15.5 percent overall). The third symbol (X16) was unusual in that numerous

errors occurred for the easiest viewing condition (14.3 percent), fewer in the

intermediate condition (10.7 percent), and none in the most difficult condition.

This symbol was the most complex one, showing a hand pulling on a boot, and

portrayed the boot from an unusual angle. The lower error rate obtained under

the most difficult viewing conditions may reflect a message that appears more distinguishable from "exit" or an image that loses meaning altogether.

Symbols X19 and Z19 are intended to identify the location of electric shutoff

panels; Y19 is a similar symbol for gas shutoff valves. These three symbols

are graphically similar and produced similar error rates of 13-14 percent,

overall. Conceptually there seems little reason to expect confusions with the

"exit" message. The errors may again be attributable to the basic rectangular

shape suggesting a door; the throw switch on the electrical shutoff symbols

might also be viewed as some form of door handle. Whatever the source of con- fusion, these symbols could be dangerous in emergencies if they lead viewers

into utility areas rather than toward exits.

Symbols X30 and Z30 are intended to convey the location of fire department hookups to charged water sources. To distinguish these water supplies from hookups into which water is pumped, the symbol indicates a water flow from the

connector. Symbol X30 does this by showing water drops; Z30 shows arrows. The

comparison of the error rates indicates that the arrow contributes to confusion

with "exit". Symbol Z30 has a much higher error rate (25 vs 3.6 percent) under

the best viewing condition, when the small arrows are most visible.

Three similar symbols depict a flame to communicate the danger of combustion.

Unlike Y25 and Z25, more errors occurred for symbol X25 (17.9 percent) under

the intermediate viewing condition. The three symbols differed not only in the

form of the flame, but also in flame size, surround shape, and color, all of

which may have contributed to the findings. Overall, however, the low error

28
rate for these symbols (12 percent, 2 percent and 5 percent) does not suggest

that a flame by itself is frequently interpreted as indicating a fire exit.

4.5.2 Features of Foil Symbols Related to Exit Message Confusions

The review of those messages and symbols most frequently misinterpreted as exit symbols suggests a number of graphic features that may contribute to

confusion. These include surround shape, human figure, feet, arrow, and doorshape. Since these features were not systematically varied, many graphic and

conceptual features may be confounded, and the effect of a given feature may be

only inferred. Although any conclusions are necessarily tentative, the evidence

suggesting the role of each of these features is discussed below.

Surround shape appears to be a significant factor in confusions for exit

messages. It is difficult, however, to assess the effect of the symbol

surround shape alone since it is confounded with message type, color, size of

the enclosed image, and the pictogram image itself. Nonetheless, across the

variety of symbols investigated, there is the definite indication that surround

shape is a significant factor in producing exit symbol confusions. This appears

to be especially true under the most difficult viewing condition, where the

pictogram image is least visible. Four basic surround shapes — square, circle,

circle with diagonal slash, and triangle (apex up) — were used for all but

two of the 108 foil stimuli. In the most difficult viewing condition, fewer

than one-fourth of the symbols produced error rates in excess of 15 percent;

yet these were distributed very differently across the four shapes. Fourteen

of 43 (33 percent) symbols with square surrounds resulted in high error rates;

9 of 31 (29 percent) symbols with circular surrounds; 1 of 12 (8 percent) with

circle-and-slash surrounds; and none of 20 symbols with triangular surrounds.

Thus, across all messages, variation in surround shape for the foil symbols

appears to increase the likelihood of confusions with the exit message. Where

symbols for the same message are paired with more than one surround shape,

further comparison is possible. For nine messages, two or more different surround shapes were used. Table 5 lists the symbols and their surround shapes in

ascending order of errors during difficult viewing conditions, for each of

these messages. With some exceptions, the table indicates an ordering of fewest

errors for triangular surrounds, more errors for circular surrounds, and most

errors for square surrounds. In summary, surround shape is an informative

dimension, both on the grounds of common sign coding conventions and on the

basis of the exit symbols included for this study. Yet the extent to which sign users rely on surround shape, especially as a function of symbol visibility,

remains an interesting issue. Shape stereotypes for some messages may exist

(Easterby and Hakiel, 1977), and experimental subjects may detect shape changes

in signs (Adams and Hsu, 1981), but there is little research on the functional

importance of symbol surround shape to sign users.

The presence of a full human figure in a pictogram also appears to be related

to misinterpretations as "exit". While only 13 of the 108 foil symbols con- tained a human figure, eight of the 34 symbols with overall error rates exceeding 10 percent contained such a figure. Thus, such symbols occurred among the

problem stimuli at twice the expected rate. Further, of the five symbols

29
Table 5 Percent Errors (Difficult Viewing Condition) for

Symbols with Different Surround Shapes

Message Symbol Surround % Errors

Explosion Hazard XI triangle 14.3

Z23 circle 21.4

X23 square 25.0

Entanglement Hazard Y6 triangle 0.0

X24 circle 7.1

X36 square 17.9

Fork Lift Traffic Y3 triangle 10.7

X3 triangle 10.7

Z24 circle 17.9

General Hazard X6 triangle 10.7

Z6 triangle 14.3

XI

8

circle 35.0

Corrosion Hazard Y24 circle 0.0

Y2 triangle 3.6

X32 triangle 7.1

Electrical Hazard Z33 circle 7.1

X35 square 7.1

X2 triangle 14.3

Flammable Y1 triangle 3.6

X25 circle 7.1

Slip, Trip, Fall Y4 triangle 3.6

X33 circle 7.1

Z4 triangle 10.7

X4 triangle 10.7

Y36 square 14.3

Z34 square 25.0

Not an Exit Y34 triangle 14.3

Y8 circle 17.9

Z8 circle, slash 21.4

X7 square 60.7

30
containing a figure but having error rates less than 10 percent, three of these were "no entry" symbols which incorporated the prohibitory circle and slash.

As discussed above, use of the circle and slash as a surround shape appears to

result in low probabilities of "exit" interpretations.

In contrast to the full human figure, depictions which show only the head or torso seldom produce high rates of confusion (only two cases occur where the

error rate exceeds 10 percent). While this may relate in part to the different

referent messages symbolized, the data suggest that, where a head or torso can

be substituted for the full figure in a non-exit message, confusions under poor

visibility may be reduced.

Although only six symbols contained the image of feet or boots, four of these

were among the symbols with relatively high rates of confusion. Interestingly,

none of the actual exit symbols included in the experiment used such an image,

yet "exit" interpretations for feet or boots still occurred. These confusions

suggest that the "foot” portion of the body appears more related to "exit"

than does the head or torso.

All five symbols that contained an arrow produced error rates exceeding 10

percent. Furthermore, an electrical hazard symbol (X2) with an arrowhead at

the end of an electrical bolt produced a higher error rate (9.5 percent) than a similar bolt without the arrowhead (Z33; error rate of 3.6 percent). This

occurred even though symbol X2 was enclosed in a triangle surround and Z33 in

a circular surround. The contribution of the arrow to the "exit" connotation

of a symbol has been discussed by Lerner (1981). The present findings reinforce his contention. Any use of an arrow in a non-exit message must be done

with extreme caution.

All four foil symbols (X7, Y8, Y18, Z8) that included images of doors resulted

in error rates exceeding 10 percent. Five other symbols (X19, Y19, Z19, Z20,

Z29) had large vertical rectangular areas that were proportioned similarly to

a doorway; all of these also produced error rates exceeding 10 percent. These

findings suggest that it may be advisable to avoid door-shaped images or background shapes in non-exit symbols.

Representations of various types of flames and smoke appear in some of the

symbols, but some of these do not depict "fire hazard". Two (X10, Z25) show a flame on a match; two (Y10, Z10) show a smoldering cigarette; and one (Y19)

has a flame symbol indicating natural gas. Of the eight symbols actually con- taining representation of a fire, only two produced more than a 10 percent

error rate; for all thirteen symbols with any sort of flame or smoke, only

three produced more than 10 percent errors. Since about one-third of all symbols resulted in error rates above 10 percent, the frequency of images with

flame or smoke in the exit confusion category is even less than might be

expected. Thus, there is no evidence that images of fire tend to increase

confusions with "exit." This occurs even though three of the exit symbols

included in the experiment contained flames along with their other graphic

elements

.

31
4.6 SUMMARY - SYMBOL FEATURES RELATED TO THE SUCCESSFUL EXIT MESSAGE

Based on the detailed consideration of the exit and foil symbols, some generalizations for exit symbology may be summarized. These generalizations

are all tentative, subject to the limitations discussed previously.

For exit symbols, a square surround appears preferrable to a circular surround,

and white with green or black may be preferable colors to white and red.

Triangular surrounds are clearly not associated with the message of exit.

Filled figures are more visible than outline figures. No common pictogram

element was clearly more critical than others; however, the combination of a human figure with a doorway or arrow appears to be effective in conveying the

exit message under most viewing conditions. The arrow also appears effective.

The interactions of the graphic elements (human figures and doorways) should

be simplified; however, with figures presented against an uncomplicated background. In contrast, the highly abstract symbols did not evidence any advantage

in visibility that would offset their poor understandability to subjects not

familiarized with them.

For the non-exit symbols, confusions with exit can be reduced by use of a triangular surround, but increased by using rectangular surrounds. If a person

is shown, portraying just the head or torso, leads to fewer such confusions than

showing the entire human figure. On the other hand, feet tend to encourage

"exit" interpretations. Doorways, or rectangular shapes proportioned as doorways, should be avoided in non-exit symbols. Arrows also tend to lead to

confusions with "exit", and should be used cautiously in non-exit symbols.

4.7 COMPARISON WITH OTHER EXIT SYMBOL EVALUATIONS

The subject's task in the present experiment was an attempt to simulate the task

confronting a person in an emergency situation. The subject looked for an exit

message under viewing conditions degraded to make that decision more realistic

and difficult. A number of other evaluations of safety and informational symbols have assessed the meaningfulness of symbols for the exit message, without

introducing any degradation in viewing. Results from these other experiments

can be examined to provide further insight about the meaningfulness of the

specific exit symbols studied in the present experiment.

Of the 18 exit symbols studied in the present experiment, all but 5 have been

assessed elsewhere for meaningfulness. Table 6 summarizes the data from these

assessments for each symbol, in terms of percentage of correct identification,

scoring criterion (strict or lenient), number of subjects, method, and authors

of the reported research. The percentages of correct identifications in the

various experiments should not be taken too literally or treated as directly

comparable due to many methodological differences. They are presented here

to give some idea of the overall "meaningfulness" of each exit symbol, as indicated by the percentage of times that people can correctly indicate that a symbol means "exit". These findings may be compared with the results of the

present experiment given in table 2. (Note, however, that table 2 presents

error rates, while table 6 presents percentage correct data).

32
Table 6. Supplementary Data on the Understandability of Selected Exit Symbols

Percentage Correct

Number

Symbol of Ss Method Authors

Strict

Criterion

Lenient

Criterion

A 2.3 26.7 86 Definition Collins et al., 1982

1.6 6.6 61 Definition

B 2.2 62.2 45 Definition Lerner & Collins, 1980

57.8 46 Multiple choice

25.0 143 Definition Collins & Pierman, 1979

C 2.2 6.7 45 Definition Lerner & Collins, 1980

22.2 Multiple choice

17.0 143 Collins & Pierman, 1979

D 66 .0 Matching Zwaga & Boersema

37.6 200 Definition Easterby & Graydon, 1981

E 39.8 59.1 88 Definition Collins et al., 1982

68.5 83.3 54

72.1 129 Multiple choice Collins, in prep.

Variant - Easterby & F 37.1 200 Definition Graydon, 1981

G 86.7 91.1 45 Definition Lerner & Collins, 1980

95.7 46 Multiple choice

90.7 93.0 86 Definition Collins et al., 1982

82.0 82.0 61 Definition

89.3 131 Multiple choice Collins, in prep.

H 90.4 95.7 94 Definition Collins et al. , 1982

83.0 88.7 53 Definition

I — — — — —

J 68.9 86.7 45 Definition Lerner & Collins, 1980

69.2 Multiple choice

64.8 72.7 88 Definition Collins et al., 1982

68.5 83.3 54 Definition

K 91.5 130 Multiple choice Collins, in prep.

L 82.9 90.3 94 Definition Collins et al.

79.2 86.7 53 Definition

M 53.2 200 Definition Easterby & Graydon, 1981

N 55.7 122 Multiple choice Collins, in prep.

0

P

Q

R —

33
Inspection of table 7 reveals that the various candidate exit symbols differed

widely in terms of percentage of correct identification. Symbols, A, B, and

C, for example, were generally understood by fewer than 25 percent of the

participants, depending on the method and scoring criterion used. Symbols D,

E, F, J, M, and N received higher percentages of correct responses, but with

scores generally below 75 percent correct. ISO has previously suggested that

symbols with scores below this range are not acceptable as substitutes for

word messages. Only symbols G, H, K, and L received percentages of correct

responses above 75 percent.

Compared with research from experiments in which subjects defined exit symbols

only as a subset of safety symbols, there was a greater tendency to identify

symbols as "exit" symbols in the present experiment. Agreement was very close

for some symbols (A, C, G, H) and quite different for others (D, E, F, J, M,

N) . There was also a greater tendency to interpret other non-exit symbols as "exit" more frequently in the present experiment. It should be remembered that

the subject's task here was to determine if a symbol were an exit symbol or not,

and that each subject was familiarized with a subset of exit symbols. Consequently, subjects were somewhat biased toward identifying a particular symbol

as an "exit". This increased tendency to identify symbols as indicating "exit” can be interpreted in a number of ways. Guessing in the absence of information

might account for some of the increase, although the generally low rates of errors for foil stimuli limit the extent to which this can account for the data.

More likely, since subjects were specifically told to look for "exit" symbols,

the procedure may have caused a shift in a subject's criteria for decision.

The poor viewing conditions may also have altered search strategies, so that

symbols were evaluated more in terms of isolated features than holistically.

Further, since subjects were searching for a class of symbols, performance may

have been based on a comparison with some internal model, or "search image."

In other research contexts, performance has been related to how "representative"

an item is as an example of its class (Mervis and Rosch, 1981). Whatever the

reason, the present increase in "exit" interpretations emphasizes two points.

First, competing messages from other signage during an emergency can cause con- fusion and a significant amount of serious error. Any sign bearing resemblence

to an exit symbol may be interpreted as indicating "a way out." Secondly, what

may appear to be relatively minor features of a symbol, for exit or other

messages, may have a significant influence on interpretation under the poor

viewing conditions existing in emergency conditions.

34
5. CONCLUSIONS

In the preceding pages, experimental data on the visibility of exit and foil

symbols were presented for a series of degraded viewing conditions. The

present experiment attempted to separate the effects of familiarity and visibility by familiarizing subjects with a random half of the exit symbols. This

attempt isolated a number of exit symbols which could be correctly identified

as exit under poor viewing conditions, only if familiarized. It also isolated

another set of exit symbols with low error rates regardless of familiarization.

This latter class of symbols is important because of the authors’ conviction

that a good exit symbol should have good initial understandability and good

visibility under all viewing conditions. Furthermore, under the stress of a building emergency, a more inherently meaningful image may retain its

effectiveness to a greater extent than one which must be learned.

When combined with other research on exit symbols, data from the present

experiment, including the use of foil symbols, allowed the identification of a

a number of graphic features which appear to contribute to the understandability

and visibility of an exit symbol. These features include: use of solid figures, use of square/rectangular surrounds, use of full human figures, and minimization of interaction among symbol elements. The data obtained for the foil

symbols indicate a variety of features that are associated with the successful

exit message. Analysis of those symbols frequently confused with "exit" indicates that they contain features which appear to contribute to accurate identification of exit messages. These include: presence of a full human figure,

vertical rectangular elements, arrows, and human feet. Features which do not seem to lead to confusions with the exit message include: use of a triangular

surround, presence of flames, and presence of a human head, hands, or torso.

The data suggest that Symbolic versions of the exit message which combined a human figure with a doorway or an arrow appeared to be most effective under

all viewing/familiarization conditions.

Data from the present experiment, when combined with data from those experiments

which determined initial understandability, strongly suggest that a symbol which

contains the graphic features of symbol K (see figure 2) can effectively symbolize the message "exit", even under the poorest viewing conditions. Symbol K,

showing a person and an open door, demonstrated both good initial understandability and good visibility for all viewing conditions, regardless of familiarization. Although symbol J contains many of the graphic features of symbol K,

and has good initial understandability, it received a much greater number of errors than symbol K in the poorest viewing conditions of the present experiment. Although the number of errors for symbol A when familiarized is almost

as low as for symbol K under poor viewing conditions, the dramatic increase in errors (from 11.1 to 82.5 percent) for symbol A when NOT familiarized suggests

that this symbol may have limited effectiveness. Its very poor initial understandability (between 2 and 25 percent in Collins et al. , 1982) would appear

to reinforce this contention. Consequently, symbol K appears to be one of the

most effective symbols studied in the present experiment. Japanese research

(1980) has also indicated the effectiveness of this symbol in smoke conditions.

As a result, the symbol which is in wide use in Japan (see figure 4), has been

recommended by the Japanese (1980) to ISO for consideration as an Exit symbol.

35
Figure 4. Japanese exit symbol in use

36
Its apparent effectiveness in communicating the exit message to people in the

U.S. and Japan, as well as its good visibility under poor viewing conditions

suggest that this proposal deserves further consideration.

In conclusion, the results of the preceding experiment indicate that there are

exit symbols which are both visible under degraded viewing conditions such as smoke, and understandable without prior, deliberate familiarization. Although

word messages can be used to reinforce the understandability of a symbolic

indicator, it is essential to select life-safety symbols which have good

initial understandability and good visibility under all viewing conditions.

Such symbols have been identified in the present experiment.

37
6.

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40
APPENDIX A - FOIL SYMBOLS

FOIL SYMBOLS FROM LIST X

6 . General Warning

9 . No Entrance

12. Fire Extinguisher

15. Wear Respirator

18. General Warning

41
LIST X—CONTINUED

19. Electricity Shut-Off

28. Alarm Call Point

0

31. Shut-Off

23. Explosion 24. Entanglement

29. Connection 30. Connection

32. Corrosion 33. Trip

42

34. Use Stairs/Fire 36. Entanglement
FOIL SYMBOLS FROM LIST Y

4. Slip

7. Do Not Enter

6. Entanglement

9. Do Not Enter

43 '

18. Keep Door Closed
LIST Y—CONTI..TED

28. Fire Alarm

31. Water Connection

20. Eyewash

23. Fire Phone

26. Fire Bucket

32. Respirator

35. Wear Safety Glasses

21. Safety Shower

30. Sprinkler Connection

36. Slip

44
FOIL SYMBOLS FROM LIST Z

7. No Entrance

10. No Smoking

13. Wear Hard Hat

16. Wear Safety Shoes

11. Do Not Block

14. Wear Safety Glasses

17. Wear Safety Gloves

6. General Warning

9. No Entrance

12. Fire Extinguisher

15. Wear Respirator

18. Ear Protection

45
LIST Z—CONTINUED

19. Electricity Shut-off 20. Eyewash

22. First Aid

28. Direction

31. Connection

34. Fall

26. Fire Ladder

29. Hose & Reel

32. Noise Hazard

35. Wear Goggles

21. Safety Shower

27. Alarm Call Point

36. Overhead Hazard

46
APPENDIX B - INSTRUCTIONS TO SUBJECTS

INSTRUCTIONS (PART A)

The purpose of this experiment is to determine how visible various picture

signs are. We will be showing you many slides of picture signs, or symbols,

that convey a variety of different messages. Some of these signs may be

familiar to you, such as the "no smoking" symbol; others you never have seen

before.

Your task is very simple: for each slide you see, you must decide whether or not the symbol indicates an exit . The majority of the signs you see will be

for other messages but many will be picture signs that do stand for "exit".

Before beginning the experiment, we are going to show you some of the exit

symbols so that you can become familiar with them. Take your time and look

them over carefully. During the experiment you will also be seeing other exit

symbols as well.

INSTRUCTIONS (PART B)

You will be viewing symbols, one at a time, through the eyepiece in front of

you. Every time you push the telegraph key, you will see a red dot, which is

the "ready" signal. When the red dot goes off, a slide will appear for 4

seconds. Your task is to indicate whether the symbol shown is meant to indicate

the idea of "exit".

For each symbol, indicate a "yes" on the answer sheet if the sign is for an

exit; indicate a "no" if the symbol is for any other message. For each slide

you see you must indicate a "yes" or a "no", filling in the blanks in the answer

sheet going down each column. Continue doing this until you have gone down

each column and the answer form is full.

The majority of the symbols you see will be for other messages, but many do

mean "exit". Some of these you have already seen, but there are others that

you have not yet seen. Be sure to write a "yes" for every exit sign you see,

whether or not it is one you have seen before.

We are interested in how well symbol signs can be comprehended when the

visibility is very poor. For this reason, many times the symbols you see will

be very faint — in fact, you may sometimes feel that you do not see anything.

It is very important that you concentrate and make your best guess. You must

indicate "yes" or "no" for every slide you are shown, even when a decision is

very difficult.

47
NBS-114A (REV. 2-8C) U.S. DEPT. OF COMM. 1. PUBLICATION OR 2. Performing Organ. Report No. 3. Publication Date BIBLIOGRAPHIC DATA

REPORT NO.

SHEET (See instructions) NBSIR 83-2675 April 1983

TITLE AND SUBTITLE

AN EVALUATION OF EXIT SYMBOL VISIBILITY

5. AUTHOR(S)

Belinda L. Collins and Neil D. Lerner

6. PERFORMING ORGANIZATION (If joint or other than NBS. see instructions)

national bureau of standards

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

8. Type of Report & Period Covered

9.

SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City, Slate, ZIP)

National Bureau of Standards

Department of Commerce

Washington, DC 20234

10.

SUPPLEMENTARY NOTES

J Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11.

ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here) The performance of exit symbols was assessed in a laboratory experiment using

viewing conditions degraded to resemble smoke. Research participants were presented with color slides showing symbol signs designed to be used in

buildings. For each slide the participant indicated if the symbol conveyed

the message of "exit'.' A total of 108 symbol slides were used, of which 18 were exit symbols. Each of the 42 participants were familiarized with a random

set of 9 of the 18 exit symbols, prior to data collection. During the experiment, the symbol of slides were presented under three levels of viewing difficulty.

In general, errors increased as the viewing conditions became more degraded

but the increase in errors became much more severe for some symbols than others.

Fewer errors were made for some of the symbols that had been familiarized. The

data suggested that increased errors under degraded viewing conditions were related to graphic features of the symbols. A number of specific symbol features

that influence exit symbol effectiveness were identified along with features of

non-exit symbols that produce oonfusions. Finally, recommendations for exit

symbol design are presented that may lessen egress-related confusions during

building emergencies.

12.

KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons)

Exit symbols; fire safety; legibility; symbols; understandability ; visibility;

visual alerting.

13.

AVAILABILITY

(xxj Unlimited

| | For Official Distribution. Do Not Release to NTIS

Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

52

15. Price

$ 10.00

USCOMM-DC 6043-P80