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NBSIR 81-2268

Evaluation of Exit Directional

Symbols

Neil D. Lerner

Environmental Design Research Division

Center for Building Technology

National Engineering Laboratory

U.S. Department of Commerce

National Bureau of Standards

Washington, DC 20234

May 1981

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U.S DEPARTMENT OF COMMERCE

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NBSIR 81-2268

EVALUATION OF EXIT DIRECTIONAL

SYMBOLS

Neil D. Lerner

Environmental Design Research Division

Center for Building Technology

National Engineering Laboratory

U.S. Department of Commerce

National Bureau of Standards

Washington, DC 20234

May 1981

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

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
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ABSTRACT

This paper discusses visibility considerations for exit symbols and the

relationship between understandability and visibility concerns. Two experiments evaluated directional indicators (arrows) in the context of building

exit signage. The first experiment compared the visibility of 16 arrows under

degraded visual conditions that were comparable to a smoke environment. This

experiment had two objectives: (1) the development of a methodology for

assessing exit pictogram visibility; and (2) a comparison of the visibilities

of the specific arrows tested. A second experiment obtained subjective rankings of the arrow types on the basis of several criteria of concern for exit

signage. These criteria included connotative meaning, uniqueness from other

directional indicators, and appropriateness.

The visibility procedures were statistically sensitive and demonstrated

differences in the visibility of different arrows. An analysis of the type of

confusions that occurred in errors for each arrow suggests certain relations

between graphic features and errors in detection. The second experment indicates substantial agreement between participants in ranking the arrows and

revealed strong relationships between the several criteria. Together the

results of the two experiments were used to evaluate the set of arrows for

appropriateness for use with exit designators.

Methodological issues in evaluating symbol visibility are considered and

other issues of concern in testing exit signage, such as special user groups,

are also discussed.

iii
TABLE OF CONTENTS

Page

1. INTRODUCTION 1

1.1 PICTORIAL EXIT SYMBOLS 1 1.2 EXIT SYMBOL VISIBILITY 2 1.3 VISIBILITY AND UNDERSTANDABILITY 3

1.4 THE ARROW AS AN EXIT DESIGNATOR 5 1.5 THE POSSIBILITY OF A SPECIFIC ARROW FOR USE WITH EXIT

DESIGNATORS 7 1.6 SUMMARY: THE EXIT SYMBOL PROBLEM 8

2. SCOPE AND RATIONALE OF EXPERIMENTS 10

3. VISIBILITY EXPERIMENT 12

3.1 VISIBILITY METHOD 12

3.1.1 Research Participants 12

3.1.2 Stimuli 12

3*1.3 Apparatus 12

3.1.4 Stimulus Sequences and Visibility Conditions 14

3.1.5 Procedure 15

3.2 VISIBILITY RESULTS 15

3.2.1 Practice Trial 15

3.2.2 General Performance 16

3.2.3 Effect of Stimulus Variables 16

3.2.4 Type of Error 17

4. RANKING EXPERIMENT 21

4.1 METHOD 21

4.2 RESULTS 21

5. DISCUSSION 27

5.1 EVALUATION OF VISIBILITY METHODOLOGY 27

5.2 VISIBILITY OF THE ARROWS TESTED 2 7 5.3 COMPARISON WITH OTHER SYMBOL VISIBILITY RESEARCH 29

5.3.1 Visibility Manipulation 29

5.3.2 Participant's Response 30

5.3.3 Other Research Comparing Arrows 33

5.4 ARROW RANKINGS 34

5.5 COMPARISON OF ARROWS FOR POTENTIAL USE WITH EXIT DESIGNATORS . 35

5.6 FURTHER CONSIDERATIONS IN TESTING OF PROPOSED EXIT SYMBOLS ... 35

iv
TABLE OF CONTENTS (cont.)

6. SUMMARY 38

REFERENCES , 39

APPENDIX A 42

APPENDIX B 43

APPENDIX C 46

v

1. INTRODUCTION

Directional indicators, or "arrows," play an important role in building

emergency signage. This is especially so in designating exits, where highly

visible and readily comprehended directional information can be crucial to

life safety. The manner of indicating direction is only one aspect of the

larger issue of developing optimal graphic symbols to designate the location

of exits. Therefore, broader issues of exit symbol visibility and understandability are discussed below. In this context, the special role and limitations of arrows in conveying the egress message become more apparent. The

two experiments described in this report investigate the adequacy of various

arrows. The results of this research are applicable both to directional

indicators in particular and to building emergency signage in general.

1.1 PICTORIAL EXIT SYMBOLS

Pictorial signs are increasingly used as alternatives to written signs

because they have a number of potential advantages as communication devices

(Collins and Pierman, 1979). Although highway applications are probably

the most commonly encountered pictorial signs, many public buildings now

use symbols to provide informational, safety, and emergency messages to

occupants. The terms "symbol", "pictogram", and "pictorial sign" refer

here to any graphic image, whether highly representational, abstract, or arbitrary, that is used in place of written messages in signs. Unfortunately, although some pictograms are well understood by the public (e.g.,

"no smoking" symbols, Lerner and Collins, 1980), other messages remain

difficult to communicate symbolically. Among these is the critical message

of "exit". Outside of English speaking countries, the word "exit" is not

widely used (American Institute of Graphic Arts (AIGA), 1979); thus, a sign

based on this written message is not likely to be effective to foreigners

visiting the U.S., nor are Americans abroad likely to encounter it. A

meaningful exit pictogram would be of obvious value. However, an effective

exit symbol not only must be well-understood, but must also meet demands

of visibility as well. The exit message may be the most crucial life safety

message to the general public during fire or other emergencies, and so the

performance of an exit symbol may be most critical at a distance under

conditions of emergency lighting or smoke. Thus, an ideal exit symbol

would unambiguously convey to occupants the message of egress with optimal

visibility (the term "visibility" is defined below).

Many symbolic versions of the "exit" message have been developed, including

efforts by various international and national standards groups and agencies.

These symbols show a great range of variability, both conceptually and graphically. For example, some exit symbols are simple, bold geometric shapes,

based on highly abstracted (e.g., rectangle proportioned as a door) or arbitrary (e.g., bisected disc) images. At the other extreme there are highly

detailed pictograms of a realistic figure fleeing flames, with an outside

view of trees visible through a doorway. As these few examples may suggest,

symbols may vary widely both in their meaningfulness to the public and in

their visibility. Most examples have not been explicitly tested for these

qualities, but several experimental evaluations (e.g., Lerner and Collins,

1
1980; Japanese proposal, 1980) have, in fact, demonstrated important differences

in either of these factors.

The concern in this report is primarily with visibility. However, in any

evaluation of exit symbol performance, understandability and visibility must be

jointly considered. Tbe term "visibility" is used in this report to refer

generally to perception under poor visual conditions. In fact, depending upon

the psychological response (detection, discrimination, recognition, interpretation, identification), a variety of technical terms have specific (though not

always agreed upon and sometimes overlapping) operational meanings. These

terms include "detectability," "discriminability , " "readability," "legibility,"

"visibility," "conspicuity , " and others. Since, visibility has been used

widely in experimental literature similar to that described in this report

(e.g. Smith and Weir, 1978; Jacobs, Johnston, and Cole, 1975), it is adopted

throughout. However, it should be noted that the term has sometimes been

restricted to the process of simple detection (presence or absence of a stimulus), and not to higher-order perceptual processes. The broader use of the

term is followed here. "Understandability" refers to the comprehension of the

intended sign message by potential users. Many different methods have been

used to assess understandability (reviewed by Collins, 1981), such as having

research participants provide definitions for a symbol, match symbols and

messages, rate the meaningfulness of a symbol on some subjective scale, or engage in behavior as directed by a symbol sign. While the understandability

of a symbol would certainly decrease as visibility is degraded, the understandability of exit symbols bas typically been evaluated under optimal viewing

conditions. Therefore, as used in this report, understandability may be interpreted as a measure of how well the intended symbol meaning is comprehended

under good viewing conditions.

In the following sections, the issue of exit symbol visibility will be discussed,

and then the problem of symbol understandability and its relation to visibility

will be briefly considered. Finally, a special concern with exit directional

indicators ("arrows") will be discussed. The experiments that follow focus on

these directional indicators.

1 .2 EXIT SYMBOL VISIBILITY

The visibility of an exit indicator during emergency conditions is an important

concern. Smoke is a principal threat to life during fires, since problems of

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

toxic effects of fires (Gross, Loftus, and Robertson, 1966). Compounding the

visual disruption of way-finding by smoke are the disorienting effects of

smoke, fear, lachr ymation , and possibly even confusion due to central nervous

system interference by some noxious smoke products (Phillips, 1978). While

this disruption serves to emphasize the importance of egress signage during

emergencies, smoke obscuration can be a special problem for signs: since

smoke density increases with distance above the floor, obscuration may be

greater at the level of the signs (such as above a door) than toward the floor

(e.g., Demaree, 1979). Automatic sprinkler systems can drastically influence

the pattern of smoke as well. Tests of simulated hospital room fires reveal

that initiation of the sprinklers can invert the flow of gases from a burning

2
room to a corridor (O'Neill, Hayes, and Zile, 1980). This rapidly results in

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

Thus, while sprinklers may be an effective means of fire containment, they can also serve to accelerate visibility problems. The increased use of automatic

sprinkler systems therefore should lead to even more concern with exit signage

visibility.

Although there has been research on the visibility of signs in smoke, 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 (e.g., Demaree, 1979; Bono and Breed, 1965; Jin, 1970).

Almost no research has focused specifically on the visibility of symbol signs

for building environments. Some reports have compared the visibility of

symbols versus word signs for highway applications (e.g., Jacobs, Johnston, and

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

generally were more visible than written messages, these experiments used

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

conditions for buildings, however appropriate for highways.

One reported experiment has directly evaluated symbolic exit signs for visibility in buildings during emergencies (Japanese proposal, 1980). The Japanese

proposal to the International Organization for Standardization (ISO) describes

visibility experiments conducted by T. Jin. This research was part of a larger

Japanese project evaluating exit symbols. Unfortunately, the translated report

of the work does not provide great detail on research methods. Jin obtained

"visual distances" for various symbols based on observations by 30 participants

in a smoke-filled 14 m-long corridor. Thirteen pictographs were compared, most

of which had been selected from a much larger set of images on the basis of

judgments of graphic quality and general preference. Despite this preselection

process, the 13 symbols still varied substantially in visibility, with the most

visible having a visual distance about 35 percent greater than the least visible.

Jin’s results are difficult to evaluate due to the sketchy discussion of

methodology and uncertainty about what response was required of participants

and how "visual distance" was determined. Hopefully, a more detailed translation of this work will be reported. Nonetheless, Jin's findings are valuable in

providing a quantitative demonstration of how symbols can vary on the critical

quality of visibility. In fact, given the preselection of symbols prior to the

visibility experiment, Jin's data probably are quite conservative in revealing

the range of visibility that could exist among currently used or proposed

symbols.

1.3 VISIBILITY AND UNDERSTANDABILITY

Proposed exit symbols not only differ in their visibility but also in their

understandability. Several previous research efforts at the National Bureau of

Standards (NBS) concerned with the understandability of symbols for building and

workplace safety (Collins and Pierman, 1979; Lerner and Collins, 1980; Collins

and Lerner, 1980) included various exit designations among the symbols

investigated. As a result, information has been collected for ten different

"exit" and "emergency exit" symbols. The percentage of research participants

3
that correctly identified the meaning of a given symbol ranged from under five

percent to over 90 percent. The symbols most readily comprehended tended to

be the most literal, showing walking or running figures, doors, and flames in

various degrees of realism and detail. At the other extreme, highly symbolic,

simple images were least understood.

Another finding emerging from the NBS studies was that symbols with intended

meanings unrelated to egress may often be interpreted as indicating exit or refuge. These confusions raise the danger of an ambiguous symbol causing a person to seek safety in an inappropriate direction. With one exception the

common feature of these symbols was their ambiguity, lacking any image of an identifiable object. An arrow was present in several, probably contributing to

the egress interpretation (discussed further below).

These experiments not only indicate the need to explicitly evaluate the

understandability of a symbol set; the data also suggest a relationship between

understandability and visibility. The literal and relatively detailed images

of the most readily understood images may be expected to be the least visible,

while the simple, geometric images of the abstract symbols may be expected to

be the most visible. While actual data on the visibility of most of the symbols

is not available, these inferences may be grossly made by considering the features that contribute to perception of an image. These features include the

size of major contrasting areas, size of critical detail, figure-ground relationships, continuity, simplicity, and contrast boundaries (Easterby, 1967;

Follis and Hammer, 1979; Overington, 1976).

An interesting example of the trade-off between understandability and

visibility comes from ISO's proposed emergency exit symbols. In the case of

these two symbols there is in fact some data available on visibility. ISO

initially proposed a symbol consisting of a white rectangle on a green background. In response to criticism that this symbol was unintelligible, ISO

eventually replaced it with a new proposed image: a stylized figure running

through a simplified image of a half-open door. This led to a substantial

increase in understandability, as shown by Lerner and Collins (1980). Yet

comparing visibility data from two similar experiments described in the 1980

Japanese proposal to ISO, this change decreased by about one-third the distance

at which the symbol can be identified in a smoke-filled environment. Thus

better understandability was achieved at a substantial cost in visibility.

The apparent inverse relationship between the understandability and visibility

of exit symbols may not necessarily be true for other symbols. For instance,

pictograms to designate the location of equipment ("fire extinguisher") or the use of required safety gear ("hard hat area") communicate effectively using

simple, and probably highly perceptible, images. No single stereotypical image

exists for the concept of emergency exit. Various images can contribute to

the egress message — figures, doors, arrows, fire, diagrams — and these have

been used in numerous combinations to produce exit pictograms. The design

challenge is to simplify and minimize these images and their combination so

as to maximize visibility while maintaining understandability. Consequently,

the need to evaluate candidate exit symbols concurrently for both visibility

and understandability is imperative. Testing and selecting a symbol on the

4
basis of only one of these properties is likely to result in less-effective

performance on the other property.

1.4 THE ARROW AS AN EXIT DESIGNATOR

Although no common stereotypical image exists for the concept of "exit", the arrow is probably the strongest element related to the exit idea. Lerner and

Collins (1980) presented data to support this view. Participants in one portion of their experiment were asked to draw (produce) symbols to communicate

various fire and safety messages, including "exit" and "fire exit."

"Exit" proved to be extremely difficult for participants to symbolize. Seven

percent of the participants drew no image at all. Further, despite instructions not to use words (generally well-followed for other messages), another

42 percent of the participants included the word "exit” as all or part of the

image. No common stereotype image was found, although the most frequently

occurring image was an arrow. An arrow was incorporated into about 20 percent

of all responses, and nearly 40 percent of those responses that did not use the

word "exit." Thirteen percent of all responses used the arrow as the entire

image

.

For the "fire exit" message, participants again used the word "exit", this time

in nearly one-third of the responses. Flame was a very common element of the

images, occurring in about three-quarters of all responses. The arrow was again

a frequent image, being incorporated into about one-third of the drawings.

An examination of existing and proposed exit symbols confirms the result of the

Lerner and Collins experiment. The variety of different conceptualizations

suggests that designers, too, do not share a stereotypical idea for exit. But

again, the arrow emerges as a frequent component of the exit symbol. Figure 1 presents a number of examples of the ways in which arrows have been incorporated

into exit symbols.

Another indication of the "exit" connotation of arrows comes from confusions in

symbol meaning. In testing a set of fire-safety symbols, Lerner and Collins

(1980) noted that ambiguous symbols that incorporated arrows were likely to be

misinterpreted as suggesting egress. For example, a symbol showing an arrow

entering a sauare area, on a triangular field, was proposed by ISO indicate

"not an exit." More participants interpreted this symbol as egress-related

than the correct "no egress" interpretation.

Despite its connotation of exit, an arrow by itself is not adequate to denote

an exit unambiguously. Lerner and Collins (1980) included an arrow among the

symbols they tested for under standability . An arrow was clearly interpreted

to mean "exit" by only about one-third of the participants. Virtually all participants recognized the symbol as providing directional information, but most

did not explicitly state this to be direction to an exit. This parallels the

ubiquitous use of the arrow for all sorts of directional signage (Follis and

Hammer, 1979), so that the meaning of an arrow by itself is ambiguous.

5
FIGURE 1. Use of arrows in exit symbols
Thus, the contribution of an arrow to building signage is not straightforward.

As with many other messages, "exit" often requires some form of directional

indicator to be used with it. In this case, however, the arrow also appears to

contribute to the message itself. At the same time, the arrow can cause confusion from other messages, and is by itself insufficient to communicate the idea

of an exit in an unambiguous manner. If an arrow is integrated into an exit

symbol consisting of other elements, there is the further concern that the added

feature may increase complexity and possibly reduce the size of the individual

features, and so reduce the perceptibility of the symbol.

1.5 THE POSSIBILITY OF A SPECIFIC ARROW FOR USE WITH EXIT DESIGNATORS

The previous section indicated that despite its connotations, the arrow may

not be desirable as a major element of an exit symbol. The American Institute

of Graphic Arts (AIGA, 1979) has also discussed some problems with incorporating the arrow into the symbol itself. Nonetheless, it is clear that any exit

sign, whether in symbol or word form, will frequently be used in conjunction

with a directional indicator. Because existing exit symbols are often unclear

in meaning, and because an arrow connotes "exit", a unique and effective directional indicator for use only in conjunction with exit signage may help reinforce the exit message. Making the use of a particular arrow specific to

exits, and selecting an arrow that is distinct from other directional indicators, may reduce confusability with other signs and symbols.

Thus, the use of a unique directional indicator to be used on ly in conjunction

with exit signs (but not in isolation) could provide the following advantages:

1. The arrow may reinforce the exit message both by contributing its own connotative meaning and by providing redundancy in the visual message.

2. The uniqueness of the arrow may reduce confusability with other messages,

especially for poorly understood symbols and symbols containing arrows.

Signs and symbols containing no arrow or an arrow other than the "exit

arrow” could be interpreted as unrelated to exit even if their actual

meaning remained ambiguous.

3. The arrow may increase the "learnability" of a standardized exit symbol.

Many candidate exit pictograms are simply not well understood. Furthermore, as the drawings of Lerner and Collins' (1980) participants suggest,

the "exit" word sign may be entrenched in the public mind as the way to

indicate egress. These two factors impede the adoption of a standardized

exit symbol, despite the potential advantages such a symbol may provide.

If a unique arrow were adopted, it could be used with existing exit designators as well as symbols, and so become associated with the exit message.

It could then be effective in helping to bridge understanding in those

situations where observers are unfamiliar with the exit symbol.

A. The arrow may serve to increase the visibility of exit designators,

especially under emergency conditions, such as smoke or emergency lighting. Some proposed symbols have poor legibility, whereas some arrows may have much better legibility. Problems of exit symbol interpretation

7
and confusion from other symbols would be more severe under poor

visibility, and so the contribution of a unique arrow to the exit

message might be amplified.

To realize these potential benefits of a unique exit-related arrow, the choice

of the specific arrow may be critical. One goal of the experiments in this

report is to provide initial data on visibility and other criteria important to

exit directional indicators.

1.6 SUMMARY: THE EXIT SYMBOL PROBLEM

There is a recognized need for a standardized symbol to designate the location

of exits. Many symbols have been used or proposed that fail to be well understood. Others may not he sufficiently visible under emergency conditions, such

as smoke, during which symbol effectiveness may be critical. The most visible

symbols, in fact, appear to be among the least understood although there are few empirical data to support this apparent relationship. Serious confusions

with other symbols also exist, so that unrelated messages may be interpreted

as related to egress. Furthermore, no strong single stereotypical image appear

to exist among people for symbolizing the exit idea. The closest approximation

to such a stereotype is the arrow, which by itself is too ambiguous and

ubiquitous to function as the sole exit designator. Thus although the proliferation of exit symbols is itself a problem, emphasizing the need for standard

ization, no candidate symbol appears clearly superior and entirely adequate.

To mitigate this problem, it is suggested that a distinct arrow could be

standardized uniquely for use with exit symbols or exit word signs. This could

help reinforce the meaning, reduce confusability with other messages, increase

visibility, and possibly aid in the learning or interpreting of newly

encountered exit symbols. Adopting such a standard directional indicator for

exits represents a partial solution. Development of an effective meaningful

exit symbol is ultimately the optimal solution.

Although understandability and visibility have been emphasized here as the

primary criteria for a standard exit symbol, other considerations exist as well

One such factor is the symbol's discriminability from other existing signage.

Additionally, if a symbol is to find general acceptance it must be graphically

compatible with other signage and be generally satisfactory to the design com- munity. Specific attention may need to be paid to certain special user groups

as well: these might include children or the elderly, for example. Despite

these and other additional considerations, however, the primary step in selecting an effective exit symbol will be to identify an image that is well understood and highly visible for the general public.

One purpose of the research presented in this report is to develop an effective

and efficient laboratory procedure for assessing the visibility of exit symbols

The discussion of exit symbol performance points up the need for explicitly

testing proposed symbols for both understandability and visibility. In the case of understandability, a variety of evaluation methods have been employed

and a sizable research literature exists (Collins, 1981). In contrast, there

has been little research appropriate for comparing the visibility of graphic

8
alternatives for building signs. Thus the visibility research reported here is

addressed to the methodological problem of establishing an appropriate general

procedure, rather than determining the visibility of any specific set of exit

symbols. At the same time, this research presents an opportunity to explore

further the suggestion of standardizing a directional arrow for exclusive use with exit designators. The following section provides an overview of the

specific goals and approach of the experiments. Sections 3 and 4 will describe

the method and results of each experiment in detail.

9
2. SCOPE AND RATIONALE OF EXPERIMENTS

Two experiments are described in this report. The first concerns the visibility

of a set of directional indicators ("arrows") under conditions of poor visibility.

The means of manipulating visibility to simulate emergency viewing conditions

is described in section 3. The purpose of the experiment included both methodological issues regarding the general evaluation of symbol visibility and

specific comparisions of directional indicators.

A specific set of arrows, described in the next section, was selected for

evaluation. The visibility of the specific arrows is of interest both because

of the widespread use of arrows, and also because of the susggestion that a unique arrow be specified for use with exit signage. The visibility experiment

provided some initial comparison of various arrows and arrow features.

In addition to the interest in the performance of specific arrows, directional

indicators are of value for addressing more general methodological questions

in symbol visibility. Response measures to arrows are unambiguous and not

strongly dependent on the symbol set. A participant merely indicates the direction in which an arrow is pointing, and the response is scored as correct or

incorrect. In contrast, when pictograms are presented, answers may be more

ambiguous, for example, a verbal description of what was seen. A variety of

problems can arise, discussed in detail in section 5.5. To mention some of

these briefly, performance may vary with the familiarity of the symbols, and

this factor will itself vary during the course of experience in the experiment.

Furthermore, recognition of symbols may be based on comparison of features

within the set tested. For example, only one symbol in a set may have a strong

diagonal component or a dark area in the lower left corner. Such factors may

be irrelevent to how people perceive a symbol in a real environment, but may

be a reliable means for experimental participants to distinguish symbols within

a set. Data interpretation and scoring problems can also arise. Many of these

problems have been encountered in other research (e.g., Zwaga, 1979), and using

a directional response avoids them.

Among the questions concerning method are issues of the sensitivity of the

procedure and the parameters selected: that is, are the data sensitive to

variations in the visibility parameters selected, and can the visibility of the

various stimuli be reliably discriminated. Another question concerns the

stability of the performance of the research participants through the course of

the experiment.

Data on arrow visibility also will be useful in providing reliable data for

comparisons with future observations that may be made in smoke chambers. It is

considerably more difficult and expensive to obtain psychophysical data from an actual smoke environment, and there are problems in maintaining a precise and

uniform smoke field in a large area for durations typical of psychophysical

experiments. The use of the more simple directional arrow procedure over more

complex symbol recognition methods may be especially valuable in this case. Small-scale experiments with actual smoke situations could provide data against

10
which laboratory procedures in the present experiment could eventually be

compared and validated.

The second experiment was designed to supplement the first by providing data on the subjective responses of participants to the various directional indicators. At issue was whether research participants would show substantial agreement in evaluating how well various arrows served to connote the direction to an exit, how appropriate and attractive each arrow was, and how unique each

arrow appeared. If there were to be substantial agreement between participants,

then these data could provide further information on the suitability of

different arrows as elements of exit designators.

The research described in this report was designed to develop a rationale,

procedure, and working hypotheses for the systematic evaluation of exit indicators. It was intended as preliminary research, and therefore the findings

should not be taken as recommendations for selecting any specific directional

arrow. The set of arrows tested, and the sample of observers used, were determined by the requirements of an initial methodological investigation.

The arrows employed in the experiment were selected to provide a range of

different graphic concepts. Several of these arrows are in common use and are

sold widely through sign catalogues; others represent modifications of more

common designs. Some were adapted from an experiment by Smith and Weir (1978).

Some arrows differ from one another only in the value of some parameter (e.g.,

shaft width, head angle). This range of arrow types was intended to permit an evaluation of the sensitivity of the method to the form and parameters of the

arrows, and to help suggest hypotheses about effective arrow elements or types.

The collection of arrows was not intended to represent a set of candidates to

be chosen from.

Similarly, the research participants were selected to meet the needs of a methodological pilot experiment. To assure a relatively homogeneous group with

good acuity, all participants in the visibility experiment were females under

thirty, with corrected-to-normal acuity and no reported visual defects.

While this may increase the sensitivity of the experiment, it obviously requires

greater caution in generalizing the results to the general population.

1 A number of age-related changes (some of which interact with sex) occur

in visual perception (acuity, sensitivity to low illumination, difference

thresholds for contrast) as well as in the physical and optical properties

of the eye (Fozard, et al., 1977; Illuminating Engineering Society (IES),

1972; U.S. Public Health Service, 1964; Weale, 1963).

11
3.1 3. VISIBILITY EXPERIMENT

VISIBILITY METHOD

In the visibility experiment, viewing conditions were designed to simulate

smoke effects. Smoke degrades visibility by two primary mechanisms: first,

it reduces the light coming from the target; second, it scatters light from

other regions into the viewing path, reducing contrast (Middleton, 1952). In

the visibility experiment, light from the stimulus source was reduced by placing a neutral density filter in front of the stimulus slide projector. A

second light source projected a veiling light superimposed upon the projected

stimulus image. In addition, the ambient room lighting was dim (in the mesopic

range) to typify emergency lighting and smoke conditions. The general procedure was adapted from research on highway signage described by Smith and Weir

(1978), although a number of changes were made to better reflect a building

emergency environment.

3.1.1 Research Participants

The participants were seven female volunteers, ranging in age from 18 to 28

years (mean = 21.3). They were recruited from the Gaithersburg, Maryland, area through local advertising and paid for participation. All reported normal

or corrected-to-normal vision.

3.1.2 Stimuli

The stimuli were 32 directional indicators ("arrows"). Each of the 16 basic arrow shapes occured once as a black figure on a white background and again

as a white figure on a black background. The 16 shapes are shown (as black on white) in figure 2. The stimuli were initially drafted as 15.2 cm x 15.2 cm

(6 in x 6 in) placards, with the largest dimension of each arrow being 12.7 cm

(5 in). The only exception was stimulus F (11.4 cm, 4.5 in), which was the same size as the identical portion of stimulus E.

For the visibility experiment, the stimuli were projected as slides. Each

placard was photographed against a medium grey background. The projected image

was square, with the placard centered. The length of the placard image was - 83 percent of the overall dimension of the slide image, so that the placard

occupied approximately 70 percent of the area of the projected image.

3.1.3 Apparatus

The arrows were presented as rear-projected slides, with the participant seated

3.05 m (10 ft) from the screen. The image was at approximate eye level, 1.12 m (44 in) above the floor. The size of the projected image was 8.4 cm per side,

which subtended a visual angle of 1.6°; the width of the placard alone subtended

a visual angle of 1.3°; and the greatest dimension of the arrow itself subtended

1.1°. A 1.3° projection of the placard is equivalent to a 12 in placard viewed

from about 44 feet.

12
FIGURE 2 .
Stimulus presentation was controlled by a two-channel projection tacbistoscope

system. One projector was used to present the arrow slides, while the other

projector presented a veiling light. The two rear-projection images could be

optically combined at the screen. The veiling light was projected through a 4.0 log unit neutral density filter and was on continuously during the experiment. This served two functions: a) it reduced contrast between figure (arrow)

and ground when combined with the projected arrow slide; b) it provided a dim

uniform visual field for illuminating the room. The only other source of room illumination was a shaded 4-watt night-light, located 1.2 m (4 ft) behind the

observer, 1.4 m (55 in) above the floor. These light sources produced an ambient

illumination level, measured at the seat of the participant's chair, of 0.21 lx.

Neutral density filters were affixed to the front of the shutter through which

the arrows were projected. Thus, the observer viewed an image that was first

projected through a neutral density filter and then combined at the screen with

the veiling light from the second projector. Three levels of filtering of the

stimulus projector image were included: 4.6, 5.0, and 5.1 log units.

Luminance measurements of the projected image were made using a 1° luminance

meter. The night-light was on during these measurements. Due to the fact that

the brightness of the screen was not perfectly uniform, the luminance values are approximate. The luminance from the veiling light projector only, projected

through the 4.0 log unit filter, was 0.68 cd/m^. Since the luminance of the

veiling light was roughly an order of magnitude greater than the stimulus image,

this value did not change substantially when the stimulus image was added to it.

Figure-ground contrast for the arrow slides was measured with the veiling light

projector off and no filter on the stimulus projector (night light on) . The

luminance of black areas was in the range of 50 to 140 cd/m^, with the luminance

of white areas in the range of 4600 to 5100 cd/m^ (variability is due to minor

nonunformity of the screen and slides). Thus the ratio of the luminances of

white and black elements of the slides was in the range of 100-to-l to 100-to-3.

3.1.4 Stimulus Sequences and Visibility Conditions

Sixteen sequences of slides were constructed, each sequence consisting of the

32 different arrows. The order of the arrows and the direction in which each arrow pointed —up, down, left, or right—were randomly determined, with the

following constraints:

a) Each direction occurred eight times per sequence.

b) For each block of four sequences (1-4, 4-8, 9-12, 13-16), each

direction occurred once for each arrow.

c) For each block of four sequences, each arrow occurred once in each

each quarter of the list.

For actual presentation during the experiment, the series were shown in pairs,

e.g., series one and two, series three and four, etc. Thus there were eight

sets of 64 slides each. During the experiment a participant viewed a total of

18 such sets, so that each particular set was viewed two or three times. The

14
sequence in which the sets were presented is shown in appendix A. As the

appendix indicates, three sets (excluding practice) were viewed on days one and

five, and four sets were viewed on days two, three, and four.

Three different visibility conditions were included in the experiment. The

visibility condition was determined by the value of the neutral density filter

through which the arrow was projected: A. 6, 5.0, or 5.1 log units. A given

set of 64 slides was viewed under a given visibility condition. Since there were 18 sets of slides viewed, each visibility condition occurred six times per

participant. The sequence of visibility conditions was different for each

person, and was determined as follows. Since there are factorial 3 (3!) = 6

different orderings of three conditions, each participant received each of the

six orderings of visibility conditions, thus completing the 18 sets. The six

sequence of the six orderings was randomized for each participant, with the

following constraints: a) each visibility condition occurred at least once within the three or four sets presented each day; and h) the same condition did

not occur twice in a row within a day. Appendix A presents the sequence of

visibility conditions for each participant.

3.1.5 Procedure

Each session began with a five-minute visual adaptation period. Following this,

the participant viewed the stimuli while seated in the chair and recorded

responses on an answer form. A stimulus slide was presented for 3 s, followed

by a 5 s period in which the participant recorded the direction—up, down,

left, or right—in which she believed the arrow pointed. A tone indicated the

duration of the answer period; when the tone went off, the next slide was shown.

An entire series of 64 slides was shown in sequence, all under the same visibility condition. This was followed by another set of 64 slides under a different

visibility condition. Except for the first and last days of the experiment, a session consisted of four sets of 64 slides each. The slides were shown in the same sequence for each participant, but the visibility condition in effect for

each list varied between participants, as discussed above.

In the first session, the participant read the instructions and was given a page containing an example of each arrow (appendix B) . The instructions emphasized the importance of recording an answer for every slide, even when guessing

was required. After familiarization with the arrow set, a practice list was

presented. This differed from the final procedure in that only 32 slides were

presented, and the slide image was not projected through a filter. Following

this, the practice list was again presented, but this time projected through

the 4.6 log unit filter. Subsequently actual data collection was begun. Six

sets of 64 slides were viewed under each of the three visibility conditions

during the five days of data collection.

3.2 VISIBILITY RESULTS

3.2.1 Practice Trial

None of the participants made any errors on the practice list when no filter

was used to degrade the stimulus image. This indicates that all 16 directional

i 15
indicators, with both positive and negative contrast, were interpreted

correctly. Thus, errors observed under reduced visibility may be attributed to

the visibility condition and are not confounded with problems of interpreting

the arrow.

3.2.2 General Performance

The effectiveness of the filtering variable in manipulating visibility, and the

stability of performance over the course of the experiment, were assessed by an analysis of variance. The mean number of errors per set of 64 slides was the

dependent variable. The day s-by-visibility repeated measures analysis (Keppel,

1973) is summarized in table 1 (this and all subsequent statistical tests were

conducted at the a = 0.05 confidence level). The visibility variable was highly

significant, F (2,12) = 37.04, p < 0.001, and accounted for more than half of

the variance among the scores, as estimated by a>2 ( co^ = 0.55). The mean

number of errors varied from only 1.24 per set (two percent) under the most

visible condition, up to 21.69 per set (34 percent) under the least visible

condition. Pairwise comparisons (Newman-Keuls test, Winer, 1971) among the

three visibility conditions indicated that they all differed significantly from

one another (p < 0.01 in each case). Performance was stable during the five

days; neither the main effect of days nor the interaction of days with visibility were statistically significant factors.

Table 1. Summary of Days-by-Visibility Analysis

Source Sum of Square df Mean Square F

Subjects (S) 2637.08 6 439.51

Visibility (V) 7334.98 2 3667 .49 37.04 (p<0.001)

(V)x(S) 1188.21 12 99.02

Days (D) 144.86 4 36.22 1.72 (not signi-

(D)x(S) 504.54 24 21.02 f leant)

Visibility x Days 103.91 8 12.99 1.03 (not signi-

(V)x(D)x(S) 605.81 48 12.62 ficant)

12519.34 104

3.2.3 Effect of Stimulus Variables

The percentage of incorrect answers for each arrow, under each visibility

condition, is presented in table 2. Each percentage is based on 84 observations (6 occurrences of each visibility condition x 2 stimulus lists per occurrence x 7 participants). As the table indicates, only arrow N showed a substantial rate of errors (about 20-26 percent) under the most visible viewing

condition (4.6 filter), with some difficulty for arrow P also indicated (about

3. 6-4. 8 percent errors). Under the more difficult viewing conditions, a wide

16
range of differences between arrows was observed: from 2.4 percent to 56.0

percent errors with the 5.0 log unit filter, and from 8.3 percent to 65.5 percent errors with the 5.1 log unit filter. To assess these data, a visibilityby-arrow-by-direction of figure-ground contrast repeated-measures analysis of

variance (Keppel, 1973) was performed, and the results are summarized in table

3. The analysis included only two of the three levels of the visibility factor.

The 4.6 log unit filter condition was omitted since its inclusion would (a) badly

violate statistical assumptions of homogeneity of variance and normal distribution (since there were almost no errors); and (b) the high error rate for only a single arrow (N) could in itself produce an arrow-by-visihility interaction, and

thus could mask the possible existence of such an interaction between the other

two visibility conditions.

As table 3 indicates, the main effects of visibility and arrow were highly

significant fF(l,6) = 89.10; F(15,90) = 26.91; p' s < 0.001], accounting for

approximately nine and 35 percent of the variance (w^ = 0.091 and 0.350,

respectively). The main effect of the direction of contrast was not significant, but this factor did interact with the arrow factor fF(15,90) = 4.43; p < 0.001]; that is, the effect of the direction of contrast depended on the particular arrow. The magnitude of this interaction was small, however (u^ = 0.023)

.

3.2.4 Type of Error

Incorrect responses were broken into two categories: those in which the

participant's response differed from the correct answer by 90°, and those in

which the response differed from the correct answer by 180°. If incorrect answers represented random guessing, the expected number of 90° errors would be

double the number of 180° errors. However the data differed substantially from

this expectation. Table 2 presents the ratio of 90° errors to 180° errors for

each arrow, under each visibility condition (numbers in parentheses indicate

that the ratio is based on fewer than ten errors).

For comparing the type of errors, the data for each arrow were collapsed over

the visibility conditions and direction of contrast. For three arrows— N, 0,

and F — the majority of errors are at 180°. These are the arrows with predominant shafts, so that the orientation of the arrow (horizontal or vertical) may

be detectable even when the head is difficult to distinguish. More surprising

is the occurrence of 90° errors in greater than a two-to-one frequency for the

remaining group of arrows. The actual ratio of 90°-to-180° errors for these 13 arrows taken together was better than three-to-one . Only three arrows (E, H, I)

showed ratios of about two-to-one; for the remaining ten arrows the ratios

ranged from 2.6 to 8.0 (see table 2). All seven participants showed greater

than two-to-one errors at 90°, averaged over the 13 arrows (range of 2.5 to 5.0).

Thus there was a substantial tendency for participants to make 90° errors (excluding the data from arrows N, 0, P)

.

To be certain that no special guessing strategy or response bias could account

for the pattern of errors, responses to three different arrows (A,F,K) were

analyzed in detail. The analysis included both directions of contrast (black on

white, white on black), but was confined to the 5.1 log unit filter condition.

17
Table 2. Error Rate and Ratio of 90° to 180° Errors for Each

Arrow Under Each Experimental Condition

Contrast Arrow

4.6 Log Filter 5.0 Log Filter 5.1 Log Filter

% Errors 90°/180° % Errors 90° /180 ° % Errors 90°/180°

Black A 0 8.33 (2.50) 16.67 3.67 on B 1.19 (1.00)* 13.10 2.67 21.43 3.50

White C 0 - 2.38 (°°) 8.33 (6.00)

D 2.38 (0.50) 45.78 5.33 57.14 2.83

E 0 - 28.57 5.00 39.29 1.54

F 0 - 21.43 17.00 40.48 4.67

G 1.19 (1.00) 22.62 00 41.67 4.83

H 0 - 14.29 2.00 32.14 3.50

I 0 - 17.86 0.88 36.90 1.58

J 0 - 4.76 (1.00) 23.81 1.22

K 0 - 11.90 2.33 17.86 4.00

L 0 - 13.10 1.20 22.62 2.17

M n - 10.71 (3.50) 15.48 1.60

N 20.24 0 45.24 0.15 65.48 0.83

0 2.38 (0) 39 .29 0.32 57.83 0.81

P 4.76 (0.33) 27.38 0.64 52.38 1.10

White A 0 — 11.90 4.00 23.81 3.00

on B 0 - 8.33 (6.00) 21.43 5.00

Black C 0 - 4.76 (3.00) 19.05 7 .00

D 1.19 _** 44.05 4.29 65.48 2.44

E 0 - 5.95 (1.50) 26.19 1.44

F 1.19 (1.00) 17.86 2.75 38.10 5.40

G 0 - 10.71 (CO) 20.24 4.67

H 0 - 9.52 (1.67) 30.12 1.50

I 0 - 15.48 0.86 35.71 5.00

J 0 - 23.81 9.00 36.90 2.88

K 0

- 5.95 (°°) 28.57 3.80

L 0 - 5.95 (“) 13.10 10.00

M 0 - 2.38 (°o) 10.71 (3.50)

N 26.19 0.05 55.95 0.81 60.71 0.65

0 1.19 (0) 33 .33 0.42 52.38 0.38

P 3.57 (0) 30.95 0.62 47.62 0.90

* parentheses indicate ratio is based on fewer than ten errors

** error of omission - answer was skipped

18
Table 3. Summary of Visibility-by-Arrow-by-Direction of Contrast Analysis

Source Sum of Squares df Mean Square F

Subjects (S) 829.69 6 138.28

Visibility (V) 341.26 1 341.26 89.10 (p<0.001)

V x S 22.98 6 3.83

Contrast (C) 5.36 1 5.36 2.52 (not signiC x S 12.75 6 2.12 f leant)

Arrow (A) 1340.23 15 89.35 26.91 (p<0.001)

A x S 298.60 90 3.32

Visibility x Contrast 0.64 1 0.64 (<1.0) (not signi

V x C x S 10.03 6 1.67 f leant)

Visibility x Arrow 29.78 15 1.98 1.24 (not signifi

V x A x S 144.23 90 1.60 cant)

Contrast x Arrow 108.11 15 7.21 4.43 (p<0.001)

C x A x S 146.53 90 1.63

Visibility x Contrast x Arrow 25.25 15 1.68 (<1.0) (not signi

V x C x A x S 234.33 90 2.60 f icant)

3549.77 447

Table 4. Percentage of Responses in Each Direction for

of the Stimulus Arrow

Each Direction

Response

A V > < (N)

A 73.3 5.5 11.0 10.3 (146)

V 1.6 75.2 11.2 12.0 (125)

St imulus

> 12.0 11.1 69.2 7.7 (117)

< 8.6 12 .1 7.8 71.6 (116)
A summary of these data are presented in table 4 in the form of a response

matrix: for each direction the actual stimulus arrow pointed, the percentage of

each direction of response is given. The data are grouped for all three arrows,

and represent a total of 504 observations.

The percentage of correct responses was very similar (72.3 percent + 3 percent)

regardless of the direction the arrow actually pointed. Ninety degree errors predominated (four-to-one over all), and the number of errors at +90° and -90°

was quite similar in every case. A chi-square test found no significant change

in the distribution of responses among the categories "correct", "90° error,”

and "180° error" as a function of the direction of the stimulus arrow ( = 6.1,

df = 6). There was however some suggestion of more 90° errors for the vertical

arrows, although the ratio of 90° to 180° errors exceeded two-to-one in every

case. There was no apparent response bias, each response occuring with a similar frequency as an error. Thus, for the group of seven participants (although

not necessarily for individuals) there was no substantial response bias and no apparent pattern of responding that could account for the preponderance of 90° errors

.

20
4. RANKING EXPERIMENT

4 . 1 METHOD

The ranking experiment provided further information on the suitability of a set

of arrows (taken from the visibility experiment) for use as directional indicators for exits. Each arrow was ranked on several subjective dimensions relevant to building exit signage, which are described below. The results of this

experiment, taken together with the visibility findings, can help identify

effective arrows, or arrow features, for exit applications.

Thirteen arrow shapes were tested. Only the black figures on white backgrounds

were used, with arrows F, J, and L omitted (to avoid highly similar stimuli).

Each arrow was presented on a separate 21 cm x 28 cm (8 1/2 in x 11 in) sheet.

The image was a same-size photocopy of the original 15.2 cm x 15.2 cm arrow

placard described under the visibility experiment method. Each participant

received a packet of 13 sheets, one sheet for each arrow tested.

Participants were 52 female students in upper level undergraduate psychology

courses at Hood College, in Frederick, Maryland.

Each arrow was rank-ordered by participants according to one of four criteria:

1) how well the arrow conveyed the idea of "exit"; 2) how well the arrow served

to indicate direction; 3) how unique the arrow appeared, relative to ordinarily

encountered directional arrows; and 4) how attractive and appropriate the arrow

would look as a sign in a building. (Exact instructions for ranking are attached

in appendix C.)

Each participant rank-ordered the arrows according to only one criterion

(randomly assigned). A total of 12 to 14 participants was included for each

criterion. Each participant was given a packet of 13 randomly ordered sheets,

with a different arrow on each sheet. The participants then reordered the

sheets according to the required criterion.

4.2 RESULTS

A rank of one was assigned to the arrow a participant judged to possess most

the quality being rated, and a rank of 13 was assigned to the arrow judged to

least possess that quality. Table 5 presents the mean rank given each arrow by

the participants in each of the four groups. These group means are based on a highly significant degree of agreement between the participants within each

group. Table 6 (first numerical column) indicates the degree of agreement

between participants expressed by the coefficient of concordance (W) . For all

four stimulus criteria, W is significant ( approximation, Hays, 1963, pg. 658)

beyond the a = 0.001 level.

Given significant agreement among participants, pairwise comparisons of group

rankings of individual arrows for a given dimension were made. A multiple comparison procedure (Hollander and Wolfe, 1973, pg. 151) was used to protect

against spurious differences; however, given the large number of pairwise comparisons (78 for each dimension), such a test is necessarily relatively

21
Table 5. Ranking of Arrows for Four Different Criteria

EXIT DIRECTION APPEARANCE UNIQUENESS

Mean of

Individual

Rankings

Rank of

Group

Mean

Mean of

Individual

Rankings

Rank of

Group

Means

Mean of

Individual

Rankings

Rank of

Group

Means

Mean of

Individual

Rankings

Rank of

Group

Means

Arrow

A 2.71 1 3.15 4 4.08 3 10.42 10.5

B 3.57 3.5 5.77 6 3.69 1.5 5.25 5 C 7.36 7 7.08 7 6.38 6 6.25 6 D 8.36 8 7.92 8 7.00 7 6.42 7 E 3.50 2 3.08 3 4.46 4 10.92 12

G 8.43 9 10.23 10 9.31 10 6.50 8 H 11.21 12 11.31 12.5 11.38 13 4.00 3

I 10.93 11 10.15 9 9.62 11 4 .08 4

K 11.50 13 10.77 11 10.38 12 3.83 2 M 10.71 10 11.31 12.5 8.38 9 1.50 1 N 5.43 6 4.46 5 7.31 8 11.08 13

0 3.71 5 2.92 2 5.31 5 10.33 9 P 3.57 3.5 2.85 1 3.69 1.5 10.42 10.5

Table 6. Rater Agreement for Arrow Rankings

Criterion

Exit

Concordance (W)

0.76

2 X

127 .85 p<0.001

Direction 0.79 123.86 p <0.001

Uniqueness 0.71 101.66 p<0.001

Appearance 0.47 72.70 p <0.001

22
insensitive. The results of the pairwise comparisons are presented in table 7.

As the table indicates, many of the comparisons were significant, despite the

conservative test. Furthermore, there was good agreement among the four criteria as to which pairs of arrows differed significantly from one another.

The degree of agreement between the group rankings of each stimulus criterion

is shown as a rank-order correlation in table 8. The rank for each arrow, from

first through thirteenth, was ordered by the group mean rank of each arrow

(table 5). The rank correlation for each pair of criteria is presented in

table 8. All of these correlations are significant beyond the a = 0.05 level.

The "Exit", "Direction", and "Appearance" dimensions show a strong positive

correlation with one another (rho's from 4- 0.84 to + 0.93); all three show a negative correlation with "Uniqueness" (rho’s from - 0.57 to -0.82). Thus an arrow ranked high on the "Exit" dimension would also tend to rank high on the

"Direction" and "Appearance" dimensions and low on the "Uniqueness" dimension.

Figure 3 shows these relationships as scatterplots , with each arrow indicated

by the letter corresponding with figure 2.

23
Table 7. Pairwise Comparison of Arrow Rankings

Arrow A B C D E G H i K M

A Exit * ** kk   **  ** Direction * kk kk kk ** ** Appearance kk kk ** ** Uniqueness * kk kk ** **

B Exit * k kk kk kk ** Direction kk k ** Appearance kk kk kk kk Uniqueness ** ** *

P

*

C Exit

Direction

Appearance

Uniqueness

D Exit

Direction

Appearance

Uniqueness

•k k

k kk

k

E Exit kk ** kk kk kk Direction kk kk kk kk kk Appearance k kk kk kk Uniqueness kk kk kk kk

G Exit k k Direction ** ** kk Appearance kk Uniqueness *

H Exit kk ** kk

Direction   kk Appearance **  kk Uniqueness ** ** kk

I Exit kk kk kk Direction kk kk kk Appearance kk Uniqueness kk kk kk

K Exit kk kk kk Direction kk kk kk Appearance kk kk Uniqueness kk kk kk

M Exit ** kk kk Direction ** kk kk Appearance

Uniqueness kk kk kk

N Exit

Direction

Appearance

Uniqueness

0 Exit

Direction

Appearance

Uniqueness

P Exit

Direction

Appearance

Uniqueness

* p<0.10

p<0 . 05

24
Table 8. Rank Correlations (rbo) Between Arrow Rating Criteria

Exit Direction Uniqueness Appearance

Exit — +0.87*** -0.7 6** +0.93***

Direction — — -0.82*** +0.84***

Uniqueness — — — -0.57*

Appearance — — — —

* p<0 .05

** p<0.01

*** p<0.001

Table 9. Composite Ranking of Arrows

Visibility Uniqueness

Exit Direction

Connotation

Means of

Ranks

Rank

of Means

A 3 10.5 2.5 5.33 4

B 4.5 5 5 4.83 3

C 1 6 7 4.67 1.5

D 12 7 8 9.00 12

E 8 12 2,5 7.50 8

G 7 8 9 8.00 10.5

H 6 3 13 7.33 7

I 9 4 10 7.67 9

K 4.5 2 12 6.17 5

M 2 1 11 4.67 1.5

N 13 13 6 10.67 13

0 11 9 4 8.00 10.5

P 10 10.5 1 7.17 6

25
DIRECTION

mm

DIRECTION

Mm

AREA

RANGE

RANK

APPEARANCE RANK

ro ^cnaooio

DIRECTION RANK

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Figure 3. Pair wise comparisons of arrow rankings for four different criteria

26

EXIT

VS.

DIRECTION

EXIT

VS.

APPEARANCE

EXIT

VS.

UNIQUENESS
5. DISCUSSION

5.1 EVALUATION OF VISIBILITY METHODOLOGY

The method used to manipulate visibility appeared to be quite successful.

Performance was related in a highly significant (p<0.001) manner to the visibility manipulation, with the visibility condition variable accounting for over

half ( 0)2 = 0.55) of the variability in the data (Visibility-by-Days analysis).

The method discriminated well between arrows (p<0.001), with the percentage of

correct responses per arrow varying widely (44 to 92 percent in the most difficult viewing condition) . This sensitivity was achieved despite the relatively

small number of participants and the large set of stimuli among which the

observations were divided. Furthermore, performance remained stable, with no significant effect of days and no interaction of days with visibility condition.

Thus, the method appears to be a relatively sensitive and efficient means of

evaluating the relative visibility of arrows under different viewing conditions,

and the values of the visual parameters employed were effective.

This procedure differs from most experiments on symbol visibility in aspects of

both stimulus presentation and the participant's response. These methodological

issues are further discussed in section 5.3.

5.2 VISIBILITY OF THE ARROWS TESTED

The arrows differed widely in visibility, with D, N, 0, and P consistently poor,

and with C and M most visible overall. A, B, K, and L were also among the

better-seen arrows. The arrows differed not only in how frequently they were incorrectly responded to, but also in the types of errors that were made. Three

of the 16 arrows (N, 0, P) showed predominantly 180° confusions; in contrast,

ten arrows showed 90° confusions in greater than a two-to-one ratio to 180° errors

.

The predominance of 90° errors for ten of the arrows is an interesting finding.

Close analysis did not suggest that this result was related to any overt

response bias or obvious guessing strategies. One possible explanation is that

such errors may be made when a participant detects an arrow feature that is 90°

out of phase with the actual arrow direction. In fact, arrows with a dominant

perpendicular element and points (F, G) did show a strong bias toward 90° errors. However, other stimuli also showing this error bias have no perpendicular elements at all (e.g., B, C, J, K) . Another possibility is that the errors may be related to search strategies used by the observer. As an example,

an observer may try to match the image on the screen to a "search image"

oriented in a particular way; that is, to search for an arrow pointing either

up, down, or to one side. If failing to match the search image were to differentially favor either detection of stimuli 180° out of phase or evoke answers

90° out of phase, it could establish the preponderance of 90° answers. Quite

possibly, graphic features and perceptual strategies both contribute in some way to the distribution of error types. While no satisfactory account of the error data is obvious, the finding of predominantly 90° errors may be worthy

of further attention. The non-random distribution of the errors indicates

that even when a participant answered incorrectly, some information about the

27
stimulus must have been obtained. Uncovering the source of the error bias may

help reveal how people search for signage in poor visibility or what graphic

features reduce symbol effectiveness.

In comparing tbe various arrows, the effect of the arrow shaft as a graphic

feature is interesting. For three different arrow types, a comparison of the arrow with and without a shaft is possible (A and B vs. C; E vs. F; L and M

vs. K) ; in addition, three arrows (N, 0, P) have a predominant shaft, with

only shaft width varying between two of them (0 and P) . The shaft appears to

increase the number of 180° errors relative to 90° errors, but whether it serves to increase or reduce the overall number of errors depends upon the

particular arrow. When the head is made more predominant relative to the

shaft (P vs. 0, E vs. N) , performance improves. Removing the shaft altogether

actually increased the percentage correct for C (vs. A and B) , but not for F

(vs. E) or M (or L) (vs. K) . One interpretation of these effects is that the

shaft may serve to improve performance by reducing dominant perpendicular

cues (strong vertical edge in E) and by reinforcing the directional message

(as in L and M) , but can also interfere by contributing conflicting cues,

180° out of phase with the arrow head. The positive effect of the shaft may

have been somewhat obscured by a possible experimental artifact. If most of

the information is contained in the head, then since each arrow was centered

on the background, for some of the arrow heads without shafts (C, F, G) , the

most informative portion of the figure was centered in the display. It is not

possible to assess the effect, if any, of this factor. The relatively long

display time (3s) is ample to allow search of the entire display area, and so should help reduce this possibility. However, it is interesting to note that

most visibility experiments do center the images and use very brief display

times (see section 5.3.1), so that a bias may exist in much of these data. An

optimal procedure may be to vary tbe location of the stimulus within the display

field

.

In any case, the data show that for some arrows the shaft can contribute

substantially to improved performance, particularly for arrow M. This may have

been an especially effective case because the sides of the shaft itself are not

perpendicular to the intended direction and the tapering shaft results in multiple points at the vertex. Although the various comparisons among the arrows

with different shaft types suggest a number of hypotheses, perhaps the main

conclusion is that the arrow head should be the dominant graphic element. The

shaft may be useful in reinforcing the message, but should be a secondary feature. Interestingly, the uniqueness rankings provided by participants, as well

as a review of sign catalogues, suggests that arrows with predominant shafts

(e.g., N, 0, P) have actually been the most frequently used. Nonetheless,

arrows more similar to A are now used and recommended for building signage

(Follis and Hammer, 1979), and more recent guides and standards for informational signs have favored arrows more similar to A (e.g., ISO, 1979; Veteran's

Administration, 1980).

The direction of figure-ground contrast had relatively little effect on visibility. There was no overall advantage to either black on white or white

on black. Although the interaction of the direction of contrast with the

particular arrow type was significant, the difference in percentage correct

28
between the two contrast conditions was small for most arrows (see table 2).

No obvious features appear to distinguish the arrows that seem to show a direction of contrast effect, and of course, some of the apparent differences could

be fortuitous. In fact, the literature on figure-ground relationship shows

generally small effects of the direction of contrast, and any effect may be

highly specific to graphic, illumination, or methodological details (Konz and

Mohan, 1972). In practice, the direction of contrast employed may also need

to take into account factors in addition to visibility, such as compatability

with other signage and contrast with building elements.

5.3 COMPARISON WITH OTHER SYMBOL VISIBILITY RESEARCH

5.3.1 Visibility Manipulation

The visibility of a symbol has been manipulated in a variety of ways in

laboratory research. These have included manipulations of contrast (Smith and

Weir, 1978), size (or correspondingly, distance) (Mackett-Stout and Dewar, in

press), blur (Smith and Weir, 1978), and viewing time (Markowitz, Dietrich,

Lees, and Farman, 1968). The viewing conditions and the means of manipulating

visibility are not necessarily arbitrary or interchangable, since the relative

performance of different symbols can vary with these factors. Several experiments in which symbols or arrows were compared under multiple viewing conditions

indicate this. For example, Mackett-Stout and Dewar (in press) compared 32

public information symbols for both "glance legibility" (stimulus duration

varied) and "distance visibility" (viewing distance varied) . The authors

reported a correlation between these two measures of 0.25, which only

"approached" statistical significance. Smith and Weir (1978) compared the

visibility of eight directional arrows in two experiments: one in which blur was varied (to simulate differences in acuity) and one in which contrast was varied (related to glare). The rank-order correlation for the arrows between

the two experiments was 0.14. Jacobs, Johnston, and Cole (1975) varied blur

in comparing a set of 16 symbols for traffic signs (they also included word

signs) . The rank-order correlation between conditions of no blur and the most

severe blur was 0.58. Jin (Japanese proposal, 1980) compared the visibility

of 13 exit symbols under both "normal" illumination and in smoke. The rankorder correlation for the set of symbols in the two conditions was 0.04. To some extent the low correlations observed in all these experiments may be

attributed to possible experimental artifacts or to large variability in the

measures relative to the differences between symbols. Nonetheless, it is

obvious that a reasonable simulation of actual conditions of interest is desirable, since generalization from one condition to another may not be warranted.

With the exception of Jin’s work, the experiments on symbol and arrow visibility

did not use procedures most appropriate for evaluation of building emergency

signs. However, many of the experiments were explicitly directed at the highway

driving situation.

Two parameters of viewing conditions should be addressed in particular. One is

the temporal conditions of viewing. In the present experiment, participants had

ample viewing time. However, duration is an easily manipulated experimental

variable and has often been used to degrade performance in visibility experiments

(e.g., King, 1971, 1975; Dewar, 1976). Sometimes the duration may be only

29
milliseconds (e.g. 15 to 30 ms, Markowitz et al, 1968); in other cases duration

may be longer, but still brief enough to stress the viewer under difficult

viewing conditions (e.g. 0.5 s, Smith and Weir, 1978). Such brief times may be

related to "glance legibility" for the highway driving situation. Brief durations may also be useful in manipulating task demand and stress, and can be used

to study the visual information processing chain in sign perception. However,

such brief presentation intervals are not necessarily appropriate for simulating

viewing conditions in a building environment, and the validity of extending

these observations to building applications is not demonstrated. The poor

correlations between measurements made under very different viewing conditions

(including "glance" vs. "distance" viewing) demands caution in generalizing

results obtained with brief viewing times. The three-second stimulus duration

of the present experiment was not demanding, with participants typically recording their responses before the viewing time was even complete.

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. The results of the experiments on building symbols were

transformed, using the relationship tan visual angle = size/distance, to determine at what distance a 12 in (30.5 cm) sign would be recognized. Jin's

(Japanese proposal, 1980) results for exit signs indicate distances of about 48

to 92 m (about 150 to 300 ft). Mackett-Stout and Dewar's (in press) data 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 distances 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). Thus

symbols generally appear adequately visible under ideal viewing conditions.

But given the often poor correspondence between relative visibility measures

obtained under different 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 visual conditions of true concern. The

subtended visual angle of 1.3° is equivalent to viewing a 12 in sign at 13.4 m

(44 ft), while stimulus presentation simulated emergency lighting and smoke.

5.3.2 Participant's Response

Another methodological factor in visibility research is the task which the

research participant must perform. There have been three general categories of

response: (1) for directional indicators, the participant indicates the

30
appropriate direction; (2) for other symbols, the participant indicates which

of a specified set of stimuli was presented ("matching" or "recognition"); or

(3) for unfamiliar or unspecified symbols, the participant describes or interprets what was presented. The particular measure based on the response is most

often proportion correct, although reaction time of the response, or distance

at which the response occurs, have also been used. Although there has been

little formal comparison of these methods, the participant's task can be an important factor in symbol visibility research.

This experiment used arrows as stimuli not only because of an interest in

specific arrows, but also because of the methodological advantages inherent in

using a directional response (section 2.0). There are no "partially correct"

or ambiguous answers, and performance for any given arrow is not strongly

influenced by which particular arrows comprise the test set. The procedure

appears useful not only for explicitly comparing directional indicators, but

also for assessing a number of graphic and display variables of concern for any

signage under emergency viewing conditions. These would include such factors

as the type and level of symbol illumination, color, contrast, size, graphic

features, symbol surround, location, clutter from competing visual elements,

and so on.

In directly comparing various non-directional symbols, such as exit designators,

for visibility, the directional response used with arrows is not possible. The

selection of an appropriate response measure has been a significant problem in

the assessment of symbol visibility. Typically a small set of symbols is used,

and the response is to indicate which member of this known set has been presented. This is often done by matching from among a list of of alternative

choices

.

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 a set of symbols can be discriminated from one another, rather than how well any individual

symbol can be identified when encountered 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. These may be unrelated to the features which are actually used to

recognize a symbol encountered in a real environment. For example, Zwaga (1979)

examined the legibility of public information symbols proposed by ISO. He compared the results obtained by two methods. In one procedure, participants were

made familiar 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 the 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 flaw in this general procedure is that "visibility" is strongly determined by exhaustive knowledge of all the symbols that might occur and the

relationship between the specific symbols included.

31
Another possibility is to use a relatively large set of familiar stimuli. This

may help reduce reliance on a sub-set of discrimative cues. It will not eliminate the problem however, and for specific stimuli, some feature might remain

a reliable indicator. Furthermore, this method faces the practical problem of

establishing, demonstrating, and maintaining the familiarity of the large set

of stimulus alternatives.

As an alternative to having participants be familiar with the set of symbols,

the symbols can be presented without prior exposure. There are a number of

problems with this approach. One is simply the question of how the observer

indicates what he saw and how to score what he reports. This method also confounds the visibility of a symbol with its meaningfulness, which may be a particular problem for proposed exit symbols since they differ widely in understandability . Another problem is that the symbols become more familiar as they

are seen during the course of the experiment. Either each symbol may be seen

by each participant only once, which may be an inefficient or impractical procedure; or familiarity is confounded with experience in the experiment, and the

problem of discrimination on the basis of possibly minor cues again occurs.

Each of the possible procedures discussed must also face the issue of how well

it approximates the real-life situation to which the findings may be applied.

It would seem unlikely that a person would have good knowledge of the entire

set of symbols that might be encountered. (This issue distinguishes research

on symbols from the many experiments that have investigated legibility using

alphabetic characters. Letters are in fact a set for which appropriate participants may be assumed to have exhaustive knowledge.) Using a totally unfamiliar

set of symbols may not be appropriate either, except to simulate the first

encounter a person may have with a particular symbol. This not only introduces

the confounding of visibility with understandability , but also is unlike the more typical case in which some familiarity with the symbol under good visibility

has preceded the poor-visibility encounter.

One procedure that appears to be practical and realistic does not seem to have

been used to assess symbol visibility. This would be to familiarize participants with a selected group of target stimuli and then present those stimuli

in the context of a large number of unfamiliar distractor stimuli. For example, to adapt this procedure for exit symbols, the participant would first

become familiarized with a number of exit symbols. These would then be presented along with a large number of unspecified symbols, which may also include

some additional (unfamiliar) exit symbols. The participant would respond in a yes-no manner, to indicate whether or not each stimulus presented was an exit

symbol

.

This procedure would provide an objective, scorable response. It is realistic

in that the observer is familiar with possible exit symbols, but not with the

range of possible symbols that might also occur. This would also make featureby-feature comparison unadaptive, since the graphic details of the non-exit

symbols are unknown. This means that some minor graphic detail, which might in

fact make one stimulus especially discriminable from some sub-set of symbols,

can not be identified and used to discriminate it from all potential symbols

that could occur in an experiment. This procedure would also have the

32
additional advantage of identifying symbols that might be mistakenly interpreted

as exit designators.

5.3.3 Other Research Comparing Arrows

There have been a number of studies which have compared the visibility of

various directional indicators. All of these have been addressed to highway

applications rather than building signage.

The most similar research to the present one is that of Smith and Weir (1978).

They compared a set of arrows in two experiments. In one, blur was used to

degrade visibility. In the other, a veiling illumination was used to reduce

contrast, as in the present experiment. However, certain experimental parameters were very different, due to the highway driving application. While lumi- nance levels were not specified, they were undoubtedly much higher, as the

veiling light was used to simulate glare from sunlight. Furthermore, the

stimuli were very small (visual angle circumscribed 8.6 min of arc, about 1/9

the size of the present experiment) and were presented for only 0.5 s. Only

black arrows on a white background were used.

The Smith and Weir results showed only moderate agreement between the blur and

glare conditions. The correlation for the scores of the arrows under the two

conditions was r = 0.49, with a rank-order correlation of rho = 0.14. There

was some overlap with the arrows used in the present experiment: these are

arrows H and J and versions similar to A and E. A chevron of intermediate

width to C and D was also included. Because only H and J were identical, it is

difficult to know to what extent any differences in results were due to graphic

differences. Furthermore, the results for many of Smith and Weir's arrows were

not statistically discriminable , so that performance can only be meaningfully

described for groupings of arrows. Despite this, one clear discrepancy emerges

with the results of the present experiment. The arrow comparable to arrow H

performed most poorly in both of Smith and Weir's experiments. This arrow was intermediate in the present experiment. The many procedural differences make

this disagreement difficult to account for.

Markowitz et al (1968) examined seven arrows using a glance legibility

procedure. The size and luminance of the stimuli were not reported, but presentation times were extremely brief: 15 to 30 msec. The arrows were all similar in having relatively long shafts. One finding to emerge from the experiment

was much better performance for arrows in vertical, rather than horizontal,

orientations. No such bias was found in the present experiment (sec. 3.2.4),

and the possibility of some experimental artifact must be considered. One

interesting finding was that the best performing arrow was one that had a tapering shaft. While very different graphically from arrows L and M of the

present experiment (more like arrow E with a much longer, tapered shaft), the

finding of good visibility in both studies for the arrows with tapered shafts

suggests a possible area for further investigation.

Carr (1969) summarized British research on highway arrow visibility. These

studies also used very brief (5 to 40 msec) presentation times. The main

finding emphasized by Carr is that the visibility of one arrow relative to

33
another is strongly dependent on the viewing conditions: "sunlight", "fog",

or "night". Very different rank-orderings were obtained for 10 arrows under

the three conditions. Carr also warned of possible differences when illuminated

vs. non-illuminated signs are used. The arrow set used in these experiments is

not readily compared to the present experiment.

Because there have been important differences in procedure and little overlap

in the stimulus sets, comparisons between arrow visibility experiments are difficult. General recommendations or rules bearing on arrow visibility are

tenuous. Perhaps the most general conclusion to emerge is again the importance

of testing each visibility condition of concern in as appropriate a manner as possible

.

Although the arrow visibility issue is complex, even definitive results would

present only a partial answer to the selection of an exit directional indicator.

The arrow should also contribute to the egress message as much as possible, and

furthermore be compatible as an interior design element. The arrow ranking

experiment addressed these issues. The following section discusses the ranking

experiment. Subsequently, a composite evaluation of the arrows is presented,

based on both the visibility and ranking results.

5. A ARROW RANKINGS

Participants ranked the arrows in a meaningful way, as indicated by the

substantial coefficients of concordance. Agreement was poorest on the "appearance" criterion, but for all four criteria it remained highly significant. Even

with the test insensitivity engendered by the large number of pairwise comparisons, and the relatively small number of participants (12 to 14) ranking on a given dimension, many comparisons of pairs of arrows showed statistically significant differences. Thus the ranking procedure appears to be a simple and

efficient means of collecting statistically sensitive data on subjective

evaluations of these arrows.

The rankings showed a substantial amount of agreement between dimensions.

Arrows most strongly suggesting exit also tended most strongly to indicate

direction, and furthermore these tended to be considered the most attractive

and appropriate. In contrast, the negative correlations with uniqueness

rankings indicated that more familiar arrows were typically viewed as more

attractive and better functionally.

Arrows rated most highly on the "exit", "direction", and "appearance" dimensions

tended to be A, B, E, 0, and P. Those rated as most unique were B, H, I, K, and

M. Arrow B is the only one included in both sets, although not rated first on any dimension. The scatter plots involving the "Uniqueness" criterion (figure

3) confirm that B is the only arrow for which the data point is substantially

below the cluster of negatively correlated points.

34
5.5 COMPARISON OF ARROWS FOR POTENTIAL USE WITH EXIT DESIGNATORS

In an attempt to provide an overall evaluation of the arrows tested as possible

exit designators, the visibility and ranking data were combined. Each arrow was considered on three dimensions: visibility, uniqueness, and connotation of

"direction to an exit" ("exit" and "direction" rankings combined). Table 9 presents this summarization, with each of 13 arrows ranked on the three qualities.

The "visibility" rank is based on the mean number of errors for each arrow,

collapsed across visibility conditions and direction of contrast. A rank of one indicates the fewest errors; a rank of 13 indicates the most errors. The

"uniqueness" rank simply presents the ordering of the arrows, based upon mean

rank for that criterion in the ranking experiment. For the "exit direction

connotation," the mean ranks across participants for "exit" and "direction"

rankings were combined; these combined totals were then ranked, so that a rank

of one indicates the arrow that most suggests "exit" and "direction".

In the fourth column of table 9 the ranks are combined and averaged for the

three qualities; these means are then themselves ranked in the far right column.

This final column, then, provides a composite ranking for each arrow on a com- bination of desirable dimensions for an exit-related arrow: its visibility, its

distinctiveness from other arrows, and its ability to suggest the idea of direction to exit. While the most appropriate weighting to give each factor may be

an open question, this summation at least reflects each major factor.

As the final rankings indicate, the best-rated arrows are C, M, B and A. Thus,

if one were restricted to the set of thirteen arrows tested, these four might

be considered as the most reasonable candidates for a standard arrow to be used

in conjunction with exit signage. Of these, A is less desirable because similar versions are included in recent standards for informational signage, and

its use in applications other than egress will be counter productive. Arrow C

has also been included as an acceptable directional arrow in a proposed ISO

standard (ISO, 1977) . Since arrow M received such a low rating in terms of its

connotation, B may be the best alternative. B also rated highly in appearance,

suggesting its esthetic acceptability. Thus arrow B emerged as a possible can- didate should a standard exit arrow be desired. However, as emphasized earlier,

the arrows in the set tested were chosen to provide a range of graphic types for

methodological reasons. Many other candidate arrows might have been included.

Arrow B may only be considered as the most appropriate among the set tested.

The success of arrow B does suggest one strategy in developing an exit-related

arrow that is visible and compatible with other signage, yet has a unique quality. That is to modify the arrow shaft, which appears to contribute little to

visibility if the arrow head is effective.

5.6 FURTHER CONSIDERATIONS IN TESTING OF PROPOSED EXIT SYMBOLS

To provide a sufficiently sensitive test of methodology with a relatively small

group of participants, the present experiments employed a homogeneous set of

observers, with normal or corrected-to-normal vision. If a set of exit designators is to be empirically evaluated for its understandability and visibility

for the general public, broader and more extensive sampling is of course

35
required. In addition to the need to be broadly representative, however, is

the need to give specific attention to special user groups. These include the

aged and the visually impaired, children, and the illiterate.

Symbol signs may be especially effective for these groups, since problems in

seeing, reading, or interpreting written messages limit the usefulness of word

signs. These special groups are also those who may most need the benefit of

egress directions. Death rates from fire in public settings (as well as for

all settings combined) are disproportionately high for children and those over

sixty-five (National Safety Council, 1979). Yet several researchers (e.g.,

Easterby and Hakiel, 1977; Hulbert, Beers, and Fowler, 1979; Lerner and Collins,

1980) have reported poorer comprehension of symbols for the elderly (under good

viewing conditions), and a number of visual defects are common in older vision

which may alter sign perception (Fozard, Wolf, Bell, McFarland, and Podolsky,

1977; Koncelik, 1979). Children may also interpret symbols in a manner quite

different from adults. If these special groups are ignored, or undifferentiated

as a subset of the "general public," important life safety considerations in

exit symbology may be overlooked.

Another special consideration in sign effectiveness concerns the role of alcohol

and drug effects. A disproportionately high number of fire victims show significant levels of alcohol or drugs (Berl and Halpin, 1979). Although the need

for unambiguous alerting may be critical for an intoxicated person, or even someone on medication, perception of neither word nor symbol signs appears to

have been investigated for these conditions. Such research might contribute to

life safety during building emergencies, and could be of obvious benefit as well

for traffic symbols.

In summary, a complete evaluation of symbol effectiveness must not only consider

who may encounter the sign, but also for emergency alerting, who the potential

victims are likely to be.

Another aspect concerns the international usage of symbols. If an exit

designator is to communicate to foreign visitors to this country, or is to be

used internationally, the need to take cultural factors into account is apparent. Cross-cultural comparisons of symbols have been undertaken for some symbol sets (e.g., Easterby and Zwaga, 1976). However, the obvious difficulties

of any full scale effort, especially if not under the auspices of some international group, have probably severely limited cross-cultural testing.

As a final consideration, there are a number of pragmatic concerns that must be

taken into account in evaluating a symbol. These may include reproducibility,

compliance with existing standards, compatibility with other signage, potential

for vandalism, and so forth. However, understandability is paramount for any

symbol, and visibility may be critical for exit designators. Thus, while other

factors require attention, understandability and visibility should be the focus

of research efforts. Related to these are questions of salience ("attention

getting" quality), memorability, and behavioral effectiveness.

The symbol image is but a single consideration in exit signage, with other

concerns including usage, location, size, illumination, and so on. Problems

36
of signage enter the broader issue of rapid and safe egress from public

buildings, transportation, and workplaces. The prevalence of the exit message

and its critical importance to life safety stresses the importance of optimizing all components of the egress system. This paper has considered some of

the problems in identifying and interpreting the exit message in symbol signs

and has discussed some approaches to those problems. The research reported

has concerned an important element of egress signage: the directional indicator to identify the appropriate direction to an exit. Specific issues in the use of directional arrows, as well as more general issues in evaluating exitrelated symbols, were explored. Careful consideration of these issues in subsequent design, research, and standardization may contribute significantly to

increased public safety.

37
6 . SUMMARY

The increasing usage of pictorial signage and recent efforts to standardize

such signs have underscored the need for an effective symbol to represent

the "exit" idea. Exit symbols were discussed in this report in terms of

two primary criteria: understandability to users and visibility under

degraded visual conditions. Despite the absence of much formal evaluation

(especially for visibility), the adequacy of many suggested exit symbols

appears questionable. Furthermore, there seems to be an apparent trade-off

among existing symbols between meaningfulness and visibility.

Among the problems contributing to the development of a good exit symbol is

the absence of a common stereotype image (graphic concept). In previous

research (Lerner and Collins, 1980), participants showed relatively little

agreement in proposing exit pictograms, except for the frequent use of a directional arrow.

The arrow was discussed as a graphic element in exit designation. While it

appears to connote "exit" strongly, the arrow itself is too ambiguous and too

widely used to serve as the primary element of an exit symbol. On the other

hand, a number of advantages were noted for standardizing some particular arrow uniquely for use with exit designators. These advantages include

increased understandability of the exit message, reduced confusability with

irrelevant signage, better learnability for exit symbols, and improved

visibility.

Two experiments were described in this report. Tbe first concerned the

visibility of a set of 32 arrows under conditions of reduced luminance and

contrast. The experiment was directed at investigating a methodology for

assessing symbol visibility, and also at comparing the visibilities of the

specific arrows tested. The second experiment obtained subjective rankings

of thirteen arrows according to how well they suggested "exit", how well they

indicated direction, how unique they were, and how appropriate and attractive

they appeared.

The visibility experiment procedure proved to be an effective method, and

wide differences in visibility among the arrows were detected. The arrows

also differed in the type of confusion they engendered when an error in perception occurred. The subjective arrow rankings showed substantial agreement

among participants, and strong correlations between the subjective dimensions.

Together, the visibility and ranking data were used to compare the set of arrows for appropriateness for use with exit designators, and suggestions

were made for developing other candidate arrows.

Some methodological problems in assessing the visibility of pictograms were

discussed, and a procedure was recommended.

Finally, the need to give special consideration to some specific groups of

potential symbol users—including the elderly, children, and others—was emphasized. It may not be sufficient simply to sample broadly in evaluating

a symbol, if the problems for groups of special concern become lost in the

collective data.

38
REFERENCES

1. AIGA. The development of passenger/pedestrian oriented symbols for use

in transportation-related facilities, U.S. Department of Transportation,

D0T-RSPA-DPB-40-79-2, 1979.

2. Berl, W. G. and Halpin, B. M. , "Human fatalities from unwanted fires,"

Fire Journal , 1979, ^73, pp . 105-115, 123.

3. Bono, J. A., and Breed, B. K. , "Study of smoke ratings developed in

standard fire tests in relation to visual observations," Underwriters * Laboratories Bulletin of Research , 1965, 56, pp. 1-59.

4. Carr, R. , "The legibility of signs," Print , 1969, pp . 28-31.

5. Collins, B. L. "The development and evaluation of effective symbols,"

National Bureau of Standards, NBSIR 1981, in preparation.

6. Collins, B. L. and Lerner, N. D. , "Preliminary assessment of workplace

safety symbols: pilot study results," unpublished letter report, 1980,

(to be published as part of larger report, in preparation).

7. Collins, B. L. and Pierman, B. P. , "Evaluation of safety symbols,"

National Bureau of Standards, NBSIR-79-1760 , 1979.

8. Demaree, J. E., "A preliminary examination of interior aircraft emergency

lighting under simulated postcrash fire and smoke conditions," Federal

Aviation Administration, NA-79-46-LR, 1979.

9. Dewar, R. E., "The slash obscures the symbol on prohibitive traffic signs,

Human Factors , 1976, _18^, pp . 253-258.

10.

Dewar, R. E. and Ells, J. G. , "Comparison of three methods for evaluating

traffic signs," Transportation Research Record, 1974, 503 , pp . 38-47.

11.

Dewar, F. E. and Swanson, H. A., "Recognition of traffic control signs,

Highway Research Record, 1972 , 414, pp . 16-23.

12. Easterby, R. S., "Perceptual organization in static displays for man/

machine systems," Ergonomics , 1967, 10, pp . 193-205.

13. Easterby, R. S. and Hakiel, S. R., "Safety labelling and consumer products

field studies of sign recognition," AP Report 76, Applied Psychology

Department, University of Aston, Birmingham, England, 1977.

14. Easterby, R. S. and Zwaga, H. T. G. , "Evaluation of public information

symbols, ISO tests: 1975 series," AP Report 60, Applied Psychology Depart

ment, University of Aston, Birminghmam, England, 1976.

15. Follis, J. and Hammer, D. , "Architectural signing and graphics," New York:

Whitney Library of Design, 1979.

39
16. Fozard, J. I., Wolf, E., Bell, B., McFarland, R. A., and Podolsky, S.,

"Visual perception and communication," In J. E. Birren and Schaie, K. W.

(Eds) Handbook of the Psychology of Aging , New York: Van Nostrand Reinhold

Company, 1977.

17. Gross, D. , Loftus, J. J. , and Robertson, A. F., "Method for measuring

smoke from burning materials," in ASTM, Symposium on Fire Test Methods - Restraint and Smoke , Philadelphia, PA, American Society for Testing

and Materials, 1966.

18. Hollander, M. and Wolfe, D. A., "Nonparametric Statistical Methods,"

New York, John Wiley and Sons, 1973.

19. Hulhert, S., Beers, J., and Fowler, P., "Motorists’ understanding of traffic

control devices," AAA Foundation for Traffic Safety, Falls Church, VA, 1979.

20. IES. IES Lighting Handbook, New York, Illuminating Engineering Society,

1972 .

21. IS0/TC80, "Safety colours and safety signs," draft International Standard

ISO/DIS3864 .3 , Geneva, International Organization for Standardization,

1979.

22. ISO/TC145, "Graphic symbols - use of arrows," ISO/4196, Geneva, International

Organization for Standardization, 1977.

23. Jacobs, R. J., Johnston, A. W. , and Cole, B. L. , "The visibility of

alphabetic and symbolic traffic signs," Australian Road Research , 1975,

5, pp. 68-86.

24. Japanese Proposal of Pictograph Regarding IS0/TC21/SC1 N25, DP6309 Safety

Sign No. 4 "Emergency Exit," May 1980.

25. Jin, T., "Visibility through fire smoke," Report of Fire Research Institute

of Japan, No. 30, 1970.

26. Keppel, G. , Design and Analysis: A Researcher’s Handbook , Englewood Cliffs,

NJ, Prentice Hall, 1973.

27. King, L. E., "A laboratory comparison of symbol and word roadway signs,"

Traffic Engineering and Control , 1971, 12^, pp . 518-520.

28. King, L. E., "Recognition of symbol and word traffic signs,” Journal of

Safety Research , 1975 , 7, pp . 80-84.

29. Koncelik, J. A., "Human factors and environmental design for the aging:

aspects of physiological change and sensory loss as design criteria,"

in T . 0. Byerts, S. C. Howell, and L. A. Pastalan (Eds.), Environmental

Context of Aging , New York, Garland STPM Press, 1979.

40
30. Konz, S. and Mohan, R. , "The effect of illumination level, stroke width,

and figure ground on legibility of Namel numbers," Proceedings of the Human

Factors Society , 1972, pp. 431-435.

31. Lerner, N. D. and Collins, B. L. , "The assessment of safety symbol understandability by different testing methods," National Bureau of Standards,

NBSIR-80-2088 , 1980.

32. Mackett-Stout , J. and Dewar, R. , "Evaluation of symbolic public information

signs," Human Factors , in press.

33. Markowitz, J., Dietrich, C. W., Lees, W. J., and Farman, M. , "An investigation of the design and performance of traffic control devices," Bolt

Beranek and Newman, Report No. 1726, 1968.

34. Middleton, W. E., Vision Through the Atmosphere , Toronto, University of

Toronto Press, 1952.

35. National Safety Council, Accident Facts , Chicago, IL, National Safety

Council, 1979.

36. O’Neill, J. G. , Hayes, W. D. , and Zile, R. H., "Full-scale fire tests with

automatic sprinklers in a patient's room: Phase II," National Bureau of

Standards, NBSIR-80-2097 , 1980.

37. Overington, I., Vision and Acquisition , New York, Crane, Russak, and

Company, 1976.

38. Phillips, A. W., "The effects of smoke on human behavior," Fire Journal,

1978, 72, pp. 69-77 , 122-123.

39. Sharry, J. A. (Ed.), Life Safety Code Handbook , Boston, National Fire Protection Association, 1978.

40. Smith, G. and Weir, R. , "Laboratory visibility studies of directional

symbols used for traffic control signals," Ergonomics, 1978, 21, pp. 247-

252.

41. U.S. Public Health Service, Binocular Visual Acuity of Adults , U.S. Department of Health, Education, and Welfare, 1964.

42. Veterans Administration, Signage System Standards Manual , Washington, D.C.,

Veterans Administration, 1980.

43. Weale, R. A., The Aging Eye , London, H. K. Lewis, 1963.

44. Winer, B. J., Statistical Principles in Experimental Design, New York,

McGraw-Hill, 1971.

45.

Zwaga, H. J., "Legibility of public information symbols," Proceedings of

the Human Factors Society, 1979, pp . 448 (Abstract).

41
APPENDIX A

Sequence of Stimulus Sets and Visibility Condition (Filter) 3

Participants

Day Lists 1 2 3 4 5 6 7

Day 1 P 0 0 0 0 0 0 0

P 4.6 4.6 4.6 4 .

6

4 .

6

4.6 4.6

1-2 4.6 4.6 5.1 5.0 4.6 5.1 5.0

3-4 5.1 5.0 4.6 4.6 5.1 5.0 5.1

5-6 5.0 5.1 5.0 5.1 5.0 4.6 4.6

Day 2 100

r-' 5.1 5.0 4.6 5.1 4.6 5.0 4.6

9-10 5.0 5.1 5.0 5.0 5.0 5.1 5.0

11-12 4.6 4.6 5.1 4.6 5.1 4.6 5.1

13-14 5.0 5.1 5.0 5.1 5.0 5.0 4.6

Day 3 15-16 5.1 5.0 5.1 4.6 5.1 4.6 5.1

5-6 4.6 4.6 4.6 5.0 4.6 5.1 5.0

3-4 5.0 5.1 5.1 4.6 5.1 4.6 5.1

1-2 4.6 4.6 5.0 5.1 5.0 5.0 4.6

Day 4 13-14 5.1 5.0 4.6 5.0 4.6 5.1 5.0

11-12 4.6 4.6 5.0 4 .

6

5.1 4.6 5.1

9-10 5.0 5.1 4.6 5.0 4.6 5.1 5.0

7-8 5.1 5.0 5.1 5.1 5.0 5.0 4.6

Day 5 15-16 5.1 5.0 5.0 5.0 5.0 5.1 5.0

1-2 4.6 4.6 4.6 5.1 4.6 4 .6 4.6

3-4 5.0 5.1 5.1 4.6 5.1 5.0 5.1

3 Each entry in the main body of the table is the optical density (D) of the

filter through which the arrow image was projected.

42
Appendix B. Instructions for visibility experiment

INSTRUCTIONS (A)

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

"arrows" are under difficult viewing conditions. We will show you slides of

arrows, and for each slide you will be asked to indicate the direction in which

the arrow is pointing.

Before we start, we would like you to become familiar with the sorts of arrows

you will see. On the attached page are copies of all the arrows in the set.

Notice that each one occurs as both a black figure on a white background and

again as a white figure on a black background. All of the arrows are pointing

in the same direction (up). During the actual tests, the arrows will occur in

a random sequence and may point in any direction.

Take a few minutes to familiarize yourself with these directional arrows before

we go on.

43
44
INSTRUCTIONS (B)

Be seated in the chair directly in front of the screen. You will see arrows

appear on the screen, one at a time. For each arrow, indicate on the answer

sheet the direction the arrow is pointing: up, down, left, or right. Indicate

the direction by drawing an arrowhead in the appropriate direction: A, if what

you see points up; V, if what you see points down; <, if what you see points

left; >, if what you see points right.

Each arrow will appear on the screen for 3 seconds, followed by 5 seconds with

nothing on the screen. Then the next arrow will appear for 3 seconds, and so

on. Use the 5 seconds between arrows to write down your answer. A tone will

indicate this answer period—when the tone goes off, the next slide will be

presented

.

We will do a practice list to become familiar with the procedure. Be sure to

write down an answer for each slide. If you are not sure, then guess. There

must be an answer written down for every slide you see.

Although the arrows in the practice list will appear quite plain to you, they

will be much more difficult to see once we begin the actual experiment. This

is because we are interested in the limits of visibility—everything you see,

except for the practice list, will be faint. At some times you may feel that

you don’t see anything. It is very important that you concentrate and make

your best guess. This is because in a task such as this, even when people feel

they are only "guessing," they actually turn out to be correct much more often

than they think. Be sure to make your best guess for every slide you see.

45
Appendix C. Instructions for Arrow Ranking Experiment

(Directional Criterion)

We would like you to rank various arrows according to how well each arrow

serves as an indicator of which direction to go. The arrow that you feel best serves to indicate direction should be placed on the top of the stack, and the one that you feel least serves to indicate direction should be placed at the

bottom, with the others ordered in between.

46
(Appearance Criterion)

We would like you to rank various arrows according to how well you like each

arrow's appearance. Consider how attractive and appropriate an arrow would

look when displayed as a sign in a public building. Order the sheets from best

appearance to worst. The most attractive and appropriate arrow should be placed

at the top of the stack, and the least attractive and appropriate should be

placed at the bottom, with the others ordered in between.

47
(Exit Criterion)

We would like you to rank various arrows according to how well each arrow

conveys the idea of "exit." Order the sheets from the one that you feel most

suggests exit to the one you feel least suggests exit. The arrow that best

denotes exit should be placed on the top of the stack, and the one that least

denotes exit should be placed at the bottom, with the others ordered in between.

48
(Uniqueness Criterion)

We would like you to rank various arrows acording to how unique or distinct you

feel each arrow is. Order the sheets from the one you feel is most unique com- pared to directional arrows you might ordinarily see to the one you feel is most

typical of the sorts of arrows you might ordinarily see. The most unique arrow

should be placed on the top of the stack, and the least unique should be placed

at the bottom, with the others ordered in between.

49
NBS-114A irev. 2 - 60 ) U.S. DEPT. OF COMM.

4.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR 2 REPORT NO.

NBSIR 81-2268

. Performing Organ. Report NoJ 3.

TITLE AND SUBTITLE

Publication Date

May 1981

Evaluation of exit directional symbols

5. AUTHOR(S)

Neil D. Lerner

6. PERFORMING ORGANIZATION (If joint or other than NBS, see in struction s) 7 , Contract/Grant No. national bureau of standards

DEPARTMENT OF COMMERCE 8. Type of Report & Period Covered

WASHINGTON, D.C. 20234

Final

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State , ZIP)

National Bureau of Standards

Department of Commerce

Washington, D.C. 20234

10. SUPPLEMENTARY NOTES

] 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 si gnificant

bibliography or literature survey, mention it here)

This paper discusses visibility considerations for exit symbols and the relationship

between understandability and visibility concerns. Two experiments evaluated directional indicators (arrows) in the context of building exit signage. The first experiment compared the visibility of 32 arrows under degraded visual conditions that were

comparable to a smoke environment. This experiment had two objectives: (1) the

development of a methodology for assessing exit pictogram visibility; and (2) a com- parison of the visibilities of the specific arrows tested. A second experiment obtained subjective rankings of the arrow types on the basis of several criteria of

concern for exit signage. These criteria included connotative meaning, uniqueness

from other directional indicators, and appropriateness.

The visibility procedure proved to be statistically sensitive and demonstrated

differences in the visibility of different arrows. An analysis of the type of con- fusions that occurred in errors for each arrow suggested certain relations between

graphic features and errors in detection. The second experiment indicated substantial

agreement between participants in ranking the arrows and revealed strong relationships

between the several criteria. Together the results of the two experiments were used

to evaluate the set of arrows for appropriateness for use with exit designators.

Methodological issues in evaluating symbol visibility were considered and other

issues of concern in testing exit signage, such as special user groups, were also

d.Lariiiiaa(L

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons)

/ fixit signs; directional arrows; fire safety; pictograms; symbols; understandability;

visibility; visual alerting

13.

AVAILABILITY

[y~| Unlimited

| | For Official Distribution. Do Not Release to NTIS

Z\ Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

20402.

[XJ Order From National Technical Information Service (NTIS), Springfield, VA. 22161

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