DOT/FAA/AM-02/16

Garnet A. McLean

Cynthia L. Corbett

Kenneth G. Larcher

Jerry R. McDown

David A. Palmerton

Keith A. Porter

Robert M. Shaffstall

Civil Aerospace Medical Institute

Federal Aviation Administration

Oklahoma City, OK 73125

Rita S. Odom

Advancia Corporation

655 Research Parkway

Oklahoma City, OK 73104

August 2002

Final Report

This document is available to the public

through the National Technical Information

Service, Springfield, VA 22161.

Access-To-Egress I: Interactive Effects

of Factors That Control the

Emergency Evacuation of Naïve

Passengers Through the Transport

Airplane Type-III Overwing Exit

Office of Aerospace Medicine

Washington, DC 20591
NOTICE

This document is disseminated under the sponsorship of

the U.S. Department of Transportation in the interest of

information exchange. The United States Government

assumes no liability for the contents thereof.
i

Technical Report Documentation Page

1. Report No.

DOT/FAA/AM-02/16

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

5. Report Date

August 2002

4. Title And Subtitle

Access-To-Egress I: Interactive Effects of Factors That Control the Emergency

Evacuation of Naïve Passengers Through the Transport Airplane Type-III

Overwing Exit

6. Performing Organization Code

7. Author(s) 8. Performing Organization Report No.

(1) McLean, GA; Corbett, CL; Larcher, KG; McDown, JR; Palmerton, DA;

Porter, KA; Shaffstall, RM; and (2) Odom, RS

9. Performing Organization Name and Address

(1) FAA Civil Aerospace Medical Institute (2) Advancia Corporation

 P.O. Box 25082 455 Research Parkway

 Oklahoma City, OK 73125 Oklahoma City, OK 73104

10. Work Unit No. (TRAIS)

12. Sponsoring Agency Name and Address 11. Contract or Grant No

Office of Aerospace Medicine

Federal Aviation Administration

800 Independence Ave.

Washington, DC 20591

13. Type of Report and Period Covered

15. Supplemental Notes 14. Sponsoring Agency Code

This work was performed under task AM-B-01-PRS-93.

16. Abstract

Simulated emergency evacuations were conducted from a narrow-body transport airplane simulator through a

Type-III overwing exit. The independent variables were passageway configuration, hatch disposal location,

subject group size, and subject group motivation level. Additional variables of interest included individual subject

characteristics, i.e., gender, age, waist size, and height, all of which had been shown in previous studies to

significantly affect emergency egress. Participants were restricted to those who had no previous emergency

evacuation (research) history. The dependent variables of interest included hatch operation time and the time for

individual subjects to egress.

Evacuation trials were conducted with 48 groups of either 30, 50, or 70 subjects per group, for a total of 2,544

subject participants. Each subject group completed 4 evacuation trials, totaling 192 evacuations. Results reported

for hatch operation time include data from all trials, since each trial had a different, naïve hatch operator. The

egress time results include data only from each group’s first evacuation trial in which every subject was naïve.

Significant main effects of hatch disposal location on both Exit-Ready-To-Use Time (p<.004) and First-PersonOut Time (p<.008) were revealed, without effects of the other variables. Significant main effects on individual

subject egress time were found for waist size (p<.0001), gender (p<.0001), and age (p<.0001). A small, but

significant, main effect was also found for passageway configuration (p<.001), which was confounded by

improper hatch disposal and a between-groups imbalance in individual subject characteristics. This situation

produced a significant (4-way) passageway configuration by hatch disposal location by subject group density by

subject group motivation level interaction effect (p<.008).

The findings replicate prior research showing that passageway configuration has only minimal effects on

emergency egress, as long as ergonomic minimums are respected. In contrast, differences in the physical

characteristics of individual subjects produce large differences in emergency evacuation performance, as does

subject naïveté.

17. Key Words

Aircraft Evacuation, Passageway Configuration, Hatch

Operation, Competitive Egress, Individual Subject

Characteristics

18. Distribution Statement

Document is available to the public through

the National Technical Information Service,

Springfield, VA 22161

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Unclassified

21. No. of Pages

40

22. Price

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

ACKNOWLEDGMENTS

The authors heartily acknowledge the untiring efforts of those who gave so generously of their time and energy

toward the success of this project. The dedication each of them displayed is a tribute to the professionalism embodied

in the personnel of the Civil Aerospace Medical Institute and their willingness to assist almost any time or day.

Among those who contributed, special thanks go to our research support staff:

Tracie Allison Joe Beasley Rick Butler Patricia Calvert

Kristi Craft Chuck DeJohn David DeSelms Rick DeWeese

Dave Dyer Jerrod Epple Wilma Fairman Van Gowdy

Rusty Lewis Edward Matheke Ronnie Minnick Becky Orman

Donna Potter Bryan Provine Lori Samuel Steve Veronneau

James Whinnery Greg Winters Alex Wolbrink Kathi Wood

The project could also not have been accomplished without many contract personnel, who recruited and managed

our subjects, helped out with conducting the evacuation trials, and maintained the evacuation simulator, which was

under constant threat of demolition by the onslaught of zealous evacuees. Those in our debt include:

Jason Garvin Suanne Hanson Linda Hoover John Howard

Julianne Jacks Jerry Johnson Jim King Lorri King

Robert McCawley Heather Munn Dave Ruppel Stephanie Sanders

Buck Walker Vicky Wilson

The staff of the Continental Airlines Inflight Training department were also invaluable to the success of the

project. Without their support, especially the flight attendants who performed so admirably in the evacuation trials,

the results would not have been nearly as applicable to “real world” applications, nor would the research subjects

have gained such a valid perspective of the safety role that flight attendants are called on daily to fill.

We also thank the fine paramedics from EMSA, who helped us those few times when things went awry.

Thank you all for a project well done.
1

ACCESS-TO-EGRESS I: INTERACTIVE EFFECTS OF FACTORS THAT CONTROL THE

EMERGENCY EVACUATION OF NAÏVE PASSENGERS THROUGH THE TRANSPORT

AIRPLANE TYPE-III OVERWING EXIT

INTRODUCTION

Over the last 15 years, a research program of international scope has been dedicated to examining emergency evacuations through the transport airplane

Type-III overwing emergency exit. Two laboratories,

one in the Aviation Psychology Department of

Cranfield University in the United Kingdom and the

other at the Federal Aviation Administration (FAA)

Civil Aerospace Medical Institute (CAMI) in Oklahoma City, OK, have conducted the research. The

genesis of this activity was the 1985 crash of the

British Airtours Boeing 737 airplane at Manchester,

England, in which a number of passengers died in an

apparent attempt to approach and egress through the

Type-III overwing exit (AAIB Report 8/88). Further

impetus was provided by another accident involving

a B-737 and a Fairchild Metroliner at Los Angeles

International airport in 1991 (NTSB/AAR-91/08), in

which more deaths were associated with attempts to

use the Type-III exit. Analysis of these accidents

suggested that restrictive cabin interior configurations adjacent to the Type-III exits may have limited

access to those emergency egress portals, thereby preventing timely evacuation of the airplanes. The resultant research program was instated to address this

issue, studying a range of passageway configurations

from the center aisle of a narrow-body transport

category airplane to the Type-III overwing exit, accompanied by a variety of interactive evacuation conditions, to assess the importance of cabin configuration

adjacent to the exit. A recent report, Access-To-Egress:

A Meta-Analysis of the Factors That Control Emergency

Evacuations Through the Transport Airplane Type-III

Overwing Exit (McLean, 2001), forms a capstone for

those efforts, systematizing the major findings of the

research program through the year 2000. That report

should be consulted for a detailed understanding of

the relevant issues.

A significant debate has arisen in recent years

concerning the research program findings, especially

with regard to the ability of different cabin interior

configurations to provide acceptable evacuation capability through the Type-III exit, i.e., proper access to

egress. The debate exists in spite of the many studies,

involving passageway configurations from 3” to 34”

wide and employing a range of distances of aft seat

encroachment into the projected exit opening, in

which the results have been quite consistent. These

results have been obtained with a variety of ancillary

evacuation conditions, such as cooperative and competitive egress, clear-air and smoke-filled cabin interiors, different hatch disposal locations, and presence or

absence of cabin crew. The combined results have

established that intermediate passageway configurations, i.e., those 13” to 25” wide, having aft seat

encroachments no farther forward than the exit

centerline, provide for essentially equivalent evacuation performance (see McLean, 2001). In fact, passageways no wider than 10” have been shown to be

comparable in several of those investigations. However, for some who have appraised the findings, this

breadth of equivalence is counterintuitive and gives

reason to question the entire enterprise.

The research studies were conducted to assist in the

certification of transport category airplanes equipped

with Type-III overwing exits; however, the intensity

of the discussion surrounding the research program

findings has sidetracked this application. The principal issue has been the fact that regulatory use of the

research program findings would permit a range of

cabin interior configurations, as opposed to some

optimum arrangement having a wider passageway and

lesser aft seat encroachment — a circumstance patently more valid to some. Current efforts toward

harmonization of emergency exit access regulations

by the FAA and the European Joint Aviation Authority (JAA), as well as renewed interest in the Type-III

exit access-to-egress issue by the National Transportation Safety Board (NTSB/SS-00/01), have presented

another occasion to resolve the issue.

The report presented here marks the resultant effort to gauge again the effects of cabin interior configuration on access to the Type-III overwing exit,

potentially providing a final culmination of the accessto-egress research program. Many of the criticisms

that have delayed the formalization of program findings in regulatory language have been acknowledged

in the development of the research design, as well as its

execution, and much care has been taken to establish

an evacuation research project unequivocally worthy

of regulatory application.
2

 This attention to detail has been no greater than in

past studies; however, with every decision to effect a

particular method or produce a particular experimental contingency, attempts have been made to address

points of contention relative to earlier investigations.

For example, pure subject naiveté with regard to

emergency evacuations, as would be found among the

general flying public, has replaced the use of repeatedmeasures designs or practice protocols designed to

control human performance variability (e.g., McLean

& George, 1995). Similarly, a more complex research

design, using motivational inducements and larger

subject complements in consideration of subject

naïveté, has been employed to achieve greater realism

and generalizability. Additional subjects, confirmed

to be naïve with respect to exit operation and instructed only via graphics taken from current airline

safety briefing cards, were made specifically responsible for opening the Type-III exit and disposing of

the hatch, as would be expected in typical emergency

operations. Again, realism was the defining construct.

The result is the largest, most complex, most logistically difficult, and most interactive investigation in

the history of research into the effects on emergency

evacuation of hatch operation and cabin interior configuration adjacent to the Type-III overwing exit.

METHODS

Research Design. Although passageway configuration was the main independent variable of interest,

the study employed a 4-way (Passageway Configuration x Hatch Disposal Location x Subject Group

Motivation Level x Subject Group Density) factorial

design. Motivation level was nested within subject

group density, which was distributed uniformly across

passageway configuration nested within hatch disposal location (see Table 1). Subjects were screened

out for prior participation in evacuation research,

since the intent was to determine the typical effects of

the treatments on naïve airline passengers. It was

discovered after the fact that (only) one of the 2,544

subjects had been in an actual emergency airplane

evacuation.

In addition to passageway configuration, the other

independent variables in the design were selected for

their known effects on egress performance, as well as

their potential for interactions with passageway configuration, that could address the issue of access to

egress. As such, hatch disposal location was chosen as

an additional airplane-related independent variable,

because of the potential for the hatch to negatively

influence access space at the exit and interfere with

Table 1

Research Design with Total Group Evacuation Times*

Hatch Location: Inside Outside

Passageway:

Density Motive

6” 10” 13” 20” 6” 10” 13” 20”

Low 49.30 51.30 55.97 53.97 60.00 71.13 51.23 50.47 Low

(30) High 52.97 57.23 59.30 45.17 56.23 47.90 49.30 50.67

Low 91.40 91.87 90.40 94.20 86.17 89.33 95.97 76.40 Medium

(50) High 87.77 82.77 87.67 83.20 86.77 94.03 80.17 80.77

Low 128.97 121.43 144.40 117.03 122.27 133.13 124.47 108.37 High

(70) High 107.73 117.07 160.80 111.03 115.33 118.83 108.67 112.50

* Each cell contains the group evacuation time in seconds.
3

subject egress. Subject motivation level was included

because of the demonstrated ability of financial incentives to produce extreme subject behaviors and interact with other independent variables that also altered

egress substantially (e.g., Muir, Bottomley, & Hall,

1992). Subject group density was incorporated because of research that had shown nonlinear increases

in evacuation time, as the number of subjects per

group was increased (McLean, Corbett, and George,

1999), and the potential for that to provide additional

discriminatory power with regard to regulatory application of the research findings.

Each subject group completed four evacuation trials, although only the first experimental trial for each

group is included here in the results related to individual evacuation time. This between-groups approach

to the data provides only a single data point for each

subject (group) and is intended to preserve the complete essence of subject naiveté. Additional withinsubjects analyses will be conducted and described in a

subsequent report of the cumulative effects of individual subject experience and motivation on hatch

operation and evacuation time.

Apparatus. The aircraft simulator was configured

with six-abreast seating (e.g., B-737) and equipped

with a single Type-III overwing exit located on the

right side of the airplane cabin 40% of the total

distance aft of the front door. The exit opening was

20” wide and 38” high, with a step-up distance of 18”

inside the simulator and a step-down of 27” from the

centerline of the exit to a sloped winglet outside the

simulator. The weight of the hatch was set at 45

pounds for all trials.

Passageway Configuration. Four different passageway configurations leading from the main aisle to the exit

were used in the study; three of these included single

passageways between triple seat assemblies, while the

fourth employed 2 passageways, one fore and one aft of

a seat assembly in which the outboard seat had been

removed. The single passageways employed 3 different

passageway widths with 3 different aft seat encroachment distances; the dual passageway configuration with

the outboard seat removed was established such that the

seat assembly was placed directly adjacent to the Type-III

exit. Figures 1 through 4 depict the passageway configurations employed. The tray tables in the passageway seat

Figure 1

20” Passageway With 5” Encroachment

5”

20”

EXIT
4

Figure 2

13” Passageway With 10” Encroachment

10”

13”

EXIT

Figure 3

10” Passageway With 14” Encroachment

14”

10”

EXIT
5

Figure 4

Dual 6” Passageways With Outboard Seat Removed

6” 6”

EXIT

assemplies were stowed in the rigid arm rests, and all seat

backs throughout the cabin were locked to prevent

breakover. Remaining seat pitch was set at 31 inches.

Hatch Disposal Location. At the start of each

evacuation trial, the Type-III exit hatch was to be

removed by the hatch operator from its typical location in the side of the fuselage and placed either inside

or outside the simulator, depending on the specific

experimental condition. Inside hatch disposal was

achieved by having the hatch operator place the hatch

on the seat where s/he had been sitting (e.g., Figure 5).

Outside hatch disposal was achieved by having the

hatch operator throw it through the exit opening onto

the winglet (e.g., Figure 6), where a research confederate would pull it out of the way to prevent subject

injury during the ensuing evacuation. In both cases

the hatch operator would then climb through the exit,

either leading the evacuation or not, depending on

whether another subject had squeezed through first.

Subjects were selected to be hatch operators by

random assignment as they entered the laboratory and

were sequestered away from the rest of their evacuation group after having completed initial paperwork.

At that point they were visually briefed regarding

hatch operation via graphics taken from a typical

airline safety briefing card. (Figure 7 contains the

briefing cards used for both hatch disposal locations.)

Any questions they raised regarding specific aspects of

hatch operation and/or disposal location were answered by referring them back to the briefing card for

further study. No verbal instruction was given to

them about the procedure or the evacuation trial for

which they would be opening the exit, except to note

that a buzzer would be used to start the evacuation.

The hatch operators continued to be held inside the

laboratory, away from the simulator during evacuation trials prior to their participation, to prevent them

from gaining insight about hatch operation and aircraft evacuation. Immediately before the evacuation

trial in which each hatch operator participated, s/he

was escorted to the simulator and seated adjacent to

the Type-III exit. After each of the first three trials, the

hatch operator was relocated to another area to preclude the possibility of information sharing with

subsequent hatch operators.

Participants. Subjects were apportioned among 48

experimental groups, one-third of which contained

either 30, 50, or 70 subjects, for a total of 2,400
6

Figure 6

Typical Outside Hatch Disposal Location



	



7

Figure 7

Hatch Operator Briefing Cards

Inside Hatch Disposal 

Outside Hatch Disposal 

evacuees. An additional 144 subjects were added to

the subject pool as hatch operators, since 192 (one

naïve hatch operator per evacuation trial) were needed

for opening the Type-III exit and disposing of the

hatch. This resulted in a total of 2,544 human subjects

being employed in the study. The pool of subjects,

comprised of 51% males and 49% females, ranged in

age from 18 to 65 years of age, in weight from 95 to

416 pounds, and in height from 54 to 81 inches.

The research staff included 31 FAA employees, 15

contractor personnel, and a contingent of professional flight attendants. The contract employees were

responsible for subject delivery and administrative

processing functions, as well as maintenance of the

research facility; FAA personnel were devoted to subject processing, medical management, and execution

of the experimental trials. Two flight attendants were

employed on each trial for passenger management

during the evacuations.

Motivation. The low motivation condition, often

termed cooperative egress, was established by a briefing

given in the simulator by the principal investigator

prior to each trial. In the briefing, subjects were told

that the airplane had crashed and was on fire, and that

to stay alive they had to hurry to get out.

The higher motivation condition, competitive egress,

was induced by offering double pay to subjects in half

of the groups; individual success would be achieved by

those who were among the first 25% of their group to

evacuate the aircraft simulator, averaged across all 4

evacuation trials. This offer was made in addition to

providing them with instructions identical to those

given to the low motivation subjects. The technique

of averaging across trials was intended to assure sustained competition among all subjects in any individual trial; seat assignment was rotated on trials to

give all subjects equal opportunity to earn the bonus.

Flight Attendant Participation. Two flight attendants, one in the front of the cabin and one in the rear,

were seated in jumpseats at the start of each trial. At

the sound of the start buzzer, the forward flight

attendant pointed at the exit and commanded the

hatch operator to “Open That Hatch.” Both flight

attendants immediately started commanding “Unbuckle Your Seatbelts... “Evacuate... Get Out... Get

Out... Hurry,” as they started herding the subjects

toward the Type-III exit. The flight attendants continued to command the evacuation throughout the

entire trial, but were not allowed to physically assist
8

subjects in any way. Their purpose was to keep subjects on task as would be expected in an actual emergency evacuation.

Procedure. Prospective subjects were in-processed

and informed about the requirements of the study,

after which they executed informed consent. Subjects

then completed a personal demographics questionnaire, the Transport Canada Personality Profileã

(TCPP, 2000), and a questionnaire that gauged their

attention to, and knowledge about, actual preflight

safety briefings on airliners. Their physical attributes

were then measured, and they were photographed for

identification purposes. Afterward, they were escorted

to the simulator to become visually familiar with the

exterior layout; they were issued a boarding card with

their first seat assignment; they entered the simulator;

and they seated themselves accordingly. Upon completion of the safety briefing for the trial, subjects were

allowed to ask questions.

Following any questions, and after subjects confirmed their readiness to proceed, the principal investigator read the preflight briefing and exited the cabin,

leaving only the flight attendants with the subjects.

The start buzzer was sounded after a variable interval

of 5 to 30 seconds, whereupon the flight attendants

began shouting and gesturing for the subjects to

unbuckle their seatbelts and proceed through the exit.

The hatch operator, seated next to the exit, removed

the hatch and disposed of it, allowing the evacuation

flow to begin. Research personnel stationed outside

the simulator recorded subject vest numbers for subsequent analysis of bonus payments. After the trial was

completed, subjects were regrouped for the next trial.

Data Archival, Reduction, and Analysis. Eight

video cameras, 4 inside the simulator and 4 outside,

recorded all experimental trials (see Figure 8). The

videotapes were recorded at the National Television

System Committee (NTSC) standard of 30 frames per

second and superimposed with an electronic time

code providing a temporal resolution of 33.3 milliseconds. Videotapes of each trial were examined manually to obtain group and individual evacuation times;

these times were combined in a database with the

individual subject characteristics. The data were analyzed using the multiple regression, analysis-ofvariance, and analysis-of-covariance routines in SPSS®

10.0 (1999).

Total group evacuation time for each trial was

defined as beginning at the time the start buzzer

initially sounded and lasting until the last subject had

cleared the Type-III exit opening (see cells in Table 1).

Because of the differences in the number of subjects

within the groups, however, no predictive analyses

were conducted on these group times. Instead, the

times were divided into hatch removal and disposal

times, as well as the times for individual subjects to

Figure 8

Data Acquisition and Archival
9

egress, to allow for between-subject analyses of the

effects of the independent variables and their interactions. Individual subject egress time was defined as

the period lasting from the time (videotape frame) at

which one subject was completely through the exit

opening until the time the next subject was completely through the opening. The effects on hatch

operation and individual subject egress have been

organized within subcategories for reporting purposes, so as not to lose continuity of thought for each

type of effect.

RESULTS

Note that, in the figures presented below, solid

lines are used to connect interval data points within

any category, whereas dotted lines are used to connect

data points for discrete classes of a variable. For

example, dual 6” passageway data points are connected to the single 10” passageway data points via a

dotted line, while the 10”, 13”, and 20” passageway

data points are connected via solid lines. This particular distinction was made to highlight the fact that it

was the additional passageway available for egress

with the most restrictive (6”) passageway configuration that afforded individual egress times generally

comparable to those produced by the more ergonomically-generous single passageway configurations.

Hatch Operation. Because there was a naïve subject responsible for operating the hatch on every trial,

the effects of the independent variables on the time

required to remove and dispose of the hatch were

analyzed for all 192 evacuation trials, not just the first

trial for each group. The total hatch operation and

disposal time was separated into 3 different periods.

These included Exit-Ready-To-Use Time, which denotes preparation of the exit for egress, First-SubjectOut Time, which is the time at which the first person

had fully cleared the exit opening, and HatchOperator-Out Time, the time at which the operator

was completely out. Four-way Analysis of Variance

(ANOVA) was used to analyze the data for each of

these times.

Exit-Ready-To-Use Time began at the initial sound

of the start buzzer and lasted until the first person

began to emerge from the exit. The ANOVA revealed

a significant main effect on Exit-Ready-To-Use Time

for hatch location (p<.005; Figure 9); there was also a

large interaction of hatch location with passageway

configuration (p<.001; Figure 10). This interaction effect was produced by significantly elevated outside hatch

disposal times in the 10” passageway configuration,

resulting from the increased ergonomic difficulty produced by excessive forward encroachment of the aft

seat assembly. However, the passageway configuration main effect failed to achieve significance (p<.08;

Figure 9

Exit-Ready-To-Use Time

Hatch Disposal Location Main Effect

6.15

5.11

0

2

4

6

8

10

In Out

Hatch Location

p < .005
10

Figure 11), as did the subject group motivation level

(p<.52) and subject group density (p<.54) main effects. None of the individual hatch operator characteristics influenced exit operation significantly, nor

did they interact with any of the other variables.

Disposing of the hatch inside the cabin led to shorter

overall Exit-Ready-To-Use Times.

First-Subject-Out Time was computed to provide

a starting point for the individual subject egress time

computations. This time began at the end of the ExitReady-To-Use Time. Generally, this period was about

equal to the sum of Exit-Ready-To-Use Time and the

mean individual subject egress time for any particular

trial. However, behavioral interactions among subjects and delays in completely disposing of the hatch

sometimes lengthened this initial egress period. On

six of the trials, the hatch operator was not the first

person out of the exit, complicating the computation

of this dependent variable. A significant main effect

on First-Subject-Out Time was discovered for hatch

location (p<.01; Figure 12), and there was an interaction of hatch location with passageway configuration

(p<.015) largely reminiscent of that seen for Exit-ReadyTo-Use Time. Again, the interaction effect was

dependent on significantly increased times associated

with operation of the hatch in only the 10” passageway configuration (see Figure 13). However, the passageway configuration main effect failed to achieve

significance (p<.10; Figure 14), as before; main effects

for subject group motivation level (p<.34) and subject

group density (p<.42) were similarly insignificant.

None of the individual hatch operator characteristics

were predictive of First-Subject-Out Time, nor did

they interact with any of the independent variables.

These effects were remarkably similar to those seen

for Exit-Ready-To-Use Time, and indicate that the

time required for removal and disposal of the hatch

was the primary variable in launching the evacuation

flow. This relationship can be seen easily by comparing Figures 9, 10, and 11 for Exit-Ready-To-Use

Time with Figures 12, 13, and 14 for First-SubjectOut Time. The lack of significance regarding differences in motivation level was somewhat surprising,

given the general perception of greatly increased chaos

at the start of the high motivation trials, especially

when the designated hatch disposal location was inside the cabin.

Hatch-Operator-Out Time was derived to measure the effects of differential hatch operation on the

ability of the hatch operator to egress. A related

question was focused on the effects of subject motivation level on the efficiency of hatch operation. This

time period began at the sounding of the start buzzer

and ended when the hatch operator had cleared the

exit. The expectation had been that the hatch operator

would be the first person out of the exit, which led to

Figure 10

Exit-Ready-To-Use Time

Passageway Configuration X Hatch Disposal Location Interaction

5.65

4.57

5.05

5.14 5.54

5.07

5.95

8.03

3

4

5

6

7

8

9

10

11

6" 10" 13" 20"

Passageway Configuration

In Out

p < .001

 Hatch Location:
11

Figure 11

Exit Ready-To-Use Time

Passageway Configuration Main Effect

5.80

6.30

5.29 5.10

0

2

4

6

8

10

6" 10" 13" 20"

Passageway Configuration

p < .08

Figure 12

First-Subject-Out Time

Hatch Disposal Location Main Effect

7.55

6.70

0

2

4

6

8

10

In Out

Hatch Location

P < .01
12

Figure 13

First-Subject-Out Time

Passageway Configuration X Hatch Disposal Location Interaction

7.40

6.63

6.26

6.48

9.33

7.41

6.84

6.60

3

4

5

6

7

8

9

10

11

6" 10" 13" 20"

Passageway Configuration

In Out

 p < .015

Hatch Location:

Figure 14

First-Subject-Out Time 

Passageway Configuration Main Effect

6.54 7.79 6.74

7.41

0

2

4

6

8

10

6" 10" 13" 20"

Passageway Configuration

p < .10
13

Figure 15

Hatch-Operator-Out Time 

Hatch Disposal Location Main Effect

7.92 8.22

0

2

4

6

8

10

12

In Out

Hatch Location

p < .63

the expectation that the Hatch-Operator-Out Times

would mirror the First-Subject-Out Times. This,

however, proved not always to be the case, since the

hatch operator was not always the first person out,

principally in the dual passageway configuration.

The significance of the prior hatch location main

effects was lost on Hatch-Operator-Out Time (p<.63;

Figure 15), as was the significance of the hatch location by passageway configuration interaction effect

(p<.20; Figure 16), which was somewhat similar to

that for the First-Subject-Out Time. In contrast,

passageway configuration was found to exert a significant main effect on Hatch-Operator-Out Time

(p<.012; Figure 17), resulting from a monotonic

increase in the time the hatch operator needed to

egress as the single passageway configurations became

more restrictive ergonomically. This time increased

even more in the dual passageway configuration, both

because of the increased distance between the exit and

the seat where the hatch operator had been sitting, and

where the hatch was to be placed, as well as competition for use of the exit produced by subjects using the

aft passageway. However, there was no main effect for

subject group motivation level (p<.86) or interaction

of motivation level with passageway configuration

(p<.53), again in the face of perceptible chaos. There

were also no main effects or interactions of subject

group density (p<.94) with any of the individual

hatch operator characteristics. Thus, the delays in

hatch operator egress created by the more restrictive

passageway configurations and competition for the

exit produced minimal effects on the start of the

evacuations and on total group evacuation time.

Hatch Operation Discussion. The ability of the

hatch operators to prepare the Type-III exit for egress

was remarkably good, although the techniques they

used for removing the hatch were often inefficient.

Many times the hatch operators would use the wrong

hand to grasp the handle, which caused them to labor

with the weight and bulk of the hatch, and often they

would turn counter-clockwise to place the hatch on

the seat. This rotational direction unnecessarily slowed

the start of those evacuation trials, especially when

other subjects were pressing against them in a harried

attempt to reach the exit. However, they almost unerringly placed the hatch in the designated location. Of

the few incorrect hatch disposal locations, all of which

happened during trials in the inside hatch disposal

condition, the hatch was intentionally stood on the

floor against the back of the outboard seat immediately forward of the passageway 3 times in the highmotivation condition (e.g., Figure 18), and it was

knocked from the seat onto the floor once more.

Three of these events occurred in the dual passageway

configuration, while one of the intentional floor

placements occurred in the 20” single passageway
14

Figure 16

Hatch-Operator-Out Time

Passageway Configuration X Hatch Disposal Location Interaction

10.04

7.16

7.46

6.91

9.16

9.75

7.31

6.71

3

4

5

6

7

8

9

10

11

6" 10" 13" 20"

Passageway Configuration

In Out

p < .20

 Hatch Location: 

Figure 17

Hatch-Operator-Out Time

Passageway Configuration Main Effect

6.81

7.38

8.46

9.60

3

4

5

6

7

8

9

10

11

6" 10" 13" 20"

Passageway Configuration

p < .012
15

Figure 18

Hatch Stood on Passageway Floor

configuration. Three other times the hatch came to

rest on the seat assembly one row behind the passageway, and once it was passed across the main aisle

during the evacuation. The only other erroneous

hatch disposal location occurred when the hatch was

wedged between the exit row seat assembly and the

side of the fuselage, which had no discernible effect on

the evacuation. The usually compliant nature of hatch

operation, vis-à-vis the briefing card, indicates that the

hatch operators were fully aware of the intended task

and, furthermore, they were quite willing to perform as

instructed. This circumstance bodes well with regard to

what can be expected of typical airline passengers who are

fully informed about their responsibilities when seated

adjacent to the Type-III overwing exit.

The effects of the independent variables on hatch

operation and the start of subject egress through the

Type-III exit were minor. Hatch disposal location

produced small effects on exit preparation time and,

therefore, the time for the first person to egress. It was

generally the case that inside hatch disposal allowed

the fastest evacuation start times by about one second,

on average, relative to outside disposal. Passageway

configuration, on the other hand, had little effect on

hatch operation and the start of the evacuations,

except where the most ergonomically restrictive passageway configuration slowed hatch operator egress.

The interaction of outside hatch disposal with the

single 10” passageway configuration almost doubled

evacuation start times; this effect resulted from the

difficulty hatch operators experienced in leaning over

the seat cushion to remove the hatch and throw it

outside. In contrast, placing the hatch inside the cabin

in the 10” configuration resulted in the fastest exit

preparation times. Combined, these results indicate

that, in terms of Type-III exit operation and the

effects of hatch disposal location on the start of an

evacuation, either hatch disposal location could be justifiably chosen for airline operations, as long as aft seat

encroachment is limited to the centerline of the exit.

Once the exit was ready to use, there was little else

that delayed the start of the evacuation. While the

chaotic appearance of the evacuation trials associated

with the high motivation condition created the perception of increased exit preparation times and delayed evacuation start times, there were only small

numerical differences in start time between motivation levels. This result was maintained even in the

dual passageway configuration. Differences in subject

group density failed to influence exit preparation and

evacuation start times, generally because exit preparation was completed before distant subjects neared the
16

exit. Individual hatch operator characteristics were

also not predictive of exit preparation, except in a

couple of instances where the hatch was too heavy for

the assigned operator and was manipulated by another

subject. This latter circumstance supports the current

practice of requiring passengers sitting adjacent to the

Type-III exit to be older than 15 years of age, and

further suggests that small female adults should not be

seated next to the overwing exit. In sum, the ability of

the typical hatch operator to prepare the exit for an

evacuation was not particularly dependent on any of

the independent variables except hatch disposal location, unless the passageway was offset from the exit

opening too far to provide an ergonomicallyappropriate

workspace. In those instances, hatch operator strength

and technique were important.

Evacuation. Although there were 48 first-trial total

group evacuation times, the complexity of the experimental design and the statistical variability this complexity produced among individual groups precluded

analysis of total group evacuation times. In addition,

there was a clear lack of comparability between certain

groups that made such comparisons immaterial. For

example, no meaningful comparison could be made

between the total group evacuation times for groups

comprised of 30 and 70 subjects, although comparison of the egress time for the first 30 subjects in all

groups was possible. Analysis of those first-30-subject

egress times revealed no significant differences among

the groups. In consideration, the total group evacuation times were deconstructed into individual subject

egress times, the first of which began at the FirstPerson-Out Time and ended when the second subject

was completely through the exit. This one-subjectcompletely-out to next-subject-completely-out algorithm was used until the individual egress times for all

subjects in each evacuation trial were derived. This

procedure provided a database of 2,352 individual

subject egress times by which to calculate the effects of

the independent variables (Design Factors), as well as

the effects of the individual (Human Subject) characteristics. The large number of observations provided

an enormous amount of statistical power, allowing

the data to be screened for significant egress time

outliers, i.e., those whose times were greater than 3

standard deviations above the mean for each passageway configuration. This resulted in the removal of 41

individual subject egress times, with minimum times

of 4.1 seconds with the 20” configuration, 4.9 seconds

with the 13” configuration, 4.5 seconds with the 6”

configuration, and 4.4 seconds with the 10” configuration. Examination of the videotapes showed that the

outlying egress times generally resulted from errant

individual subject behavior, such as improper egress

techniques/delays getting through the exit opening,

getting a foot or leg caught between seats, and from

the exit being jammed with subjects during egress.

However, no evacuation trial was halted because of exit

blockade. The table in Appendix A provides the details

of all outlying individual egress times.

All variables, including both design factors and

subject characteristics, were subjected to an initial

multiple regression analysis to assess relative significance with regard to individual subject egress time.

The results indicated that subject waist size accounted

for the greatest amount of variance in the data

(p<.0001), followed next by gender (p<.0001), and

then age (p<.0001). Neither subject height nor any of

the independent variables added further to the regression model. This was the first evidence that the

individual subject characteristics were significantly

more important to the evacuation outcomes than

were the independent variables.

Design Factors Effects. After the regression analysis was completed, a univariate analysis of covariance

(ANCOVA ) was computed to assess the interactive

effects of the independent variables. The covariates

included the 3 human subject characteristics found to

be significant in the regression model; all 4 of the

independent variables were used as the experimental

design factors. The ANCOVA failed to find significant main effects of hatch disposal location (p<.96)

and subject group density (p<.32), as the disposal

locations and group densities all produced nearly

identical mean individual egress times (see Figures 19

and 20). However, a significant hatch disposal location by subject group density interaction effect was

identified (p<.05; Figure 21) that resulted from a

small increase in individual subject egress times as

group density increased in the inside hatch disposal

condition, relative to egress times that remained essentially flat with increased group density in the

outside hatch disposal condition. The main effect of

subject group motivation level on egress times also

proved not to be significant (p<.78; Figure 22). However, the data unexpectedly showed that individual

subject egress in the high-motivation condition had

been faster, a result in contravention to the numerous

reports of slowed evacuations for high-motivation

subjects in studies employing financial incentives to

create the high-motivation condition (for review see

McLean, 2001).

Passageway configuration was shown to produce

significant main effects on individual subject egress

times (p<.001; Figure 23), resulting from small (0.16

second) differences in mean individual egress times
17

Figure 19

Individual Subject Egress Time

Hatch Disposal Location Main Effect

1.60 1.59

0.0

0.5

1.0

1.5

2.0

2.5

In Out

Hatch Disposal Location

 p < .96

Figure 20

Individual Subject Egress Time 

Subject Group Density Main Effect

1.61 1.60 1.56

0.0

0.5

1.0

1.5

2.0

2.5

Low (30) Medium (50) High (70)

Group Density

p < .32
18

Figure 21

Individual Subject Egress Time 

Hatch Disposal Location X Group Density Interaction

0.0

0.5

1.0

1.5

2.0

2.5

Low (30) Medium (50) High (70)

Group Density

Hatch Disposal Location: In Out

p < .05

Figure 22

Individual Subject Egress Time 

Subject Group Motivation Main Effect

1.64

1.55

0.0

0.5

1.0

1.5

2.0

2.5

Low High

Group Motivation

p < .78
19

among the passageway configurations. An interaction

of passageway configuration with subject group density (p<.01; Figure 24) was produced by a relative

shuffling of egress times for each density condition

within the 10” and 13” passageway configurations.

This effect was accompanied by an interaction of

passageway configuration with hatch disposal location (p<.001; Figure 25), created by elevated egress

times with the 13” passageway configuration with

inside hatch disposal and the 10” configuration with

outside hatch disposal.

The relative character of these times was puzzling,

since the most ergonomically restrictive passageway

configuration provided faster egress with the hatch

placed inside, when compared with the less restrictive

configurations in the same hatch disposal condition.

The disorderly nature of both interaction effects suggested that much was to be learned from the individual egress times in the 10” and 13” passageway

configurations, which led to additional scrutiny of the

interactions among these and the other independent

variables. The higher-order interactions were particularly instructive.

While the passageway configuration by group motivation interaction effect failed to achieve significance (p<.27; Figure 26), a significant (3-way)

passageway configuration by group density by group

motivation level interaction effect (p<.015) was evidenced, as was a significant (4-way) passageway configuration by hatch disposal location by subject group

density by subject group motivation level interaction

effect (p<.008). The basis of this 4-way interaction

effect can be seen in Figures 27 and 28, which show

that (1) the individual subject egress times in the 13”

passageway configuration with inside hatch disposal

were greater for the high-density subject groups, especially in the high motivation condition, and (2) the

individual subject egress times in the 10” passageway

configuration with outside hatch disposal were much

greater for the low motivation group in the low

density condition and the medium density group in

the high motivation condition. These results led to a

further review of the videotapes of those trials for an

explanation. The reasons for the elevated times became clear immediately.

Closely after the start of the high-motivation, highdensity trial with the 13” passageway configuration

with inside hatch disposal, the hatch was knocked

from its upright position, falling flat on the seat and

laying across the exit opening (see Figure 29). This

produced an obstruction to egress, significantly increasing individual subject egress times. The low

motivation trial was beset with a similar problem. In

that trial the hatch was also knocked onto the seat

Figure 23

Individual Subject EgressTime 

Passageway Configuration Main Effect

1.50

1.66 1.66

1.56

0.0

0.5

1.0

1.5

2.0

2.5

6" 10" 13" 20"

Passageway Configuration

p < .001
20

Figure 24

Individual Subject Egress Time 

Passageway Configuration X Group Density Interaction

0.0

0.5

1.0

1.5

2.0

2.5

6" 10" 13" 20"

Passageway Configuration

Group Density: Low(30) Medium(50) High(70)

p < .01

Figure 25

Individual Subject EgressTime 

Passageway Configuration X Hatch Disposal Location Interaction

1.54

1.75

1.58 1.54 1.47

1.58

1.74

1.58

0.0

0.5

1.0

1.5

2.0

2.5

6" 10" 13" 20"

Passageway Configuration

Hatch Disposal: In Out

p < .001
21

Figure 26

Individual Subject Egress Time 

Passageway Configuration X Subject Group Motivation Interaction 

1.54

1.72 1.71

1.60

1.46

1.60 1.62 1.52

0.0

0.5

1.0

1.5

2.0

2.5

6" 10" 13" 20"

Passageway Configuration

Group Motivation: Low High

 p < .27

Figure 27

Individual Subject Egress Time 

Passageway Configuration X Hatch Disposal Location X Group Density X Group Motivation 

Inside Hatch Disposal Location

0.0

0.5

1.0

1.5

2.0

2.5

6"

Low Group

Motivation

10" 13" 20" 6"

High Group

Motivation

10" 13" 20"

Passageway Configuration

Group Density: Low (30) Medium (50) High (70)

p < .008
22

Figure 28

Individual Subject Egress Time 

Passageway Configuration X Hatch Disposal Location X Group Density X Group Motivation 

Outside Hatch Disposal Location

0.0

0.5

1.0

1.5

2.0

2.5

6"

Low Group

Motivation

10" 13" 20" 6"

High Group

Motivation

10" 13" 20"

Passageway Configuration

Group Density: Low (30) Medium (50) High (70)

p < .008

Figure 29

Exit Obstructed by Hatch
23

cushion, landing longitudinally with respect to the

exit and forming a slide to the exit (see Figure 30) that

slowed the evacuation until the 39th subject to egress

threw the hatch outside. Together, these 2 trials

significantly inflated the mean individual subject egress

times in the 13” passageway configuration and produced several of the egress time outliers in the 13”

passageway configuration.

Since the results of these trials depended not on

passageway configuration, per se, but on partial obstruction of the exit caused by improper hatch disposal, an adjustment to the mean egress times for

those 2 trials was made to remove the temporal influence of the obstructions. This statistical compensation brought the mean times for those 2 trials more in

line with the other 13” passageway configuration

results, thereby eliminating the 13” component of the

passageway configuration main effect, as well as the

significance of the interaction between passageway

configuration and both hatch disposal location and

subject group density. This left only the egress times

from the 10” passageway configuration with outside

hatch disposal location as being significantly different

from the rest.

Human Subject Effects. Upon arrival at the laboratory, subject age and gender were recorded, and

subjects were measured to obtain their weight, waist

size, and height. All measurements were taken with

subjects wearing street clothing and shoes, which

slightly inflated the recorded dimensions. Because

weight and waist size were so highly correlated (r =

.90), but weight was not correlated significantly with

height, waist size is reported here to distinguish the

effects of subject width versus subject height.

Subsequent to the multiple regression and ANCOVA

analyses described above, the individual subject characteristics were categorized to provide interval data that

would unveil more discrete views of the subject effects.

Five subcategories of age, waist size, and height, distributed to achieve a similar number of subjects per subcategory, were created in addition to gender. These grouped

variables were then combined with passageway configuration, the only significant independent variable, and

analyzed for interactions by 5-way ANOVA.

Not unexpectedly, significant main effects were

replicated for waist size (p<.0001; Figure 31) age

(p<.0001; Figure 32), gender (p<.0001; Figure 33),

and passageway configuration (p<.031); subject height

Figure 30

Slide to Exit Formed by Hatch
24

also reached marginal significance (p<.03; Figure 34).

There were no significant interactions among any of

the individual subject characteristics; nor were there

2-way interactions between passageway configuration

and any of the individual subject characteristics (see

Figures 3538). However, there was a (3-way) passageway configuration by gender by age interaction effect

(P<.005; Figure 39), that appeared to result from

shorter egress times for older males, relative to older

females, especially with the 6” and 20” passageway

configurations. The importance of this distinction

was not that older males appeared to be faster than

older females in those 2 particular passageway configurations, but that the regression toward the

grand mean for the entire group of older subjects,

produced for whatever reason by the relatively shorter

individual egress times of those older males, might

have masked the significance of an interaction between passageway configuration and subject age typical of older individuals. This appeared to be the case,

since older male subject egress times with both the 10-

and 13-inch passageway configuration were greater

than those of their younger cohorts, as well as being

quite similar to those of the older females.

Significant interactions between passageway configuration and the other (older) subject characteristics

might have also been obscured, given the significant

positive correlations (p<.01) of both waist size and

(unexpectedly) height with age.

To investigate this possibility, simple effects analyses were conducted for the interactions of passageway

configuration with all subcategories of all individual

subject characteristics investigated.

A simple effect of passageway configuration (p<.005;

Figure 40) was found for subjects older than 42 years

of age, who were significantly slower to egress with the

10” passageway configuration, relative to the other

passageway configurations. Subject waist sizes greater

than 38” produced essentially identical effects (p<.02;

Figure 41). The effect of passageway configuration on

subjects whose height was greater than 6 feet tall was

also found to be significant (p<.001; Figure 42), as

egress was slowed for those subjects with both the 6”

and 10” passageway configurations. These results

confirmed that, in particular, the 10” passageway

configuration was remarkably more difficult for older,

wider, and taller subjects to use, especially subjects in

whom these characteristics were combined.

The results also led to revisiting the significant (4-

way) passageway configuration by hatch disposal location by subject group density by subject group

motivation interaction effect on individual subject

Figure 31

Individual Subject Egress Time 

Subject Waist Size Main Effect

1.35 1.43 1.51

1.72

1.96

0.0

0.5

1.0

1.5

2.0

2.5

23-31 32-34 35-38 39-41 41-62

Waist Size in Inches

p < .0001
25

Figure 32

Individual Subject Egress Time 

Subject Age Main Effect

1.57

1.44 1.34

1.71

2.01

0.0

0.5

1.0

1.5

2.0

2.5

18-22 23-32 33-42 43-52 53-65

Age in Years

p<.0001

Figure 33

Individual Subject Egress Time 

Subject Gender Main Effect

1.70

1.49

0.0

0.5

1.0

1.5

2.0

2.5

Male Female

Subject Gender

p < .0001
26

Figure 34

Individual Subject Egress Time 

Subject Height Main Effect

1.59 1.52 1.55

1.58

1.74

0.0

0.5

1.0

1.5

2.0

2.5

57-64 65-66 67-68 69-71 72-79

Subject Height in Inches

p < .03

Figure 35

Individual Subject Egress Time 

Passageway Configuration X Subject Gender Interaction

1.35

1.53 1.58 1.51

1.61

1.73 1.81

1.66

0.0

0.5

1.0

1.5

2.0

2.5

6" 10" 13" 20"

Passageway Configuration

Males Females

p < .35
27

Figure 36

Individual Subject Egress Time 

Passageway Configuration X Subject Age Interaction

0.0

0.5

1.0

1.5

2.0

2.5

3.0

18-22 23-32 33-42 43-52 53-65

Subject Age Range

Passageway Configuration: 6" 10" 13" 20"

p < .15

Figure 37

Individual Subject Egress Time

Passageway Configuration X Subject Waist Size Interaction

0.0

0.5

1.0

1.5

2.0

2.5

23-30 31-33 34-37 38-40 41-62

Subject Waist Size in Inches

Passageway Configuration: 6" 10" 13" 20"

p < .52
28

Figure 38

Individual Subject Egress Time 

Passageway Configuration X Subject Height Interaction

0.0

0.5

1.0

1.5

2.0

2.5

57-64 65-66 67-68 69-71 72-79

Subject Height in Inches

Passageway Configuration: 6" 10" 13" 20"

p < .36

Figure 39

Individual Subject Egress Time

Passageway Configuration X Subject Gender X Subject Age Interaction

0.0

0.5

1.0

1.5

2.0

2.5

3.0

18 to 22

Male

23-32 33-42 43-52 53-65 18 to 22

Female

23-32 33-42 43-52 53-65

Age in Years

Passageway Configuration: 6" 10" 13" 20"

p < .005
29

Figure 40

Individual Subject Egress Time

Subjects Older Than 42 Years Of Age

1.72

1.97

1.85 1.79

0.0

0.5

1.0

1.5

2.0

2.5

6" 10" 13" 20"

Passageway Configuration

p < .005

Figure 41

Individual Subject Egress Time 

Subjects With Waist Size Greater Than 38"

1.73

1.86

1.96

1.84

0.0

0.5

1.0

1.5

2.0

2.5

6" 10" 13" 20"

Passageway Configuration

p < .02
30

Figure 42

Individual Subject Egress Time 

Subjects Taller Than 72" 

1.36

1.54

1.76

1.66

0.0

0.5

1.0

1.5

2.0

2.5

6" 10" 13" 20"

Passageway Configuration

p <.001

egress times, which had been shown earlier to be

partially dependent on limited hatch-produced obstructions of the exit with the 13” passageway configuration (Figure 27). In addition to those effects,

there had been an additional component of that

interaction effect dependent on elevated egress times

with the 10” passageway configuration with outside

hatch disposal (see Figure 28). The simple effects

described above for the older, wider, taller subjects

with the 10” passageway configuration suggested that

another review of the videotapes, examining the characteristics of the subjects in the 10” passageway configuration trials with outside hatch disposal for the

low-motivation, low-density group and the highmotivation, medium-density group, might shed further light on this higher-order interaction.

The videotape review revealed that subjects in the

low-motivation, low-density condition appeared to

be generally in much less of a hurry than was typical;

and they almost all adhered to the “step-through-footfirst” command used continuously by the flight attendants. This combination produced generally-slowed

individual egress times. The high-motivation, medium-density group included a preponderance of overweight (wider) females, who were also more clumsy

than usual, that combination producing generallydelayed egress for themselves and those who immediately followed. Together, this situation seemed to

create a between-groups imbalance in subject behavior and the distribution of individual subject characteristics, and this imbalance appeared to be responsible

for the 10” passageway configuration component of

the higher-order interaction effect. Statistically compensating for this bias, as was done by adjusting the

individual egress times for the 13” passageway configuration confounded by improper hatch disposal,

eliminated the residual significance of the passageway

configuration main effect, as well as the significance

of the remaining interaction effects found among the

independent variables.

This mathematical procedure controlled for the

variance induced by the imbalance in the betweengroups distribution of behavioral and individual subject characteristics, recapitulating the initial multiple

regression analysis, by targeting specific cells in the

research design for which waist size, gender, and age

were in control of the mean individual egress time.

Thus, the multiple regression analysis alone would

have been sufficient to demonstrate the significance

of the various egress factor effects on individual subject egress times. However, without having completed

the subsequent analyses, there would have been an

inability to describe as fully the various interactions

among all of the factors that influenced the evacuations, especially the contributions of the human subject characteristics.
31

To complete the description of the importance of

the various effects, the amount of variance attributable to each independent variable and human characteristic, as well as that attributable to their interactions,

has been displayed graphically in Figure 43. There,

the preeminent significance of individual human subject characteristics in the control of the evacuations is

clearly demonstrated.

Evacuation Discussion. The effects on evacuation

performance described above replicate fully the research program findings on access to the Type-III exit

recounted by McLean (2001). In sum, the specific

cabin interior configuration at the Type-III overwing

exit was again shown to be of little significance in

emergency evacuations, as long as ergonomic minimums were respected. In contrast, the effects of human subject characteristics were shown to be

particularly significant, especially those characteristics related to ergonomic considerations. The outermost cases of both configural and human subject

variables accounted for the overall significance of any

particular egress factor, as it related individually to

evacuation performance, as well as its interactions

with the other egress factors that influenced the evacuations detrimentally.

The independent variables employed in this study,

especially passageway configuration, were typical of

those used in previous investigations. The primary

research question had been whether the current regulatory requirement, i.e., the 20” passageway configuration with 5” aft seat encroachment, provided more

efficient evacuations than the other configurations

studied. The significant main effect of passageway

configuration appeared to confirm that possibility for

the single passageway configurations, although the

actual differences in individual subject egress times

evidenced among the different passageway configurations rendered the significance much more statistical

than practical. In fact, it was the enormous statistical

power of the research design that allowed very small

differences in egress time to achieve significance. As

shown in Figure 43, the proportion of the identified

effects on evacuation time that passageway configuration generally represents is challenged for insignificance only by the effects of the other independent

variables and individual subject height.

The interactions between passageway configuration and the other independent variables also appeared initially to suggest important interactive

constraints on egress. As indicated above, however,

Figure 43

Relative Magnitude of Effects 

on Individual Subject Egress Time

0

3

6

9

12

15

Group

Motivation

Hatch

Location

Group

Density

Subject

Height

Passageway

Width

Design Factor

Interactions

Subject 

Age

Subject

Gender

Within

Subject

Interactions

Subject Waist

Size

Egress Factors
32

these interaction effects were actually dependent only

on limited obstructions of the exit opening produced

by a couple of errant hatch disposal attitudes with the

13” passageway configuration that belie the general

lack of significance found for hatch disposal location.

Although such hatch disposal problems could be

potentially injurious in actual practice, solutions aimed

at preventing hatch-produced exit obstructions could

be implemented to avert that possibility. Among these

would be hatches that are automatically stowed outside the evacuation path upon opening or an operational principle that requires the hatch to be discarded

outside the airplane when cabin interior configurations more easily promote potential exit obstructions.

Any specific solution would need to be chosen with

full consideration of the seat encroachment distance

in a particular configuration.

A prejudicial combination of behavior and individual subject characteristics in two subject groups

using the 10” passageway configuration produced an

apparent interaction between passageway configuration and subject group density, as reflected in exceptionally slowed egress in the 2 related trials. Controlling

for this imbalance of individual subject characteristics

eliminated this effect to illustrate more properly the

average contribution to egress time of passageway

configuration. Interestingly, however, it was this imbalance in the between-groups distribution of individual subject characteristics that suggested further

examination of the simple interactions between passageway configuration and specific human subject

characteristics. The character of these effects showed

clearly that, of the single passageway configurations

employed, only the 10” passageway configuration

produced ergonomic restrictions significant with respect to egress performance, specifically for older,

wider, and taller subjects. These results replicate those

described by McLean and George (1995), and attest

again to the inability of the 10” passageway configuration to provide an egress route that is as effective or

as efficient as the other configurations for a significant

portion of the flying population.

The expected effects of subject group motivation

level on individual egress times failed to materialize,

as the average difference in egress times between highand low-motivation groups was small. Unexpectedly,

the high-motivation groups were slightly faster than

were the low-motivation groups, a finding not previously reported. In fact, prior use of financial incentives to achieve highly motivated subjects generally

resulted in a large degree of behavioral chaos that

often produced jammed exits that slowed egress significantly. While some amount of chaotic behavior

was evident in the current study, that type of behavior

typically occurred in the latter evacuation trials for

each group.

In addition, the differences in behavioral intensity

between group motivation levels appeared to be less

than seen previously. There appeared to be three

factors that produced these differences in results.

First, the pre-trial briefing in the current study included a statement read to each group immediately

before each trial that had not been used before; i.e.,

“Remember, the airplane has crashed and is on fire,

and to stay alive we must get out of here as fast as we

can. HURRY!” This admonition appeared to energize

the low-motivation level subjects beyond what had

been typical, as they often climbed across seats to

approach the exit in much the same way as the highmotivation level subjects. Second, the current study

employed two professional flight attendants on every

trial. They herded the subjects toward the exit from

both the front and rear of the cabin, and their general

attitude and skill in commanding the evacuations was

exemplary. Their ability to verbally adjust subject

behavior at the exit was considerable, and whenever

an exit became nearly jammed, they would augment

their command set to include “One at a time! One at

a time!” This appeared to reduce the incidence of

jamming significantly. Third, and perhaps most importantly, the results presented here are restricted to

data from the first trial for each group (in which all

subjects were truly naïve). It appeared that only after

subjects had completed the first, and subsequent,

trial(s) did the high-motivation groups become fully

aware of how competitive they could be, which progressively exacerbated the behavioral chaos in latter trials.

Combined, these factors produced a situation in

which the high-motivation level subjects seemed to

benefit from the lure of financial incentives, performing as fast as possible, without the jamming and

interruptions in egress produced by overly aggressive

behavior associated with repeated high-motivation

evacuation trials. Comparisons of motivation level

effects in the current study with those found in previous (repeated-trial) studies will await the repeatedmeasures analysis of motivation-level effects in the

current study.

Of much greater significance overall were the individual subject characteristics, which accounted for

32% of the variance in the results, when withinsubjects interactions are included. Subject waist size

was the most significant predictor of individual subject egress time, as wider subjects had more trouble

negotiating the exit opening. It should be noted that

one subject, who weighed 416 pounds, still managed
33

to traverse the exit with minimal difficulty, if not

great speed. Gender was the next most significant

individual subject characteristic following waist size,

as females were revealed to be slower to egress than

males. Mean differences in athleticism have generally

been considered responsible for this much-replicated

finding. Advanced age also slowed egress significantly,

again because of the reduced agility attendant to

aging. While subject height was only of marginal

significance, generally increased egress times were

seen for short (legged) females who had difficulty with

the step-up and step-down required for egress through

the exit. Males taller than 6 feet were significantly

slowed in the most restrictive passageway configurations. The interactions of the human subject variables

also added significantly to their influence on evacuation performance. As seen in previous studies, the

combination of female gender with advanced age and

large waist sizes was particularly harmful vis-à-vis

evacuation performance through the Type-III exit.

Thus, the effects of both configural and human

subject variables replicate and extend those found in

prior studies, particularly the investigation by McLean

and George (1995). That study employed a practice

protocol to control individual subject performance

variability in a split age group, repeated-measures

research design that received controversy for its statistical combination of the data from the two age groups

and, by implication, its rumored lack of generalizability

to the naïve flying public. In fact, the large betweengroups design employed in the current study was

implemented specifically to address the age stratification issue, as well as the behavioral inconsistency that

the practice protocol was used to eliminate.

The report of that 1995 study includes a graph

(Figure 9), similar to the one illustrated here in Figure

43, which shows the partitioning of the variance

attributable to human subject characteristics. Comparison of the figures shows the relationships among

the individual subject characteristics to be very similar

for the two studies. The small differences that were

expressed relate to the relative strength of effects of the

within-subjects characteristics in both studies, and

are apparently related to the smaller number of subjects (74) and the more truncated range of subject

characteristics employed in 1995. Importantly, the

larger subject sample used here provided increases in

both statistical power and diversity of subject characteristics that authenticate the more modest 1995 results, reinforcing their generalizability. Combined,

these studies clearly delineate the effects of individual

human subject physical characteristics on evacuations

through the Type-III overwing exit.

In addition to the significance of these human

subject characteristics in controlling egress through

the Type-III exit, the naiveté that predominates in

actual emergency evacuations, i.e., a lack of the knowledge, experience, and skill that would promote evacuation efficiency, has also been shown to be paramount.

The effects of subject naïveté were clearly identified in

the meta-analysis by McLean (2001) as the primary

undercurrent in the findings of the lengthy Type-III

exit evacuation research program; however, any ability to uncover the specific contributions of limited

subject knowledge and behavioral inexperience has

been hindered by the lack of pooled raw data by which

to make statistical comparisons among studies. Importantly, differences between laboratories, research

techniques, and subject populations could minimize

the validity of any such analyses.

The performance effects of naïveté are generally

hidden in the residual, unapportioned variance in the

results typically referred to as the error variance, i.e.,

the proportion of the results for which no cause can be

ascribed. In terms of the current study, the cumulative

amount of variance that can be attributed to the

investigated egress factors is almost 38%, which leaves

about 62% of the total variance to be partitioned, if

possible. Without the program of research already

conducted on evacuations through the Type-III

overwing exit, especially the study by McLean and

George (1995), the ability to explain any part of this

unapportioned variance would likely go wanting.

However, the practice protocol used in that 1995

study allows instructive comparisons of the differences in the magnitude of the human subject effects

between studies, potentially revealing the variability

in performance associated with naïveté and behavioral

inexperience. Note that both studies were conducted

by the same principal investigator, in the same airplane simulator, using the same evacuation procedures and controls, and drawing subjects from the

same general population. Thus, similarity of the residual, unapportioned true measurement error in both

studies is likely, allowing an estimate of the variability

conserved through evacuation experience to be made.

Recall that the current research protocol used a

between-groups research design in which a single

individual egress time was collected for 2,352 totally

inexperienced subjects. As described above, the amount

of between-subjects variability was huge. In contrast,

the 1995 research protocol included only 74 subjects

who were allowed to reach asymptotic egress performance prior to the start of data collection, which

assembled individual egress times for every subject in

33 separate evacuation trials. This repeated-measures
34

design produced a set of about 2,400 individual egress

times, i.e., an equivalent database for comparison

with the current results.

Regarding the amount of variance explained in

each study, the within-subjects design has a computational advantage, as the associated analysis of individual egress times adjusts for the common covariances

resulting from repetitive use of the same subjects. In

contrast, the analysis of between-subjects data uses

only one data point for each subject and, therefore,

cannot benefit from this procedural advantage. The

extensive set of practice-enhanced individual egress

time clusters for each subject in the 1995 study makes

the application of this covariance adjustment even

more effective, by reducing the actual variability in

individual egress times to highlight the proportion of

the results dependent on the physical characteristics

of individual subjects.

Thus, 71% of the total variance in the (1995)

McLean and George study was explained by the effects of individual subject characteristics, in addition

to a small amount of variance contributed by passageway configuration. In the current study, passageway

configuration maintained its very small contribution,

as all of the independent variables together accounted

for only about 6% of the total variance in the results.

The proportion of the results attributable to individual subject characteristics was only 23%, with the

interactions among these individual subject characteristics responsible for another 9% of the variance in

the results. Assuming that the amount of unexplained

variance produced by the true measurement error in

both studies is essentially equivalent, around 35 -

40% of the total variance in the current study is based

primarily on the effects of naïveté, i.e., procedural and

behavioral inconsistency produced by inexperience

and a lack of egress skill.

This inconsistency was evidenced in the compounded behavioral disorder seen in the current evacuations, which included struggling for position in the

egress queue near the exit, climbing over the seats fore

and aft of the passageway(s), shoving and pushing at

the exit proper, and getting jammed within the confines of the exit opening together with one or more

other subjects. Other behavioral variability in the

results was produced by subject missteps such as approaching or traversing the exit awkwardly, getting a

foot caught between the seats or between the seat and

the inside fuselage panel, head bumping into the

overhead bins and/or the exit frame that caused redirection and second attempts to egress, getting tangled

up with other subjects, and falling onto the winglet

outside the simulator, all of these hindering individual

egress differentially. While actual quantitative measurement of the specific contributions imparted by

these idiosyncratic events is unfeasible, i.e., it remains

actual error variance, comparison of the results from

these 2 studies reveals the negative influence that

naïveté has on evacuation performance and the improvements in evacuation effectiveness and efficiency

that occur when egress performance becomes more

regimented through knowledge and, particularly, experience.

Improvements in Type-III exit hatch operation in

the current study, similar to the improvements seen

for evacuation performance in the McLean and George

(1995) study, were produced by compelling the hatch

operators to review the safety briefing card prior to

their evacuation trials. Both hatch operation and

selection of hatch disposal location appeared to benefit from this improved educational experience. These

enhancements in operational effectiveness, based only

on better information, suggest that superior evacuation outcomes can be achieved in actual transport

category operations by the provision of enhanced

passenger education and training. Specific investigations of alternative methodologies have already begun, and the development of more effective educational

materials needs to be accomplished. Strategies related to

the application of these activities must also be defined.

CONCLUSION

These findings reinforce those that have come

before. The effects of cabin interior configuration

adjacent to the Type-III exit are minimal, as long as

ergonomics minimums are respected. Such effects are

completely overshadowed by what can best be described as a tour de force in human subject variability.

Differences in the physical and psychological characteristics of research subjects, as well as the naiveté that

engenders significant behavioral variability, function

in almost direct opposition to the notion that problems with emergency evacuation through the Type-III

exit are generally produced by restrictive cabin interior configurations. These findings restate the need to

address the conventional airplane emergency evacuation problem for what it really is — a failure of

passengers to understand and properly execute emergency procedures. The time has now come to move on

to a search for better information and more effective

passenger education and training techniques that will

lead to safer and more productive emergency

evacuations/survival.
35

REFERENCES

Department of Transport, Aircraft Accident Investigation Branch, Report on the Accident to Boeing

737-236 Series 1, G-BGJL at Manchester International Airport on 22 August 1985, (AAIB Report

8/88), London, 1998.

McLean, GA, Access-to-Egress: A Meta-Analysis of the

Factors That Control Emergency Evacuation

Though the Transport Airplane Type-III

Overwing Exit, Office of Aerospace Medicine

Report, DOT/ FAA/AM-01/2, Washington,

DC: FAA, January 2001.1

McLean, GA and MH George, Aircraft Evacuations

Through Type-III Exits II: Effects of Individual

Subject Differences, Office of Aerospace Medicine Report, DOT/FAA/AM-95/25, Washington,

DC: FAA, August 1995.1

Muir, H, D Bottomley, & J Hall, Aircraft Evacuations:

Competitive Evacuations in Conditions of NonToxic Smoke, Civil Aviation Authority, UK, CAA

Paper 92005, March 1992.

National Transportation Safety Board, Aircraft Accident Report, Runway Collision of USAir Flight

1493, Boeing 737 and Skywest Flight 5569

Fairchild Metroliner, Los Angeles International

Airport, Los Angeles, California, (NTSB/AAR-91/

08), Washington, DC: NTSB, February 1, 1991.

National Transportation Safety Board, Emergency

Evacuation of Commercial Airplanes, Safety Study

NTSB/SS-00/01, Washington, DC: NTSB, 2000.

SPSS Base 10.0 Applications Guide, SPSS Inc., Chicago, Il, 1999.

Transport Canada Personality Profile (TCPP), Version

2, Minister of Public Works and Government

Service, Ottawa, Canada, Copyright 2000.

1

 This document can be obtained through the National Technical Information Service, Springfield, VA 22161. It is also available at the

Civil Aerospace Medical Institute’s Web site: http://www.cami.jccbi.gov/aam-400A/Abstracts/Tech_Rep.htm
A1

Appendix A

TYPE-III EXIT EGRESS OUTLIERS

Motive/ Egress Waist

Passageway/ Order Time Z Size Height

Hatch Location Out (sec) Score Sex Age (in) (in) Egress Details

L - 6 - I 21 4.6 3.15 F 55 36.2 65.4 Step-thru delay

L - 6 - I 11 4.8 3.32 M 46 50.8 71.3 Two tries to get out; step-thru delay

L - 6 - I 1 9.4 8.16 M 42 39.4 65.4 Held onto side of opening to step-thru

L - 6 - O 12 4.6 3.11 F 63 47.2 65.9 Stepped onto sill then decided to step-thru

L - 6 - O 30 6.4 5.00 F 65 37.0 68.7 Step-thru delay; trailing foot got hung up in exit

L - 6 - O 4 7.4 6.09 F 63 39.8 62.7 Had trouble getting foot up to the exit sill

L - 6 - O 14 4.9 3.39 F 55 46.5 67.4 Two tries to get thru exit

L - 10 - I 9 6.7 5.66 M 35 33.1 71.5 Stood on hatch, foot slipped off ; two tries to get thru

L - 10 - I 31 4.7 3.39 F 41 42.9 63.8 Short legs, both feet on sill; sat down to get thru

L - 10 - O 33 4.6 3.21 F 45 43.3 67.9 Step-thru delay, sat on sill & held onto side of exit

L - 10 - O 33 4.9 3.55 F 65 41.7 66.5 Two tries to get feet on sill, jumped thru

L - 10 - O 31 4.7 3.32 M 61 27.6 62.4 Trouble getting both feet on sill; stepped down

L - 13 - I 27 5.7 3.77 F 22 31.9 65.1 Trouble getting on sill, stepped down, hatch in way

L - 13 - I 12 5.4 3.48 F 51 34.3 68.4 One, then both feet on sill; began to step thru & jumped

L - 13 - I 54 5.2 3.23 F 19 25.6 66.9 Both feet on sill then stepped down

L - 13 - I 45 6.1 4.15 F 52 48.4 67.0 Short legs, foot & knee on sill, leaned back, step-thru delay

L - 13 - O 13 6.0 4.05 F 63 45.7 69.1 Step-thru delay; trailing foot got hung up on exit

L - 20 - I 28 6.4 5.75 F 54 43.7 60.9 Step-thru delay, held onto side of exit, trailing leg caught

L - 20 - I 29 5.0 4.02 F 59 45.7 66.4 Short legs, put foot on sill, then stepped down

H - 6 - I 3 7.1 5.71 F 27 32.3 62.0 Fell partly out head first, then regrouped, both feet on sill

H - 6 - I 1 6.2 4.83 F 18 25.6 64.4 Struggled in front of hatch operator; step-thru delay

H - 6 - O 19 6.8 5.39 F 63 46.1 68.5 Trouble getting foot up on sill, step-thru delay

H - 10 - I 69 4.9 3.58 F 56 37.8 63.7 Trailing foot caught on exit

H - 10 - I 32 4.4 3.02 M 57 44.1 69.2 Hatch got in the way

H - 10 - I 23 6.4 5.24 F 65 35.4 62.4 Short legs, step-thru delay

H - 10 - I 27 6.8 5.77 M 49 43.7 67.1 Step-thru delay, trailing leg caught

H - 10 - O 6 5.0 3.66 F 47 35.8 66.8 Foot on sill, bent down, step-thru delay, trailing leg caught

H - 10 - O 48 4.9 3.63 F 50 45.7 67.1 Stood up inside, feet on sill, bent down, step-thru delay

H - 10 - O 12 4.7 3.38 M 52 41.3 73.5 Two people getting out at same time

H - 13 - I 57 8.5 6.40 F 62 43.3 63.6 Sat on hatch, turned, then slid out

H - 13 - I 48 9.2 7.06 F 39 31.9 66.1 Trouble stepping up on hatch & then stepped out

H - 13 - I 14 5.3 3.33 F 25 29.5 68.8 Foot caught on exit

H - 13 - I 5 6.6 4.62 M 26 28.3 71.7 Trailing foot caught on exit

H - 13 - I 1 9.2 7.09 F 18 30.3 66.3 Two people getting out at same time

H - 13 - O 25 5.7 3.77 F 56 45.3 67.3 Knee on sill, leaned backward & stepped down

H - 13 - O 20 7.0 4.94 F 57 39.8 63.2 Trouble getting foot up on sill

H - 20 - I 1 9.5 9.34 F 27 34.3 64.8 Struggled in front of hatch operator; step thru delay

H - 20 - I 1 6.7 6.07 M 29 33.5 71.8 Struggled by the hatch operator & rolled out

H - 20 - O 24 4.2 3.11 F 45 44.5 65.8 Short legs, both feet on sill, bent down & stepped down

H - 20 - O 1 7.3 6.82 M 31 33.5 64.1 Struggled to step in front of the hatch operator

H - 20 - O 50 7.9 7.49 F 31 31.9 64.2 Step-thru delay; trailing foot caught on exit