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CHAPTER 1. INTRODUCTION
Bus operators suffer from a higher than normal rate of injury and absenteeism. It
is felt that much of this is due to the difficulty with designing an operators workstation to
accommodate a wide range of operator anthropometry in addition to the demands placed
on the operators. The workstation presented in this report will consider the seat, steering
wheel, pedal, and instrument pane! design and locations. This report presents the
procedure for design guidelines for transit bus workstations along with an example. It is
the intention of this work to develop the design guidelines such that individuals from the
5th percentile female to the 95th percentile male in stature as defined by SAL J833 are
accommodated. The guidelines are based on sound and fundamental ergonomic/
biomechanical principles: (~) visibility, (2) reach, (3) comfort, and (4) minimum force.
Additionally, ease of ingress and egress issue was considered for a bus operator to get
into and out of the workstation.
I.! Background
An unusually high incidence of absenteeism (sometimes 3 times as great as the
average for blue collar workers) and illness occur amongst transit bus operators (Evans,
1994; Winkleby et at., 1988) This in turn has caused a significant increase in the number
of workman's compensation and disability claims in the transit industry. There are many
factors that contribute to the higher than normal morbidity and mortality rates of transit
bus operators. Epidemiological studies have concentrated on identifying three main
disease categories: cardiovascular disease, gastrointestinal illness and musculoskeletal
problems. The most prevalent of these health problems are musculoskeletal, relating to
neck and back pain (Patterson et at., 1986~. Studies have found that 80.5% of operators
experienced some degree of back and neck pain, in contrast to 50.7% of non operators,
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and the incidence of reported low back pain was 20% higher for operators when
compared to non operators (Anderson, 1991). Frequent awkward postures, muscular
effort, vibration and shock, as well as whole body vibration exposure and prolonged
sitting in a constrained position all contribute to overworking the lumbar spine and its
supportive structures, causing low back pain (Bovenzi et al., 1992).
The design of a workstation based on ergonomic principles has been attempted by
several organizations (Carrier et al., 1992). Carrier et al. created a mockup of a transit
bus operator workstation that was developed using a computer package. This computer
program developed by Genicom~ combines both the statistical approach of building a
model around 3D "zones", with the theoretical modeling approach in which actual
subjects are simulated by changing numerical parameters (Carrier et al., l 992). Carrier et
al. received input from transit authorities, bus manufacturers and bus operators on the
mockup, and presented several recommendations for future workstations. One of the key
findings from this study was that the present steering wheel sizes interfere with visibility
and can "penetrate" the operator's abdomen or thighs if the operator attempts to orient the
wheel to achieve minimum visibility (Carrier et al., 1 992). Carrier et al. also found that
the steering wheel should have a more vertical than horizontal orientation. They
concluded that it is impossible to accommodate 95% of the population with existing
components (Carrier et al., 1 992).
A primary concern of the workstation design is the relationship between the seat,
steering wheel and pedals. These are the workstation components that the operator is
required to stay in constant contact with, and the location of these controls dictates the
operator's posture. Consequently, most studies have concentrated on the relationship of
these components. However, operators have demonstrated a higher priority in leg
comfort than arm reach when positioning their seats (Philipart et al., 1 986).
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Courtney and Evans demonstrates! that a workstation based on inappropriate
anthropometry results in an erroneous design (Courtney et al., 1987). They tested their
hypothesis by examining the workstations of several buses in Hong Kong that were
originally designed and built in the United Kingdom based on European anthropometry,
but used by smaller Cantonese operators. The result of this mismatch is an attempt by
operators to modify the work environment to fit their own needs. Specifically, the
Cantonese operators had installed seat inserts, a brick or a piece of wood for footrests,
and padding of rags or rubber shoe bottoms on the pedals (Courtney et al., 1987~. The
addition of items by the operator to compensate for workstation deficiencies is not
uncommon. Several transit districts in the U.S. and Canada supply their operators with
blocks to be placed at the base of the pedals to improve reach.
B.C. Transit of Vancouver, British Columbia has addressed some of the above
concerns (Krantz, 1994). B.C. Transit developed a set of standards which are applied to
the workstations of every new bus purchased by B.C. Transit. The modifications have
included replacing spring suspension seats with pneumatic ride seats, installing tilt and
telescope columns, installing power assist steering, installing left side convex mirrors and
relocating the farebox. The result of these modifications is a 78% reduction in the
frequency of workstation related injuries and an 86% reduction in the amount of time off
per injury which is an indication of the severity of the injury (Bovenzi et al., 1992).
Similar design requirements have been adopted by Seattle Metro (Anon, 1993).
The Society of Automotive Engineers presents design guidelines for vehicle
workstations. The most common workstation design approach is based on the seating
reference position (SgRP) and locating the controls in relation to this point. The Society
of Automotive Engineers (S.A.E.) recommends this approach in the S.A.E. handbook
(SAE, 1995). These standards can be utilized in a particular order to develop the
workstation of a Class B vehicle as defined by S.A.E. J1100. Transit buses are typically
considered to be Class B vehicles. Some of the S.A.E. terminology must be understood
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before applying the practices, consequently Table 1.1 contains a list of selected
definitions.
Table Id: Selected S.A.E. Terminology
Terminology Definition
H-Point ~ the pivot center for the ~ peso and the thigh (at the hip)
Design H-Point the H-Point on the two dimensional seating drafting template
placed in any designated seating position
Pedal Plane the plane that is parallel to the treadle pedal surface and
represents the bottom of the mannequin shoe
Seating Reference I a unique H-Point with t e following properties: l
Point (SgRP) . located at the rearmost adjustment of the seat
| . simulates position of ivot center of torso and thigh
. used as the reference point employed to position the two
| dimensional drafting tea Plate with ofthe 95th percentile leg
Accelerator Heel I the lowest point at the i rtersection of the mannequin heel and
Point (AMP) the depressed floor covering with the shoe on the
undepressed accelerator pedal
Ball of Foot (BOF) a point on a straight line tangent to the bottom of the
mannequin's shoe in the side-view, 203 mm from the AHP
Il516 'Accommodation Tool Reference' provides a good start to the development
of the workstation. This procedure locates an accommodation reference line which is a
function of the H-point height and which provides a reference from which workspace
accommodation tools can be located. This practice also locates the accommodation heel
reference point which Is the intersection of the pedal plane and the floor. Both reference
tools can be determined for any of three operator populations. The standard
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anthropometry is defined in J833 'Human Physical Dimensions', and this data can be
helpful in locating the required H-Point of different operators. Once the accommodation
heel reference point has been determined, Jl517 'Driver Selected Seat Position' can be
used to locate where the selected operator population will position the seat horizontally
aft of the heel reference point. Once again, there are three different operator populations
to choose from.
J826 'Devices for Use in Defining and Measuring Vehicle Seating
Accommodation' provides a procedure to create an H-point template. This template can
be used to check torso positioning for any specified SgRP and back angle, front seat
operator leg and foot position for any specified accelerator heel point location, front seat
operator leg and foot position for any specified undepressed accelerator pedal location,
and front seat operator leg and foot position for specified leg room and SgRP-front to
heel distance. At this point the location of the operator's heel on the treadle pedal, H-
Point on the seat and lower leg position are known. Next it is desirable to examine the
accelerator shin-knee location. Using J1521 'Truck Driver Shin-Knee Position for Clutch
and Accelerator', side view contours of the location of the operator's accelerator knee can
be created for the target H-points.
The stomach profile of transit bus operators is another constraint on the location
of workstation tools. J1522 'Truck Driver Stomach Profile' provides a practice for
locating the contour of the operator's stomach for one of the selected population mixes as
a function of the H-point height. This contour line directly effects the location of the
steering wheel and can in some cases effect the operator's visibility and reach. Once the
positioning of the lower half of the body is defined, it is important to locate the operator
eyes to establish the operators field of view. With the H-point range determined from
J1517, the elliptical model of the eye locations (or eyellipse) can be developed using the
procedure of J941 'Motor Vehicle Driver's Eye Locations'. This two or three
dimensional region identifies the range of locations of operator's eyes based on one of the
three operator populations. With the accommodation tool reference line from J1516, and
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the eyellipses from J941, the head contour location profiles are determined from the
target H-points using the procedure described in J1052 'Motor Vehicle Driver and
Passenger Head Position'. This practice describes the location of the head for the
operator while forward' side and rear viewing.
I.2 Operator Task Analysis
In recent work, Bucciaglia (1995) conducted a task analysis of the operators in
order to define how the operators interact with the workstation. The tasks analysis was
conducted by direct observation and video analysis of several operators in State College,
Altoona, Johnstown, and Harrisburg in Pennsylvania. The tasks were broken down into
groups and itemized as shown by Table 1.2.
Table 1.2: Transit Bus Operating Task Analysis
PRE-DRIVING TASKS
. _ _
TASK NAME TASK DESCRIPTION
enter bus I typically enter thr ugh the front door l
store personal
items
adjust seat
adjust steering
wheel
adjust mirrors
apply safety belt
store personal items such as coat and lunch in appropriate
locations
adjust the seat height, fore/aft location, seat back angle and head
rest based on comfort and visibility
adjust steering wheel telescope and tilt to accommodate reach
and visibility
adjustment of outside and interior mirrors for optimal viewing
l
application of the safety belt
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Table 1.2: Transit Bus Operating Task Analysis (cons)
start engine
diagnostic check
select proper mode of operation on the run selector knob and
press the ignition button, typically located on the left
once the bus is on, the operator will scan the indicator lights for
any operating problems
climate controls
defrost mirrors
and windshield
change
destination sign
engage
transmission
release parking
brake
TASK NAME
accelerate bus
turn the bus
communication
climate controls
defrost mirrors
and windshield
monitor stop
request
adjustment of temperature for operator workstation and coach
apply mirror and windshield defrost when necessary
change the external destination sign to correspond with current
bus route by using keypad usually located on the left above the
operators' head.
while depressing the service brake, shift the bus into gear
release the parking brake, usually located to the left of the
operator
ON-ROAD DRIVING TASKS
...
TASK DESCRIPTION
rotate the treadle pedal to accelerate the bus
activate the floor mounted turn signal, inspect oncoming traffic
through the windshield, side windows and door windows,
decelerate the bus if necessary and perform a hand over hand
steering maneuver
I.) communicate with transit dispatch, and other bus operators
2.) public announcements inside and outside of the bus
adjust climate controls for changing conditions
adjust the defrost on the mirrors and windshield when
appropriate
monitor the indicator and bell tl=
to get off the bus
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Table 1.2: Transit Bus Operating Task Analysis (cons)
PICKING UP/DEPOSITING PASSENGERS
TASK NAME
activate four
way flashers
decelerate and
approach stop
stop the bus
activate the
kneeling mode
open bus doors
inspect
passenger
ingress
_
check farebox
update ride
passes
distribute
transfer tickets
TASK DESCRIPTION
prior to decelerating the bus, activate the four way flashers to
alert following traffic
apply the service brake to decelerate the bus
it~the stop will be long, operator may engage the parking brake
once the bus has reached a complete stop, the operator activates
the kneeling mode if the bus is equipped with it
the operator opens the front door to let passengers fin am ~e
rear door to let passengers off when necessary
1.) assist passengers that may need help
2.) if a handicapped passenger is entering the bus, the operator
must egress the workstation, lower the wheel chair lift, secure the
wheelchair, raise the lift, and move and secure the wheelchair on
the bus
depending on the mode! of farebox, the amount placed inside
may have to be inspected before allowing it to drop into the
collection container
ride passes have to be updated for each use
transfer tickets need to be issued to passengers that are
transferring to another bus
record passenger
data
close bus doors
deactivate
kneeling mode
some transit districts require the operator to record the type of
fare of all passengers
in preparing to depart a stop, the first task is close all doors
deactivate the kneeling mode
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Table 1.2: Transit Bus Operating Task Analysis (cons)
check passengers
for seating status
deactivate four-
way flashers
release parking
brake
accelerate bus
insure that all passengers are seated) or behind the minimum
safety lines near the doors and windshield
apply the left turn signal, and then deactivate the four way
flashers
if the parking brake has been set, release it
remove the service brake and apply pressure to the accelerator
1.3 Bus Operator Survey
A survey was conducted to obtain input from bus operators (Bucciaglia, 1995~. A
complete description of the survey including the form and raw data is presented in
Appendix A. The purpose of the survey was to obtain recommendations from bus
operators for the design and location of the workstation elements. The survey was
distributed to four transit districts in Pennsylvania through the months of September and
October of 1994. A total of 138 operators responded to the survey, and this input was
used to develop the workstation that will be presented later. The average respondent was
1 75 cm in stature with a standard deviation of 6.6 cm. The smallest operator was 1 55 cm
and the tallest operator was 196 cm. There were 122 male and 16 female respondents.
Table 1.3 shows the operators' response relating to control usage. Steering wheel, brake
and accelerator are essential and critical controls and therefore, were not included in the
survey such that they would not overshadow the other controls. The top rankings that are
shown are not statistically different from one another. Also, all operators were presented
with the same survey and therefore, some ordering effect may be present.
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Table ~ .3: Top Ranked Controls and Displays
# Frequency Ranked by
Average
1
Turn Signals
2
Door Open
3
Hazard Lights
s
4 ~i~
Speedometer
Destination Sign Control
7 ~ Har d Brake
8 ~ -
9
10
11
12
13
14
15
Importance Ranked by
Average
Turn Signals
Hazarc! Lights
Air Pressure
Door Open
Defrost
Speedometer
Hand Brake
Heater
Stop Request
Air Conditioner
Heater
Windshield Wiper
Destination Sign Control
Air Conditioner
Ventilation
-
Mirror Adjustment
Stop Request
Horn
The survey asked the operators through open-ended questions to comment on
their present vehicle workstation. The comments were analyzed through a keyword count
to snow the operators mayor concerns.
.
Many operators, particularly large operators,
complained of hitting the farebox with the knee or other body parts when ingressing and
egressing. Many large males also complained of hitting the steering wheel, and several
operators commented that the seat did not travel far enough back to allow for proper
egress. Power steering, plenty of leg room and a comfortable seat were all cited as
positive features. Complicated seat adjustments, lack of outside mirror control and poor
control layout were cited as elements of deficient workstation designs.
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Representative terms from entire chapter:
bus operators
