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Bus Operator Workstation Evaluation and Design Guidelines: Final Report (1997)

Chapter: Chapter 2. Work Station Design

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Suggested Citation:"Chapter 2. Work Station Design." Transportation Research Board. 1997. Bus Operator Workstation Evaluation and Design Guidelines: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6343.
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Suggested Citation:"Chapter 2. Work Station Design." Transportation Research Board. 1997. Bus Operator Workstation Evaluation and Design Guidelines: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6343.
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Suggested Citation:"Chapter 2. Work Station Design." Transportation Research Board. 1997. Bus Operator Workstation Evaluation and Design Guidelines: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6343.
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Suggested Citation:"Chapter 2. Work Station Design." Transportation Research Board. 1997. Bus Operator Workstation Evaluation and Design Guidelines: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6343.
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Suggested Citation:"Chapter 2. Work Station Design." Transportation Research Board. 1997. Bus Operator Workstation Evaluation and Design Guidelines: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6343.
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Suggested Citation:"Chapter 2. Work Station Design." Transportation Research Board. 1997. Bus Operator Workstation Evaluation and Design Guidelines: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6343.
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Suggested Citation:"Chapter 2. Work Station Design." Transportation Research Board. 1997. Bus Operator Workstation Evaluation and Design Guidelines: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6343.
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Suggested Citation:"Chapter 2. Work Station Design." Transportation Research Board. 1997. Bus Operator Workstation Evaluation and Design Guidelines: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6343.
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Suggested Citation:"Chapter 2. Work Station Design." Transportation Research Board. 1997. Bus Operator Workstation Evaluation and Design Guidelines: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6343.
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Suggested Citation:"Chapter 2. Work Station Design." Transportation Research Board. 1997. Bus Operator Workstation Evaluation and Design Guidelines: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6343.
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Suggested Citation:"Chapter 2. Work Station Design." Transportation Research Board. 1997. Bus Operator Workstation Evaluation and Design Guidelines: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6343.
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Suggested Citation:"Chapter 2. Work Station Design." Transportation Research Board. 1997. Bus Operator Workstation Evaluation and Design Guidelines: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6343.
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Suggested Citation:"Chapter 2. Work Station Design." Transportation Research Board. 1997. Bus Operator Workstation Evaluation and Design Guidelines: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6343.
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Suggested Citation:"Chapter 2. Work Station Design." Transportation Research Board. 1997. Bus Operator Workstation Evaluation and Design Guidelines: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6343.
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Suggested Citation:"Chapter 2. Work Station Design." Transportation Research Board. 1997. Bus Operator Workstation Evaluation and Design Guidelines: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6343.
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Suggested Citation:"Chapter 2. Work Station Design." Transportation Research Board. 1997. Bus Operator Workstation Evaluation and Design Guidelines: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6343.
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Suggested Citation:"Chapter 2. Work Station Design." Transportation Research Board. 1997. Bus Operator Workstation Evaluation and Design Guidelines: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6343.
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Suggested Citation:"Chapter 2. Work Station Design." Transportation Research Board. 1997. Bus Operator Workstation Evaluation and Design Guidelines: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6343.
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Suggested Citation:"Chapter 2. Work Station Design." Transportation Research Board. 1997. Bus Operator Workstation Evaluation and Design Guidelines: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6343.
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Suggested Citation:"Chapter 2. Work Station Design." Transportation Research Board. 1997. Bus Operator Workstation Evaluation and Design Guidelines: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6343.
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Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

CHAPTER 2. WORK STATION DESIGN 2.~ Design Concept The general objectives of the design methodology are to develop a work station which will accommodate the population extremes with minimum mechanical adjustment. Priority was given to design concepts which do not degrade safety. For example, the operator should be able to keep his or her feet firmly planted on the pedals and due to safety the pedal mounting points should be fixed to the bus. Previous approaches such as Carrier et al. (1992) suggested a movable pedal to accommodate operators of different height. This type of adjustment was discarded due to safety concerns. Other objectives include: visibility, reach, comfort, and adjustability. This study has suggested novel design concepts on the work station components of transit buses such as steering wheel, pedals, instrument panels to resolve the problems described by the operators in the survey and discussed by other researchers. In parallel, a systematic design approach was developed in order to analytically determine the positions, orientations, and adjustment ranges of the components, which will be discussed in the following section. The steering wheel control was designed regarding its orientation, size, and adjustment mechanism. Regarding the wheel orientation, Carrier et al. (1992) pointed out that the steering wheel should be more vertical than what is commonly used. This has two advantages: the ranges of motion of the body parts (back, shoulder, elbow, and wrist) related to steering wheel maneuvering are decreased for the typical operator and therefore his or her fatigue level would be reduced, and the 5th percentile female would be able to operate the steering wheel in a more appropriate and biomechanically efficient manner. - 2.]

As for the wheel size, a larger horizontal steering wheel whose diameter ranges from 508 to 559 mm causes many operators to reach forward and therefore to loosen the contact and support between the torso and the seat back. SAE J1100 recommends a steering wheel diameter of 450 to 560 mm for Class B vehicles. The wheel diameter was determined to a size (457 mm in this study) within the recommended range with which the operators can maintain comfortable steering maneuvering postures. Lastly, in order for the steering wheel to accommodate all of the positions and orientations required to provide sufficient visibility and comfortable reach for the small and large operators, the wheel must have three degrees of freedom: a hub orientation adjustment, a column telescope adjustment, and a column tilt adjustment at the base of the steering column. Since an existing steering wheel system provides two degrees of freedom such as the hub tilt and the telescope, only a column tilt adjustment was added to the wheel assembly. The selection of pedal style is critical in the pedal design. Presently, the majority of transit buses use treadle pedals with an orientation angle between 40 and 50 degrees (Diffrient et al., 1981). The treadle pedal allows for little variability in placing the operator heel assuming the heel must be at the base of the treadle pedal for an efficient and safe pedal activation. Also, for most small operators, the extremely steep orientation of the accelerator results in an uncomfortable lower leg posture, which can cause unnatural extension or rotation about an ankle. In order to resolve the problems resulted from using treadle pedals, a hanging pedal was employed and evaluated in this study. The hanging pedal allows the operators to place the heel at more various locations on the work station platform than the treadle pedal. The orientations, activation angles, locations of accelerator and brake pedals with a hanging pedal style were determined based on comfortable reach of the right legs utilizing a kinematic model developed in this study, which is discussed in detail in Appendix E. The instrument panels containing displays and controls were investigated designing the adjustment range, panel layout, size, and locations (Appendix F). All instrument panels are adjustable to accommodate the population extremes in visibility - 2.2

and comfortable reach. The displays and controls are grouped according to their functional characteristics and systematically arranged into three areas: the left, central and right instrument panels. The functional purpose of the left instrument panel is to provide easy access for all operators to the secondary controls or controls that are used during the predriving tasks. These controls are the parking brake, the exterior mirror remote adjustment knobs, the exterior mirror defrost control, the internal and external public announcement systems, the radio controls, the run selector knob, the transmission and the ignition switch. The size of the left instrument panel is determined by the space required for the controls and the instrument panel is located in the side and plan views based upon comfortable reach of the left arms. The central instrument panel is intended to provide the operator with the operating status of the bus. Any information that does not require continuous monitoring by a particular gauge is replaced with an indicator light. To accommodate tell-tale indicators without giving up 0.95 cm by 1.27 cm of space for each of those indicators, it is proposed that the central instrumental panel have a small screen which can provide any of these tell-tales with the colors and required alarms. Since time is a large concern for operators and a significant part of their duties, a clock is also provided. The two most regularly monitored items on the central instrument panel are the speedometer and air pressure gauge. For this reason, traditional large dial readouts are provided. The intention of mounting the instrument panel directly on the steering column is that downward visibility will be improved. The purpose of the right instrument panel is to locate primary controls for driving and passenger pickup and depositing in an accessible and easy manner for all operators. The right instrument panel will contain a keypad with a small display called an operator digital assistant (ODA). The functions that can be accomplished through the digital assistant include: present the bus route schedule, control the farebox, perform automatic counting and categorization of the fares if used in conjunction with a card reading farebox or manually inventorying of the passengers when using a traditional farebox, print - 2.3

transfer tickets, monitor the gas mileage, change the destination sign, and in the future, possibly link with a global positioning system (GPS) for real time location of buses, and planning of proper routing to avoid delays. The data collected by this digital assistant can be easily downloaded at the end of the work day to a "home base" computer for analysis. The dimensions of the right instrument panel are based on the controls that it will contain. Also, comfortable reach of the right arms are considered in the determination of the right instrument panel location. - 2.4

2.2 Ergonomic Design Process The complexity of a bus operator workstation requires a systematic, welI-defined set of procedures, i.e., a systems approach, throughout workstation development stages. The techniques and analysis methods of a systems approach should be effective for a designer to define a complex system analytically, to identify crucial problems quantitatively, to manifest a design mechanism integratedly, and to suggest design guidelines rationally. A systematic design structure was constructed for the ergonomic bus operator workstation development in order to consider relevant ergonomic knowledge, design principles, and practices from contributing disciplines in an integrated way. The systematic design structure shown in Figure 2.! consists of four stages: (~) identification of design scope, (2) relationship analysis of design and anthropometric variables, (3) development of functional design relationship, and (4) synthesis of design guideline. 2.2.1 Design Scope Identification The design scope of a bus operator workstation was identified by choosing a design datum point, setting design criteria focused on the workstation design, defining static and dynamic bus driving postures, and establishing hierarchies of design and anthropometric variables. 2.2.~.1 Workstation Design Approach Three common datum points for ergonomic design have been applied to vehicle workstation design: (~) design eye position (DEP) approach, (2) heel reference point (HRP) approach, and (3) neutral seat reference point (NSRP) approach. In the DEP - 2.5

;h | Identify D. sign Scope | 1 Hierarchy of Design Var. Design Approach [D] (Datum Point) . , - Entity Design Criteria | - Attribute ~ - Modifier | Driving Posture | 1 ' 1 1 - 1 Hierarchy of Anthropometric Var. [A] - Entity - Attribute - Modifier Classify the Variables by Relationship Analysis 1 1 [D] x [A] ) Master / Precedence Cause / Relative Influence / Slave Effect Dependence . - ~ . Identify Design Niche Area & Functional Den ign Relationship 1 1 1 ._ Literature Survey - Design Guideline - Design Standard - Journal/Elandbook/ Technical Report - Data Base -~ ~ Imposture CD/3D CAM ~ CTask Analysis: ~ Posture Analysis ~ ~ ~iscomfort/Caus~ ~ CPreference:) ~ Field Survey - Questionnaire - Mockup Test - Prototype Test Suggest Design Guidelines Figure 2. I: Systematic Design Structure for an Ergonomic Bus Operator Workstation - 2.6

approach (Figure 2.2), the workstat~or~ design starts by setting the eye point which satisfies required visual fields along the sight line. Once the eye position is chosen, other design variables of the workstation such as the seat height and seat hack rest angle, and so on, are determined consecutively. Although this DEP approach results in good visibility, large adjustments for the seat and pedals are required to accommodate 95% of the U.S. adult population. This DEP approach is utilized primarily to design the space envelope for aircraft cockpits (Diffrient et al. ~981~. I'd Minimum Visibility Marker - Figure 2.2: Extreme Component Adjustments Required in the DEP Approac~ In contrast to the DEP approach, the HRP approach (Figure 2.3) begins by assuming that the various size operators have a common accelerator heel point (AHP). This HRP approach is applied mainly to industrial cabs such as tractors and lift trucks which require the highest possible seating to enable the operator to see down or up when bending forward (Diffrient et al., 1981). The benefit of the HRP approach is that almost - 2.7

no pedal adjustment is required, but relatively large adjustments for the seat and steering wheel are requires! to achieve the visibility requirement. A._._._ .~._.__ Cal L ~ '.. \ i Minimum Visibility Marker Figure 2.3: Visibility Cones Resulting from the HRP Approach The NSRP approach (Figure 2.4), which is employed in this study, encompasses the advantages from both the DEP and HRP approaches, with minimal component adjustments of the seat, steering wheel, and pedals. The SRP is defined as a point on the sagittal or medial plane of the seat located by the intersection of two planes: the compressed seat pan and seat-back. The SRP can easily be represented by either the hip pivot point (H-point) or seat index point (SIP) (Diffrient et al., 198 11. However, the SRP is not easily determined because the compressed planes are imaginary (Diffrient et al., 19811. Thus, auto makers have preferred to use the seating reference point (SgRP), which is the H-point (hip pivot point) of the 95th percentile person of the U.S. population (SAL I! 1001. According to SAE IS26 and SAE I! 100, the

SRP is located 13.4 cm behind and 9.8 cm below of the H-point which correspond to the profile of the deflected seating contour of the H-point machine as shown by Figure 2.5. Minimum Visibility Marker Figure 2.4: Visibility and Reachability in the NSRP Approach \~\ ~ ~J Figure 2.5: Geometric Relationship between H-point (SgRP) and SRP - 2.9

The SgRP position is determined by the following two analytical equations (Eq. 1 and Eq. 2) which incorporates the geometric relationship between the H-point and SRP, the seat pan angle, and the seat-back angle. horizontal distance of SgRP from SRP = HL12 - HL11 x cos(SB11) (1) vertical distance of SgRP from SRP = HLl ~ + HLl 2 x sin(SP9) (2) where, SB ~ i: seat back neutral vertical angle SP9: seat pan neutral horizontal angle HL`1 1: vertical length from hip pivot to SRP HLl2: horizontal length from hip pivot to SRP As an example, utilizing the equations and referencing the SgRP location specified in a seat drawing in Figure 2.6, the SRP of the seat is analytically positioned as of 1 1.7 cm behind and 10.7 cm below of the SgRP. in' Figure 2.6: Illustration Example of Locating SRP position from SgRP - 2.10

The NSRP design approach is accomplished by achieving a compromise between visibility and reach in the workstation design. Typically this approach requires a floor adjustment to support a heel point for comfortable pedal operation. In this study, however, only the pedal adjustment is considered without the floor adjustment for ingress/egress and safety reasons. 2.2.~.2 Design Criteria Design criteria for the workstation were based on four ergonomic principles: (~) visibility, (2) reach, (3) comfort, and (4) force. Throughout this study, these principles have been treated with an equal importance and any possible violation against the principles has been avoided in the workstation design. The visibility principle was implemented considering interior visibility on the instrument panels and exterior visibility through the top of the steering wheel. As specified in the APTA (1977) "Baseline Specification" commonly called the "whitebook," a minimum visibility marker, an imaginary point in front of the bus (107 cm tall and 61 cm in front of the bus), was used to define the visibility constraint. This visibility requirement can not be violated for safety reasons. The metric visual constraint is geometrically approximated to a 30° downward sight line with a range of less than 3 degrees for the population (Bucciaglia, 19951. Therefore, after determining the locations of DEP from NSRP for the 5th percentile female, the 50th percentile, and the 95th percentile male in the workstation, sight lines were drawn from the DEPs to locate the instrument panels and the steering wheel below the 30° downward exterior visibility requirement. The reach, comfort, and minimum force principles were achieved together in the workstation design by utilizing data on the comfort range of motions (ROMs) of body - 2.~!

joints. In general, the recommended comfort ROMs are in the middle between the extreme limits of limb movement, and these ROMs are modified to minimize the muscular force necessary to overcome gravity as well (Diffrient, et al., ]98~. Therefore, it could be reasonably assumed that the workstation is ergonomically designed in terms of reach, comfort, and force when the joint angles of the static and the dynamic driving postures of a bus operator are within the comfort ROMs. With the bus operator's joint angles being in the comfort ROMs, the controls (e.g. steering wheel and pedals) and the instrument panels were located so that all bus operators who are in the 5th percentile female to the 95th percentile male range could reach and operate them conveniently. 2.2.~.3 Standard Bus Driving Postures To design the workstation from the ergonomic viewpoint, it is necessary to first define a standard bus driving posture. The standard driving posture should ensure that a bus operator is able to conduct all driving tasks with a comfortable reach, and consider musculoskeletal and biomechanical factors because body joint position of a given posture greatly affects the muscular capability and force needed to accomplish a given task. These requirements were reflected in the choice of body joint angles; both the static and dynamic driving postures were defined within the comfort zones of the joint angles. Figure 2.7 shows the defined static bus driving posture where the operator holds the steering wheel at '9 and 3' o'clock positions(CDL Manual, 1994), and rests his or her foot on the accelerator pedal. In contrast, the dynamic bus driving posture (Figure 2.~) was defined with the operator reaching to operate controls on the right and left instrument panels, and with the operator fully depressing the accelerator pedal, while maintaining the static torso angle. Each joint angle must remain within the comfort zones, even while performing a dynamic driving task. - 2.12

10. (a) plan View __ If. _ it, ~ ~ I 100 ~ j:~ I side view ~ ) ~ ~ \ (c) front view . Figure 2.7: Static Driving Posture - 2.13

~ - ~ - - - as ~j =, 1~ 1_} oat = O sit (? ~ ~=. Figure 2 8: Dynamic Driving Posture -2.14 ~ - ) ~ = E ~

2.2.~.4 Structure of Bus Operator Workstation Design Variables 2.2.~.4.l Hierarchy of Design Variables A hierarchy of a system is generally established by following the two sequential procedures: (~) defining elements that constitute a system, and (2) organizing identified elements into a stratified structure. An established hierarchy helps an analysts to understand and define a system systematically to be studied (Saaty, 1982~. Hence, the hierarchy of the design variables for a bus operator workstation is constructed so as to make clear the boundary and the resolution of the system to be designed. In order to define the design variables of a bus operator's workstation in a systematic way, a bus operator workstation system, at first, was decomposed largely into ~ subsystems: (~) seat, (2) steering, (3) pedals, (4) instrument panels, (5) mirror, (6) windshield, (7) farebox, and (~) peripheral workspace. These subsystems were also subdivided into sub-subsystems when necessary. For example, the subsystem seat was broken into four sub-subsystems: (~) headrest, (2) seat back, (3) seat pan, and (4) seat belt. In addition, the following 14 dimensional attributes which characterize the design variables of the subsystems or the sub-subsystems were defined in order to identify the design variables more efficiently: (~) length, (2) width, (3) depth, (4) diameter, (5) thickness, (6) curvature, (7) shape, (~) angle, (9) adjustment range, (10) location, (~) travel distance, ~ ~ 2) resistance, ~ ~ 3) control/ response(CR) ratio, and ~ ~ 4) material property. Accordingly, the identification of the design variables was conducted by breaking the system into the subsystems or into the sub-subsystems if necessary and then matching the dimensional attributes to the sub-subsystems consecutively. As a result, 242 design variables have been defined for a bus operator's workstation design. - 2.15

After decomposing the system into the specific design variables, the hierarchy of the design variables was established by stratifying them into four levels: subsystems, sub- subsystems, dimensional attributes, and specific design variables. Table 2.} summarizes the nomenclature of the design variables and Figure 2.9 provides the drawings of the reference locations. Table 2.2 shows the hierarchy of the design variables developed; each variable is assigned a "Code," as shown by the last column, for notation purposes. Also, the number of design variables defined for each workstation component is summarized in Table 2.3. - 2.16

Table 2. I: Nomenclature of Design Variables Abbreviation Description l APRP | Accelerator Pe al Reference Point. Located on the center of the top | surface of the accelerator pedal plate. If the pedal plate pivots about the pedal arm, then the reference point is to be located at the pivot location projected normal onto the pedal plate surface BPRP Brake Pedal Plate Reference Point. Located on the center of the top surface of the brake pedal plate. If the pedal plate pivots about the pedal arm, then the reference point is to be located at the pivot location projected normal onto the Pedal plate surface . ~ . . CR Ratio Control-Response Ratio FRP Farebox Reference Point LIPRP I Left Instrument anel Instrument Panel. Located in the center of the top surface of the left instrument pane] NAPRP Neutral Accelerator Pedal Reference Point NBPRP Neutral Brake Pedal Reference Point NCIRP Neutral Center Instrument Pane] Reference Point NDEP Neutral Design E e Point ~ Y NLIRP Neutral Left Instrument Pane] Reference Point NESCMRP Neutral Left Side Convex Mirror Reference Point NLSFMRP I Neutral Left sit Flat Mirror Reference Point NPMCMRP Neutral Passenger Monitor Convex Mirror Reference Point NPRP Neutral Pedal Reference Point NRIRP Neutral Right Instrument Pane] Reference Point NRSCMRP Neutral Right Side Convex Mirror Reference Point _ NRSFMRP Neutral Right Side Flat Mirror Reference Point NRVMRP Neutral Rear View Mirror Reference Point NSRP | Neutral Seat Re erence Point. The SRP of the 50th percentile person. NSWRP Neutral Steering Wheel Reference Point PLRP Personal Locker Reference Point RIPRP Right Instrument Pane] Reference Point. Located in the center of the top surface of the right instrument pane] _ SBRP Seat Belt Reference Point SgRP Seating Reference Point. H-point (hip pivot point) of the 95th percentile person of the US population as defined by SAE J1 100. SRP Seat Reference Point. The point on the sagittal plane located by two intersecting planes - the compressed seat pan and seat back. SWRP Steering Wheel Reference Point. Located in the center of the plane of the steering wheel WO Workstation Origin. Located on the workstation platform directly below the NSRP, i.e., determined by projecting the NSRP down onto the platform. - 2.17

1 Plon ~ - 1 I . ~ _ _ ~ W_ | LlPRP_95 ~ ~ ~ L~_5 | 1 -~\ ~ 1 _ ~ _ 1 ~ B1~ ~ y L I~}/r - <3 k 1 ~ r ~ Edgy J J ~P_5 1 | BPPRP ~ ~ Figure 2.9a: Reference Locations of a Bus Operator Workstation - Plan View - 2.18

I Arch tow ~1P ord ~ rot ~1 in! W.,\ I' ~ ~ \ L 1 Phi 1 ! ____. __ __- __i P_5 ~ E: Plo~tEcr~ ~ X | Non SdL~ L1~ 00 ~ ~ Pot | 1~ t I I/ - ~ SWFP_5 | BPPRP ~ [A Figure 2.9b: Reference Locations of a Bus Operator Workstation - Side View (Left and right instrument panels are not shown) - 2.19

[ ~ - ~ m~ Whet ~ ~ 1 3- SEP_50 _ L air 1 RlPRP_50 1 J _ I .~ ~11 3' nonfat l ~ 1 LlPE?P_50 1 ~ X I Not Sdrd Lees Dee SIDi;h Pel-4-l1`e Peons I tE3 ;": Figure 2.9c: Reference Locations of a Bus Operator Workstation - Side View (Steering wheel is not shown) - 2.20

Table 2.2a: Hierarchy of Design Variables for a Bus Workstation Design ~ ~ of 6) . , ~ Design Variables . 1 st Level 2nd Level 3rd Level 4th Level Seat headrest length ~ (S) (H) width . depth . curvature . angle location material seat back length (B) ~ Abe angle adjustment 10cabon material seat pan length (P) width angle l location 5th Level Code headrest length SH1 . headrest width headrest depth headrest radius _ headrest vertical angle headrest vertical adjustment range . headrest vertical adjustment increment _ headrest vertical angle adjustment range _ horizontal distance of NDEP from NSRF _ vertical distance of NDEP from NSRP headrest cover texture _ headrest cushion material density seat back length upper seat back width middle seat back width _ lower seat back width upper seat back depth . middle seat back depth lower seat back depth upper seat back curvature middle seat back curvature lower seat back curvature seat back neutral vertical angle seat back angle adjustment range vertical distance of lumbar support distance from NSRP seat back cover texture seat back cushion material density seat pan length SH2 SH3 SH4 SH5 SH6 SH7 SHE SH9 SH10 SH11 SH12 SB1 SB2 SB3 SB4 SB5 SB6 SB7 SB8 SB9 SBio seat pan width front seat pan depth middle seat pan depth rear seat pan depth front seat pan curvature . middle seat pan curvature . rear seat pan curvature . seat pan neutral horizontal angle . seat pan angle adjustment range seat forward adjustment range seat backward adjustment range seat upward adjustment range seat downward adjustment range vertical distance of NSRP from WO seat pan cover texture seat pan cushion material density seat spring stiffness seat damping coefficient - 2.21 SB11 SB1 2 SB1 3 SB14 SB15 SP1 SP2 SP3 SP4 SP5 SP6 SP7 SP8 SP9 SP10 SP11 SP1 2 SP1 3 SP1 4 SP1 5 SP1 6 SP17 SP1 8 SP1 9

Table 2.2b: Hierarchy of Design Variables for a Bus Workstation Design (2 of 6) 5th Level Design Variables 1st Level 2nd Level 3rd Level 4th Level Seat seat belt length l (S) (L) width . (continued) ~it tension material Steering steering diameter (T) wheel (W) shape angle location resistance CR rat material spokes width (S) thickness angle material Pedals brake pedal plate length (P) pedal widths (B) thickness shape material pedal arm length width thickness shape material pedal length mounting width base Thickness angle resistance Code seat belt length , SL1 | seat belt width SL2 lateral distance of SBRP from NSRP SL3 horizontal distance of SBRP from NSRP SL4 SL5 SL6 SL7 vertical distance of SBRP from NSRP seat belt tension seat belt texture wheel diameter TW1 TW2 TW3 TW4 TW5 TWO TW7 TWO TW9 TW10 TW11 TW12 grip diameter wheel shape grip shape wheel plane neutral horizontal angle wheel column neutral vertical angle wheel telescope adjustment range wheel plane horizontal angle adjustment range . wheel column vertical angle adjustment range horizontal distance of NSWRP from NSRP vertical distance of NSWRP from NSRP steering wheel resistance force leering wheel CR ratio steering wheel material spoke width spoke thickness spoke angle relative to wheel plane spoke orientation angle steering wheel spoke material. brake pedalplatelength~ ~ ~ ~ . brake pedal plate width brake pedal plate thickness brake pedal plate shape brake pedal plate lateral angle brake pedal plate~honzontal angle . brake pedal plate pivot angle range lateral distance of BPRP from NSRP horizontal distance of BPRP from NSRP vertical distance of BPRP from WO brake pedal plate material brake pedal arm length brake pedal arm width brake pedal arm thickness brake pedal arm shape brake pedal arm material brake pedal mounting base length brake pedal mounting base width brake pedal mounting base thickness brake pedal actuation angle brake pedal actuation force brake pedal recovery force - 2.22 TW13 TW14 TS1 TS2 TS3 TS4 TS5 - PB1 PB2 PB3 PB4 PB5 PB6 PB7 PB8 PB9 PB10 PB11 PB12 PB13 PB14 PB15 PB16 PB17 PB18 . PB19 PB20 PB21 PB22

Table 2.2c: Hierarchy of Design Variables for a Bus Workstation Design (3 of 6) Design Variables 1 st Level T 2nd Level l 3rd Level l 4th Level Pedals brake pedalpedal location (P) (B)mounting base material (Continued) accelerator pedal plate length pedal width (A) thickness shape Fin material pedal arm length width thickness shape material pedal length mounting width base thickness angle resistance location material Instrument left length Panels instrument width (I) panel thickness . (L) curvature angle material . central length instrument width panel thickness (C) curvature . angled location material . 5th Level brake pedal mounting base location brake pedal mounting base material Code PB23 PB24 PA1 PA2 PA3 PA4 PA5 PA6 PA7 PA8 PA9 PA10 PA11 PA12 PA13 PA14 PA15 PA1 6 PA17 PA18 PA19 PA20 PA21 PA22 PA23 PA24 IL1 IL2 IL3 accelerator pedal plate length accelerator pedal plate width accelerator pedal plate thickness accelerator pedal plate shape accelerator pedal plate lateral angle accelerator pedal plate horizontal angle accelerator pedal plate pivot angle range lateral distance of APRP from NSRP horizontal distance of APRP from NSRP vertical distance of APRP from WO accelerator pedal plate material accelerator pedal arm length accelerator pedal arm width accelerator pedal arm thickness accelerator pedal arm shape accelerator pedal arm material accelerator pedal mounting base length accelerator pedal mounting base width accelerator pedal mounting base thickness accelerator pedal actuation angle accelerator pedal actuation force at celerator pedal recovery force . accelerator pedal mounting base location accelerator pedal mounting base material left instrument panel length left instrument panel width left instrument panel thickness left instrument panel curvature left instrument panel horizontal angle left instrument panel horizontal adjustment range left instrument panel vertical adjustment range lateral distance of NLIRP from NSRP horizontal distance of NLIRP from NSRP vertical distance of NLIRP from NSRP left instrument panel material left instrument panel surface finish central instrument panel length central instrument panel width central instrument panel thickness central instrument panel curvature central instrument panel vertical angle horizontal distance of NCIRP from NSRP vertical distance of NCIRP from NSRP central instrument panel material central instrument panel surface finish - 2.23 IL4 IL5 IL6 IL7 IL8 IL9 IL1 0 IL1 1 IL1 2 ICI IC2 IC3 IC4 IC5 IC6 IC7 IC8 IC9

Table 2.2~: Hierarchy of Design Variables for a Bus Workstation Design (4 of 6) Design Variables . . 1 st Level 2nd Level 3rd Level 4th Level I nstrument right length Panels instrument width (I) panel thickness (Contin ued) (R) curvature angle material Mirrors left side length (M) flat mirror width (L) angle adjust ent location material left side length convex width mirror curvature (L) angle location material rear view length mirror width (V) angle adjushT ent location material right side length flat mirror width (R) angle 5th Level _ right instrument panel length _ _ Code IR1 IR2 IR3 IR4 IRE IR6 . right instrument panel width _ ig~ ~ cJ ~_ . _ right instrument panel horizontal angle _ ~_ right instrument panel horizontal adjustment range right instrument panel vertical adjustment range ~_ lateral distance of NRIRP from NSRP _ _ ve~= ~ s~e ~ FIR ~- t~ NS d' _ right instrument panel material right instrument panel surface finish left side flat mirror length left side flat mirror width Oft side flat mirror lateral angle IR7 IR8 IR9 IR1 0 IR1 1 IR1 2 ML1 ML2 ML3 ML4 ML5 eft side flat mirror vertical angle _ eft side flat mirror lateral angle adjustment _ range _ _ eft side flat mirror vertical angle adjustment _ range lateral distance of NLSFMRP from NDEP _ ML6 ML7 ML8 ML9 ML1 0 ML1 1 ML1 2 ML1 3 ML14 ML1 5 ML1 6 ML1 7 ML1 8 ML1 9 MV1 MV2 MV3 MV4 MV5 MV6 horizontal distance of NLSFMRP from NDEP vertical distance of NLSFMRP from NDEP left side flat mirror reflectance left side convex mirror length eft side convex mirror width . eft side convex mirror curvature left side convex mirror lateral angle left side convex mirror vertical angle _~ ~ ~ ~ ~sora.'~ ADS horizontal distance of NLSCMRP from NDEP ertcal distance of NLSCMRP from NDEP eft side convex mirror reflectance rear view mirror length ~ V~ ~r w~1 rear view mirror lateral angle rear view mirror vertical angle _ rear view mirror lateral angle adjustment range _ rear view mirror vertical angle adjustment range lateral distance of NRVMRP from NDEP _ horizontal distance of NRVMRP from NDEP vertical distance of NRVMRP from NDEP rear view mirror reflectance right side mirror length right side mirror width right side flat mirror lateral angle right side flat mirror vertical angle - 2.24 MV7 MV8 MV9 MV10 MR1 MR2 MR3 MR4

Table 2.2e: Hierarchy of Design Variables for a Bus Workstation Design (5 of 6) Design Variables 1st Level 2nd Level 3rd Level 4th Level Mirrors right side adjustment (M) flat mirror (Continued) (R) material right side length convex width mirror curvature (R) angle material passenger length monitor width convex curvature mirror angle (P) it: material Windshield windshield length (W) (W) width curvature angle location material pillar length (P) width thickness Farebox length (FA) width depth location Peripheral personal length Workspace locker width (E) (P) depth Code 5th Level _ right side flat mirror lateral angle adjustment range right side flat mirror vertical angle adjustment range MR5 MR6 . _ lateral distance of NRSFMRP from NDEP horizontal distance of NRSFMRP from NDEP vertical distance of NRSFMRP from NDEP right side flat mirror reflectance right side convex mirror length right side convex mirror width right side convex mirror curvature right side convex mirror lateral angle right side convex mirror vertical angle lateral distance of NRSCMRP from NDEP MR7 MR8 MR9 MR10 MR1 1 MR12 MR1 3 MR14 MR15 MR1 6 MR1 7 . MR1 8 MR1 9 MP1 MP2 MP3 MP4 MP5 horizontal distance of NRSCMRP from NDEP vertical distance of NRSCMRP from NDEP right side convex mirror reflectance passenger monitor convex mirror length passenger monitor convex mirror width passenger monitor convex mirror curvature passenger monitor convex mirror lateral angle . passenger monitor convex mirror vertical angle lateral distance of NPMCMRP from NDEP horizontal distance of NPMCMRP from NDEP . vertical distance of NPMCMRP from NDEP passenger monitor convex mirror reflectance . windshield length windshield width windshield curvature windshield vertical angle windshield lower side height from WO . windshield glare reflectance . pillar length . pillar width pillar thickness farebox length farebox width farebox depth lateral distance of FRP from NSRP horizontal distance of FRP from NSRP vertical distance of FRP from NSRP personal locker length personal locker width personal locker depth lateral distance of PLRP from NSRP horizontal distance of PLRP from NSRP lock location - 2.25 MP6 MP7 MP8 MP9 WW1 WW2 WW3 WW4 WW5 WW6 WP1 WP2 WP3 FBI FB2 FB3 FB4 FB5 FB6 EP1 EP2 EP3 EP4 EP5 EP6

Table 2.2f: Hierarchy of Design Variables for a Bus Workstation Design (6 of 6) . _ modesty panel length _ modesty panel width modesty panel thickness . horizontal distance of the front face of modesty panel from NSRP _ Design Variables _ 1 st Level 2nd Level 3rd Level 4th Level Peripheral modesty length Workspace panel width (E) (M) thickness (Continued) location material . cold blast length protector width . (C) thickness location wastebasket length (W) width depth 5th Level Code EM I EM2 EMS EM4 modesty panel translucence cold blast protector length cold blast protector width cold blast protector thickness lateral distance of the left face of cold blast protector from NSRP EMS EC1 EC2 EC3 EC4 wastebasket length wastebasket width wastebasket depth EW1 EW2 EW3 - 2.26

Table 2.3: Summary of the Number of Design Variables of a Bus Operator Workstation Bus Operator Workstation Component | Number of Design Variables Ist Level 2nd Level # of 2nd Level # of fist Level Headrest T 12 ~ Seat l Seat Back T IS 1 53 I Seat Pan T 19 1 l ~Seat Belt T 7 l Steering l Wheel | 14 | 19 Spokes 5 Pedals T Brake Pedal T 24 T 48 Accelerator Pedal 24 l Left Instrument Pane] | 12 ~ Instrument Panel ~ Center Instrument Pan' I T 9 1 33 I Right Instrument Pane T 12 l I Left Side Flat Mirror I lo T 1 I Left Side ConvexMirr'~r T 9 1 ~Rear View Mirror ~10 l Mirror | Right Side Flat Mirro: | 10 | 57 | Right Side Convex Mir' fir | 9 l Passenger Monitor Convex Mirror Windshield I Windshield T 6 1 l Pillar 3 Farebox I T 6 T 6 l I PersonalLocker I 6 T Peripheral l Modesty 'anel | 5 | 17 Workspace I Cold Blast P otector T 4 l l Wastebasket T 3 . Total 24 2 - 2.27

2.2.~.4.2 Classification on Design Variables While constructing the hierarchy of design variables, it has been noticed that some design variables can be resolved by ergonomic considerations, whereas others are associated with mechanical or just aesthetic considerations. As an example, an anthropometric analysis is needed to detains the seat back neutral vertical angle (SB 1 1 ), while a mechanical analysis is typically required for the seat damping coefficient (SP19), or a consideration of an aesthetic point is enough to design the seat back cover texture (SB141. From this standpoint, the design variables were classified (Appendix B. 1 ~ into following three groups according to their associated methodological characteristics: (1) ergonomic design variable, (2) mechanical design variable, and (3) aesthetic design variable. In this part of the study, only ergonomic design variables have been focused in the development of ergonomic design guidelines for a bus operator workstation. Other issues like ride vibration characteristics are mainly discussed in Appendix D. In addition, in order to consider complicated relationships existing between the design variables, the design variables were roughly categorized into following four groups in terms of cause-effect relationship: (1) simple design variable, (2) master design variable, (3) slave design variable, and (4) complex design variable, as shown by Figure 2.10. A simple design variable represents the design variable that has very little interaction with others so that it can be designed independently. For example, the seat back length (SB1) and the seat back cover texture (SB14) are considered as simple design variables because they have insignificant relationships with others. In contrast, a complex design variable is the design variable that has very complicated interactions with others so that it needs much effort to be designed adequately. Any design variable has not been categorized as a complex design variable in this study. A master design variable is the design variable that has a large effect on other variables but is little affected in return and thus it demands much concern in a design - 2.28

process. On the other hand, a slave design variable indicates the design variable that has a little effect on others but is largely affected from many other design variables so that its value is highly dependent on others. For example, the seat forward adjustment range (SP! I) or the seat backward adjustment range (SPl2) are classified into master design variables because their dimensions could influence other design variables such as the wheel plane horizontal angle adjustment range (TW8), the left instrument pane] horizontal adjustment range (~6), and so on. Conversely, the wheel plane horizontal angle adjustment range (TWO) and the left instrument pane] horizontal adjustment range (TWO) are categorized into slave design variables. (To) I. Simple Design Var. - little influence - little clependence . IV. Complex Design Var. - large influence - large dependence Cause(From) (Note) 11 & 111 : Design Target Var. Figure 2. 1 0: Strategic Classification Portfolio of Design Variables with respect to Cause / Effect Relationship In order to classify the design variables into the simple / master / slave / complex design variables with respect to cause-effect relationship precisely, 29,040 (2422/2-242) pairwise comparisons are needed. Since these thorough pairwise comparisons require too much time and effort, subjective judgments of the researchers have been employed for grouping the design variables into four categories as presented in Appendix B.~. The - 2.29

simple design variables and the complex design variables were identified at first, and then the rest of the design variables were classified into the master and the slave design variables which need a more detail analysis regarding their relational features. Table 2.4 illustrates the preceding two classification schemes: the related methodological characteristics and the cause-effect relationships. Table 2.4: Example of Classification of Design Variables with respect to Related Methodological Characteristics and Cause-Effect Relationships Code | Methodological Ch:lr:~cteri5tic . SB1 SB2 SB3 SB4 upper seat back depth SB5 middle seat back depth SB6 lower seat back depth SB7 upper seat back curvature SB8 middle seat back curvature SB9 lower seat back curvature SB10 seat back neutral vertical SB11 angle seat back angle adjustment SB12 range vertical distance of lumbar SB13 support from NSRP seat back cover texture SB14 seat back cushion material SB15 den . . (Note ED-Ergono ic design var., MD-Mechanical design var., AD-Aesthetic design var. P-Simple design var., M-Master design var., S-Slave design var., C-Complex design var.) Design Vary 1st Level 3rd Level 5tb 1~[ Seat Seat back seat back length (S) (B) ~t b~ m~ middle seat back width lower seat back width This ergonomic design study has mainly focused on the master and the slave design variables which are related to ergonomic characteristics for the development of design guidelines. Some pertinent simple design variables are also selected for providing ergonomic design guidelines. - 2.30

2.2.~.5 Structure of Bus Operator Anthropometric Variables 2.2.~.5.1 Hierarchy of Anthropometic Variables In order to apply anthropometric characteristics to the workstation design in a systematic way, 46 anthropometric variables are selected. The anthropometric variables were also organized into a hierarchical form by following the same procedures used for the hierarchy of design variables. The hierarchy of the anthropometric variables has three levels. In the first level, the anthropometric variables are categorized into two groups: linear dimensions (Table 2.5 and Figure 2.11) and angular dimensions (Table 2.6 and Figure 2.12).1n the second level, they are grouped with respect to dimensional attributes. Lastly, in the final level, the specific anthropometric variables are specified. The figures present graphical definitions of the anthropometric variables. 2.2.~.5.2 Anthropometric Data Set of the U.S. Population Data for 46 anthropometric variables were obtained from SAE J833 and other ergonomic design handbooks: Diffrient et al. (1981), Kroemer et al. (1994), Sanders and McCormick (1994), Woodson (1981). The anthropometric data of linear dimensions (Table 2.5) such as length, depth, height, etc., are collected with regard to the 5'h percentile female, the 50'h percentile person, and the 95'h percentile male of the U.S. population; anthropometric measures of angular dimensions (Table 2.6) such as visual field and movement ROM are summarized as for both values of the population extremes, comfort ranges, and the joint angles for standard driving posture assumed in this study. - 2.31

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2.2.2 Relationship analysis While constructing the hierarchies of the design and anthropometric variables, 242 design and 46 anthropometric variables have been identified for an ergonomic bus workstation design. However, it is not practical to resolve all of those design variables ergonomically without acknowledging the relative importance between them (Lee et al., 19931. In addition, Rebiffe (1966) cites Morant in stating that "there are complex relations between the different dimensions and in most cases a change in one or more of those measurements of a driving position would necessitate changes in the other dimensions." Thus, it is not appropriate to determine the design variables independently because there are complicated relationships between the design and anthropometric variables. Consequently, the relationships of those variables need to be clarified analytically so as to reflect their intrinsic relational features in the design process. 2.2.2.l Intra-Relationship Analysis of Design Variables An intra-relationship analysis was conducted in terms of the cause-effect relationship between the design variables (Appendix B.21. In the analysis, a three-point scale method was used to evaluate the relational intensity between paired design variables: blank (or zero) for no relationship, 'l' for a weak relationship, and '2' for a strong relationship. Table 2.7 illustrates the cause-effect matrix of the intra-relationship analysis. For example, the vertical distance of NDEP from NSRP (SHIO) is strongly determined by the seat back neutral vertical angle (SBll). In other words, since the change of seat back neutral vertical angle (SB! I) causes the vertical distance of NDEP from NSRP (SHIO) to change directly, '2' is recorded in the crossed cell. Note that no value is registered in the opposite cell along the diagonal since the vertical distance of NDEP from NSRP (SHIO) does not cause any change on the seat back neutral vertical angle (SB ~ I). - 2.40

Table 2.7: Example of Intra-Relationship Analysis of Design Variables ~= Master ~ Or ' ~ ~ `is tic : i:n D ~{O CL Ct ~Cal cn U) An u' SB1 1 SB12 SP9 ~P10 1 1 1 1 2 1 2 1 1 | 1 1 1 1 | 1 2 T 1 1 1 1 T 1 1 1 1 I 1 1 1 1 1 No Master Design Variable (Cause) _ 1 vertical distance of NDEP from NSRP 2 seat back neutral vertical angle 3 seat back angle adjustment range ~ seat pan neutral horizontal angle 5 seat pan angle adjustment range 6 Seat forward adjustment range 7 seat backward adjustment range 8 seat upward adjustment range 9 seat downward adjustment range 0 vertical distance of NSRP from WO _ uJ us ._ He , _ d Q (A Z E Q UJ Z O C Cal .m Ct .O a, SH10 SH10 SB11 SB12 SP9 SP10 SP11 SP12 SP13 SP14 SP15 em, - . a' can c , ct =5 co _ ce a) In _ ~1 = I Varlal . . ~ car c c , cat ce D CO . - SP1 2 1 . 1 . 1 1 i. r : 1 - l . Based on the results of the intra-relationship analysis, the relative influence and dependence of the design variables were identified. The relative influence (or dependence) of a design variable is defined as the proportion of the sum of the relational intensities in the row (or column) associated with the design variable to the sum total of the relational intensities of all the design variables. The relative influence of the master design variables and the relative dependence of the slave design variables are included in Appendix B.3 and Appendix B.4, respectively. Table 2.8 demonstrates the top ten master design variables that have a large relative influence on other design variables. Noticeably, the vertical distance of NDEP from NSRP (SHIO) and the seat back neutral vertical angle (SBll) are identified as the most influential design variables (about 33370 total). These two design variables are associated with visibility, and therefore need to be considered with high priorities for optimal visibility. Consequently, it is desirable to determine the vertical distance of NDEP from NSRP (SHIO) and the seat back neutral vertical angle (SB 1 ~ ~ before other design variables - 2.41

Table 2.8: Example of Relative Influence of Master Design Variables No 1 2 3 4 6 7 8 9 10 Master Design Variable vertical distance of NDEP from NSRP . seat back neutral vertical angle horizontal distance of NPRP* from NSRP seat pan neutral horizontal angle . seat upward adjustment range seat downward adjustment range seat back angle adjustment range seat backward adjustment range seat forward adjustment range vertical distance of NPRP* from WO PA10, PB10 * NPRP denotes NAPRP or NBPRP Relative Influence (Unit: %) SH10 SB11 PA9, PB9 SP9 SB13 SB14 11 D23 SB12 SB11 18.67 14.32 6.14 5.63 5.12 5.12 . 4.86 4.60 3.84 3.32 In contrast, Table 2.9 shows the top ten slave design variables that are highly dependent upon other design variables. The table indicates that the adjustment ranges of the steering wheel, the instrument panels, and the pedal pivots may be determined after resolving the higher priority design variables. Table 2.9: Example of Relative Dependence of Slave Design Variables No Slave Design Variable Relative Dependence i| (Unit: %) ~ ma= ~ pi] !~ · ·~ ~ Mu WWS 5.~l 2 wheel plane horizontal angle adjustment range TWO 1 4.74 3 wheel plane neutral horizontal angle TW5 4.01 4 wheel telescope adjustment range TW7 | 4.01 5 wheel column vertical angle adjustment range TW9 1 4.01 6 brake pedal plate pivot angle range PB7 1 3.65 7 accelerator pedal plate pivot angle range PA7 1 3.65 8 right instrument panel vertical adjustment range TR7 1 3.65 9 wheel column neutral vertical angle TWO 2.92 LO Right instrument panel horizontal adjustment range ~ TR6 ~2.92 ~- * NPRP denotes NAPRP or NBPRP - 2.42

Furthermore, the overall relative influence (or dependence) of each design subsystem was assessed by summing the relative influences (or dependencies) of the corresponding design variables with the design subsystem. Figure 2.13 indicates that the seat is a crucial design subsystem because it has a large influence on the design dimensions of other subsystems. Thus, it is necessary to analyze the seat dimensions more thoroughly to obtain correct design results. The steering wheel, pedals, instrument panels, and mirror locations are highly dependent on the design dimensions of the seat. The dimensions of these dependent subsystems can be determined easily once their relational attributes to the seat anc!anthropometric variables are defined. The windshield and peripheral design subsystems such as the personal locker are identified as simple design components which can be designed independently. 70 61.9 be. 60 ~ ·Relabve Influence | ~ Relative Dependence ' 40- - Q ~ e ~30.3 ~ .0W ~ ~' in DO, 7 Seat Steering Pedals Dash- Mirrors Vine Peripheral Wheel board hi ' ~Fare box W k Subsystems of Bus Operator's Worl~tion Figure 2. ~ 3: Relative Influence and Dependence of Design Subsystems - 2.43

2.2.2.2 Inter-Relationship Analysis of Design Variables ant! Anthropometric Variables The inter-relationships between the design and anthropometric variables were evaluated based on the three point scale method previously employed (Appendix B.41. This analysis ensures that anthropometric characteristics are reflected in the workstation design in a systematic way. As an example of the application of the evaluation procedure, shown in Table 2. 10, the seat forward adjustment range (SP! I) should accommodate the variation of the associated anthropometric dimensions such as the lower body link length and joint angles from the 5th percentile female to the 95th percentile male. However, the magnitude of variation is different among the related anthropometric variables. In particular, the horizontal length from hip pivot to SRP, sitting (HLl2), the vertical length from hip pivot to SRP, sitting (HEll), and the knee flexion (HAl7) have dominant effects on the determination of the seat forward adjustment range (SP] I) because of their Table 2.10: Example of Inter-Relationship Analysis of Design and Anthropometr~c Variables Master Desian Variable No | Anthropometric Variable 1 . 2 3 4 5 6 7 8 _ 10 11 2 13 _ hip adduclion/abduction knee flexion ankle dorsal/planter flexion hip width (sitting) vertical length from hip pivot to SRP (sitting) horizontal length Tom hip pivot to SRP (sitting) . . _ thigh thickness (sitting) femoral link horizontal length from ankle pivot to ball-of-foot shoe length THAW l HA15 HA17 HAIR HL10 HL1I HL12 HL13 HL14 HL15 HL16 HL19 HL20 - 2.44

high variation. Thus, all are given a rating of '2'. In contrast, the variations of the shoe length (HL20), and the ankle flexion (HAl9) are relatively small and thus have minimal effect on the determination of the seat forward adjustment range (SP} I). Therefore, both are given a rating of 'l'. The results of this inter-relationship analysis are utilized in the functional design relationship development phase. 2.2.3 Development on Functional Design Relationship 2.2.3.! Definition and Advantages of Functional Design Relationship The functional design relationships for the design variables have been developed based on the results of the relationship analyses completed in the previous stages. A functional design relationship of a design variable is defined as the function that represents a geometric relation between the design variable and its related design and anthropometric variables. A designer can easily obtain a specific value of the design variable by substituting known values or data of its related design variables and anthropometric variables into the functional design relationship. The advantage of these functional relationships is that there is no ambiguity in the final design because every workstation design variable is explicitly determined by defining the geometric relations of the design and anthropometric variables. Once these relationships are established, the creation of a workstation for a different or specific population can be accomplished by inputting a new set of anthropometric data. The flexibility of the functional design relationship to anthropometric data can be useful in two ways. First, since the size of humans is always changing, a workstation design of the future would only be a matter of inputting the updated anthropometry. - 2.45

Secondly, if this design procedure were to be applied to a country with anthropometry that is different from that of the U.S., it would also only be a simple matter of inputting a different anthropometric data set. Even though the functional design relationships are significantly useful in the workstation design, not much work has been done on these relationships for transit bus operator workstations. SAE Handbook (1994) provides several techniques for describing the location of the operator in the workstation. These procedures are given for both the Class A and Class B (which applies to transit buses) vehicles, and for three different classes of operator heights, the Ah percentile female, the half way position between large and small humans, and the 95th percentile male. The basis for these formulas is the location of the H-point or hip point, and based on the H-point, various envelopes of operator position can be determined. The most notable of these envelopes are the eyellipses, or elliptical model of the eye positions (J941), the shin and knee locations for the accelerator pedal (J1521), and the operator stomach profiles (J1522). Although these recommended practices allow the designer to understand where the various parts of the operator are located, and thus may provide some constraints for component location, the standards provide little information on the location and required adjustment ranges of the workstation elements. Another similar approach to the functional relationship is found in Humanscale (Diffrient et al., 1981), a notable source for workstation design. Humanscale primarily provides methods for locating important datum points of the operator by using some mathematical equations. However, Humanscale does not provide an understanding of the dependency of one datum location on the other workstation elements. Almost all of the applicable standards and design recommendations, such as Humanscale (Diffrient e! al., 1981), SAE (1994) and Woodson (1981), do not provide validation for the design values that they provide. Consequently, the functional relationship design procedure is necessary to examine the interdependency of workstation elements. - 2.46

2.2.3.2 Functional Design Relationship Development and Design Synthesis Functional relationships can be developed, as mentioned in section '2.2. 1.1 Workstation Design Approach,' based on one of three locations; design eye point (DEP), neutral seat reference point (NSRP), and heel resting point (HRP). In the present study, the NSRP is used as the datum point on the grounds that visibility and comfortable reach could both be optimized or negotiated with a reasonable amount of adjustment ranges. The general procedure for functional design relationship development is shown in Figure 2.14. The first phase of the procedure is to summarize the intra- and inter- relationships analyzed earlier for each design variable. In addition, a key design concept is stated for each design variable. In the second phase, a drawing is used to manifest the effect of the design and anthropometric variables on the design variable to be solved in a geometric form. Lastly, based on the geometric configuration, a mathematical function is formulated, and this design function is used to derive the design value for the design variable. , . Related Related Anthropometric Variables _ Design Variables | Geometric Drawing | . . | Functional Design Relationship | Key Design Concept Figure 2.14: Algorithm of Functional Design Relationship Development - 2.47

For example, as depicted in Table 2.11, the horizontal distance of APRP from NSRP (PA9) is determined by the geometric relation of the linear and angular dimensions of the related design and anthropometric variables. Projecting this geometric configuration into the horizontal plane, the functional design relationship of the horizontal distance of APRP from NSRP (PA9) is represented by a design function, {(HL12 + HL14) x cos (SP9) + (HL15 + HL17) x sin (90° + SP9 - HA17) + HL19 x cos(PA6)} x cos (HA15 + HA16 + HA18). The design value for this design variable is calculated for the hip abduction (HA15) of 10°, the hip rotation (HA16) of 0°, the knee flexion (HA17) of 65°, and the knee rotation (HA18) of 2° from the standard static driving posture. The suggested design value of 86.4 cm is close to those of Diffrient et al. (1981) and Carrier et al. (1992). When establishing the functional relationship for a design variable, the underlying design process for this design variable is explicitly elucidated. Thus, this design process can be easily applied when a different standard bus driving posture or a different design target population is considered. This study has developed design functions (Table 2.12) for 40 selected design variables that have a geometric relationship between their associated design and human variables. Most of the variables are master and slave design variables. Using the design functions and the relevant guidelines surveyed, the present study specified design values for 53 design variables (Table 2.12). Also, included are graphical illustrations and detail descriptions on the design values in Appendix B.6 when available. - 2.48

Table 2. ~ I: Illustration of a Functional Relationship Developed Desian Var. ~. Related Design Variable (From) _~ ~ -- ~ PA6. brake pedal plate horizontal angle (30°) HL12. horizontal length from hip pivot to SRP HL14. femoral link HL15. shank link HL17. ankle pivot height from floor with shoes HL19. horizontal length from ankle pivot to ball-of-foot HA15. hip abduction (10°) HA16. hip rotation (0°) HA17. knee flexion (65°) HA18. knee rotation (2°) Lm t ~) - The horizontal distance of pedal plate reference point (touched by the ball-of-foot) should be 77.7 to 94.0 cm, and thus its median value is 85.9 cm (p. 20~. Carrier et al.~1992) - The median of SRP horizontal distance from heel resting point (HRP) should be 69.0 cm, which is equivalent to horizontal distance from NSRP to pedal plate reference point of 82..4 cm (p. 311. Classification ~Master Related Anthropometric Variable Related Design Guideline Key Design Concept 1. maintain the comfortable ROM ranges of the hip, knee, and ankle. 2. maintain reachability of foot controls with the ball of foot on the pedal plate pivot. I' Drawing ~ / ................... ~ . , ~ ~: :c i:: . ':::jC::: C ,b,: _ 2, .......... By, ....... .. ~ .. +. >a> c ... cix....~.,....i Icy I. s ... i... cth~*~2{ ~ 75~ Add; ^~ all-~ > ~ ~' ~ · ~ ~-~ \~= ~ 2s;i ~_ L ~' l 1 ~ ~v Design Function ~ me. A--- ~_ A~ PA9 = { (HL12 + HL14) x cos(SP9) + (HL15 + HL17) x sin(90°+SP9 - HA17) +HL19 x cos( PA6) ~ x cos(HA15 + HA16 + HA18) = median of [77.3, 95.7] cm = 86.4 cm (range of PA9 = 18.4 cm) PA9 = 86.4 cm The horizontal adjustment range of seat (SP1 1/SP12) needs to incorporate the range of PA9 (18.4 cm) to accommodate the US population from the 5th percentile female to 95th percentile male. Design Value Comment - 2.49

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2.2.4 Conclusion A bus operator workstation is the work area in which a bus operator directly interacts with the bus and passengers. A bus operator workstation designed neglecting human characteristics brings about undesirable effects such as injuries and discomfort. Accordingly, sound ergonomic knowledge must be considered in the workstation design process. The workstation design is complex since various design objectives need to be considered simultaneously and trade-offs exist between the objectives. Also, many design variables are intricately related to one another. The complex workstation design can be resolved by a well-defined set of procedures based on system characteristics. The established systematic design structure comprises various broad and detailed analyses to produce ergonomic design guidelines for a bus operator's workstation. In the ergonomic design process, the design scope was defined by the identification of design variable and human variable hierarchies, the selection of design criteria and reference point, and the determination of standard bus driving postures. The design strategy was established by performing the intra-relationship analysis of the design variables in terms of cause and effect. In addition, the inter-relationships between the design and anthropometric variables were also considered to apply the anthropometric characteristics to the design variables in a comprehensive way. The primary concern of the workstation design was' to identify the relationships between the seat, steering wheel and pedals in conjunction with the standard bus driving postures. Consequently, the functional design relationships have been formulated based on the results of the intra- and inter-relationship analyses. The established functional relationship explicitly represents a geometric relation between the given design variable and its related design and anthropometric variables. The functional design relationships are expected to facilitate the flexibility of this ergonomic design study by quickly - 2.53

recalculating relevant ergonomic design values for different population groups. Thus, particular vehicles can be efficiently "tailored" to particular customers, i.e., transit systems, depending upon their anthropometric characteristics. - 2.54 ,

2.3 Mockup Test The goals of the present mockup test were to confirm the standard driving postures chosen for workstation design (see section 2.2.~.3 or Table 2.6) surveying positions of the controls selected by a jury with a wide anthropometric range, anti to evaluate the workstation in terms of visibility, reach, comfort, adjustability, and ease of ingress/egress. The mockup included the entire workstation as well as the first 200 cm of a typical bus. The bus width was taken to be 244 cm, and the dimensions for the front door, steps and firewall were obtained from a Neoplan bus. Presented are a photograph (Figure 2. ~ 5) and dimensions (Figure 2. ~ 6) of the mockup constructed in this study. _ ~ - _ _ - __ ~. 7~ C - - Hanain~ Pedals Left Instrument Panel (LIP) Right Instrument Panel (RIP) - Center Instrument Panel mounted on Tilt-Telescope-Tilt Steering Wheel Turn Signals and High Beams Farebox Figure 2.15: View of Workstation Mockup - 2.55

Led Unspent Pane! Reference Point Smog Female ~ ~- Large Male Right Instrument Pane] Reference Point ~ meal I| - Am, . ~ r _ ~ ' ~ Aft X~ ,~ Steering Wheel ~ 54.928 ~ =0 ~ ~ ' ~1 ~ T ~ 2.54 Workstation Origin Notes: I) Length units are in cm. 2) Reference points were mock-up specific; the reference points were changed after the mockup evaluation. Figure 2. 16a: Mockup Dimensions, Top View - 2.56

Steering Wheel Reference Point OWE Reference Point ~ Hub Tilt 15 - 94' :3.97 to 61.91 Seat Reference ~ )~\ \\~1~ m ~07 to lL '8 l Driver 30 4g _ _ Platfonn: ~ _--~ TO Pedal Plate / 7.94 ~ _ PiYotPo~nt ~ -, 76.84 ) 52.07 113.03 69.85 Steering Column BasePiYotPoint ~ 6196 ~ i ~ .65 _\ g57 Workstation Origin Notes: I) Length units are in cm. 2) Angle units are in deg. 3) Reference points were mock-up specific; the reference points were changed after the mockup evaluation. Figure 2.16b: Mockup Dimensions, Side View (RIP not Shown) - 2.57

I= ~ ;-~' r r ~ Is m 66.04 48.5g nib ,~ i' I, 72.39 41.28 _Workstation Origin Notes: I) Length units are in cm. 2) Reference points were mockup specific; the reference points were changed after the mockup evaluation. Figure 2.16c: Mockup Dimensions, Side View (LIP not Shown) - 2.58

2.3.1 Evaluation Procedure Each juror's demographic data such as stature, weight, and age were recorded. The jurors were asked to position the seat and steering wheel such that their feet reached the pedals and they had a 30° downward view over the top of the steering wheel. They were then asked to make the final adjustments based on comfort. Their body joint angles and component adjustments were then recorded. The jurors, after a brief explanation of the controls and tasks, were instructed to perform a series of simulated driving tasks with a videotape acting as a prompt for turns, and other actions. In this way, all jurors performed the same tasks in a quasi-dynamic simulation. The jurors were observed during their simulated driving for ease of reach. Finally, the jurors evaluated the mockup on the basis of several factors such as visibility, reach, and so on. 2.3.2 Test Results For analysis purposes, the jury was divided into stature categories of small, medium, and large, as shown by Table 2.13. 103 jurors evaluated the mockup. The jury consisted of 64 males, 39 females, with 14 professional bus operators or transit personnel. The average small female was actually 0.8 cm taller than the 5'h percentile female specified in SAE J833; the average large male was I.5 cm shorter than the 95th percentile male defined in SAE J833. The standard deviations for both of these subject groups extend beyond the 5th percentile range and the 95th percentile range, respectively. The weight of the average subject was 74 kg, which is similar to the SAE 1833 value of 73 kg. Table 2.13: Stature Category Definition Small (<30th percentile) Male < 172 cm (8) Medium Large Vr~ in= Female ~ 160 cm (13) 160 ~ 166 cm (17) 1 166 cm < (9) Note: a number in parentheses denotes the number of jurors of corresponding group. - 2.59

Table 2.14 summarizes the body joint angles of the jurors of each population group measured while being seated in the mockup; Table 2.15 presents the average results of the joint angles along with the acceptable joint angle comfort ranges as specified by Diffrient et al. (1981). The tables indicate that the entire jury was able to assume an appropriate posture within the comfort ranges in the mockup. Flexion Elbow Hip Knee Ankle Table 2.14: Body loins Angles Selected by Jury Small Female Med. Female Large Female Small Male Med. Male (avg stature = (avg stature (avg stature (avg stature = (avg stature = 156 cm, =163 cm, =171 cm, 169 cm, 176 cm, s.d.=3) s.d.=2) s.d.=4) s.d.=3) s.d.=2) 71.5 (12.6) 65.9 (14.8) 71.2 (12.1) 77.0 (9.4) 62.2 (13.4) 69.8 (4.5) 71.8 (5.4) 73.4 (2.7) 72.4 (5.4) 69.4 (4.4) 122.3 (7.8) 125.8 (7.2) 119.1 (7.0) 125.5 (10.1) 122.3 (8.1) 2.5 (4~9) 1.5 (5~5) -0.9 (10.3) -1.1 (6.0) 3.0 (6.7) Large Female (avg stature =171 cm, s.d.=4) . 71.2 (12.1) . 73.4 (2.7) . 119.1 (7.0) . -0.9 (10.3) Small Male (avg stature = 169 cm, s.d.=3) 77.0 (9.4) 72.4 (5.4) 125.5 (10.1) -1.1 (6.0) Large Male (avg stature =186 cm, s.d.=5)] 59.6 (13.6) 73.0 (6.7) 120.1 (10.3) 2.4 (5.9) (Note) Average angles in units of degrees, standard deviation shown in parentheses) Table 2.15: loins Angle Comparison Joint Angle Comfort Ranges l (unit: degrees) | 15~ 110 60 ~ 85 95 ~ 135 -5 ~ 20 Elbow FIexion Hip FIexion Knee FIexion Ankle Plantar (Note) x: mean, Ad.: standard deviation Test Results (unit: degrees) _ x=65.0(s.d.=14.1) x = 71.7 (s.d. = 5.6) _ x=122.1(s.d.=9.0) _ x = 1.8 (s.d. = 6.3) Figure 2.17 demonstrates the viewing angles for the forward downward views over the steering wheel and the right instrument pane] of the mockup. Any viewing angle below the minimum required would be unacceptable. Note that the APTA "Baseline Specification," commonly called the "whitebook," states that the operator must be able to see a 107 cm post 61 cm in front of the bus (APTA, 19721. The visibility requirement, however, is not an absolute quantity in terms of viewing angle but a function of the operator's des~gn eye point (DEP) height from the floor, bus floor height, and so on. The minimum viewing angles presented in Figure 2.17 were determined on this basis using - 2.60

numbers from the jury averages for each population group and were estimated with worst-case bus dimensions such as an operator platform height from the ground of 91 cm. Newer buses, such as having a low-floor, would have a much lower platform from the ground and therefore the visibility requirement get smaller. 40 35 30 25 Viewing Angle 20 (Degrees) 15 10 5- _ a- 1 Small Med. Large Female Female Female · Min. Required _ · downward · over right IP . Small Med. Large Total Male Male Male Population Group Figure 2.17: Viewing Angles in the Mockup The jurors were asked to rate the mock-up for visibility (Figure 2.~), reach (Figure 2.19), comfort (Figure 2.20), adjustability (Figure 2.21), and ease of ingress/egress (Figure 2.22) using a rating scale of 1 = unsatisfactory, 2 = poor, 3 = satisfactory, 4 = good and 5 = very good. These results demonstrate that no significant differences existed between gender or stature groups at the level of 5%. The relative flatness of the plots (with the exception of ingress/egress) show that the workstation received similar ratings for all population groups. Moreover, it was noted that the transit bus operators tended to evaluate the workstation more highly than the non-operators. - 2.61

5 - 4.5 j ·4 6 ~ 6 ~4.5 ~- 3.5 3 Rating 2.5 2 1.5 1 0.5 o v , I , , . i Small Med. Large Small Med. Large Total Female Female Female Male Male Male Population Group Figure 2.1 8: Visibility Evaluation Result of Mock-up 5 4.5 4 3.5 Rating 2.5 1.5 0.5 .4.6 ___ ______________ _______ .4.4 .4.3 44.3 ,`4.2 ___ - .4 44.4 O v Small Med. Large Small Med. Large Total Female Female Female Male Male Male Population Group Figure 2.19: Reach Evaluation Result of Mock-up - 2.62

4.5 ~ p-6 ·4 ~- .6 +.6 44~3 .4.2 3.5 3 Rating 2.5 1.5 0.5 o Small Med. Large Female Female Female -~.4 Small Med. Large Total Male Male Male Population Group Figure 2.20: Comfort Evaluation Result of Mock-up 5 5 - - - _ _ _ _ _ _ _ ~- .4.8 44.8 4.5 ~ 3.5 3 Rating 2.5 0.5 Small Med. Large Female Female Female _ _ _-*4.5 Small Med. Large Total Male Male Male Population Group Figure 2.2 i: Adjustability Evaluation Result of Mock-up - 2.63

5 - 4.5 4 - _ . 3.5 _ ~. . 3 Rating 2.5 2 1.5 1 ~ A _._ _ ~443 · ~ 0.5 __ _ O Small Med.Large Female FemaleFemale I O - - *4 Small Med. Large Total Male Male Male Population Group Figure 2.22: Ease of Ingress/Egress Evaluation Result of Mock-up The standard deviations for visibility, reach, comfort and adjustability are close to each other at values of about 0.6. The measure of ease of ingress/egress, a topic which many people offered comments, had a larger standard deviation, a value about 1. One reason for this may come from the fact that many jurors suggested that the seat should swivel. However, a swivel seat may not provide sufficient mechanical reliability. The placement of the adjustable components as determined by the jury is tabulated (Table 2.16). This information is helpful in order to determine the actual required adjustment ranges or to verify if a particular adjustment is even required. The table shows that the adjustment of the pedals is so small and thus it may be possible to fix the pedal location without adjustment. - 2.64

Table 2.16: Adjustable Components and the Settings from Jury Evaluation Component . Steering wheel Seat (NSRP) Left instrument pane! (NL,IRP) Right instrument pane] (NRIPRP) Pedals (NPRP) Variables Hub Orientation Column Tilt Column Telescope Fore-aft Vertical Fore-aft Vertical Fore-aft Vertical Fore-aft Vertical Mean value 40.4~ 33.3 o - 8.1 cm 90.9 cm * (0.0 cm) 37.6 cm . 67.8 cm* (23.1 cm) 50.0 cm 59.7 cm* (31.2 cm) 59.9 cm 0.0 cm* (90.9 cm) 50.0 cm S.D. . 10.9" 5.90 5.6 cm . 7.6 cm . 3.0 cm 6.1 cm 3.8 cm . 4.3 cm 4.6 cm N/A . ~ 3.8 cm , (Note) The locations of the reference points were measured from the workstation origin (WO) (located on the platform underneath of NPRP) defined in the mockup (see Figure 2.16~. Thus, for example, the average horizontal distance of NSRP from NPRP is 90.9 cm. Later, the definition of the WO was changed to the location determined by projecting the NSRP onto the platform (see Table 2.1 and Figure 2.9) without changing the WO height. The boldfaced numbers are those recalculated from the newly defined WO. 2.3.3 Summary The population was grouped according to their stature and gender. By this grouping, average height of the small female group was close (within a standard deviation) to that for the 5'h percentile female. Similarly, the large male group average height was also close (within a standard deviation) of the 95th percentile male. Therefore, the population extremes were included in the mockup evaluation and, to some extent, over represented when compared to the general population. From the results of the evaluation, three major comments can be made: (~) the workstation is able to accommodate a population ranging from the 5th percentile female to the 95th percentile male, (2) with this implementation of the workstation, the - 2.65

evaluation provides a general idea for the amount of adjustment required to accommodate the above population range. For example, the jury evaluation showed that increased seat travel relative to typical production moclels in both fore-aft and vertical directions would be helpful, and lastly, (3) the jury evaluations demonstrated positive indications on the workstation on the average in terms of visibility, reach, comfort, and adjustability. These ratings and their standard deviations were consistent for all population groups. However, the last measure, ease of ingress/egress, had a larger standard deviation than the previous measures. This is indicative of many jurors' opinion that the operator seat should swivel. To remedy this situation, large seat travel should be included in the prototype. - 2.66

2.4 JACKS Computer Simulation Computer simulations have been used to verify workstation designs before they are actually implemented as working prototypes. A variety of software tools (SAMME, COMBIMAN, CREWCHIEF, JACK@, etc.) are available to mode] a human graphically and simulate his/her tasks within a designed workstation. These tools provide an analytical way to ensure that the intended users of a workstation will be able to perform their tasks with underlying ergonomic design principles. The bus workstation design was evaluated with JACKS 5.9 in this study. JACKS is a software system for 3-D human modeling and simulation which runs on SG} IRIS workstations. JACKS incorporates sophisticated algorithms for anthropometric human figure generation, multiple limb positioning under constraints, motion animation over a specific interval of time, visibility and reach assessments, and strength performance simulation of human figures (Computer Graphics Research Laboratory, 19941. A detailed presentation of this work is included in Appendix C. The objectives of the computer simulation, in this study, are to: Identify the expected performance of a bus operator in the context of the designed transit bus operator's workstation. Validate the adjustment ranges of the workstation components (seat/ steering wheel/ instrument panels) to accommodate 95 percent of the US adult population presented in SAE IS33 (SAE, 1994), and also to provide sufficient visibility, acceptable reach, and comfortable driving posture for the population while performing the bus operating tasks. · Evaluate the bus workstation with a human model simulating the bus operating tasks in terms of - visibility of the displays on the instrument panel and out-of-windows, - 2.67

- reach to the steering wheel, the controls on the instrument panels, and the pedals, and - adjustability of the workstation components for the intended user population such that comfortable postures can be maintained while driving the bus. 2.4.1 Simulation Mode] Development The three human models (5th percentile female, 50th percentile, 95th percentile male) were created using the anthropometric data set designated in the SAL IS33. Since the SAE anthropometric data are not sufficient to specify a complete 3-D human mode} in JACK@, unavailable anthropometric data were found. The unavailable data were mostly anthropometric dimensions related to thickness and circumference of body parts, which were of less significance in the evaluation of workstation design in terms of visibility and comfortable reach. ~ order to complement the anthropometric data, NASA (1978) and ARMY (1988) anthropometry studies were referred and applied to the analytical determination of the missing data by assuming the proportionality of human body dimensions and a cylindrical shape of body parts as discussed in Appendix C. Seventeen typical bus operating tasks (Table 2.17) identified by the bus operating task analysis (discussed in section I.2 Operator Task Analysis) were simulated for the human models in JACKS. During the simulation of the bus operating tasks, the human model motions were governed by a set of virtual kinematic constraints related to each bus operating task. For example, during the simulation related to steering wheel maneuvering, the hands were constrained on the steering wheel to identify the upper-limb joint configuration; in the simulation corresponding to pedal activation, the right foot was restricted to the brake or accelerator pedal and the hip pivot point was fixed to a designated location over the seat according to the SRP and hip pivot point relationship (see Figure 2.51. - 2.68

Table 2.17: Example of Bus Operating Tasks and Metrics Bus Operating Task · ~ pre-c riving task on-road driving task picking-up/ depositing passengers seat adjustment steering wheel adjustment transmission engagement parking brake release four-way flasher activation kneeling activation Adjust the seat horizontally and vertically in relation to the pedal location. This is to ensure that a mannequin maintains its comfortable hip, knee, and ankle orientation. Metrics comfort, adjustability Tilt and telescope the steering column, or tilt the steering wheel based on the seat position maintaining the static driving posture and the 30 degree downward visibility requirement simultaneously. Shift the bus into gear on the left instrument panel. Release the parking brake on the right instrument panel. Activate the four way flasher on the right instrument panel. Evaluate the activation postures of the right arm and the visibility of the four way flasher. Activate the kneeling mode on the right instrument panel. Evaluate the activation postures of the right arm and the visibility of the kneeling switch. . .. . . v~S~bi Ity, comfort, adjustability . .. . . vlSlbl. .lty, reach, adjustability visibility, reach, adjustability . . . . vlslblllty, reach, adjustability visibility, reach, _ adjustability During the simulation, the bus workstation was evaluated in terms of visibility, reach, comfort, and adjustability. To facilitate this workstation evaluation, the simulation system generated two types of output files at the end of each bus operating task; one recorded the body joint angles of the human model, and the other recorded the selected locations of the workstation components. The simulation system developed utilizing JACK@' s capabilities allows a user to: · Setup the simulation environment such as displaying site labels, shading windows, generating orthogonal windows, and displaying rulers between sites. . . Select a 3-D human mode] among three population groups which are pre-defined by using the anthropometric data from the SAE 1833. Manipulate the locations of the adjustable workstation components (seat, steering wheel, instrument panels) interactively. Simulate motions of the human figure which are controlled through a set of kinematic constraints for 17 bus operating tasks. - 2.69

Create simulation result files which include the postures of the human figure and the specified adjustment values of the workstation components for each bus operating task. and Execute simulations of the bus operating tasks through either an interactive mode or a batch mode. 2.4.2 Simulation and Design Validation The simulation started by importing the workstation components from a CAD environment and integrating them with a 3-D human model. The human was located on the seat using the H-pt and SRP relationship (Diffrient et al., 1981~. Simulating the bus operating tasks under the kinematic constraints previously declared, the adjustable components were located iteratively until the human-workstation mode] satisfied ergonomic principles such as visibility, reach, and comfort. The locations of the components and joint angles of the human were recorded in result files. The workstation design was evaluated in terms of visibility, reach, comfort, and adjustability by observing human motions during animation and analyzing the resulting posture files. Based on the evaluation results, design modifications were made to improve the workstation design. Evaluation results regarding visibility, reach, comfort, and adjustability for the steering wheel adjustment are illustrated as an example in Table 2. ~ 8. - 2.70

Table 2.~: Workstation Design Simulation for Steering Wheel Adjustment Task | steering wheeladjust]nent Task Category adjusting workstation components Tilt and telescope the steering column, or tilt the steering wheel based on the seat Scenario position maintaining the static driving posture and the 30° downward visibility requirement simultaneously. . ==1 ~ ~ _I [ ~ . , ~L 1 1 111511~_ 1. _ __ If_ L 1 1~ ~ _~61~ ~1 mustrabon ~ _ ~ ~_ 1 · ~1 · ~1 steering wheel column tilt 10 deg (clockwise: +, counterclockwise: -) i Design Values steering wheel column telescope 11 cm (upward +, downward: -) steering wheel hub tilt 10 deg (clockwise: +, counterclockwise: -) Simulation Results Population Group ~=~_ column tilt 5 O O o telescope -5.5 cm 0 cm hub tilt -5 ° O o shoulder flexion 21.8 ° (4) 29.9 ° (2) shoulder abduction 4.1 ° (4) 7.6 ° (5) shoulder rotation 24.3 ° (4) 9.5 O (5) elbow flexion 56.9 ° (5) 45.0 O (4) wrist flexion 0 ° (5) 0 o (5) visibility 5 . . reach 5 5 5 comfort 4.4 4.2 adjustability 4.7 Remarks l - 2.71 95 th Percentile Male 5.5 cm s o 30.8 ° (2) . . 1 5 2 ° (5) 143 °~4) 45 7 O (4) o o (s) 4

The adjustment ranges shown in Table 2.19 were validated through iterative design modifications and simulations. Table 2. ~ 9: Adjustment ranges of workstation components tested in simulation Design Variable Ad ustment Range ~J ~ Seat Horizontal 18.5 cm (7.3 in.) Vertical 6.7 cm (2.6 in.) Seatback Angle 10 deg. Steering wheel Column Tilt 10 deg. Telescope ~ I.0 cm (4.3 in.) Hub Tilt 10 deg. Left Instrument Panel Horizontal 9.9 cm (3.9 in.) Vertical 4.0 cm (1.6 in.) Right Instrument Pane! Horizontal 13.3 cm (5.2 in.) Vertical 4.5 cm (~.S in.) 2.4.3 Summary A computer simulation mode] was developed to validate the bus operator's workstation design. Utilizing JACK~'s capabilities, the simulation mode} provided the following functions: setup of simulation environment. selection of human models with the SAE 1833 anthropometry. adjustment of workstation components. simulation of bus operating tasks under specified kinematic constraints. creation of simulation result files. mode! execution in an interactive mode or a batch mode. The SAE 1833 anthropometric data were used to generate three different size human models (5th percentile female, 50th percentile, 95th percentile male). Estimations - 2.72

were made to complement unavailable anthropometric data for three dimensional human modeling. The simulation system was designed to simulate 17 typical bus operating tasks. The simulation system determined the expected behavior and visual field of a human for each bus operating task in the context of the workstation. The human behaviors were controlled by the designated kinematic constraints during simulation. In simulating each bus operating task, the locations of the workstation components were manipulated within the adjustment ranges. Design modifications were made wherever inappropriate design was found. The designated adjustment ranges were evaluated with respect to the degree of satisfying ergonomic requirements such as good visibility, acceptable reach, postural comfort, and sufficient adjustability. A valid transit bus operator's workstation design was produced through iterative design modifications and simulations. Also, animation of the bus operating tasks facilitated the evaluation of the workstation in dynamic situations. - 2.73

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