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

Chapter: Chapter 3. Prototype Construction and Testing

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Suggested Citation:"Chapter 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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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Page 89
Suggested Citation:"Chapter 3. Prototype Construction and Testing." 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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Page 90
Suggested Citation:"Chapter 3. Prototype Construction and Testing." 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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Page 91
Suggested Citation:"Chapter 3. Prototype Construction and Testing." 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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Page 92
Suggested Citation:"Chapter 3. Prototype Construction and Testing." 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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Page 93
Suggested Citation:"Chapter 3. Prototype Construction and Testing." 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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Page 94
Suggested Citation:"Chapter 3. Prototype Construction and Testing." 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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Page 95
Suggested Citation:"Chapter 3. Prototype Construction and Testing." 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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Page 96
Suggested Citation:"Chapter 3. Prototype Construction and Testing." 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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Page 97
Suggested Citation:"Chapter 3. Prototype Construction and Testing." 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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Page 98
Suggested Citation:"Chapter 3. Prototype Construction and Testing." 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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Page 99
Suggested Citation:"Chapter 3. Prototype Construction and Testing." 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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Page 100
Suggested Citation:"Chapter 3. Prototype Construction and Testing." 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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Page 101
Suggested Citation:"Chapter 3. Prototype Construction and Testing." 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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Page 102
Suggested Citation:"Chapter 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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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Page 104
Suggested Citation:"Chapter 3. Prototype Construction and Testing." 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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Page 105
Suggested Citation:"Chapter 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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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Page 107
Suggested Citation:"Chapter 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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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Page 112
Suggested Citation:"Chapter 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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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Page 121
Suggested Citation:"Chapter 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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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Page 124
Suggested Citation:"Chapter 3. Prototype Construction and Testing." 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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Page 125
Suggested Citation:"Chapter 3. Prototype Construction and Testing." 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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Page 126
Suggested Citation:"Chapter 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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 3. Prototype Construction and Testing." 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 3. PROTOTYPE CONSTRUCTION AND TESTING 3.1 Prototype Construction Using the previously developed design specifications, the next task was to make the specifications a reality by implementing them into a 1973 GMC bus contributed by the Centre Area Transit Authority (CATA). evaluate and validate the design guidelines. The goal of the prototype testing was to Figure 3.! shows a photograph of the original workstation in the GMC. The first major task was to remove the seat, instrument panels, front heater, modesty panel, steering wheel, etc. from the workstation. Figure 3.2 shows a photo of the retrofitted workstation. In essence, most of the previous workstation was removed to make way for the retrofitted design. The first step was to locate the workstation origin (W.O.) in the GMC workstation. The workstation origin is defined to be a datum point which is on the floor directly below the SRP for the 50th percentile person. First, the W.O. was located relative to the base of the steering wheel column from the data of the NSRP approach. Once this was accomplished, the positioning of the components could begin. The following paragraphs are devoted to specifically addressing each workstation component and detailing their design, construction, and constraints in the development of the prototype. - 3.!

.' - ~ ~ - : c! If Figure 3.~: Original GMC Workstation - ~: ~. ~ ~ . . ~ . J.~. . ~ ~ ~ ~ . .. ~ ~ . .. ~:~.~.~ ::! _ . . .. it_ Figure 3.2: Retrofitted Workstation - 3.2 \ . : i \ . . . it.. .~............. .

Although installing the seat was one of the less difficult components to put into the prototype, some prior testing was required. Seven different bus operator seats were evaluated. The evaluation used the PTI ride quality simulator and the test track facilities. Seats with all pin jointed links appeared to have the best performance. The seats which used a slider in the suspension appeared to have been subject to some "stiction" in their motion. "Stiction" could cause the suspension not to move easily. Two seats appeared to be favorable and provide sufficient adjustment in both the vertical and fore-aft directions. These seats also had independent adjustment for vertical height and suspension stiffness. The difference between them was that one isolated the vibrations over a broad frequency band while the other seat was better at the specific resonant frequencies of a seated human. The seat that attenuates vibrations at a human's natural frequency was used for the prototype since the concern was lower back injury. More details of this evaluation can be found in Appendix D of the report or in Oesterling (1997). It was found that Seat #3 met the necessary conditions to be used in the prototype testing. Before the seat could be positioned in the workstation, the seat reference point (SRP) had to be determined (Diffrient et at., 1981~. The SRP is defined as the point on the sagittal plane located by two intersecting planes - the compressed seat pan and seat back. This was found from analytical equations which locate the SRP relative to the SgRP (Seating Reference Point), which is a common reference point supplied by seat manufacturer data. After locating the SRP on the seat, the seat could be placed in the workstation. Note that the seat was adjusted to its middle fore-aft position, and the seat was placed such that the SRP was directly above the W.O. This was due to the fact that the 50th percentile SRP projected onto the floor was designated as the W.O. The left instrument panel (LIP) needed to be constructed to provide the necessary adjustment required by the design specifications. A major constraint in this endeavor was the width of the GMC bus itself, which was smaller than most newer buses. Therefore, due to the width of the LIP, minimal clearance existed between the seat and the LIP panel. The LIP was constructed out of a plywood box with a sheet metal top face to house controls. The existing controls in the bus were simply rewired to extend to the new - 3.3

panel. Any controls specified but not in the existing bus were "dummied", with exception of the remote mirror controls. Also, to provide the adjustability specified by the guidelines, two pairs of sliding clamps were used, which allowed the LIP to slide with an infinite adjustment in the specified range in the horizontal and vertical directions. The right instrument panel (RIP), as above with the LIP, needed to be located as per the specifications, and provide the necessary adjustment range, as well as house the controls. The RIP was also constructed out of plywood with a sheet metal top face to hold the control switches. Adjustment was built into the pedestal for this instrument panel. It was made up of a vertical aluminum bar which telescoped vertically, and a set of wheels mounted to the top of the bar. A horizontal bar could then slide horizontally fore and aft using these wheels as guides. The RIP was then mounted to this horizontal bar, which allowed the RIP the 2 degrees of freedom that was required. Finally, most of the controls on the RIP were "dummied", except the door control which was modified to a switch controlling two solenoids in the door air system, the hazards, and the Talking bus system which was placed on the right side of the RIP. Both the accelerator and brake pedals were mounted onto wooden blocks which in turn were bolted to the front of the bus, which was the best that could be done due to the lack of structural support in the front of the bus. Appendix E describes the pedal design approach. The old brake pedal was removed, and a hanging pedal was installed in its place. Subsequently, the air lines to the brake had to be replumbed. Next, the existing accelerator pedal was modified by extending a plate from the pedal surface left of the pedal and using the arm of the new hanging pedal to push this plate, thus pushing the original pedal. To install an entirely new accelerator linkage would have been a major engineering task in itself. As a result, the force required to push the modified pedal was higher than desired, due to the original accelerator linkage. The force required to actuate each pedal in the completed prototype was measured. Since the accelerator pedal is a modification of the existing treadle pedal, the - 3.4

force required to press the old pedal at the middle of the pedal plate and near the top of the pedal were recorded also. Three trials were performed at each position, and the data is shown in Table 3. ~ and Table 3.2. Table 3.1: Brake Pedal Force Trial 1 2 3 Mean l s d Force (N) at Location (cm) 2 cm below from BPRP BPRP 214.0 19.8 235.2 9.8 . 2 cm above from BPRP 215.6 230.3 210.7 218.9 _ 10.2, (BPRP: Brake Pedal Reference Pi int, a point in the n fiddle of brake pedal) Table 3.2: New and Old Accelerator Pedal Force Fol ce (N) at Location (cm) | New Pedal 1 APRP Trial Old Pedal APRP 8.25 cm above from APRP 215.6 196.0 215.6 209. 1 11. (APRP: Accelerator Pedal Reference ~ 'oint, a point in He n fiddle of accelerator 1 medals Several sources define ranges for pedal force resistance. For the brake pedal, maximums were set at 232.6 N and 178 N by Diffrient et al. (1981) and Woodson (1981), respectively. Also, a range of 35.6 - 267 N was proposed by Van Cott and Kinkade (1972) for the brake pedal. From these guidelines, the force required to actuate the prototype brake pedal is in the upper range of the allowable requirement. Note that the pedal force is dependent upon the brake air system configuration and not the pedal itself. Therefore, it is unlikely that a change in pedal type will reduce the actuation force. - 3.5

However, the hanging brake pedal does have the advantage of accommodating a larger amount of people. For the accelerator pedal forces, the guidelines suggest much smaller values. Diffrient et al. (1981) suggests a range of 26.7 - 44.5 N. while Van Colt and Kinkade (1972) stated a range of 28.9 - 40 N. Comparing these ranges to those of the prototype accelerator pedal, it can be seen that the prototype accelerator pedal forces are much higher. But, the original pedal force requirements were higher at the equivalent accelerator pedal reference point (APRP) than the modified pedal. Therefore, the high force requirements were a function of the existing accelerator linkage, which would have been a major engineering task to replace. Also, as a result of the high accelerator force, the right ankle, right knee, right thigh, and lower back would be subject to a higher stress, leading to greater body discomfort. This is supported by the 24 subjects' slight degradation of comfort in these areas over the 90 minutes of the driving simulation. The Talking Bus system by Digital Recorders was installed into the prototype. This system is an integrated sign and announcement system, with anticipated connectivity to the farebox and other functions. The computer components of the Talking Bus were installed under a passenger seat, and the operator control unit (OCU) or keypad control was installed onto the right face of the right instrument panel. Also, the talking bus was connected to the internal bus sign contributed by Sunrise Sign Systems. The sign was installed above the windshield in the center of the bus, directly above the center pillar of the windshield. Several other components were constructed and / or installed into the prototype. One of these components was the center instrument panel (CIP). The CIP was primarily made of plywood to house the turn signals, air pressure gauge, and speedometer. The CIP was installed onto the steering column by using two U-bolts. Also, a modesty panel was constructed, which was installed behind the operator. In addition, the farebox was contributed by GFI, and it was installed in its proper location, near the entrance aisle and - 3.6

towards the front of the bus. Finally, the platform height of the GMC workstation was led) at 3 inches above the floor of the bus, compared to the 6 inch platform height in the static mockup. The floor height was not changed in the GMC because the accelerator pedal linkage system and steering gearbox would have needed to be redesigned, remounted, and relocated. Also, the relative distance between operator and ceiling would have decreased. The largest constraint in the workstation was the location of the steering gearbox under the column base. The location of the gear box was fixed, and to relocate it would have entailed a total redesign of the bus steering linkage. Another constraint involved the lack of structural support at the front of the bus. pedestal had to be mounted on the floor. Thus, the steering column support Also, the hub tilt was not included into the prototype since a suitable commercial item was not available. Table 3.3 summarizes the dimensional constraints. Table 3.3: GMC Workstation Constraints Steering gearbox in a fixed location Windows, existing Electrical circuit box location decreases lateral width Existing structural supports are inadequate Existing accelerator control linkage was utilized Dimensional Constraints: Dimension GMC Lateral horn work st at ~ 5 inches centerline to wall Total vehicle width 91 inches Workstation longitudinal 56 inches length Neoplan 19 inches 96 inches 77 inches - 3.7

3.2 Testing 3.2.! Metrics In order to evaluate the relevant features of the proposed workstation, the test metrics contain those used in the mockup evaluation plus which can be added due to the dynamic driving environment. They include visibility, postural comfort, reach, adjustability, ease of ingress / egress, and ride quality as summarized in Appendix G.1.1.1. For the measurement of the test metrics, several instruments were used: questionnaires, anthropometers, force measurement gloves, a hand dynamometer, a video camera' and a video analysis system. Overall subjective judgments with six aspects (visibility, postural comfort, reach, adjustability, ease of ingress/egress, strength requirement) except ride quality were conducted in the original GMC bus (hereafter refered to the standard bus) and prototype workstations respectively using a rating scale from 1 (poor) to 5 (good). In addition, postural comfort in the prototype workstation was evaluated more in detail investigating the comfort level of each body region with a rating scale from -7 (most uncomfortable) to 7 (most comfortable). Visibility was quantitatively evaluated by assessing the operatorts field of view over the steering wheel, central instrument panel, right instrument panel, farebox, and left and right mirrors using a visibility pole, a tape measure, and a protractor. Postural comfort was quantified by grading body angles measured in a static driving position and/ or videotaped while driving according to an evaluation scheme. The videotaped driving postures were digitized using Vision 3000_, a video analysis system. Maximum hand grip forces were measured using a hand dynamometer and grip forces on the steering - 3.8

wheel while maneuvering the prototype were determined using a glove with force sensitive resistors (FSRs). Finally, ride quality of the prototype addressed by investigating the acceleration transmissibilities at both floor and seat while driving. 3.2.2 Testing Protocol The testing procedures (Appendix G.~.2.~) and instructions (Appendix G.~.2.2) consisted of four phases: introduction, pre-driving, driving, and post-driving. During the introduction the test administrators explained the testing to a subject. The participant arrived at the test dressed as they do for a typical work day. Background data of the participant was recorded by measuring the standing height, weight, and maximum hand grip forces. More information was obtained by angling about previous driving experience, bus models and makes. The subject was placed in the standard bus and the prototype each to measure the subject's posture and record subjective ratings of the bus workstations. The standard bus was evaluated only in a static driving condition, while the prototype was tested both in a static and a dynamic driving conditions. The workstation components were adjusted to the operator's satisfaction. The subject was asked to first adjust the seat vertically and horizontally in relation to the pedal location and without regard to their location relative to the steering wheel and other driving components. This was to ensure that the participant determines their optimal hip, knee and ankle orientation. The seat adjustment was conducted in both the GMC bus and prototype workstations. Additional adjustments such as the steering wheel, left and right instrument panels, and left and right side mirrors were made only in the prototype. The steering wheel was located so that the operator was comfortable, but still maintained sufficient downward visibility. The test administrators explained the operation and purpose of the - 3.9

controls on both the left and right instrument panels. These instrument panels were then adjusted vertically and horizontally to meet the operators reach needs. Lastly, the left and right side mirrors were adjusted for good rear view visibility. After adjusting the workstation components, the subject was asked to assume a standard driving posture with hands at '9 and 3' on the steering wheel, and with their right foot just resting on the accelerator pedal with no activation. The body angles for the participant in this position were measured and recorded. The participant was then asked to depress the accelerator and brake pedal fully. The lower body angles for these positions were measured and recorded. Finally, the subject was asked to reach the reference points on the instrument panels and the upper body angles were measured. After the pre-trip adjustments, the subject proceeded to operate the prototype bus out of the garage and onto the oval track. The oval track is one mile in length with a posted speed of 35 mph. Since during a typical bus route, an operator makes an average of four stops per mile according to the APIA (1977) "Whitebook," the testing includes four stops on the one mile oval track. The operator drove once around the oval track to become familiar with the vehicle. Then the operator proceeded to a simulated bus stop to pick-up a passenger. Four bus stops were set-up around the oval. The subject stopped at each stop and performed the functions related to picking-up passengers. The operator then re-entered the driving lane. The merging from and onto the oval track and the bus stops were to simulate entering and leaving traffic. The subject made 20 laps for a I.5 to 2 hour duration test. A final driving exercise included a series of lock-to-lock turns. A video camera was mounted in the prototype to record the subject's posture during lap 2, lap 19, and during the lock-to-lock driving. This video was to do a dynamic posture analysis. A body discomfort assessment was used to measure the subject's comfort over the approximately 90 minutes of driving. The assessment was given to the - 3.10

operator before driving, after ~ O laps of driving, after 20 laps of driving, and finally after the lock-to-Iock driving. Also, accelerometers were used to measure vibration between floor and seat for each operator. In addition, a force measurement glove was used to measure forces applied by the subject's hand during the lock-to-Iock driving segment. Finally, the subject drove back to the garage. The components were readjusted and the bocly joint angles were measured again if the subject wanted to change the component locations originally selected. The prototype workstation was reevaluated with the same aspects used in the pre-driving condition to investigate the rating change of the subject while driving. The test procedure ended with a structured set of questions about the workstation layout. Comments and recommendations from the subject on the workstation design for improvement were recorded. All participants were then thanked for their time and then excused. The course layout is shown in Figure 3.3 where the letters denote events that are defined in Table 3.4. The driving portion of the test required approximately 90 minutes, the entire test per subject required about three and a half hours. - 3.~]

- ~ / l / / ~- \ ~of A~B,G \ - ,xB=s Stop 4~ E /' ~ - - - ~ F Garage Buts Durability ~.,ourse \. Stop- whirl, D ~i,ght Carol Terra X / Bets Stop 1, E: Double flare Charge \ _ -- X , - - - B=s Sto~ Buts Stop 2, E: Figure 3.3: Driving Course Layout of the PT! Test Track - 3.12 \ \ l

Table 3.4: Driving Exercise Procedure Event - A Description Operator Task Pre-driving summary, sign an informed consent enter bus, store personal items, start engine, form, introduction to workstation diagnostic check, change destination sign Adjustment of components to fit operator adjust seat, adjust steering wheel, adjust mirrors, apply safety belt, climate adjust, defrost mirrors/windows, Drive once around oval track for familiarization engage transmission, release parking brake, accelerate bus, turn the bus, inspect oncoming and side traffic, activate turn signal, steering Stop at a stop-sign and traffic intersection turn the bus from a stop (simulates a left hand turn from a red light), inspect oncoming and side traffic, activate turn signal, steering, deceleration or stop, accelerate bus On subsequent trips around oval track, pull over monitor stop request indicators, to the side and pick up and deposit passengers at decelerate/approach bus stop, activate four way "bus stops 1 through 4" flashers, stop the bus, activate bus kneeling, open bus door, inspect ingress of passengers, check farebox or farebox display, empty coins from farebox to drum, update ride pass, distribute transfer ticket, record passenger data (this requires the use of the ODA), activate unkneeling of bus, close bus door, check passengers for seating status, deactivate four way flashers, inspect oncoming and side traffic, activate turn signal, accelerate bus Enter durability track for 1 lap, at the ends of turn the bus, inspect oncoming and side traffic, the track to turn bus around, the steering will be activate turn signal, steering, deceleration or stop, operated from lock-to-lock. accelerate bus, communication with other transit operators and passengers, climate control adjustment, activate headlights~igh beams, activate windshield wipers Return to garage, exit interview includes the turn the bus, inspect oncoming and side traffic, juror evaluation of a baseline bus for activate turn signal, steering, deceleration and stop comparison. the bus B D E F G 3.2.3 Composition of the Jury The jury was composed of twenty-four people. This was statistically sufficient for analysis purposes. A detailed participant profile is shown by Appendix G.~.3.~. A third of the jurors were females. For analysis purposes, three stature groups were defined: the - 3.13

5t]1 percentile female through the 1S'h percentile female are considered as small while the 85th percentile male upwards are defined as large. Therefore, the jury was composed of about 20% small females (a mean height of 158.5 cm), 25% large males (a mean height of ~ 86.7 cm) and the remaining 55% fit in the medium size group (a mean height of ~ 72.9 cm) as shown in Figure 3.4. The jury was composed of actual transit bus operators with an average of 8.4 years of experience. The jurors were screened for history relating to injury and other factors which could have biased the evaluation. All appeared to be in a reasonable physical condition. Participants' Profile - Stature 6 - SrrallGroup _ _ Medium Groups . ~ Large Group 5 4 ~- ._ ._ ~3 ~ 0 ~ · , 0 Z 1 ' t O . I 5 1 5 2 4 1~ ~ 3 150.6 159.4 164.2 5th Motile 15th Motile Female Female Statu re (u n it: cm ) 169.1 173.9 178.8 183.6 188.0 50th Motile 85th Motile 95th Motile M ale M ale Figure 3.4: Stature Distribution of the Subjects Participated - 3.14

3.3 Test Results & Analysis 3.3.1 Workstation Component Locations The reference point (RP) locations of each workstation component (seat, steering wheel, left and right instrument panels) adjusted by the bus operators were recorded in the standard (Appendix G.2.1.1) and prototype bus workstations (Appendix G.2.1.2) respectively. The locations were recorded in terms of a workstation origin (W.O.) defined as a point on a workstation platform underneath of a neutral seat reference point (NSRP), a SRP of the 50th percentile person. Table 3.5 compares the test results to the design values (Table 2.12 in Chapter 2.2.3. Development of Functional Design Relationship) in terms of minimum and maximum locations and adjustment range. Only singular values were recorded for the locations of steering wheel and left instrument panel of the standard bus because they are fixed. Any adjustability in the standard bus is limited comparing to the recommended design except the seat height adjustment and seatback angle adjustment. Also the comparison between the design values and the prototype results are graphically demonstrated in Figure 3.5 to 3.7. The figures show that the seat was located at a lower position and the steering wheel and the right instrument panel of the prototype were located at a farther and higher location from the W.O. than those of the design specifications. This produced larger shoulder and elbow flexion angles while driving than the assumed standard driving postures, which will be discussed in section 3.3.4. 1: Static Driving Posture. The stretched-out posture of shoulder-arm could be due to a driving preference which have been developed by driving conventional bus workstations, which require an erect upper body and large flexion angles of shoulder and elbow. - 3.15

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| Flon `w Spent via Pro~typa R~lt:s ~ 1 EE, y L Figure 3 ] L]pEp_ -Tl' I SWRP_50 ~W'r~-! ,~ i10 1 1 1 1 ,4 ~ fx~ | R]PRP_~ tJ AX jAPPRP | Comparison of the Design Values and the Prototype Test Results (Plan View) S1~ new (Steeping Wheel not S~wr) SpKrfrcatrans vs. Prototype Results EE34 [53- L PlotForr, X a' Wit _ Lo | RIPEP_50 | X An_ 1 UPRP_~ 1 | APPRP ~ An' Figure 3.6: Comparison of Design Values and Prototype Test Results (Side View) - 3.17

Uncle Crew ~1P, ~ ret s~> S~rf~ca~ar~ vs ~toty~ Posits l J ~ Platform X NIX [ ~-~1 /1 SWRP_~ . {- its-~3 Cat - _~ Figure 3.7: Comparison of Design Values and Prototype Test Results (Side View) - 3.18

3.3.2 Overall Subjective Judgment Overall subjective judgments on the standard and prototype bus workstations were made by the bus operators for a total of three test conditions (standard bus workstation without driving, prototype bus workstation before and after driving each). The operators were asked to evaluate the bus workstations using a rating scale from 1 (poor) to 5 (good) with respect to six criteria: visibility, postural comfort, reach, adjustability' ease of ingress/egress' and strength requirement. The criteria were selectively employed for each test condition depending on test characteristics as shown in Table 3.6. For example, the criterion 'ease of ingress/egress' was not included in the test condition 'pre-driving of the prototype bus' because the workstation components were required to move back and forth for the evaluation. The component locations originally selected by a subject would have been changed after the testing so that the following test results might be affected. The criterion 'strength requirement' was only measured for the testing condition 'post-driving of the prototype bus' because it was expected that a subject would make realistic judgment on the strength requirement of a bus workstation only after a sufficient time for utilization. Criteria Visibility Postural Comfort Reach Adjustability Ingress/Egress Strength Requirement Table 3.6: Criteria Used in Overall Subjective Judgment on Bus Operator's Workstations (. - employed, blank - unemployed) No. 2 3 4 s 6 Standard bus, Pre-driving . . - 3.19 Test Condition . Prototype bus, Pre-driving Prototype bus, Post-driving : :

The means and 95 percent confidence intervals of the subjective judgments for the three test conditions (Appendix G.2.2.1) are depicted in Figure 3.8. The graph shows that the prototype workstation was preferred overall to the standard bus workstation by the operators and that only slightly different evaluations were given before and after driving of the prototype workstation. 5 4 . 3 . . ~ i a, 2 . oh 1 . Test Result of Overall Subjective Judgment I'm r F :~ AL ~1~ : 0. .. ~ ,~ ~ . visibility postural comfort ~ ~' . i reach !~-l adjustability ! stander u~-driving)~ ~ prototype bus (pre-driving) ma prototype bus (post-driving ease of strength ingress/egress requirement Figure 3.~: Means and 95% Confidence Intervals of Overall Subjective Judgments on Bus Operator's Workstations Analysis of variance (ANOVA) results on the subjective judgments with two fixed factors (Stature Group and Test Condition) and corresponding paired t-test results are included in Appendix G.2.2.2 and Appendix G.2.2.3 respectively. The ANOVA analyses showed no significant effect in ratings due to differences in stature (p > 0.05) on visibility, postural comfort, reach, or adjustability. This means that small and tall individuals rated the bus workstations just as good as did medium-sized operators. - 3.20

However, taller individuals did have more trouble with ease of ingress/egress than small- or medium-sized individuals (p = 0.015). The t-test result on the subjective judgments of ease of ingress/egress between stature groups revealed that the small group gave significantly higher values (p < 0.03) in the evaluation than the large group, and that the means between the other paired stature groups were not significantly different (p > 0.05). However, Figure 3.9 shows that the subjective judgment of ease of ingress/egress decreases generally as stature increases, which implies that larger individuals may prefer a larger workstation for easy access of the workstation. Overa 11 Subjective Judgment of Ease of Ingress/Egress ~ 4.3 _ ~ 3.8 3 2 a)I ~I 3 an 1 -. O ~ small group medium group large group Stature Group Figure 3.9: Means and 95% Confidence Intervals of Overall Subjective Judgment of Ease of l:ngress/Egress of Stature Groups Test Condition had a significant effect (p < 0.01) for all characteristics except for visibility. In other words, visibility was not significantly different between the standard bus workstation and the prototype workstation because windshield height and body frame structure of the standard bus, which provides sufficient downward visibility, were same - 3.21

with those of the prototype, while every other characteristic (comfort, reach, adjustability and ease of ingress/egress) was significantly (p < 0.01) improved upon with the prototype design. This was especially evident with the pairwise (by subject) comparisons as shown in Appendix G.2.2.3. Also, the pairwise comparisons of the prototype pre- and post- driving showed insignificant rating differences (p > 0.05), indicating a minimal change in subjective responses due to fatigue, but still a significantly positive improvement over the standard workstation. Finally, the interaction effect of Stature Group and Test Condition was insignificant (p > 0.05) for all criteria, which indicates l-tests on the differences between two group means could be conducted along each independent factor. A novel graphical analysis (Figure 3.10) was utilized to visually show the effectiveness of the prototype design over the standard bus workstation. The area of the pentagon is determined by five axes each showing the subjective judgment for a particular criterion (visibility, postural comfort, reach, adjustability, and ease of ingress/ egress). The solid line links the average subjective judgment for each criterion for the prototype while the dotted line links the same for the standard bus workstation. The solid line circumscribes the dotted line, indicating that all 24 operators rated the prototype better than the standard bus workstation for each of the five criteria. - 3.22

Test Result of Overall Subjective Judgment Visibility 5 . ingress/egress,/ " ~- \ ~ \ ~ adjustab 'I ~ \ "\ ~ Standard Bus (Pre-Driving) Prototype Bus ( Post-Driving) 1 I \ ~ postural comfort if ~ .- / \~. ~ ~ reach Figure 3.1 0: Means and 95% Confidence Intervals of Overall Subjective Judgment of Standard and Prototype Bus Workstations 3.3.3 Visibility In order to evaluate the visibility of the prototype workstation in an objective manner, viewing angles over the steering wheel (SW), central instrument panel (CIP), right instrument panel (RIP), farebox, and left and right mirrors were measured (Appendix G.2.3.1). Also downward viewing angles for each subject to satisfy the minimum visibility requirement (an object three and a half feet tall should be seen no more than two feet in front of the bus) recommended by APTA (1977) were calculated. Three among 24 operators did not meet the visibility requirement as shown in Table 3.7. However, the downward viewing angles of the last two operators (JXO and TXB) were slightly lower (2 degrees) than the requirements. This is because the steering wheel - 3.23

column adjustment (tilt-telescope-tilt) mechanism suggested by the preliminary design could not be completely implemented on the prototype. Also, the steering wheel adjustment was not completely restricted to the designated area from the preliminary design. This additional range in the steering wheel resulted in a significant discrepancy in driving posture from the standard driving posture assumed in the preliminary design process and will be discussed in detail in section 3.3.4. ~ Static Driving Posture. Table 3.7: Visibility Test Results Not Satisfied the Minimum VisibilitY Requirement No. [r~itials - PKM 2 JXO 3 TXB required downward viewing angle duw~wu~cl w~c~g ~e ox c: for the minimum visibility central instrument panel (unit: deg.) requirement (unit: deg.) 25 20 27 25 25 1 23 * Minimum visibility requirement: an object three and a half feet tall should be seen no more than two feet in front of bus, APTA (] 977) ANOVA analyses on the measured viewing angles were conducted to identify the effect of Stature Group (Appendix G.2.3.2~. The differences in stature did not significantly affect (p > 0.05) visibility over the steering wheel, RIP, farebox, or visibility of the left and right mirrors. Only the downward viewing angle over CIP was significantly affected (p < 0.01~; the t-test results shown in Appendix G.2.3.3 indicated that the visibility over CIP of the small group (24.7 degrees) was significantly less (p < 0.01) than those of medium (37.2 degrees) and large (35.2 degrees) individuals; no significant difference was found between the viewing angles over CIP of the medium group and those of large one. The means and 95 percent confidence intervals of the viewing angles over CIP of three stature groups are depicted in Figure 3. ~ I. - 3.24

Visibility Over Central Instrument Panel 40 a) 3 ._ > 3 3.3.4 Postural Comfort 3.3.4.! Static Driving Posture - 30 a) ~ 20 ._ 3 - 10 - ~ 24.7 - ! ~ 32.2 - ~ 32.6 small group medium group large group Stature Group Figure 3.1 I: Means and 95% Confidence intervals of Viewing Angles Over Central Instrument Pane! 1 Static driving postures were measured in the standard bus (Appendix G.2.4.~.~) and prototype bus (Appendix G.2.4. 1.2) respectively while the operators were holding the mid of steering wheel at '9 and 3' (positions of a clock), and were reaching the reference points of left instrument pane] (~IPRP), right instrument panel (RIPRP), accelerator pedal (APRP), and brake pedal (BPRP) in sequence. The joint angles measured were converted into postural comfort scores by using the postural comfort evaluation scheme (Table 3.~) - 3.25

which quantifies the magnitude of joint angle deviation from the standard driving posture within corresponding comfort range of motion (ROM). The postural comfort rating tables of selected body joints (elbow, shoulder, hip, knee, and ankle) are included in Appendix G.2.4. 1 .3. Table 3.g: Postural Comfort Evaluation Scheme Rating Scale | Range of Joint Angle _.. . 5 [a+0.56] 4 [a-0.56,a- 1.56]or[a+0.5G,a+ 1.56] [a- 1.56,a-2.56]or[a+ 1.56,a+2.56] 2 [a-2.56,a-3.56]or[a+2.56,a+3.56] 1 [ out of comfort ROM, maximum ROM ] (* a: joint angle in standard driving posture, ~ = comfort ROM/4) Table 3.9 summarizes the standard driving posture used in the development of preliminary design, the means and standard deviations of measured joint angles and their postural comfort scores of the standard and prototype bus workstations. The integrated comfort scores are 3.4 out of 5 for the standard bus and 3.9 for the prototype bus while 4.2 for the standard driving posture. - 3.26

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Large joint angle cleviations from the standard driving posture were found at shoulder (32.9 degrees of deviation) and elbow (24.4 degrees of deviation) flexion angles for holding the steering wheel in the standard bus, which indicates that the operators needed to stretch out their arms almost horizontally to grab the steering wheel. This presumably uncomfortable posture might be caused by the fixed steering column assembly with a flat (16 degrees of horizontal angle) and large (21 inches of diameter) steering wheel of the standard bus. The prototype improved the shoulder (23.1 degrees of deviation) and elbow (9.7 degrees of deviation) flexion angles for holding the steering wheel by providing a steering column telescope-tilt mechanism and a smaller size (18 inches of diameter) steering wheel for the operators. If the steering wheel adjustment had been implemented with the tilt-telescope-tilt mechanism suggested in the preliminary design and controlled only within the designated ranges, much better static posture results would have been · . anticipated. The means of shoulder and elbow flexion angles to reach the LIPRP in the standard bus were very similar to those of the standard driving posture. However, the mean of elbow flexion for LIPRP in the prototype bus was about 15 degrees larger than that of the standard driving posture, while the mean of shoulder flexion was similar to that of the standard driving posture. This larger than the assumed posture elbow flexion might explain the slightly farther (2.7 cm) location of the mean of LIPRP horizontal distance from NSRP than the neutral location of the preliminary design. The means of shoulder and elbow flexion angles for RIPRP of the prototype bus were different by approximately 5 degrees each from the standard driving posture. This postural variation could account for a farther (1 1.5 cm) location of the mean of RIPRP horizontal distance from NSRP than the neuka1 location of the preliminary design. - 3.28

In the pedal design, it was assumed that a total of knee and ankle angle movements is 20 degrees for a complete accelerator press and 30 degrees for a complete brake pedal press respectively. According to the difference of the means of knee and ankle flexion angles between un-pressed and full-pressed, the complete press of both the accelerator and brake pedals of the standard bus required 25.5 degrees of knee and ankle movements, whereas the accelerator of the prototype bus required 21.6 degree movements and the brake pedal of the prototype bus did 18.0 degree movements. The standard bus utilized a treadle pedal, while the prototype bus introduced a hanging pedal. Thus, empirically it was shown that a hanging pedal requires smaller knee and ankle movements than does a treadle pedal for the same amounts of pedal activation, which may contribute to greater comfort of the knees and ankles. 3.4.2 Dynamic Driving Posture Dynamic driving postures in the prototype workstation were analyzed to evaluate bus operators' continuously changing postures while maneuvering the prototype and to compare the results of static driving condition (discussed in section 3.3.4.1 Static Driving Posture) and dynamic driving condition in terms of postural comfort. Driving postures were videotaped for each subject in three test sessions: the second and the nineteenth laps of oval-track driving and lock-to-lock driving respectively. Elbow and shoulder motions in right side view were videotaped. Obstructions in the form of workstation components and restrictions of video camera installation in the workstation caused difficulty with videotaping other joint movements. The driving postures videotaped were sampled every 2.5 sec. and thus around 200 video frames per operator were captured in files using Vision 3000_ software system. Vision 3000_ is an ergonomic task analysis software which includes four independent - 3.29

modules: (1) posture analysis, (2) strength analysis, (3) NIOSH lift analysis, and (4) injury risk analysis. In this study, the posture analysis module was utilized to digitize the elbow and shoulder flexion angles of each video frame. The elbow and shoulder movements were graded into comfort scores according to the postural comfort evaluation scheme (Table 3.8 in Section 3.3.4.1). The distributions of joint movements of each subject were plotted (Appendix G.2.4.2.1) with respect to joint angle and postural comfort rating for the oval laps, the lock-to-lock steering maneuvers, and the aggregates ('synthesis') including the former two sets of driving postures respectively. Also a weighted postural comfort score was calculated on joint movements by summing the multiplied values of each comfort rating score and its relative occurrence ( £ comfort level(Ci)x percentage(P))). Figure 3.12 depicts an i=1 example of shoulder movement analysis on the entire video frames ('synthesis') for subject TAB, which shows 48.6% of the operator's shoulder flexion angles ranged from 5 to 15 degrees and 55.4% of the shoulder motions were rated as a most comfortable posture. In addition, a synthesized postural comfort score of the shoulder movements was 4.1 out of 5, which implies the operator maintained comfortable shoulder postures most of the time while simulating various bus operating tasks. - 3.30

Dvnamic Drivinq Posture Analysis - Shoulder Dvnamic Drivino Posture Analysis - Shoulder (subject 5, synthesis) (subject 5, synthesis) 48.6% 60% ~55.4% 40% 111 50% / ~ ~i 4 40%. 30%' I ~ ~I ~ ~ ~ ~30%- ~26.9% 19.4% ~ it 4 _ _ 20% !l 1 15.4% 20% t ~ ]0/ 1 1 15;3%403~82g~340yo 40/~ 1 1 6 ]03% -15 -5 5 15 25 35 45 55 5 4 3 2 1 Shoulder Flexion Angle (high) Comfort Level (low) l Figure 3.12: Dynamic Shoulder Movement Distributions During Operating the Prototype on the Oval-track and Lock-to-lock Courses Appendix G.2.4.2.2 presents the composite comfort scores of dynamic driving postures for two test session maneuvers (oval-track and lock-to-lock driving) and their aggregates. Also, the three comfort scores of static driving postures (steering wheel, L]:PRP, and RIPRP) associated with elbow and shoulder movements respectively are included and those scores were averaged for calculation of their composite score. The ranges and means of the comfort scores are summarized in Table 3. ~ O for comparison. - 3.31

Table 3.10: Comparison of Postural Comfort Scores of Static and Dynamic Driving Postures Test Condition static . · . arlvlng posture dynamic 1 · ~ arlvlng posture Test Session- Session steering wheel LIPRP synthesis oval-lap lock-to-lock synthesis _ Range 3~5 . ~ ~ ~ ~ ~ c ~ J ~ ~ ~ ~ ~ Shoulder I T Mean | 2.2 4.0 3.4 3.2 3.2: 2.3 1 3.2 1 4.5 4.5 4.2 4.4 3.2~4.7 2.8 ~ 4.8 3.2 ~ 4.6 4.1 3.8 4.1 l Range ANOVA results on the comfort scores of dynamic driving postures (Appendix G.2.4.2.3) indicated three significant effects: joint (p < 0.001), test session (p < 0.001), and their interaction effect (p < 0.025~. The comfort scores of both elbow (p < 0.008, see Appendix G.2.4.2.4 Paired t-test Results) and shoulder (p < 0.001, see Appendix G.2.4.2.4) significantly dropped in going from the oval lap to the lock-to-lock maneuvers. For the elbow joint this drop was from a mean of 4.1 to a mean of 3.8, while for the shoulder this was a drop from 3.2 to 2.3. This is not unexpected considering the much larger range of movements required from the more dynamic lock-to-lock maneuvers. However, more importantly, there was no significant difference (p = 0.801) due to stature, which indicates this drop was statistically the same for small-, medium- or large- sized individuals. Finally, an ANOVA analysis was conducted on the synthesized comfort scores (Appendix G.2.4.2.3) of both static and dynamic driving postures to identify significance of stature, joint (elbow and shoulder) and test condition (static and dynamic driving) effects. Only a main effect of joint was found significant (p < 0.001) and the other effects were insignificant (p > 0.05~. This indicated that the shoulder comfort scores were significantly (p < 0.001, see Appendix G.2.4.2.4) lower than the elbow for all three stature groups regardless of static or dynamic test condition. In turn, this result implies - 3.32

that the prototype workstation provided statistically equivalent amounts of postural comfort for the different sized operators throughout the testing. 3.3.4.3 Body Part Discomfort Evaluation Body part discomfort was evaluated four times (here, called as Test Session) using a rating scale from 7 (most comfortable) to -7 (most uncomfortable) during the course of prototype testing (Appendix G.2.4.3.1, data of the first subject RXE were treated as missing because a different rating scale was employed for the evaluation): (1) before driving, (2) after completion of 1 0 laps of oval track driving, (3) after completion of 20 laps of oval track driving, and (4) after completion of all driving (after lock-to-lock driving). The cumulative comfort level changes (relative to comfort levels of pre-driving) while driving (Appendix G.2.4.3.2) are summarized in Table 3.1 1, with negative values indicating decreases in comfort and positive values indicating increases in comfort. increasing negative numbers indicate . increasing discomfort during the course of testing. - 3.33

Table 3. ~ 1: Cumulative Body Part Comfort Level Changes Relative to the Beginning Test Session Body Part Neck Shoulder Elbow Wrist/Hand Back Hip/Thigh Knee Ankle/Foot Left shoulder Right shoulder Left elbow After 10 laps After 20 laps After driving Mean Mean Mean o.o 0.1 o.o -0.4 -0. 1 -0.2 -0.3 -0.2 -0.3 0.0 0.2 0.1 -0.1 -0.1 0 0 0.0 0.2 0.1 0.0 0.0 0.0 -0.3 -0.5 -0.4 -0.7 - 1.6 - 1.3 _ -0.7 -1 .1 -0.9 -0.8 - 1.2 - 1.2 0.0 0.1 0.0 -0.8 -0.9 -0.9 0.2 0.2 0.2 -0.6 -0.8 -o.s Right elbow Left wrist/hand Right wrist/hand Upper back Low back Left hip/thigh Right hip/thigh Left knee Right knee Left ankle/foot Right ankle/foot This trend was found for upper and lower back, left and right hips/thighs, right knee, and right ankle/foot. The first four are primarily influenced by seat design. Thus, even though, based on vibration isolation, the best of the available seats was selected, this seat may still not be optimum and may lead to fatigue over time. On the other hand, the right knee and ankle/foot do depend primarily on the pedal design. In this particular case, the original mechanical design with a high accelerator spring constant limited the positive effects of the hanging pedal design. - 3.34

ANOVA analysis results (Appendix G.2.4.3.3) indicated three significant effects on the changes in belly part discomfort over the course of testing: stature (p ~ 0.001), test session (p < 0.004), and their interaction effect (p < 0.001) were significant. Figure 3.13 (also see Appendix G.2.4.3.4 for detail information) shows that small operators experienced a significant increase in discomfort during 10 laps of oval track driving (p 0.001) but then only a slight discomfort change for the rest of the striving. The medium and large individuals responded with insignificant amounts of comfort level changes (p > 0.05) until the completion of driving. A detailed examination on the large comfort level change of the smaller individuals by body part as shown in Figure 3.14 (also see Appendix G.2.4.3.5 for detail information) indicates that greatest changes were experienced in the low back, right and left hips/thighs. These are all most affected by the seat design and less by workstation design. - 3.35

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3.3.5 Grip Force Grip force data (Appendix G.2.5.~) were collected using a hand dynamometer and a force measurement glove to evaluate the prototype workstation in terms of strength requirement for maneuvering the prototype and to identify any potential risk which may cause undesirable injuries to bus operators. Maximum grip forces were measured three times using a hand dynamometer at the initial participant interview and three measurements were averaged. The maximum grip forces ranged from a low of 28.5 kg to a high of 61.0 kg with a mean value of 45.8 kg. Each trial on the glove force data consisted of a 20 second duration during the lock-to-lock phase of the prototype testing. The glove contained seven force sensitive resistors (FSRs), one in each finger and two in the palm of the glove. After the 20 second trial, another 20 second trial was performed where the subject squeezed as hard as possible on the steering wheel. This maximum trial was used to determine percentage of maximum grip used in the lock-to-lock driving. Root-mean-square (RMS) grip forces during prototype testing ranged from a low of 0.9% to a high of 9.4% (with a mean value of 5.~%) as normalized to each individual's maximum grip force, while peak grip forces ranged from 4.3 to 48.7% of maximum grip force. RMS values are a better indicator of the average grip force required on the job, since the peak force could result from momentary spikes in the grip force values resulting from sudden road disturbances, and so on. Another potential measure is the 'impulse' required on the job, defined as the area under the grip force vs. time curve ~ |F.dt). Normalized again to each individual's maximum grip force, these values ranged from a low of 0.5% to a high of 6.g% with a mean value of 4%. This normalization is an important consideration since the absolute grip forces are less critical than the required forces as compared to each individual bus operator's maximum force capabilities. Thus, a bus operator should not be exerting a 'significant' proportion of his or her available strength to operate a bus. This 'significant' amount of - 3.37

relative force has been considered to be approximately 15% of maximum strength (Rohmert, 1960, Monod and Scherrer, 1965), since at that level there is not any significant occlusion of blood flow to the active muscle and an individual can maintain a static contraction at 15% of max for extended periods of time (typically over several hours, at which point the experiments have been terminated). Once the relative contraction level exceeds 1 5% of max. then muscle blood begins to become occluded and endurance time starts dropping rather quickly. Therefore, this 1 5% of max level has been considered the maximum acceptable grip force level with respect to limiting muscle fatigue and reducing the risk for cumulative trauma disorders (CTDs). Even the worst RMS (9.4%) or 'impulse' values (6.~%) measured during prototype testing were always lower than this critical value of 15%. Therefore, no evidence for muscle fatigue in grip exertions during prototype steering could be found. Analysis of variance (ANOVA) analyses were performed on grip force data assuming none of interaction effects were significant (Appendix G.2.5.2). The ANOVA results indicated that maximum grip force is dependent only on gender: the average male grip force (50.9 kg) is significantly (p < 0.006) stronger than the average female grip force (35.7 kg). Both differences in stature and the length of transit bus driving experience had not a significant effect on grip force (p > 0.05), which indicates that small individuals were not less strong than medium or large individuals and that novice transit bus operators and experienced transit bus operators were equally strong respectively. In terms of the relative proportion of maximum grip force utilized during steering the prototype workstation, there was not any significant gender, stature, or transit experience effect, i.e., females or smaller individuals did not utilize more their available max grip force than males or larger individuals. Similarly, novice bus operators did not utilize more force than experienced bus operators. This is a good result from the standpoint of developing CTDs. In many industries, new and inexperienced hires may exert higher than necessary force levels and, thus, become more susceptible to CTDs.

Lastly, correlation analyses were conducted to identify relationships between the maximum grip force and exerted RMS grip force and 'impulse' grip force (Appendix G.2.5.31. No significant relationship was found (p > 0.05) between them, which indicates that the magnitude of grip force exerted for steering was determined by individual difference, not by his/her musculoskeletal capability. Figure 3.15 plots these randomly exerted grip forces along max. grip forces. so .. 8 ~ i ~ ~ ._ _ H ~ v N 6 . ~ l~ Id - I ~ 4,, - ~ ~ 4 o L ~ 46 '; S I U 2 ~ 3.3.6 Ride Quality y=0.06x ~ 2.54 R2 = 8.1 % . O , , ~ ~ 1- , i 0 10 20 30 40 50 60 70 M ax. Grip Force (unit: Kg) 1 10 ~ 8 .! ~ H ~ ~ O V ·, ~ ._ 14 ~ - ~J - 4 ~ O ~ L ·4, i c, H ~ ; I ~ 6 4 1 I y = 0.07x ~ 0.85 R2 = 14.1 % O I Figure 3. ~ 5: Insignificant Relationships between Max Grip Forces and Exerted Grip Forces 0 10 20 30 40 50 60 70 M ax. Grip Force (unit: Kg) After testing the seven transit bus operator seats in the smaller bus, one of the best seats (#3) was chosen to be used in the prototype bus testing. The bus retrofitted for the prototype testing was a 1973 GMC 40 It bus. Twenty four subjects drove the prototype in a simulated bus route with right and left turns, and stops. Two accelerometers were used; one was placed on the floor of the bus, inside the seat base, and the second transducer was placed under the seat cushion (same as position #2 in the previous seat testing). A trial consisted of a minute of data from stop #! to stop #3. The aim of the - 3.39

testing was to compare the accelerations to those measured in the seat #3 testing in the smaller bus. In order to quantify the results, RMS, Peak, Crest, RMQ, VDV, and ratios of these values between floor and seat suspension were used, as before in the previous testing. Also, results were looked at on a frequency basis, namely using PSD's of the floor and suspension accelerations, and the acceleration transmissibility between floor and suspension. Finally, using subject data such as height, weight, and different seat position parameters, the Spearman Correlation Coefficients were generated in an attempt to correlate operator data with seat performance. As shown in Table 3.12 and 3.13, the accelerations in the floor were a little less than the values found in the previous testing. However, the suspension accelerations were comparable to the previous values. In addition, RMS shouldn't be considered in a transmissibility study, because RMS represents an overall average of the time series. Therefore, only the transmissibility on a frequency basis will be considered, as before with the previous seat testing. Specifically, the transmissibility at frequencies of 4.25 Hz and 7 Hz will be examined. - 3.40

Table 3.12: Floor Accelerations No Initials RMS Peak Crest RMQ VDV 11 RAS 0.0256 0.1165 4.5501 0.0468 0.1301 12 SCR 0.0222 0.1400 6.3169 0.0495 0.1378 13 DCB 0.0259 0. 1410 5.4434 0.0511 0.1425 14 ALD 0.0260 0.1173 4.5092 0.0521 0.1448 15 RLH 0.0275 0.1150 4.1895 0.0506 0.1408 16 WAM 0.0229 0.0961 4.2076 0.0431 0.1198 20 KAK 0.0235 0.1088 4.6302 0.0443 0.1236 21 RAL 0.0268 0.1140 4.2454 0.0475 0.1322 22 CAM 0.0248 0.0985 3.9647 0.0470 0.1307 23 NRK 0.0238 0.1133 4.7508 0.0462 0.1283 24 KLM 0.0268 0.1088 4.0621 0.0474 0.1319 Table 3.13: Suspension Accelerations No. Initials RMS Peak Crest RMQ VDV 11 RAS 0.0329 0.2208 6.7142 0.0665 0.1850 12 SCR 0.0313 0.2786 8.8976 0.0768 0.2127 13 DCB ~0.0362 0.2718 7.4992 0.0772 0.2150 14 ALD 0.0339 0.2048 6.0435 0.0704 0.1957 15 RLH 0.0330 0.2330 7.0618 0.0693 0.1930 16 WAM 0.0306 0.2172 7.0894 0.0637 0.1774 20 KAK 0.0261 0.1884 7.2047 0.0554 0.1546 21 RAL 0.0281 0.1702 6.0582 0.0540 0.1503 22 CAM 0.0281 0.1757 6.2567 0.0582 0.1618 23 NRK 0.0264 0.1885 7.1466 0.0566 0.1575 24 KLM 0.0306 0.1683 5.4974 0.0578 0.1607 - 3.41 -

Figure 3 . ~ 6 and 3. ~ 7 below show the average PSD's of the floor and seat accelerations. Also, looking at Figure 3.18, the transmissibilities for both the prototype testing and the previous seat testing were comparable, with a peak around 2 Hz and attenuation at the higher frequencies. Specifically, the seat performed better at attenuating the vibration at 4.25 Hz flower back resonance) in the prototype testing, which indicates the validity of the ride quality simulator testing in the smaller bus. 0.045 0.04 0.035 0.03 I 0 025 0.02 0.015 0.01 0.005 o 0 ~ 10 15 20 Frequency (Hz) Figure 3. 1 6: Average Floor PSD - Prototype Results - 3.42

0.07 0.06 0.05 I 0 04 ~0.03 0.02 0.01 2.5 2 u u u u 1 c o . _ in c ~ 0.5 cn O ~' 0 ~10 15 20 Frequency (Hz) Figure 3.17: Average Suspension PSD - Prototype Results .` '. --- Small Bus Seat , ', ,` Comparison I' .,' ~ '` - Prototype Testing .' '` . ~ ~1.5 I '. , ., \.,. IL . ., `. , ~\ L' at \ ~, ,, A, `~? ~ ~. ,, ~ ~ ~ . O O ~ 4 6 Frequency (Hz) 8 10 Figure 3.~: Average Floor / Suspension Transmissibilities - 3.43

Finally, Spearman Correlation coefficients were calculates! using the data shown in Table 3.14. The results are shown in Table 3.15. As shown in Table 3.15, the only strong correlation which exists involving the RMS ratio is SRP height. The SRP height correlation (2.5 % significance) is due to the fact that the height is controlled by allowing more air in the air bag spring of the seat suspension. Thus, as height increases (more air), the RMS ratio decreases, as one would expect. Finally, the other strong (less than ~ % significance) correlations involve subject height and weight, subject height and SRP horizontal distance, and subject weight and SRP horizontal distance. These are intuitive and are included for completeness. - 3.44

cd c) a' v: au - as o ~ x I ~ o ~ x con ~ o o ~ ~ x o ~ x ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ l ~-~ u) .~o- is - 'e ~ ~ ~ ~ to to ~ ~ ~ ~ ' I x cn ~ ~ ~ ~ ~ 0 ~ 0 ~ x to ~ to to ~ l ~ ~ to ~ of .~ ~ ~ ~ ~ ~ ~ ~ no - u) ~ x ~ ~ ~ ~ ~ o ~ ~ x ~ ~ ~ ~ ~ o ~ ~ ~ ~ x ~ ~ . . ~ ~ ~ ~ ~ KD ~ ~ ~ ~ ~ o ~ ·= o o o o o o o o o o o ·v) ~ o o o o o o o o o o o ~v:~= ~ ~ ~ a~ 0 ~ ~ oo x ~ 0 v: 5 · · ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ = o o o o o o o o o o o ~ o o o o o o o o o o o O' -= ~ ~ ~ ~ o ~ ~ ~ o ·. ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ = o o o o o o o o o o o 0 ~s 0 0 0 0 0 0 0 0 0 0 0 U~) ~ ~ ~ 0 ~ ~ ~ X oo oo oo V: ~ ~ ~ ~ ~ ~ ~ ~ ~o `5 · · 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 oc ,0 ~_ ~ X Cd Ct · ~ _ _ _ s0 O · ~_ ~ ~ ~ ~ ~ ~ ~ ~ ,1 ~ c~ ~ ·= ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ S-s ~- - - o o o ~ ~ ~ ~ ~ ~ oo oo - o ~ ~ ·= ~ O ~ ~ _ ~ ~ _ v: ~ _ __ _ ~ x ~ ~ ~ ~ o ~ ~ o o ~ .- ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ l ~ oo ·= - O ~ _ .= . . ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ l ·= ~ ~ oo ~ ~ ~ ~ x ~ ~ ~ , ~ ~ m ~ ~ 2 ~ ~ 2 ~ 2 :- ~ ~ ~ ~ ~ 3 ~ ~ ~ z ~ 0 _ ~ ~ ~ ~ ~ 0 _ c~ z _ _ _ _ _ _ ~ ~ ~ ~ ~

Table 3.15: Correlation Coefficients Height | Weight ~ SRPHorz | SRP | Seat Back l | | Height | Angle 0.1609 -0.1326 -0.2422 ~0~5 0.1812 Sig: Sig: Sig: $~: Sig: 0.567 0.638 0.385 ~ 095 0.518 - ~ Sag ~ Sig: ............. 0.0824 0.2124 1 1 ..-.~.~. ~os.7g7o 1 ~ 0.2942 -0.3721 Sig: Sig: 0.287 0.172 -0.2619 RMS Ratio Height Weight SRP Horz SRP Height Seat Back Angle Shade Key: 5 % Significance 1 TO Significance 3.3.7 Comments and Recommendations The test concluded with a survey of comments and recommendations (Appendix G.2.7.1) on the prototype workstation from the operators. The opinions were summarized as shown in Table 3.16 according to their associated workstation component. The seat with an arm rest was preferred. However, it was observed that most of the operators did not use the arm rest since they seemed to prefer efficient steering manipulation to comfortable arm support. A seat with less bouncing was desired by three operators to stabilize their driving postures. - 3.46

Table 3.16: Summary of Comments and Recommendations on the Prototype (Note: Numbers in parenthesis denote the number of responses) Workstation I preferred design concepts ~ suggestions for improvement Component seat arm rest (1) more stability/firmness (3) steering wheel 1 8 inch size (5) hub tilt (6) padding (2) bigger size (2) pedals hanging pedal (6) smaller pedal force (6) bigger accelerator plate (2) wider spacing (2) farther pedal location from steering column (2) l | treadle pedal (1) Left Instrument more clearance for leg (4) Panel l l Right panel layout (9) more clearance for leg (2) Instrument inadvertent passenger activation (1) Pane] better control type (1) Floor Mounted floor mounted signal (1) Signal Mirrors convex mirrors for better visibility (3) Farebox lower farebox height (4) l | rearward farebox location (2) Stop synthesized voice operator announcement (1) Announcement announcement (1) System The small size (18 inch diameter) steering wheel obtained positive responses from five operators due to its easy manipulation, while a bigger steering wheel was recommended by two operators. The soft leather pad on the steering wheel was found satisfactory. The fixed steering hub should be replaced with a tillable one complying with the preliminary design for better visibility. Six bus operators responded that the hanging pedal is an improvement to treadle pedals used in conventional buses because they could apply the pedals with smaller ankle angle in conjunction with leg movements. In contrast, one operator still preferred a treadle pedal. It was identified that pedal resistance' spacing' and location should follow - 3.47

the preliminary design for ease of peda!! activation and comfortable leg posture. The accelerator pedal plate with a size of 2 in. x 5.5 in. needs to be bigger. Many of the operators appreciated the installation of right instrument pane! (RIP) and its layout because the RIP provided an easy access to controls frequently used during driving and eliminated a necessity of alternate head movements in a conventional bus to operate controls in a left instrument pane} (LIP) and monitor passengers for depositing and picking up. However, an unauthorized activation of RIP controls was concerned due to their exposure to the public and should be protected. More clearance between the seat and the LIP and RIP was recommended. Several operators suggested an installation of convex mirrors on the plane left and right mirrors for better visibility including an elimination of blind spots. Also for better visibility, the farebox with a height of 34.5 inch should be lowered and moved back in the bus. Lastly, some concerns were given to the floor mounted signal system and public announcement system. Even though only one operator gave a positive opinion on a synthesized voice system employed in the prototype, most of the operators in the test enloyed benefits ofthe digital voice system. - 3.48

Next: Chapter 4. Conclusions »
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