Bus Operator Workstation Evaluation and Design Guidelines Final Report (1997) / Chapter Skim
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Chapter 3. Prototype Construction and Testing
Chapter 3. Prototype Construction and Testing
Pages 85-132
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From page 85... ...
The first major task was to remove the seat, instrument panels, front heater, modesty panel, steering wheel, etc. from the workstation.
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From page 86... ...
.' - ~ ~ : c! If Figure 3.~: Original GMC Workstation ~: ~.
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From page 87... ...
The left instrument panel (LIP) needed to be constructed to provide the necessary adjustment required by the design specifications.
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From page 88... ...
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.
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From page 89... ...
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)
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From page 90... ...
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)
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From page 91... ...
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
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From page 92... ...
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)
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From page 93... ...
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.
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From page 94... ...
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.
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From page 95... ...
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.
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From page 96... ...
- ~ / 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!
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From page 97... ...
, 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.
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From page 98... ...
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.
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From page 99... ...
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.
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From page 101... ...
,~ i10 1 1 1 1 ,4 ~ fx~ | R] PRP_~ tJ AX jAPPRP | Comparison of the Design Values and the Prototype Test Results (Plan View)
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From page 102... ...
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)
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From page 103... ...
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)
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From page 104... ...
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)
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From page 105... ...
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
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From page 106... ...
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)
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From page 107... ...
~ ~ 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)
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From page 108... ...
~ Static Driving Posture. Table 3.7: Visibility Test Results Not Satisfied the Minimum VisibilitY Requirement No.
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From page 109... ...
1 Static driving postures were measured in the standard bus (Appendix G.2.4.~.~) and prototype bus (Appendix G.2.4.
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From page 110... ...
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.
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From page 112... ...
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.
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From page 113... ...
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.
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From page 114... ...
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.
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From page 115... ...
and their aggregates. Also, the three comfort scores of static driving postures (steering wheel, L]
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From page 116... ...
of both static and dynamic driving postures to identify significance of stature, joint (elbow and shoulder) and test condition (static and dynamic driving)
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From page 117... ...
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)
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From page 118... ...
In this particular case, the original mechanical design with a high accelerator spring constant limited the positive effects of the hanging pedal design.
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From page 119... ...
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.
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From page 120... ...
n 5 C t ~ C at: c a 1 ~To ~ .
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From page 121... ...
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.
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From page 122... ...
, 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.
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From page 123... ...
~ 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)
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From page 124... ...
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.
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From page 125... ...
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.
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From page 126... ...
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)
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From page 127... ...
Figure 3.17: Average Suspension PSD - Prototype Results .` '. -- - Small Bus Seat , ', ,` Comparison I' .,' ~ '` - Prototype Testing .' '` .
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From page 128... ...
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.
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From page 129... ...
cd c)
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From page 130... ...
A seat with less bouncing was desired by three operators to stabilize their driving postures.
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From page 131... ...
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.
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From page 132... ...
The accelerator pedal plate with a size of 2 in.
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