Questions? Call 888-624-8373

PAPERBACK
list:$125.50
Web:$112.95
add to cart

Rights & Permissions

topleft topright

TCRP Web Doc 1 Bus Operator Workstation Evaluation and Design Guidelines: Final Report (1997)
Transportation Research Board (TRB)

Page
85
bottomleft bottomright
  E-mail
 Facebook
 Digg
 Stumble
 Twitter
More
Page
85

Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 85
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.!

OCR for page 86
.' - ~ ~ - : c! If Figure 3.~: Original GMC Workstation - ~: ~. ~ ~ . . ~ . J.~. . ~ ~ ~ ~ . .. ~ ~ . .. ~:~.~.~ ::! _ . . .. it_ Figure 3.2: Retrofitted Workstation - 3.2 \ . : i \ . . . it.. .~............. .

OCR for page 87
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

OCR for page 88
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

OCR for page 89
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

OCR for page 90
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

OCR for page 91
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

OCR for page 92
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

OCR for page 93
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

OCR for page 94
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

OCR for page 95
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.~]

OCR for page 122
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.

OCR for page 123
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

OCR for page 124
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

OCR for 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. 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 -

OCR for page 126
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

OCR for page 127
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

OCR for page 128
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

OCR for page 129
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 _ _ _ _ _ _ ~ ~ ~ ~ ~

OCR for page 130
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

OCR for page 131
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

OCR for page 132
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

Representative terms from entire chapter:

grip force