Bus Operator Workstation Design for Improving Occupational Health and Safety (2016)

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80 A P P E N D I X B Bus Operator Workstation Engineering CAD Model Specifications Introduction The following information is provided in order to demonstrate the steps and specifications that were applied to the creation of the Engineering CAD Model which was then exported into the 3-D PDF Model. Bus Operator Workstation, Engineering CAD Model, Packaging Reference Components, and Points Two operator packaging points were established as the references around which the seat and steering wheel positions are based. The first point is the accelerator heel point (AHP), which is located at the centerline of the heel of the right shoe on the accelerator pedal at rest. The second point is the accommodation tool reference point (ATRP) as defined in SAE J1516. Before being able to develop these points, it was important for the research team to obtain the specification of a seat h-point either through CAD drawings released from the seat manufacturer or through methods of physical measurement. The research team was able to obtain a specification of the seat h-point from a 2-D CAD drawing that had been developed by the seat supplier. This point was a seat index point (SIP) that is constructed through a common practice (see SAE J1163) that stems from ISO 5353. Other seat h-point procedures are typically developed in other highway vehicles and referred to as the seating reference point (abbreviated SgRP). They can be constructed using the SAE J826 H- Point Machine (HPM) or using SAE J4002 HPM-II. However, the SIP can be suitably applied and provided sufficient detail to generate the necessary packaging reference points. The dimensions for the SIP in the seat drawing reference a seat-belt anchorage point (see Figure B-1).

Bus Operator Workstation Engineering CAD Model Specifications 81 Figure B-1. Seat index point (SIP) position relative to seat-belt anchorage point as defined in a seat supplier drawing. The seat position was assumed to be at the full down position. The derivation of the accelerator heel point (AHP) per SAE J1516, Equation 4, requires first selecting a seat height. The drawing provided by the seat supplier demonstrated one example of a typical h-point height range, which when measured to the pedal floor (H30) extended from 412 to 578 mm. Rather than relying on a purely theoretical H30 value or range, the research team selected the mid-vertical h-point value of 495 mm and applied it to Equation 4 to obtain the shoe plane angle (SPA) of 37°. A shoe plane was constructed to align with the accelerator pedal. The shoe plane imitated a 95th percentile male shoe from the National Institute for Occupational Safety and Health (NIOSH) survey (Guan et al. 2012). The shoe plane had a length of 334 mm and a width of 126 mm. This plane was constructed as a 3-D model. One end was aligned with the pedal floor and the plane was inclined 37° above the pedal floor. The shoe plane was brought into contact with the accelerator pedal pad. The centerline of the rear edge of the shoe plane that makes contact with the pedal floor was the AHP. This model is demonstrated in Figure B-2. Figure B-3 demonstrates the position of the AHP relative to the workstation reference system (WRS) absolute zero.

82 Bus Operator Workstation Design for Improving Occupational Health and Safety The resulting AHP coordinates in the model were as follows: Xc: 1714.9 mm Yc: 500.5 mm Zc: 0.0 mm Figure B-2. The determination of the AHP according to SAE J1516.

Bus Operator Workstation Engineering CAD Model Specifications 83 Figure B-3. The AHP reference from WRS absolute zero. The second point, the accommodation tool reference point (ATRP), is again based on the mid- vertical h-point value of 495 mm. The ATRP was derived from a 50th percentile accommodation tool reference line (ATRL) as defined per SAE J1516. A 50:50 male-to-female gender ratio was selected for the transit bus operator population (SAE J1516, Eq. 1). This decision was based on data from workforce population data on transit and other bus vocation operators per Equal Employment Opportunity (EEO) tabulation from 2006 to 2010 (U.S. Census Bureau). The resulting ATRP was 495 mm above the AHP, 578 mm rearward of the AHP, and along the operator centerline (outboard 249.7 mm) (see Figure B-4). The resulting deltas from the AHP to the ATRP in the model were as follows: X = 578.0 mm Y = 249.7 mm Z = 495.0 mm

84 Bus Operator Workstation Design for Improving Occupational Health and Safety The resulting ATRP coordinates in the model were as follows: Xc: 1136.9 mm Yc: 750.2 mm Zc: 495.0 mm Figure B-4. Seat calculated ATRP (SAE J1516) from WRS absolute zero. The suggested steering wheel diameter in the guideline is 457 mm. That same dimension was applied to the size of the steering wheel in the model (see Figure B-5). The point that is on top of the rim face and located in the center of the steering wheel diameter is commonly referred to as the steering wheel point (SWP). This point serves as another workstation packaging reference point and is useful to specify the location and range of adjustment for the steering wheel.

Bus Operator Workstation Engineering CAD Model Specifications 85 Figure B-5. Suggested steering wheel size (457 mm) with rim top/diameter center steering wheel point (SWP). Seat and Steering Wheel Adjustment Range Following the declaration of the two fiducial package points, AHP and ATRP, the seat travel range and steering wheel range were developed. The research team utilized multiple ATRLs to develop boundaries for a range of seat adjustments that accommodates 95 percent of the operator population (see Figure B-6). This was accomplished by applying the ATRL 2.5 percentile equation to define the front limit of the seat travel and the 97.5th percentile equation to define the rear limit of the seat travel. The current production seat height range example of 412 to 578 mm was inserted as the “Z-values” in the 50:50 gender ratio equations (SAE J1517, Eq. 1 “X_97.5” and Eq.1 “X_2.5”). This h-point range closely approximates the shape of a parallelogram with boundary points as specified below and demonstrated by the four outer blue spheres in Figure B-6. The SIP sphere stays fixed relative to the seat cushion as the seat is adjusted vertically and horizontally. The ATRP sphere is provided for comparison. Another sphere, the ATRP 95th sphere, represents a typical reference position for vehicle manufacturers with the seat at mid-vertical along an ATRL that follows a 95th percentile curve. This would fall in front of the rearward-most suggested seat travel line, which was set to follow the 97.5th percentile ATRL curve. The SgRP is also provided at the h-point position when the seat is located at full rearward and full down.

86 Bus Operator Workstation Design for Improving Occupational Health and Safety Full Rear, Full Up re. AHP X = 644 mm Z = 578 mm Full Rear, Full Down re. AHP (SgRP) X = 722 mm Z = 412 mm Full Forward, Full Up re. AHP X = 436 mm Z = 578 mm Full Forward, Full Down re. AHP X = 490 mm Z = 412 mm Figure B-6. Seat adjustment range as calculated using 2.5th percentile and 97.5th percentile ATRL (SAE J1517) with SIP, ATRP, and SgRP.

Bus Operator Workstation Engineering CAD Model Specifications 87 Using the SWP described along the rim top and diameter center, the steering wheel center point was positioned using a combination of vehicle data from the physical measures of a similar column and a result of the guideline development analysis. As evident in Figure B-7, the separation of the SWP from the AHP is 221 mm horizontal (SAE J1100 dimension “L11”) and 770 mm vertical (SAE J1100 dimension “H17”). The required minimum steering wheel tilt range is ±15o (suggested was ±20o). The required range was applied for the CAD guideline model along with a steering wheel telescope range of ±55 mm (see Figure B-8). The mid-range SWP position was set at 27o rear of vertical. This telescope range is known to be much larger than some current production transit bus columns provide today, but this feature would allow for a significant increase in accommodation for transit bus operators. Mid-Tilt, Mid-Telescope re. AHP X = 221 mm Z = 770 mm Y: 27° Figure B-7. Steering wheel SWP relative to AHP at the middle of the suggested tilt/telescope adjustment range.

88 Bus Operator Workstation Design for Improving Occupational Health and Safety Figure B-8. The suggested steering wheel tilt/telescope adjustment range. The angles are measured relative to vertical or SWP mid-range angle and heights are relative to AHP. Application of the SAE RPs for Bus Operator Packaging Envelopes Other packaging envelopes can be derived by applying the ATRP values into the appropriate SAE RPs such as eyellipses (SAE J941, Appendix E), shin/knee clearance contours (SAE J1521), and stomach clearance contour (SAE J1522). The Z-value of the ATRP (H30) was applied in determining the shin and knee contours for establishing clearance zones for the operator’s legs when applying the pedals, in accordance with SAE J1521. Since transit bus vehicles are almost universally driven by automatic or automated-manual transmissions, the clutch shin and knee contours were not applied. The left foot and leg are used by transit bus operators to control the foot-switch turn signals and high beams. Therefore, clearance zones for the accelerator pedal were applied to both the right leg shin and knee contours as well as the left leg shin and knee contours. A 50:50 male-to- female gender ratio was selected and the ATRP Z-value was inserted into equations 7 and 8 to obtain the delta X and Z contour reference values from the ATRP (dX = 431.8 mm forward, dZ = 19.6 mm up). This contour reference was positioned at the operator centerline. A constant-radius arc of 113.25 mm was drawn at the operator centerline from the contour reference as directed in SAE J1521. The RP does not specify the width of the clearance or the arc-length. The clearance contour was extended on both sides of the column cover to fully cover the areas of shin and knee motion. The arc-length was arbitrarily selected to extend from directly

Bus Operator Workstation Engineering CAD Model Specifications 89 above the contour reference forward and around 160°. See Figure B-9 for top and right-side views of the shin/knee contours. Figure B-9. Shin/knee contours and stomach contours referenced from the AHP. Contours pictured with steering wheel at mid-range adjustment and seat at supplier-provided position. Left- upper image is a top view of all contours. Left-lower image is a right-side view of the construction of the stomach contour. Right-lower image is a right-side view of the construction of the knee/shin contours. The stomach clearance contour was built according to SAE J1522 in a very similar fashion to the shin and knee contours. A 50:50 male-to-female gender ratio was selected and the ATRP Z-value was inserted into equations 1 and 2 to obtain the delta X and Z contour reference values from the ATRP (dX = 59.9 mm forward, dZ = 193.5 mm up). The contour reference was positioned at the operator centerline. A constant-radius arc of 157.46 mm was drawn at the operator centerline from the contour reference as directed in SAE J1521. Again, the RP does not specify the width or arc-length. The clearance contour was extended from the operator centerline both left and right to match the width of a 95th percentile Male Abdominal Breadth, Sitting dimension (471 mm) as defined by the NIOSH survey. Again an arbitrary arc-length was selected to extend from directly above the contour reference forward and around 160o. See Figure B-9 for top and right-side views of the stomach contour.

90 Bus Operator Workstation Design for Improving Occupational Health and Safety The 3-D eyellipses were constructed according to the process specified for Class B vehicles in SAE J941, Appendix E. The size of the two identical eyellipses was constructed with axes defined by a 95th percentile eyellipse and Seat Track Travel (TL23) greater than 133 mm. Each eyellipse had a centroid represented by a sphere at its axes’ centers. The two eyellipse centroids were separated by ±32.5 mm around the operator centerline such that the centroids were separated by 65 mm. The mid-point of the two eyellipse centroids is referred to as the mid-eye centroid, which simply represents a geometric reference between a user’s eyes—literally on the user’s bridge of the nose. The position of the mid-eye centroid was determined by applying the 50:50 gender ratio equations E1 (ATRP X-value rearward of AHP) and E2 (ATRP Z-value above AHP) in SAE J941, Appendix E. Additionally the process requires selection of a seat or manikin torso angle rearward of vertical (A40). The research team selected 10o for this value. This design value was obtained from the same example of a current production seat and transit bus described for determining the operator package references of the ATRP and AHP. The mid-eye centroid was aligned with the operator centerline. The eyellipses were also rotated 11.6° below horizontal and around the cross-bus axis (Y-axis). The resulting eyellipses are available to review in Figure B-10. Eyellipse Construction Specifications Axis Lengths: X = 198.9 mm Y = 105.0 mm Z = 86.0 mm Mid-Eye Centroid w.r.t. AHP X = 529.5 mm Y = 249.7 mm Z = 1150.4 mm Side-View Tilt around Y-axis: 11.6° below horizontal It is worth noting that the process for Class B vehicles in SAE J941, Appendix E, calls for a second rotation of 5.4o to the right of operator centerline in top view or toward the passenger- entry area of the bus. However, the researchers chose not to apply this rotation. This rotation has been removed from the current SAE Class A (auto) eyellipse development processes as they have been demonstrated to provide little utility in visibility analyses (SAE J941 2010; Manary et al. 1998). The same conclusion has been supported in similar exercises that are in progress to update the SAE Class B eyellipses (Reed 2005). However, it has not been removed from the current version of the Class B eyellipse process (SAE J941, Appendix E, 2010).

Bus Operator Workstation Engineering CAD Model Specifications 91 Figure B-10. Eyellipses in 3-D form as developed by SAE J941, Appendix E. Mid-eye centroid dimensions are relative to the AHP. The eyellipse envelopes can be useful for many visibility analyses. The most pertinent application for a transit bus is the demonstration of the upward and downward forward-visibility tangent 2-D curves or 3-D sheet bodies. The result of the CAD guidance eyellipses in the suggested package demonstrates that the APTA downward visibility target should be visible to most operators. Likewise, the APTA upward visibility minimum angle of 15o above horizontal passes easily under the top edge of the windshield opening (see Figure B-11).

92 Bus Operator Workstation Design for Improving Occupational Health and Safety Figure B-11. The visibility sheets extend between the eyellipse tangents and down to the APTA visibility target or up to the APTA visibility angle above horizontal. The dotted lines demonstrate a current production example of visibility performance that meets and exceeds both requirements. Application of Other Bus Operator Packaging Processes A guideline for in-vehicle display systems was developed by the Japan Automobile Manufacturers Association (JAMA 2004). One feature of this guideline is a requirement for the maximum downward viewing angle for vehicle displays. This requirement states that at least half of each display must be visible at or above the angle prescribed in the guideline. This lower limit is described for most automotive vehicles as being 30° below horizontal. However, the guideline also provides the following formula to increase the inclination of the viewing limit according to eye point height when the reference eye point is above 1,700 mm from the ground. Inclination [deg] = 0.013 × eye point from ground [mm] + 15

Bus Operator Workstation Engineering CAD Model Specifications 93 The eye point being described in the formula is referred to as the Japanese Industrial Standard (JIS) eye point, which can be determined by constant offset dimensions from the SAE eyellipse mid-eye centroid as follows (Driver Focus–Telematics Working Group [2006]): SAE Eyellipse to JIS Eye Point Constant X = 22.9 mm rearward Z = 8.4 mm up This JIS eye point was determined to be located at the following dimensions: Xc: 1162.5 mm Yc: 750.2 mm Zc: 1158.7 mm The height of this point is determined by adding the height above the AHP and the AHP to ground delta. The resulting height of the JIS was equal to 1,937.3 mm above ground. The resulting angle for the suggested workstation was 40.3° below horizontal. The resulting display downward viewing limit is demonstrated in Figure B-12, which falls approximately on the mid- length of the center gauge panel display in the model. Figure B-12. The JAMA downward display visibility limit starts at the JIS point and runs along the JAMA-calculated angle below horizontal. The JIS point to mid-eye centroid dimensions and display angle (40.3 ) are illustrated. 5°

94 Bus Operator Workstation Design for Improving Occupational Health and Safety Another useful envelope is suggested by the APTA guideline regarding front and side sun visors/shades. The guideline suggests that “the visor when deployed, shall be effective in the operator’s field of view angles more than 5° above the horizontal.” The guideline also states that the “deployment of the visor shall not restrict vision of the rearview mirrors.” This requirement would create a conflict were it not for the recent addition in the 2013 version of the guideline allowing for the alternative of roller type sunscreens. That alternative makes no mention of the coverage of view angles. Therefore, the Engineering CAD Model will include optional sun visor 5° upward view angle sheet bodies that run tangent from the eyellipses forward through the windshield and sideways through the operator-side glass. These sheet bodies can provide a useful reference for the development of sun visors or sunscreens while highlighting the balance that must be struck with top-mounted rearview mirrors as demonstrated in Figure B-13. Figure B-13. These forward and operator-side glass sheet bodies demonstrate the APTA minimum requirement for sun shade/visor performance, 5° above horizontal. An envelope was developed for the Engineering CAD Model and is demonstrated in Figure B-14. This envelope was developed using the human modeling software. Reach surfaces were developed for all six manikins that will be discussed in the section on digital human modeling validation (see Chapter 5 – Human Modeling Validation of Bus Operator Workstation Design Guidelines). The reach surfaces were constructed referencing the clavicle to index fingertip for each arm, left and right.

Bus Operator Workstation Engineering CAD Model Specifications 95 The result of these six surface section curves at Zc: 600 is visible in Figure B-15. The final reach curve was selected by comparing the six manikins based on their varying seat positions and arm reach distances. The reach curve for manikin Female U was the worst-case forward reach. Based on that result an additional reach envelope was developed for the same manikin from the clavicle to hand grasp (see Figure B-16). The worst-case forward reach was selected as the primary control reach curve along with the maximum reach curve for controls requiring the whole hand grasp, as demonstrated in Figure B-17. Both were applied in the Engineering CAD Model. Figure B-14. The reach surface envelope developed from manikin Female U represents maximum reach rotating from clavicle and extends to the index fingertip for left and right arms.

96 Bus Operator Workstation Design for Improving Occupational Health and Safety Figure B-16. The reach surface envelope developed from manikin Female U represents maximum reach rotating from clavicle and extends to hand grasp for left and right arms. Figure B-15. All manikin reach surfaces were sectioned on the surface at Zc: 600 and compared.

Bus Operator Workstation Engineering CAD Model Specifications 97 Figure B-17. The reach curve section on the surface at Zc: 600 for manikin Female U. The solid curve provides the maximum reach for primary controls that are required for safe operation of the vehicle in motion. Hand grasp controls should be kept within the dotted curve. Clearance envelopes are necessary around the bus operator’s pedals to provide unrestricted access to move the shoe and foot up and down on the accelerator pedal, transition to the brake pedal, and activate the brake smoothly without interruption. The ISO 16121-1 guideline provides a requirement that has been included in these guidelines. The right foot well envelope requires clearance across the accelerator and brake pedals with additional clearance on both sides. Per the ISO requirement, the foot well envelope provides at least 350 mm forward of the AHP (see Figure B-18).

98 Bus Operator Workstation Design for Improving Occupational Health and Safety Figure B-18. Bus operator clearance envelopes for pedal and shoulder-elbow clearance per ISO 16121-1:2012. The left image provides a forward view of the front of the bus operator workstation. The right image provides a rear-isometric view of the same envelopes. Clearance envelopes are also necessary for bus operators around their shoulders and elbows to provide sufficient clearance to rotate the steering wheel, reach for controls on the instrument panels, and turn within the seat when viewing the road environment. ISO 16121-1 also provides a requirement for this clearance that has been included in these guidelines. A rectangular envelope is centered around the bus operator seat, requiring a minimum of 400 mm on each side and a total clearance of 800 mm, as demonstrated in Figure B-18. Clearance around the steering wheel to all surrounding controls and the instrument panel is important for bus operators to provide smooth control of the bus while turning. This clearance should be provided in all steering wheel tilt and telescope adjustment positions. A minimum hand clearance of 38 mm has been constructed for this guideline based on typical hand with glove clearances required for manual labor and around vehicle access grab handles. An image of this clearance is provided in Figure B-19.

Bus Operator Workstation Engineering CAD Model Specifications 99 Figure B-19. Steering wheel hand clearance. Bus Operator Workstation Suggested Access Envelopes There are multiple elements that affect workstation access. One that is commonly provided for in at least the two physical transit buses that were benchmarked is a steering wheel tilt that is forward of vertical. This can increase the access clearance between the seat and steering wheel or seat floor and column. While this position is not practical for normal vehicle operations, it is a useful setting that has been maintained in the Engineering CAD Model. This position was set with the telescope at full up (+55 mm from mid-position) and the tilt at 5° forward of vertical as illustrated in Figure B-20. Although this concept of forward-of-vertical steering column tilt is not a novel one for transit buses today, the new steering wheel adjustment range that has been suggested may make this access position difficult to produce. One solution might be to provide a separate pivot point and quick-release lever on the column that would allow the operator to quickly move the steering wheel out of a normal driving position and then return it to a preferred position easily upon return.

100 Bus Operator Workstation Design for Improving Occupational Health and Safety Figure B-20. An additional steering wheel position which tilts forward of vertical 5° with telescope at full upward extension is demonstrated to increase operator access into and out of the workstation area. The step heights are another important element of operator workstation access. The floor height provided by the partnering manufacturer was used as an example in the model of how a balanced step height is suggested. The dimensions of that height from passenger floor to step and step to pedal floor may vary with other pedal floor heights. The guideline update provides maximum floor and step height dimensions. The APTA guideline lists dimensions for the operator-side glass to protect the operator’s direct line-of-sight view. These dimensions also provide a useful reference for an emergency access hatch for the operator. This might become more critical in the future as thermal or security enclosures are added around the operator workstation. Figure B-21 illustrates the APTA forward (840 mm rear of AHP) and upward (560 mm above AHP) limits for the glass. The SAE RP for access systems, SAE J185, suggests a minimum rectangular opening (470 × 650 mm) for this emergency access. This solution could be applied to the window opening within the operator’s sliding side-glass feature.

Bus Operator Workstation Engineering CAD Model Specifications 101 Figure B-21. Balanced step heights and optional consideration of emergency access hatch (SAE J185) through operator-side glass. The emergency access hatch has been positioned along the APTA operator-side glass rearward and upward guideline dimensions. As mentioned above, an element that may find more common application in the future is a thermal and security enclosure. An access door object was developed in the Engineering CAD Model to support the installation of such an enclosure (see Figure B-22). The height and width dimensions were set according to SAE J185. The width was set at 680 mm, and the height was set to approximately 1,981 mm, which is greater than that suggested by the J185. The taller height was a combination of the SAE J185 preferred clearance of 1,800 mm plus the 181 mm step height in the model. This consideration should provide for the increased headroom needed for operators when accessing the workstation through such an enclosure door. This clearance should account for the needs of tall females and males even when combined with taller steps, as evidenced by the NIOSH survey value for a 95th percentile Male Stature (with shoes): 1,900 mm.

102 Bus Operator Workstation Design for Improving Occupational Health and Safety Figure B-22. A minimum door access opening (SAE J185) was constructed for optional consideration of workstation enclosure with thermal/security barrier. The door height was extended above the minimum criteria listed in SAE J185 for consideration of the step, which is 181 mm above the passenger floor. The top view image shown in Figure B-23 clearly shows the need for stepping clearance on the step itself and the pedal floor. One 127 mm disc was located on the lower step as a minimum requirement. Two 127 mm discs were located on the pedal floor and against the side wall of the seat-mounting floor. Other clearances were referenced in this example to highlight the clearance path that operators must pass through in order to be seated, including seat backrest to 457 mm steering wheel at access position, grab handle to grab handle, and fare box to seat backrest-side bolster. The seat was positioned at full rearward among the suggested horizontal travel range. The passenger/operator grab handles provided in the image will not be distributed with the Engineering CAD Model since these specifications were provided by the bus manufacturing partner.

Bus Operator Workstation Engineering CAD Model Specifications 103 Figure B-23. Minimum step size (127 mm) discs (lower step – single, upper step/floor – double) are demonstrated. In addition, example dimensions of a current production bus operator workstation highlight the available clearances when combined with the suggested rearward seat position and the suggested operator-access steering wheel position.