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

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37 C H A P T E R 4 Introduction The research team completed several activities to develop the updated bus operator work­ station design guidelines. First, the team reviewed current transit bus industry guidelines related to bus operator workstation design from both the United States and international organizations. Second, the research team gathered input from the transit bus industry on the structure of effective guidelines. Third, the team applied current transit bus vehicle architecture, along with updated design guidance, to develop an updated workstation design feature guideline document, a CAD model for engineering requirement communication, and a 3­D PDF model with a user guide for procurement team communication. The SAE practices, CAD tools, and modern human modeling simulation tools used to develop Design Tool 2: Bus Operator Workstation Engineering CAD Model are intended to improve awareness of the operator’s needs by both purchasing agencies and bus manufacturers through­ out procurement. The research team’s intent was to stretch the expectations of transit agencies and manufacturers regarding the common features that should be provided in any standard transit bus operator workstation. Each activity and tool described in this chapter provides a detailed explanation of the investiga­ tion into other bus operator workstation guidelines and specification of the tools developed for this guideline. This detail may be of most interest to individuals with experience in ergonomics and vehicle packaging among procurement teams, vehicle manufacturers, and component suppliers. Review of Current Bus Operator Workstation Guidelines As part of the literature synthesis, the research team gathered transit industry bus operator workstation guidelines from the United States and Europe. • U.S. Sources: In the United States, there are two primary sources: TCRP Report 25: Bus Operator Workstation Evaluation and Design Guidelines and the Standard Bus Procurement Guidelines (APTA 2013), the latter developed by APTA as a tool to assist with the RFP process. • International Sources: Internationally, the first source is a European Commission initiative called the European Bus System of the Future (EBSF), which provides guidelines for a “next generation” of buses. As part of developing a new generation urban bus system, EBSF has developed specifications for the bus operator workplace. These specifications are contained in a document titled Recommendation for a Code of Practice of Driver’s Cabin in Line­Service Buses (European Commission 2011). The second source is ISO 16121­1:2012(en) Road Vehicles—Ergonomic Requirements for the Driver’s Workplace in Line­Service Buses, Part 1: General Description, Basic Requirements (ISO 2012). Development of Bus Operator Workstation Design Guidelines

38 Bus Operator Workstation Design for Improving Occupational Health and Safety The research team compiled comparative specifications from these publicly available sources to illustrate similarities and differences in a single International Bus Operator Workstation Design Matrix, which has been appended to Design Tool 1: Bus Operator Workstation Feature Guideline (available online). Because TCRP Project C­22 focused on updating TCRP Report 25, the research team also indicated in the matrix whether the specification was updated, added to the TCRP Report 25 guidelines, or omitted from the guidelines due to obsolescence. The back­ ground and purpose of each of these guidelines is described in detail in the next section. TCRP Report 25 Guidelines TCRP Report 25: Bus Operator Workstation Evaluation and Design Guidelines was developed through TCRP Project F­4 by the Pennsylvania Transit Institute of Pennsylvania State University during the late 1990s. The guidelines accommodate bus operators from the 5th percentile female to the 95th percentile male U.S. adult population. The key operator workstation areas addressed by the guidelines include design and location of the operator seat, steering wheel, foot controls, radio, transfer tray, public address system, sun visor, modesty panel, stanchions, controls, gauges, and other displays. To develop the guide­ lines, the TCRP Project F­4 research team reviewed previous bus operator workstation design research, conducted a task analysis of the transit bus driving task, completed a survey of transit bus operators, and evaluated an operator workstation mock­up for visibility, reach, and comfort (You et al. 1997). In reviewing the final deliverables from TCRP Project F­4, the TCRP Project C­22 research team found two important areas that became the basis for the updated guidelines in TCRP Report 185: 1. The workstation design approach was based on the neutral seat reference point (NSRP), and 2. The anthropometric data set was based on univariate linear body lengths and posture angles or range of motion. Each of these areas is briefly discussed in the remaining sections of this chapter. Examining the NSRP Approach Used in TCRP Report 25 The NSRP systematic design structure for developing the bus operator workstation guideline in TCRP Report 25 was based on a reference and methodology that focuses on a fixed seating reference point rather than using the cab floor and pedals as the basis for arranging all other workstation components. The authors of TCRP Report 25 made the assumption that the bus operators would adjust the seat and steering wheel to meet their needs for visibility, arm reach, and seating comfort. However, the NSRP approach could generate guidelines that recommend component positions and adjustment ranges that require some operators’ legs and feet (i.e., those of operators who are shorter in stature) to be suspended above the workstation floor (see Figure 5). For comparison, the TCRP Project F­4 research team examined an alternative design approach called the heel reference point (HRP). HRP uses the accelerator pedal/floor (i.e., accelerator heel point) as the fiducial point (see Figure 6). Using the HRP approach, both the 95th percentile male and 5th percentile female can place their feet on the bus floor. The authors of TCRP Report 25 concluded that, to accommodate bus operators of varying heights, guidelines based on the NSRP approach would require adjustable floors and pedals. However, the adjustable floor was not attempted in dynamic or static evaluations of the work­ station because of its potential impact on safe ingress/egress from the workstation. The authors

Development of Bus Operator Workstation Design Guidelines 39 of TCRP Report 25 also decided not to pursue adjustable pedals because of concerns about safety and reliability. Without adjustable floors or adjustable pedals, assumptions based on a fixed NSRP and optimized visibility might not be valid for operators of various sizes. The effects of the NSRP approach used in TCRP Report 25 were evident in the findings of the workstation mock­up evaluation. In the mock­up, the bus operators chose to position their seats below, and their steering wheels and instrument panels forward and above, the anticipated 5th, 50th, and 95th percentile positions (see Figure 7). Although data were not captured on the posi­ tion of the bus operators’ feet, specifically the right foot and heel, the bus operators’ choices can be explained as a result of bus operators first positioning the seat so that they could comfortably reach the pedals from the floor and then proceeding to match their arm reach with a comfort­ able steering wheel position. This explanation contrasts with the assumption that bus operators simply adjust the bus controls to match a small range of comfortable seating positions. Figure 5. NSRP workstation design approach (Pennsylvania Transportation Institute 1997). Figure 6. HRP workstation design approach (Pennsylvania Transportation Institute 1997).

40 Bus Operator Workstation Design for Improving Occupational Health and Safety Update to the HRP Approach To incorporate information and suggestions based on bus operators’ foot and heel position, the TCRP Project C­22 research team elected to update the bus operator workstation guidelines using the HRP approach. This approach provides the best strategy for designing a transit bus operator workstation that meets the needs of operators while minimizing deviation from transit bus models available on the road today. For example, core requirements for any vehicle work­ station could be that the operator’s feet can rest comfortably on the floor while not using the pedals and that the operator can maintain a stable pedal position on the accelerator pedal while resting that foot on the floor. When combined with knowledge of the current user population and simulation tools, the HRP approach will provide reliable and valid guidance for the design of transit bus operator workstations. The HRP approach has been and continues to be widely applied throughout the transporta­ tion industry across light and commercial vehicles through the application of SAE RPs. The HRP approach starts with the assumption that there is a fixed point on the floor behind the accelerator pedal that is common across all operators and independent of the size of the opera­ tor. The HRP approach is applied to packaging the controls and clearances around operators and passengers in vehicles. These RPs were referenced in TCRP Web-Only Document 1, the TCRP Project F­4 contractor’s final report. The SAE RPs address the following vehicle workstation packaging guidelines: • Fiducial point on or near the accelerator pedal (SAE J1516); • Seating reference points and positions relative to that accelerator reference (RP J1517, J826); • Operator leg positions (RP J1521); • Operator stomach profile (RP 1522); • Operator eye locations (RP J941); • Operator headroom space (RP J1052); and • Operator viewpoints and view planes (RP J1050). These workstation packaging guidelines were developed based on the collection and validation of many operators’ component positions and body positions. These data were then regressed to Figure 7. Comparison of design values and prototype evaluation results, side view (Pennsylvania Transportation Institute 1997, Fig. 3.7).

Development of Bus Operator Workstation Design Guidelines 41 determine boundary and position guidance equations that could predict how large numbers of drivers prefer vehicle workstations to be arranged. Ongoing progress is being made among commercial vehicle manufacturers and SAE com­ mittees to update the RPs that form the paradigm upon which many, if not most, light and commercial vehicles have been developed for decades. Modern simulation tools utilizing multi­ variate manikins have been applied in this update to the bus operator workstation guidelines. This approach may serve to fill some of the gaps that are being refined in the SAE RPs. Examining the Anthropometric Data Set The anthropometric data that were collected for TCRP Report 25 and applied to the 46 anthro­ pometric design functions were univariate dimensions based on a single physical dimension (i.e., stature) and a now­dated general civilian population. As applied, the data set assumed that an individual has the same percentile dimensions for all body segments. Using this univariate approach, a 95th percentile male would be considered to have 95th per­ centile leg lengths, arm lengths, stomach depths, and so forth. However, given that no individual uniformly fits a given percentile across all body segments, this univariate approach (i.e., account­ ing for one physical dimension such as stature) creates unrealistic representations of the user population. Operator packaging analyses must account for the natural anthropometric variability found in the user population (Guan et al. 2012). Only an anthropometric data set built on multivariate dimensions (i.e., accounting for several physical dimensions such as leg length and sitting eye height) can deliver such guidance for humans whose body segment lengths are not all consistent. The application of univariate body dimensions can result in erroneous workstation operator component arrangements. For example, a male in the 95th percentile (based on stature) would be assumed to also have a 95th percentile femoral (upper leg length) and a 95th percentile shank (lower leg length). Inserting the corresponding lengths into the geometric relationships and design function equations used in bus driver workstation guidelines would yield suggested seat and steering wheel adjustment positions that fit a small number of operators—those whose upper and lower leg lengths match the model—but would be unlikely to fit the true range of bus operators. A person with a 97th percentile lower leg length may have an 80th percentile upper leg length. Of greater concern, an operator may have a 1st percentile overall stature and a 26th percentile overall stomach depth. Such an operator may have to move the seat close to the pedals in order to reach them; however, the operator will also need to move the steering wheel forward, away from the stomach. Application of a multivariate approach better captures the true dimensions of the operator population. For TCRP Project C­22, the development of a data set using multivariate dimensions was com­ pleted using manikins in CAD human modeling software. This work is described in Chapter 5, with additional details provided in Appendix C. To facilitate comparison between the univari­ ate and multivariate approaches, the original anthropometry table used in TCRP Project F­4 is reproduced in Appendix C as Table C­2. APTA Guidelines APTA is an international organization that represents the interests of its membership through advocacy, innovation, and information sharing. Most APTA members are public organiza­ tions that are involved in the areas of public bus, paratransit, light rail, commuter rail, sub­ ways, waterborne passenger services, and high­speed rail. The membership includes large and

42 Bus Operator Workstation Design for Improving Occupational Health and Safety small companies who plan, design, construct, finance, supply, and operate bus and rail services worldwide. APTA members also include government agencies, metropolitan planning organi­ zations, state departments of transportation (DOTs), academic institutions, and trade publica­ tions (APTA 2014). As part of its committee work, in 2013 APTA published the Standard Bus Procurement Guidelines as a tool to assist with the RFP process (APTA 2013). The Standard Bus Procurement Guidelines were developed as a joint effort between APTA and other organizations including FTA. With assistance from many other state and city transportation authorities from across the nation, these groups developed these recommendations and guide­ lines to promote safety in transportation (APTA 2014). Specifically, these guidelines provide minimums that must be met when passenger buses are being produced or purchased. They cover many high­level details, such as service life, overall weight and capacity, maintenance and inspection protocols, and overall dimension limits. Also included are very specific details such as engine requirements, noise limits, fare box placement, glare considerations, and seat/pedal/control ratios (APTA 2013). EBSF Guidelines The EBSF project engaged members from the five leading European bus manufacturers and 42 other partners, including transport operators and national transport associations, public transport authorities, the supply industry, research centers and universities, and consultancy firms. The group was overseen by the International Association of Public Transport (UITP). EBSF’s goal was to develop a “new generation of urban bus system” for the drivers and users of the system. This goal was met by developing and validating a new bus system in seven European cities, based upon feedback from users, operators, and authorities. An end report was produced for general use (EBSF 2014). The EBSF report included guidelines and recommendations on overall bus design, as well as specific details and requirements for safety and comfort for the operator and passengers. These include, but are not limited to, size and position of steering wheel and clutch, bus operator view specifications for visibility, accelerator and brake positioning, bus operator seat minimums, and requirements for environmental factors such as noise and air quality (EBSF 2014). ISO Guidelines The ISO 16121 guideline, Road Vehicles—Ergonomic Requirements for the Driver’s Work­ place in Line­Service Buses, was developed through a technical committee, as is typical for ISO standards. The ISO 16121 guideline was prepared by the Technical Committee ISO/TC 22, Road Vehicles, Subcommittee SC 13, Ergonomics Applicable to Road Vehicles. The purpose of ISO 16121 is to provide designers of line­service buses (i.e., transit buses) with guidance on how to develop the bus operator workstation—which serves as the bus operator’s workplace, as described by the standard—to provide ergonomic accommodation. The guideline was based on a study completed in Germany (VDV 234) and also considered the recommenda­ tions of related international guidelines such as those in TCRP Report 25. ISO 16121 includes four parts as follows: • Part 1: General Description, Basic Requirements. Part 1 provides basic requirements for an ergonomic and comfortable seating position. These include size and location dimensional requirements that affect the bus operator seat, pedals, and steering wheel. • Part 2: Visibility. Part 2 provides requirements for the bus operator’s field of view forward of the vehicle, around the passenger entrance area, and within the workstation compartment.

Development of Bus Operator Workstation Design Guidelines 43 • Part 3: Information Devices and Controls. Part 3 provides requirements for the location of information devices and controls. • Part 4: Cabin Environment. Part 4 provides requirements for the bus operator workstation environment (e.g., temperature, noise, and ventilation). A review and comparison of the ISO 16121 guideline to the EBSF guideline revealed many similarities. A few elements that were not provided by other guidelines were new to the ISO guideline, including the following: minimum elbow room, foot well pedal clearance, and access to the bus operator workstation. These elements have been included in the updated bus operator workstation guideline. Capturing Industry Input to Procurement Guideline Development To gain insight on how best to construct the guidelines for industry adaptation, the research team conducted interviews with members of appropriate APTA committees, gathering feedback about members’ impressions of the current ergonomic guidelines for transit operator workstations and what elements are needed for effective guidelines. Participants The research team used professional contacts to help identify members from APTA’s Procure­ ment and Materials Management Committee, Bus Technical Maintenance Committee, and Bus Safety Committee. These committees were targeted for recruitment due to their involvement in the procurement standards used by the transit industry. Once a participant was contacted, a phone script was followed to introduce the study and screen for eligibility. Each person eligible and interested in participating was scheduled for an interview and a confirmation note was emailed along with a copy of an Informed Consent Form. A member from each committee was recruited and participated in a telephone interview. A total of three telephone interviews were conducted. Key Findings To develop this list of key findings, a member of the TCRP Project C­22 research team reviewed the three interview transcripts. In particular, the researcher looked for comments related to how best to present the research results to facilitate improvements in bus procurement practices. Interview participants had suggested attributes for the research report and also commented on ways the research might fit in with APTA’s procurement guidelines. Report Attributes Some attributes mentioned by interview participants included the following: • Taking a holistic approach to the whole operator compartment; • Looking at more than just ergonomics (e.g., proper heating, air ventilation, security, and types of lighting); • Considering issues for drivers that are not in the 95th percentile (e.g., proper mirror adjustment); • Addressing issues of potential distress to drivers, such as whole­body vibration and glare; and • Making operator safety elements a standard part of bus design and construction. Relationship to APTA Guidelines • Interview participants’ suggestions varied regarding how the research results of TCRP Project C­22 could fit in with the APTA Standard Bus Procurement Guidelines. Comments ranged

44 Bus Operator Workstation Design for Improving Occupational Health and Safety from potentially incorporating suggestions for relevant design changes into the next update of the APTA document to creating an appendix to the APTA guidelines or simply referencing the TCRP research, as appropriate. • One participant also mentioned that the research results could provide a useful resource for transit agencies that are putting together an RFP (transit organization interview August 2014). Production Transit Bus Architecture The approach selected by the research team was to provide guidance for bus operator work­ station design based upon the existing vehicle architecture of transit buses that are on the road today. The scope of this work focused on the workstation environment immediately surround­ ing the bus operator. In other words, the guidelines support components and features that the bus operators pass or can reach when accessing the seated workstation or using the seated workstation. The guidelines do not suggest deviations in the structure or glass or exterior mountings in the operator compartment section of the bus, nor do the guidelines suggest changes to the pas­ senger compartment to the rear of the bus operator. In order to apply realistic boundaries to the workstation guidelines, information from transit bus manufacturers and transit bus agencies was requested. Vehicle­level information was provided by one manufacturer in the form of 2­D drawings and 3­D solid­body data. Component and feature­level information was obtained through physical benchmarking of transit buses. Bus Manufacturer Non-Disclosure Agreement and CAD Data The research team established a Non­Disclosure Agreement (NDA) between VTTI and a prominent transit bus manufacturer to allow for exchange of transit bus data for modeling. These data provided a reliable example of a transit bus upon which the research team applied the HRP approach in developing the Bus Operator Workstation Engineering CAD Model. The research team worked with transit bus manufacturers to obtain generic transit bus CAD com­ ponents (e.g., floor heights above ground, mirror locations, relationships among the steer­ ing wheel, seat and pedal, and daylight openings) upon which the ergonomic templates for operator accommodation, reach, visibility, and ingress/egress were built. These data should increase the utility of the update to the guidelines, allowing future procurers to more closely align expectations and requested operator workstation improvements with manufacturers’ capabilities. Because of the NDA, the research team has included limited views of the vehicle CAD model in this report. These views include vehicle components such as the following: • Daylight opening glass, • Dash panel, • Operator workstation floors, • Column mounting, • Grab handles, • Ground plane, and • Generic pedal and seat supplier data. Furthermore, the research team referenced only basic packaging reference points, spheres, envelopes, and sheet bodies. Some components in the CAD model were reverse engineered from physical measures taken on site visits or found using other methods (see Figure 8). These data are considered public and

Development of Bus Operator Workstation Design Guidelines 45 are included with the Engineering CAD Model to provide application context for the related packaging recommendations. Transit Agency Site Visits The research team worked with two regional transit agencies to conduct site visits. During the two site visits, the research team collected physical measurements and photographed operator workstations in two different current production low­floor transit buses (see Figure 9 and Fig­ ure 10). Data from these visits were used to validate the CAD models and to provide additional information for the design and analyses of the operator workstation. Figure 8. Some bus operator workstation components (highlighted in orange) were reverse engineered from physical measures on site visits. Figure 9. Low-floor transit bus operator workstation, Example 1.

46 Bus Operator Workstation Design for Improving Occupational Health and Safety Updated Bus Operator Workstation Design Guideline Tools Operating a transit bus requires moderate levels of muscle activity, as well as alertness to maintain awareness of common objects in the surrounding transit bus environment, such as pedestrians, vehicles, and static obstructions. Effective posture for control and direct visibility are two key assumptions that must be upheld in any transit bus operator workstation guideline in order to deliver safe, efficient, and comfortable operation of the vehicle. This point reinforces the need for a more upright posture. It is likely that if a more relaxed and reclined workstation component arrangement were provided, the operators may be challenged to complete their necessary duties. Therefore, the SAE Class B occupant packaging paradigm was applied to the workstation seat, steering wheel, pedals, and hand controls arrangement. Common SAE Class B Operator Packaging Parameters Class B vehicles as defined by SAE include heavy trucks, medium­duty trucks, and some types of buses, including transit buses. Common Class B operator packaging parameters are listed in SAE J1516. These include the following seat and steering wheel attributes: • Torso Angle (A40): 8°-18°; • Wheel Diameter (W9): 440-560 mm; • Track Travel (TL23): ≥ 100 mm; • Track Rise (A19): 0°; and • Seat Height (H30): 405-530 mm. Using the SAE Class B operator package, defined by these dimensions, the research team sought to develop the updated bus operator workstation guideline tools—including the Bus Operator Workstation Feature Guideline and the 3­D Bus Operator Workstation Engineering CAD Model—as products that align with the rest of the commercial bus and truck industry that apply the same operator packaging paradigm. Figure 10. Low-floor transit bus operator workstation, Example 2.

Development of Bus Operator Workstation Design Guidelines 47 Bus Operator Workstation Design Tools The following bus operator workstation design tools provide component­, feature­, and vehicle­ level guidance for the development or procurement of bus operator workstations within transit buses. These tools can be accessed online from the TCRP Report 185 webpage. • Design Tool 1: Bus Operator Workstation Feature Guideline (listed online as “Bus Operator Workstation Feature Guideline”); • Design Tool 2: Bus Operator Workstation Engineering CAD Model (listed online as “Bus Operator Workstation Engineering CAD Model” and available as an IGS file or a STEP file); and • Design Tool 3: Bus Operator Workstation 3­D PDF Model (listed online as “Bus Operator Workstation 3­D PDF Model” and provided with an accompanying user guide). It is important to understand the assumptions and construction applied in the development of these design tools. Creating a Bus Operator Workstation Feature Guideline The research team used the information gained from the research to construct a stand­ alone, updated feature guideline document. The document is intended to provide design guidance for transit bus manufacturers and transit bus agencies procuring buses. The primary scope of this document is limited to the key elements of operator workstation design that impact the health and well­being of the bus operator. Based on industry feedback, the research team devised a standardized format for the updated guidelines to improve users’ comprehension of the key design criteria and their supporting rationales. Pertinent design guidelines are summarized in a table provided at the beginning of each section. The table allows readers to quickly find guideline criteria for key aspects of the operator workstation. If more information is needed to support the use of the criteria in design, additional details are provided about each guideline in sections labeled as follows: • Definition: Provides a description of each individual operator workstation feature; • Figure: Where possible, provides an illustration of each specific feature; • Design Guideline: Provides suggested design objectives based on ergonomic principles and vehicle design literature; and • Need for Design Guideline: Provides the reasoning for the design criteria as well as the factors that need to be considered when designing the operator workstation feature. Taking a holistic perspective for the operator workstation, the research team added guidelines to address issues such as whole­body vibration transmitted through the seat and steering wheel, operator workstation task lighting, glare, and control forces. Those guidelines that became obso­ lete due to changes in contemporary ergonomics were removed from the set of TCRP Report 25 guidelines. Finally, those TCRP Report 25 guidelines that required updating to reflect current literature findings were modified in the new guideline set. Creating a Bus Operator Workstation Engineering CAD Model The research team applied 2­D and 3­D data from a current production transit bus to establish the basic architecture of a transit bus operator workstation. The modeling of com­ ponents was accomplished by using two different solid­modeling CAD software applications (NX and Solidworks). The CAD images demonstrated in this report, with the exception of those images that include manikins, were created using both CAD software systems. Gaps in

48 Bus Operator Workstation Design for Improving Occupational Health and Safety the CAD data were filled by reverse engineering components from physical measurements of transit buses. The research team visited two transit bus operation centers in southwest Virginia to photo­ graph various model types and years and to capture localized component measures (e.g., ped­ als, steering wheels, and fare boxes). When the vehicle CAD model was completed, the research team had a detailed benchmark upon which to build the suggested Engineering CAD Model. SAE RPs were applied as tools to develop the operating packaging references and envelopes. Additional guidelines were applied that might enhance the Engineering CAD Model in meet­ ing the needs of today’s procurement practices and ultimately meeting the needs of the transit bus operators. Ergonomics Design Considerations An appropriate operator package will allow short­legged operators to comfortably rest their feet on the floor. This can be presumed to be possible with operators using an approximate 120° knee flexion angle. A second and related assumption is that the operator is seated such that the upper leg is approximately parallel with the workstation pedal floor. A slight incline is actually preferred, but for the sake of this general calculation, a flat (0°) seat pan angle is assumed. These assumptions can aid the users of the Engineering CAD Model in determining what minimum seat height should be targeted above the pedal floor. The designer should be aware that this will affect the decisions for the pedal­floor­to­seat­floor height, as well as the choice of seat lower/ suspension and seat upper/cushions construction. • H-Point Height: Recent anthropometric measures of 5th percentile female dimensions such as popliteal height (under­knee height to floor) and thigh clearance combined with typical minimum shoe heights can be applied to this question (Guan et al. 2012). By combining these dimensions, a minimum seat h­point height can be derived that approximates the hip heights of short­legged operators. Basing the design on this minimum seat h­point height, the needs of the remainder of operators can be accommodated using ranges of adjustment in the seat and steering wheel. These ranges of adjustment are discussed in the following sections of this chapter. • Determining the Minimum Seat H-Point Height: To determine the minimum seat h­point height, consider these dimensions: – 5th percentile female popliteal height to floor: 360 mm; – 5th percentile female thigh thickness: 143 mm; – Approximate h­point height above popliteal body reference: 71 mm; – Shoe height estimate: 25 mm; and – Estimated knee flexion angle: 120°. Combining these variables into the following equation yields the 5th percentile female h­point height: Cosine knee flexion minus 90 = seat h-point height lower leg length.o( ) Considered another way, Cosine knee flexion minus 90 lower leg length seat h-point height.o =( ) Using the dimensions listed, lower leg length will equal 360 mm plus 71 mm plus 25 mm, and the minimum seat h­point height is calculated as: cos 120 90 360mm 71mm+ 25mm 395mm.[ ] [ ]( )° − ° + =

Development of Bus Operator Workstation Design Guidelines 49 • Minimum Seat H-Point Height Considerations: – H­point accuracy range: ± 25 mm; – Accounts for anthropometry measurement standard deviations, shoe height variability, knee flexion angle preference, and h­point estimate; and – 5th percentile female h­point range: 370 to 420 mm. The selected seat h­point height played a significant role in defining the rest of the operator workstation in the Engineering CAD Model. This height is referred to as H30 in the RPs in SAE J1100: Motor Vehicle Dimensions. However, rather than arbitrarily selecting the number from within the range of vertical seat travel, the research team applied 2­D drawing and 3­D CAD data of a common transit bus seat. The lowest seat h­point height was determined to be 412 mm. The range of vertical seat adjustment above that lowest position was determined to be approximately 166 mm. These seat heights, combined with SAE RPs J1516 and J1517, were used to determine the range of seat adjustments needed in the Engineering CAD Model to fit operators of a Class B vehicle. • Visibility for Transit Bus Operators: Visibility is another very important consideration. It is the highest priority for each operator to monitor the surrounding environment and make informed decisions on what actions to take in controlling the vehicle and protecting their passengers. To that end, a robust operator workstation seat and control arrangement will maximize each operator’s capacity to maintain a direct view of the surrounding environment across the range of individual sizes that make up this vital workforce. Thus direct visibility will play a significant role in the Engineering CAD Model. Bus Operator Workstation Reference System and Fiducial Vehicle Points The SAE 3­D reference system is established in the RPs of SAE J1100: Motor Vehicle Dimensions. The location and orientation in position and angle of the workstation, com­ ponents, and human models referred to in this document are all relative to this workstation reference system (WRS). Vehicle manufacturers often choose to affix the vehicle model to easily recognizable positions and orientations, but they also commonly choose to position their engine models, interior/exterior cabin body models, and chassis models at different locations. At later stages of the vehicle design, integration exercises are performed to check the fit of the assemblies. With that predictable challenge in mind, the research team chose to select a reference sys­ tem that would be both recognizable to transit bus manufacturers who must commonly deliver vehicle dimensions for procurement activities while still placing the focus of the model on the workstation design. Therefore, the WRS illustrated in Figure 11 was set such that the axes align with the SAE references: • X­axis is fore­aft, • Y­axis is cross­bus, and • Z­axis is vertical. The origin (point 0, 0, 0) of the WRS was set such that the X­axis zero was located at the front axle center, the Y­axis zero was located at the mid­point of the bus width, and the Z­axis zero was located at the operator workstation pedal floor. The choice of the Z­axis zero was specifically made to highlight the fiducial reference of the accelerator heel point (AHP), which is the point from which the Engineering CAD Model has been built. It is important to specify the origin point as a fiducial reference point. However, to ensure that the Engineering CAD Model can be properly applied across various transit agencies’ and manufacturers’ CAD systems, other fiducial points (sometimes called packaging references in

50 Bus Operator Workstation Design for Improving Occupational Health and Safety the model) also were developed. These additional fiducial reference points allow users of the Engineering CAD Model to consider those operator workstation references without being tied down to one specific vehicle architecture and origin point. To help users identify both the origin point and other fiducial reference points, all fiducial references are represented in the model using solid­body spheres (see Figure 12). One of the packaging references was located at the forward­most point on the bumper and at the center of the vehicle, along the Y­plane. Another fiducial point was operator­centric and located under the operator’s seat at the seat­mounting hole. This seat­mounting refer­ ence should be useful for highlighting differences between the CAD guidance model and a specific vehicle’s seat­mounting height, which could have significant effects on the assump­ tion of the seat H30 dimension above the AHP and the level of operator accommodation. Lastly, the APTA (2013) visibility target, which stands 2 feet (609 mm) in front of the bus bumper and 3.5 feet (1,066 mm) above the ground, has been included as one of the fiducial points. It was located along the operator centerline. Although the visibility target would not be used to position the Engineering CAD Model, it is a significant fiducial element that ties together the bus architecture between the operator workstation and the outside world, between the operator workstation and the vehicle (bumper), and between the vehicle (bumper) and the outside world. Bus Operator Workstation Engineering CAD Model Design Tool 2: Bus Operator Workstation Engineering CAD Model was the result of com­ bining information from an existing transit bus operator workstation compartment, the bus Figure 11. The transit bus operator WRS imitates the SAE reference system (SAE J1100). [Note: Bus model data illustrated here for demonstration of vehicle orientation relative to axes only. Bus model data is not available with any format of the guideline CAD data.]

Development of Bus Operator Workstation Design Guidelines 51 operator packaging results from the application of the SAE Class B packaging, the International Bus Operator Workstation Design Matrix, and simulated human modeling validation. A num­ ber of features were combined for components in direct contact with the bus operators. These features, shown in Figure 13, are outlined in the balance of this section. • Existing transit bus architecture (manufacturer dependent) – Ground plane – Pedestrian floor Figure 12. The bus operator workstation fiducial reference points in top view (isometric inset) and side view. Figure 13. Bus Operator Workstation Engineering CAD Model guideline data (solid-body colored envelopes only) superimposed over the transit bus operator WRS with wireframe bus—contextual demonstration only.

52 Bus Operator Workstation Design for Improving Occupational Health and Safety – Operator platform – Seat floor – Accelerator pedal position\type – Steering wheel column pivot point – Center instrument gauge panel – Seat manufacturer’s h­point (fixed relative to seat cushions) 7 Seat selected by manufacturer and contract agency – Vehicle fiducial points: 7 Workstation reference system (WRS) X, Y, Z 7 Bumper point – APTA visibility target • Guidance – Operator accommodation 7 Operator fiducial points ▫ Accelerator heel point (AHP) 4 Platform floor to seat mid­vertical height 4 Manufacturer selected accelerator pedal ▫ Accommodation tool reference point (ATRP) 4 Platform floor to seat mid­vertical height ▫ Steering wheel point (SWP) – Seat h­point range 7 ATRP height above operator platform 7 Vertical seat adjustment range 7 2.5th percentile accommodation tool reference line (ATRL) to 97.5th percentile ATRL – Steering wheel tilt/telescope range 7 SWP position – Steering wheel rim size – Steering wheel clearance – Stomach and shin/knee clearance contours 7 ATRP height above operator platform – Shoulder clearance envelope – Foot well clearance envelope • Exterior visibility – Eyellipses 7 Seat horizontal fore­aft travel 7 Seat torso prescribed angle 7 ATRP height above operator platform height (AHP) 7 ATRP distance rearward of AHP – Vertical visibility 7 Upward: ATRP 15° from eyellipse 7 Downward: ATRP visibility target from ground and bumper – Operator­side glass visibility 7 APTA maximum lower height above platform floor, AHP 7 APTA minimum rearward position from AHP – Sun­visor shading (does not apply to rolling sunscreens) 7 Windshield: Eyellipse lower with 5° maximum upward 7 Operator­side glass: Eyellipse lower with 5° maximum upward • Controls – Reach curve 7 Reach curves 600 mm above AHP: Fingertip and grasp – Left instrument panel

Development of Bus Operator Workstation Design Guidelines 53 – Japan Automobile Manufacturers Association (JAMA), Japanese Industrial Standard (JIS) downward display view limit 7 Operator eye height above ground 7 Eyellipse mid­eye centroid – Foot­switch plate – Operator platform access 7 Even­split step height ▫ Manufacturer dependent operator platform height 7 Shoe clearance discs on steps ▫ Minimum of one disc on step ▫ Minimum of two discs on operator platform 7 Steering wheel position for access ▫ Steering wheel position 5° forward of vertical column tilt • Proposed guidance – Emergency access: APTA operator­side glass lower and rearward limit – Thermal/security barrier door – Fare box maximum size and position Creating a Bus Operator Workstation 3-D PDF Model and User Guide In keeping with the theme of the project—to increase awareness of the bus operator’s needs and the process by which those needs can be met through appropriate communication among the stakeholders in the procurement process—it was deemed appropriate to make a 3­D tool accessible to a wider audience than just engineers with CAD experience. To accomplish this purpose, the Bus Operator Workstation Engineering CAD Model was exported into a univer­ sal format that is available to anyone, creating Design Tool 3: Bus Operator Workstation 3­D PDF Model. An image from this model is shown in Figure 14. For readers who are unfa­ miliar with 3­D PDFs, a user guide also was developed. Both the user guide and the tool can Figure 14. A front isometric view of the Bus Operator Workstation 3-D PDF Model. Ground and bus platform, vehicle references, clearance envelopes, reach envelopes, visibility planes, seat access, and seat/steering wheel/pedal packaging references are demonstrated.

54 Bus Operator Workstation Design for Improving Occupational Health and Safety be accessed from the TCRP Report 185 webpage by going to www.trb.org and searching for “TCRP Report 185”. Multiple features of the 3­D PDF model make it accessible to non­traditional CAD users or users who are not familiar with vehicle packaging models. The model includes a tree structure that includes parent assemblies and child parts. The assemblies and parts include names that demonstrate the function of the guideline features. When parts in the model are selected using a computer mouse, the part name will appear in the tree structure (see Figure 15). Some tools, such as sectioning and dimensioning tools, are available to users with an interest in investigating the universal model in more detail. The 3­D PDF user guide walks the user through the basic steps required to open and navigate the model, in addition to selecting, sectioning, and measuring parts. Guideline Development Summary The methodology chosen to develop the updated bus operator workstation guideline deviated from the TCRP Report 25 anthropometric data and vehicle design functions. This path allowed the research team the freedom to include design requirements from multiple international guidelines. Industry feedback was collected from transit agencies that could be future users of the guidelines. The SAE Class B operator packaging RPs were applied to the location and positioning of the bus operator workstation seat, controls, and components. In order to bound the arrange­ ment of the workstation elements, the research team obtained current production vehicle data. Vehicle­level CAD data of a traditional low­floor transit bus were provided by a manufacturer. The seat supplier supplied seat drawings. Dimensions on two different transit bus manufacturers’ workstations were captured to fill in component and part data that were not provided with the manufacturer­supplied data. The exercise of combining vehicle data, supplier drawing data, Figure 15. The Bus Operator Workstation 3-D PDF Model and tree structure. The minimum downward visibility plane to the APTA minimum visibility target is selected. A green box surrounds the part in the model, and light gray highlights the related part, which is also bolded, in the tree structure.

Development of Bus Operator Workstation Design Guidelines 55 and physical benchmarking data demonstrated a need for greater integration of supplier and manufacturing data. In order to specify the appropriate position and range of positions for bus operators, the research team suggests that SAE packaging dimensions (SAE J1100) be made available on sup­ plier drawings. This is a fundamental example of one way it can be helpful to involve Tier 1 part suppliers in the procurement process along with the agency and bus manufacturers. This inclusiveness can help to ensure that communication and specification of bus operators’ needs do not stop at the vehicle level, but rather migrate to the assembly and component level. If com­ ponents such as seats, for example, carry specification detail in 2­D and 3­D CAD, this level of detail can support the next generation of transit bus engineering development and transit agency procurement. The physical benchmarking exercise also made obvious the point that flat treadle accelerator and brake pedals are common with two different major bus manufacturers. This is not neces­ sarily a negative, considering that Class B operator postures allow for a significant range in the degrees of freedom for the operator’s legs to move up and down. The research team has not made a case against the application of flat pedals in this update to the guidelines. It is the opinion of the researchers that low­force (15–40 N) treadle pedals can be applied as stable and efficient means of throttle control for transit bus operators.