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I. Introduction I.! Overview on Computer Simulation A bus operator's workstation tailored to his/her tasks will result in increased comfort and higher productivity. Also a human-centered workstation based on human capabilities and limitations will reduce the risk of injury and accidents due to an inappropriate workstation geometry. This indicates that the workstation should be designed ergonomically considering the characteristics of both the operators and their tasks. In the present study, the functional design relationship method was utilized for the workstation design. The functional design relationship method identified the geometric relationships between anthropometric variables and design variables, and then determined design values based on the constructed geometric relationships assuming standard bus driving postures defined within comfort angles (You et al., ~ 9951. A computer simulation can be used to verify and modify the workstation design before it is built. A variety of software tools have been used to mode] a human graphically and simulate his/her tasks within a workstation. These tools not only provide an analytical way to ensure that the intended users of a workstation will be able to perform their tasks with comfort, but also reduce the risk of building a workstation that is not well suited for its intended users. Three-dimensional computerized human body models are preferred to physical models in the form of templates, manikins, and dummies because of their higher flexibility ant! more precise representations of body size, shape, and proportions. Examples of such computer human models include COMBIMAN, CREW CHIEF, C-1

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SAMMIE, and JACKS, which are described briefly as follows. However the limited availability of 3-D anthropometric data causes practical difficulty in the development of computer models of the body size (Kroemer et al., ~ 994~. COMBTMAN (Computerized Biomechanical Man-model) is an interactive computer graphics model evaluating the capabilities and limitations of an human operator in a seated workplace or vehicle. This three-dimensional system creates a computerized human-model according to user-defined dimensions and encumbrances of clothing and personal protective equipment, and analyzes visual accessibility, strength, and reach capability with the arms and the legs (COMBIMAN, ~ 995~. CREW CHIEF is an interactive 3-D model of an aircraft maintenance technician. The model has been used to perform human factors evaluations of aircraft maintenance crew stations. This three dimensional system allows a designer to simulate a maintenance activity using computer-generated imagery and to determine whether required activities are feasible for a given configuration (Armstrong Laboratory Design Technology Branch, 1 992~. SAMMIE (System for Aiding Man-Machine Interaction Evaluation) is an interactive design system involving a 3-D human model, a means for modeling objects, and a language for describing the tasks to be performed by operators. The system permits the evaluations of postural comfort, reach, clearances, and visibility. Also the joint limits of human body can be specified and the dimensions and body shape of the human model can be manipulated in the system (Bonney et al., 1979~. Lastly, JACKS is a software system for 3-D human modeling and simulation. It is used for the definition, manipulation, animation, and human factors performance analysis of virtual human figures. JACKS incorporates sophisticated algorithms for anthropometric human figure generation, a flexible torso, multiple limb positioning under

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constraints, assessments of visibility and reach, and strength guided performance simulation of human figures (Computer Graphics Research Laboratory, ~ 9944. In this study, JACKS was used for the workstation design simulation. At the beginning of this study, three software packages such as COMBIMAN, CREW CHIEF, and JACKS were examined as a candidate for simulation. While JACKS is a stand-alone software, both of COMBIMAN and CREW CHIEF are clesigned to interact with the I DEAS Level V, a CAD software developed by Structural Dynamics Research Corporation (SDRC). However, they are not compatible with the I-DEAS Level VT, an upgraded version of the T-DEAS Level V, which is available in The Pennsylvania State University. Since the older version of I-DEAS is not available on campus, JACKS was chosen for this simulation study. C-3

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I.2 Objectives The objectives of the computer simulation of this study were to: . Identify the expected performance of a bus operator in the context of the designed transit bus operator's workstation. Determine the adjustment ranges of the workstation components (seat / steering wheel instrument panels) to accommodate 95 percent of the US adult population presented in SAE 1833, and also to provide sufficient visibility, normal reach, and comfortable driving posture for the population while performing the bus operating tasks. Evaluate the bus workstation with a human mode] simulating the bus driving tasks in terms of visibility of the displays on the instrument panels and the out-of-windows, - reach to the steering wheel, the controls on the instrument panels, and the pedals, and adjustability of the workstation components for the intended user population such that comfortable postures can be maintained while driving the bus. C-4

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2. Simulation Mode! Development 2.! Key Features and Configuration of Mode] A computer simulation system was developed to test and evaluate the bus workstation design (Figure ~ ~ utilizing the JACKS 5 .9 software. Therefore, the capabilities and performance of the simulation system are highly dependent on those of JACKS 5.9 that provides several commands over site labeling, window shade, object transparency' rulers' and so on to setup a simulation environment. These commands were incorporated in the menu of the simulation system so that a user can easily control the desired conditions of the environment. Figure I: Transit Bus Operator's Workstation Implemented on JACKS The simulation system provided three human models having different body dimensions: the 5th percentile female, the 50th percentile person, and the 95th percentile C-5

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male of the anthropometric data set designated by SAL J833. Since the SAE anthropometric data are not sufficient to specify a complete 3-D human model in JACKS, unavailable anthropometric data were analytically determined as presented in Table 1 assuming proportionality of human body dimensions and cylindrical form of each body part. In the determination, the NASA (1978) and the US Army (1988) anthropometry studies were used as shown in Table 2. Seventeen typical bus operating tasks (Table 3) identified by a task analysis in the previous study (Bucciaglia, 1995) were simulated in JACKS. During the simulation of a bus operating task, the human model motions were governed by a set of virtual kinematic constraints related to the task. For example, during the accelerator pedal activation, the right foot of a human model is attached to the accelerator pedal plate surface, thus the motions of the knee and ankle of the right leg are controlled depending on the accelerator movement; during the simulation related to steering wheel maneuvering, the hands were constrained on the steering wheel to identify the upper-limb joint configuration While a 3-D human model is conducting each bus driving task, the bus workstation is evaluated in terms of visibility, reach, comfort, and adjustability. In order to facilitate the workstation evaluation, the simulation system generated two types of output files at the end of each bus operating task; one recorded the body joint angles of the human model, and the other recorded the selected locations of the workstation components. C-6

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Table I: Anthropometric Data Used in Computer Simulation Body Segment Head Neck Dimensions . . . ad. SAE Anthropometry 5 th percentile female 18.4 14.5 21.3 8.8 10 1 Thickness Width Length Thickness Width Torso Pelvis Upper Leg Lower Leg Foot with Shoes Upper Arm Lower Arm Hand Eye Coordinates Circumference Length Thickness Width Circumference Length Thickness Width Circumference Length Thickness Width Circumference Length Thickness Width Circumference Length Length Width Height Thickness Width Circumference Length Thickness Width Circumference Length Thickness Width Length Body Center Interpupillary Chin 7 4 50th percentile 1? 4 9.0 95th percentile male 20.6 ~ 16.5 . 23.1 119 13.1 Estimates based on JACK default data and the ellipse circumference formula* Estimates based on JACK default data and the ellipse circumference formula* Estimates based on ARMY ( 1988) data Estimates using the ellipse circumference formula* - - Estimates using the ellipse circumference formula* Estimates based on ARMY . (1988)~a Estimates using the ellipse circumference formula* . Estimates based on NASA ( 1978) data . Estimates based on JACh default data and the ellipse . circumference formula* Estimates based on JACK default data and the ellipse . circumference formula* Estimates based on NASA . (1978) data l Estimates based on JACK default data and the ellipse . c~n:~m~nce formula' Estimates based on JACK default data and the ellipse circumference formula* l Estimates based on NASA . (1978) data l Estimates based on JACK default data and the ellipse l circumference formula* Estimates based on JACK default data and the ellipse circumference formula* Estimates based on NASA (1978) data Estimates based on NASA ( 1978) data * Ellipse circumference formula: C= 27,.~(~/2) +~12) , where C: circumference, t: thickness, and w: width C-7

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Table 2: Anthropometric Data Used for the Analytical Determination of Unavailable SAE Anthropometric Data No. Anthropometric Variable Data for SAE Source No Data for SAE Source No. l | 5 %Female | | 95 %Male | |Neck C ircumference | 29.7 T 5 T I 2 Biceps Circumference, Relaxed 22.9 3 34.7 4 . 3 ~Foreann Circumference, Relaxed ~21.7 ~3 ~30.6 ~4 ~ 4 THandlhickness ~2.2 T 2 T I I 5 Thigh Circumference, Sitting 49.3 1 65.0 4 6 Thigh Clearance, Siding ~14.4 ~5 ~19.4 ~5 7 TCalf Circumference ~306 T 3 T 410 ~4 . Anthropometric Data Source Source No. Survey Name Year Gender Sample Women of the Army Corps Separatees 1946 Female 7,563 Women of the Air Force Basic Trainees 1952 Female 852 Air Force Women 1968 Female 1,905 Air Force Flying Personnel - Total Series 1967 Male 2,420 Army Personnel 1988 Female 2,208 Male 1,774 Reference NASA (1978) * Gordon et al. (1988) ** * NASA (1978), Anthropometric Source Book, vol.2, NASA Reference Publication 1024, Ohio: Yellow Springs. ** Gordon, C.C., Churchill, T., Clauser, C.E., Bradtmiller, B., McConville, J.T., Tebbetts, I., and Walker, R.A. (1989), 1988 Anthropometry Survey of U.S. Army Personnel: Methods and Summary Statistics, Anthropology Research Project, Inc., Ohio: Yellow Springs. 2. Comparison of Statures Between Population Groups Stature SAE (1994) Army Corps (1946) Air Force (1952) Air Force (1968) Air Force (1967) 155.0 cm 5 % Female 10 TO Female 10 % Female 10 TO Female 188.0 cm 95 % Male 95 % Male C-8 Army (1988) 10 % Female 97 % Male

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Table 3. Bus Operating Tasks and Metrics Includec] in Computer Simulation System adjusting seat horizontal Adjust the seat horizontally and vertically in relation to the pedal reach, workstation and vertical location. This is to ensure that a mannequin maintains its comfortable comfort, components adjustment hip, knee, and ankle orientation. adjustability seatback angle Adjust the seatback angle forward and backward considering the reach comfort, adjustment of steering wheel and the downward visibility. adjustability steering wheel Tilt and telescope the steering column or tilt the steering wheel based visibility, adjustment on the static driving posture and the 30 degree downward visibility reach, requirement simultaneously. comfort, adjustability left instrument Adjust the left instrument panel horizontally and vertically based on visibility, panel (LIP) the dynamic driving posture. Manipulate controls on the right reach, adjustment instrument panel while keeping the shoulder blades of the mannequin comfort, on the seatback. adjustability right Adjust the right instrument panel horizontally and vertically the same visibility, instrument way as the left instrument panel adjustment. Manipulate controls on reach, panel (RIP) the right instrument panel while keeping the shoulder blades of the comfort, adjustment mannequin on the seatback. adjustability engaging diagnostic Check the displays on the front instrument panel and press the test visibility, driving check button. Evaluate the visibility of the displays and the reach of the reach, control located on the front instrument panel. comfort, adjustability transmission Shift the bus into gear on the left instrument panel. Evaluate the visibility, engagement activation postures of the left arm and the visibility of the transmission reach, engagement. comfort, adjustability parking brake Release the parking brake on the right instrument panel. Evaluate visibility, release the activation postures of the right arm and the visibility of the reach, parking brake release. comfort, adjustability accelerating/ accelerator Press down the accelerator pedal completely. Evaluate the activation ~reach, maneuvering pedal postures of the right leg. comfort activation steering wheel Turn the steering wheel clockwise and counterclockwise keeping the visibility, turning shoulder blades on the seat-back. Evaluate the reach of the arms to the reach, steering wheel and downward visibility. comfort, adjustability floor- mounted Activate three buttons (right and left turn signals, and high-beam reach, signal signal) mounted on the floor individually with the left leg. Evaluate comfort activation the activation postures of the left leg. brake pedal Press down the brake pedal completely. Evaluate the activation reach, activation postures of the right leg. comfort picking-up/ four-way Activate the four way flasher on the right instrument panel. Evaluate visibility, depositing flasher the activation postures of the right arm and the visibility of the four reach, passengers activation way flasher. comfort, adjustability kneeling ~ Activate the kneeling mode on the right instrument panel. Evaluate visibility, activation the activation postures of the right arm and the visibility of the reach, kneeling switch. comfort, adjustability door activation Activate the bus door switch on the right instrument panel. Evaluate visibility, the activation postures of the right arm and the visibility of the door reach, switch. comfort, adjustability farebox Monitor the farebox. visibility, monitoring comfort passenger data Input the type of fare of all passengers using ODA (Operator Digital visibility, input Assistant) on the right instrument panel. Evaluate the activation reach, postures of the right arm and the visibility of the ODA. comfort, adjustability C-9

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The computer simulation can be maneuvered through two modes: interactive mode and batch mode. The batch mode simulates the initial operating task through the final one for a selected human model, while the interactive mode allows a user to select a operating task to be simulated. In summary, the constructed simulation system allows the user to: Setup the simulation environment such as displaying site labels, shading windows generating orthogonal windows, and displaying rulers between sites. Select a 3-D human mode! among three population groups which are pre-defined by using the anthropometry data from the SAL 1833. Manipulate the locations of the adjustable workstation components (seat, steering wheel, instrument panels) interactively. Simulate motions of the human figure which are controlled through a set of kinematic constraints for Kneed driving lasts ror 1 / ous operating tasks. , ~ it. . . . ~. ~ . Create simulation result files which include the postures of the human figure and the specified adjustment values of the workstation components for each driving task. and Execute simulations of the bus operating tasks through either an interactive mode or a batch mode. C-IO

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2.2 Development Procedure The simulation system was constructed by conducting a series of development procedures as depicted in Figure 2. The development procedures presents how the workstation geometry, human models, bus operating tasks, and design evaluation scheme are integrated into the simulation system. Each procedure is described below in detail. Import CAD drawings of Create representative the bus operator's workstation {R~ntative Define parameters ~ Create bus drivir g posture files (d.o.f./ranges/sites/colors) of human models or w~dst~ic ~ nails ~ , 1 I Place workstation components and a human model Define kinematic constraints for each bus driving task | Construct animation and evaluation scheme for each bus driving task | Figure 2. Simulation Model Development Procedures for Bus Workstation Design The development of the simulation system was commenced by importing the geometry of the bus workstation drafted by the Silver Screens CAD package into JACKS. The 'dxf2pss' utility provided by the JACKS was used to convert DXF file C-11

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3.2 Design Validation The workstation design was simulated using the human models for each bus operating task. TIlustrated are the evaluation results regarding visibility, reach, comfort, and adjustability for the steering wheel adjustment (Table 4) as an example. The rating scales for each criterion are explained in detail as follows. 3.2.:1 Visibility (V) Rating Horizontal Viewing Zone Vertical Viewing Zone Related Workspace Scale (neck Region angle) (neck rotation angle) 5 + ~ OO 30O ~+ ~ OO 30O ~out-of-windows in front of a bus operator 4 + t 0, 30 ] + t 30, 45 ] FTP (front instrument panel) 3 + ~ 30, 60 ~+ ~ 30, 45 ~ RIP (right IP), farebox 2 + ~ 300, 60 ~+ ~ 45O, 60 ~front and middle parts of LIP (refit IP) I + ~ 60, 90 ~+ ~ 30, 60 ~middle and rear parts of LIP (~eftIP) C-16

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Side View Visibility Cones Plan View isometric View _ W

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3.2.2 Reach (R) Rating Scale Obstacles Reach Zone Related Workspace on reach pathway ~ | None | normal reach area * | steel ing wheel, controls on FTP, RIP, and LIP pedals, floor mounted signals None below controls on RIP and LIP normal reach area None above controls on RIP and LIP, normal reach area pedals, floor mounted signals 2 Blocked normal reach area none Blocked out of none normal reach area 3.2.3 Comfort (C) The magnitude of comfort in a bus workstation can be assessed on the basis of the standard driving posture determined during the workstation design process. m Ci = C/m j=1 where Cj: comfort for driving task i in the workstation, Cij: comfort of joint j for driving task i in the workstation, m: the number of joints Rating Scale | Range of Joint Angle l 5 [ a + 0.5 ~ ] a-0.56,a-1.56]or[a+0.5S,a+1.55] 1 a-1.5b,a-2.56]or[a+1.56,a+2.50] 2 T a-2.50,a-3.56]or[a+2.50,a+3.56] T [ out of comfort ROM, maximum ROM ] (* a: joint angle in standard driving posture, ~ = comfort ROM/4) C-18

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Reach Cones Front View Zone 3 Plain View Isometric View C-19 .~ ~T,

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3.2.4 Adjustability (A) Since 'adjustability' signifies whether the designed workstation provides sufficient visibility, appropriate reach, and comfort for the intended SAL population groups (5th percentile female, 50th percentile, 95th percentile male), it needs to be assessed integratedly combining the results of three criteria of each population group. 3 Al = ~ Vik / 3 + ~ Rik / 3 + ~ Cik / 3 k=] k=} k=! where Al: adjustability for driving task i in the workstation, V jk: visibility of population group k for driving task i in the workstation, Rik: reach of population group k for driving task i in the workstation, and C jk: comfort of population group k for driving task i in the workstation. C-20

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Table 4. Workstation design simulation for steering wheel adjustment Task steering wheel adjustment Task Category adjusting workstation components Tilt and telescope the steering column, or tilt the steering wheel based on the seat Scenario position maintaining the static driving posture and the 30 downward visibility requirement simultaneously. _ ~_ ~ ~ I_ a,: ~ ~ [ _ _'' . 1 - ~ Illustration ~ Hi , steering wheel column tilt to deg (clockwise: +, counterclockwise: -) Design Values | steering wheel co: Imn telescope I 11 cm (upward +, downward: -) steering wheel hub tilt 10 deg (clockwise: +, counterclockwise: -) Simulation Results Population Group 5 th percentile Female 50 th Percentile column tilt 5 O O a . telescope -5.5 cm 0 cm . hub tilt -5 O O shoulder flexion 21.8 (4) - 29.9 (2) shoulder abduction 4.1 (4) 7.6 (5) shoulder rotation 24.3 (4) 9.5 O (5) elbow flexion 56.9 (5) 45.0 (4) wrist flexion 0 (5) 0 a (5) . visibility reach comfort 4.4 4.2 adjustability 4.7 Remarks _ 95 th Percentile Male -s o 5.5 cm s o 30.8 (2) 5.2 (5) 14.3 O(4) 45.7 O (4) o o (s) s 4 C-21

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4. Conclusions A computer simulation model was developed to test and validate the bus operator's workstation design. Utilizing the JACKX's capabilities, the simulation model provided the following functions: . . . . setup of simulation environment. selection of human models with the SAE IS33 anthropometry. adjustment of workstation components. simulation of bus operating tasks under specified kinematic constraints. creation of simulation result files. model execution in an interactive mode or a batch mode. The SAE anthropometry data were utilized to generate three different size human models (Sth percentile female, 50th percentile, 95th percentile male). Estimations were made to complement unavailable anthropometric data for three dimensional human modeling. The simulation system was designed to simulate seventeen typical bus operating tasks. The simulation system determined the expected behavior and visual field of a human for each bus operating task in the context of the workstation. The human behaviors were controlled by the designated kinematic constraints during simulation. In simulating each bus operating task, the locations of the workstation components were manipulated within the adjustment ranges. Design modifications were made wherever inappropriate design was found. The designated adjustment ranges were evaluated with respect to the degree of satisfying ergonomic requirements such as good visibility, acceptable reach, postural comfort, and sufficient adjustability. C-22

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A valic] transit bus operator's workstation design (Table 5) was produced through . iterative design modifications and simulations. Also, animation of the bus operating tasks facilitated the evaluation of the workstation in dynamic situations. Table 5: Adjustment ranges of workstation components tested in simulation Design Variable Adjustment Range Seat Horizontal 18.5 cm (7.3 in.) Vertical 6.7 cm (2.6 in.) Seatback Angle 10 deg. Steering wheel Column Tilt 10 cleg. Telescope 1 1.0 cm (4.3 in.) Hub Tilt 1 0 deg. Left Instrument Panel Horizontal 9.9 cm (3.9 in.) Vertical 4.0 cm (1.6 in.) Right Instrument Panel Horizontal 13.3 cm (5.2 in.) Vertical 4.5 cm (1.8 in.) C-23

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References Armstrong Laboratory Design Technology Branch (1992) User's Guide for Crew Chief. A computer Graphics Simulation of an Aircraft Maintenance Technician (V 3 - I- DEAS A, OH, Wright-Patterson Air Force Base. Bonney, M.C., Blunsdon, C.A Case, K., and Porter, I.M. (1 979) 'Man-Machine interaction in Work Systems', International Journal of Production Research, Vol. ~ 7 (6), pp. 619-29. Bucciaglia, I. (1995) Design Synthesis and Evaluation of Bus Operator Workstation' M.S.M.E. Thesis, The Pennsylvania State University. COMBIMAN (1995) Information booklet, CSERIAC,. Computer Graphics Research Laboratory (1994), Jack User's Guide, Computer Graphics Research Laboratory, The University of Pennsylvania. Diffrient, N., Tilley, A.R. and Harman, D. (1981) Human Scale 7/~/9, Cambridge, MA, The MIT Press. Kroemer, K.H.E., Kroemer, H.B. and Kroemer-Elbert, K.E. (1994) Ergonomics. How to Design for Ease and Efficiency, NI, Prentice-Hall Incorporated. Gilmore, B.~. (~1995) Bus Operator Workstation Evaluation and Design Guidelines: Workstation Mock-up Evaluation Report, PTI 9521, The Pennsylvania Transportation Institute. C-24

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Gilmore, B.J., Bucciaglia, J., Lowe, B., You, H. and Freivalds, A. (1995) Bus Operator Workstation Evaluation and Design Guidelines -Draft Interim Report, The Pennsylvania Transportation Institute. Gordon, C.C., Churchill, T., Clauser, C.E., Bradtmiller, B., McConville, J.T., Tubbers, I., and Walker, R.A. (1989), 1988 Anthropometry Survey of U.S. Army Personnel: Methods and Summary Statistics, Anthropology Research Project, Inc., Ohio: Yellow Springs. NASA (1978), Anthropometric Source Book, vol. 2, NASA Reference Publication 1024, Ohio: Yellow Springs. OCCU-MED (1986) Southern California Rapid Transit District Anthropometic Study, Vol. 1, OCCU-MED Co. Health Service, Pasadena, CA. Rebiffe, R. (1966) 'An Ergonomic Study of the Arrangement of the Driving Position in Motor Cars', Proceedings of the Institution of Mechanical Engineers, vol. 1 ~ 1, Pt 3D, pp. 43-50. SAE (1994) 1994 SEE Handbook, vol. 3, Warrendale, PA, Society of Automotive Engineers Incorporated. You, H., Bucciaglia, J., Lowe, B., Gilmore, B.J. and Freivalds, A. (1995) Bus Operator Workstation Evaluation and Design Guidelines: An Ergonomic Design Process for a Transit Bus Operator Workstation, PTI 9523, The Pennsylvania Transportation Institute. C-25

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