The seated soldier study: posture and body shape in vehicle seats

Dates covered (From - To) September 2011- October 2013Final ReportDesigning vehicles for the safety and comfort of occupants requires detailed information on posture, position, and body shape. This report presents the methods and results of a study of soldiers as drivers and passengers in vehicle seats. A total of 257 male and 53 female soldiers were measured at three Army posts while minimally clad, wearing the Advanced Combat Uniform (ACU), with the addition of personal protective equipment (PPE), composed of the Improved Outer Tactical Vest (IOTV) and Advanced Combat Helmet (ACH), and with encumbrance (ENC) simulating the gear of either a rifleman or SAW-gunner. Standard anthropometric data, such as stature and body weight, were recorded. Participants were measured as either drivers or crew. Five driver workstation configurations (packages) were produced in a vehicle mockup by varying the steering wheel position relative to the pedals. The participants adjusted the seat to obtain a comfortable driving posture. The three-dimensional locations of body landmarks were measured using a FARO Arm coordinate digitizer. In the crew conditions, the experimenters varied the seat height and back angle and conditions included a simulated protective footrest. A whole-body laser scanner was used to record body shape at each garb level. A statistical analysis of the body landmark data was conducted to obtain models to predict soldier posture as a function of vehicle factors, such as seat height, and soldier attributes, such as stature, and garb level (ACU, PPE, or ENC). Driver posture was strongly affected by steering wheel position and crew posture by seat back angle. Adding PPE and ENC resulted in more-upright postures, but the effects on spine posture were small. Statistical models of both seated and standing body shape were developed from the scan data, including the effects of PPE and ENC on space claim. The effects of ENC on space claim were largely independent of body size. The results of this study have broad applicability for the design and assessment of military vehicles. Approved for public release.US Army Tank Automotive Research, Development, and Engineering Centerhttp://deepblue.lib.umich.edu/bitstream/2027.42/109725/1/103143.pdfDescription of 103143.pdf : Final Repor

Evaluation of the seat index point tool for military seats

This study evaluated the ISO 5353 Seat Index Point Tool (SIPT) as an alternative to the SAE J826 H-point manikin for measuring military seats. A tool was fabricated based on the ISO specification and a custom backangle measurement probe was designed and fitted to the SIPT. Comparisons between the two tools in a wide range of seating conditions showed that the mean SIP location was 5 mm aft of the H-point, with a standard deviation of 7.8 mm. Vertical location was not significantly different between the two tools (mean -0.7 mm, sd 4.0 mm). A high correlation (r=0.9) was observed between the back angle measurements from the two tools. The SIPT was slightly more repeatable across installations and installers than the J826 manikin, with most of the discrepancy arising from situations with flat seat cushion angles and either unusually upright or reclined back angles that caused the J826 manikin to be unstable. The investigators who performed the measurements indicated that the SIPT was easier to use. The data show that the SIPT is a reasonable substitute for the SAE J826 manikin when ease-of-use considerations favor the SIPT, such as restricted space around the seat, low seat heights, or low cushion angles. Human posture measurements in seats with large discrepancies between the tools will be needed to determine which provides a better prediction of sitter position.U.S. Army TARDEChttp://deepblue.lib.umich.edu/bitstream/2027.42/111823/1/103190.pd

Elderly occupants: posture, body shape, and belt fit

A laboratory study was conducted to quantify the posture, body shape, and safety belt fit of 200 adults with a wide range of age, stature, and body weight. Body and belt landmark data were gathered as participants sat in a driver mockup that was adjusted to represent nine vehicle packages spanning a large range of the vehicle fleet and in a mockup of a rear passenger seat. Whole-body surface shape data were gathered in 22 postures using a laser scanner. The data analysis showed significant effects of occupant attributes on posture and belt fit. Vehicle and seat variables had important effects on posture and position but did not have strong effects on belt fit relative to occupant attributes, particularly body mass index. Age had significant effects on both posture and belt fit, although the effect of age was smaller than the effect of body mass index across the ranges in the participant population.National Highway Traffic Safety Administrationhttp://deepblue.lib.umich.edu/bitstream/2027.42/134392/1/103250.pdfDescription of 103250.pdf : Final repor

Development of accommodation models for soldiers in vehicles: driver

Data from a previous study of soldier posture and position were analyzed to develop statistical models to define accommodation in driver and squad seating positions in military vehicles. Using methods previously developed for automotive applications, new models were created for seating accommodation, eye location, head (helmet) clearance, knee clearance, and torso clearance. The resulting models are applicable to driver positions with a fixed heel point and a range of steering wheel locations typical of tactical vehicles. The models were developed based on driver posture data but could be used for other front seat environments (e.g., commander position) with certain assumptions. All of the models include the effects of body armor and body borne gear.US Army Tank Automotive Research, Development, and Engineering Center (TARDEC)http://deepblue.lib.umich.edu/bitstream/2027.42/112059/1/103197.pd

Development of accommodation models for soldiers in vehicles: squad

Data from a previous study of Soldier posture and position were analyzed to develop statistical models to define accommodation in squad seating positions in military ground vehicles. Using methods previously developed for automotive applications, new models were created for eye location, head (helmet) contour, and knee contour for Soldiers in fixed seats. The models are applicable to a range of seat height and seat back angle. All of the models include the effects of body armor and body borne gear.US Army Tank Automotive Research, Development, and Engineering Centerhttp://deepblue.lib.umich.edu/bitstream/2027.42/120917/1/103244.pdf-1Description of 103244.pdf : Final repor

A pilot study of law ernforcement officer (LEO) anthropometry with applications to vehicle design for safety and accommodation

Law enforcement officers (LEO) are at relatively high risk of back pain and other musculoskeletal disorders. The risk is exacerbated by the poor accommodation provided by their vehicles, which are usually modified civilian vehicles. LEO are also involved in vehicle crashes at a higher rate than most other occupations, yet officers report difficulty in wearing a safety belt due to interference with their body-borne equipment. To begin to address these issues, a pilot study was conducted to demonstrate the application of three-dimensional anthropometric techniques to quantifying the influence of body-borne gear on space claim and posture in vehicles. The results demonstrated that three exemplar vehicles accommodated the officers poorly due to interference between the seat or other vehicle features and the body-borne gear. Belt fit was also adversely affected, and vehicle modifications and additions, such as the now-common center-mounted laptop computer, create awkward postures for driving, in-vehicle work, and ingress and egress. A large-scale, population-based study aimed at developing seat and vehicle design guidelines using three-dimensional anthropometric techniques is needed.Anthrotech, Inc.http://deepblue.lib.umich.edu/bitstream/2027.42/116202/1/103221.pdfDescription of 103221.pdf : Final repor

Statistical analysis to develop a three-dimensional surface model of a midsize-male foot

A representative midsize-male foot was generated via a statistical analysis of foot scans from 107 men with widely varying body size. Seventy-two surface landmarks were manually extracted from the original scan data. A template fitting method was used to represent each scan with a homologous mesh. A principal component analysis and least-squares linear regression were used to generate a foot surface model with landmarks using a reference stature of 1755 mm and a body mass of 83.19 kg. The statistical model can be used to generate a wide range of male foot sizes and shapes.US Army Tank Automotive Research, Development, and Engineering Center (TARDEC)http://deepblue.lib.umich.edu/bitstream/2027.42/116596/1/103232.pdfDescription of 103232.pdf : Final repor

Road Vehicle Passenger Behaviors: A Video Study

Technical Report FinalPassenger car cabin videos obtained in a previous naturalistic driving study of part-time belt users were coded to characterize front-seat passenger attributes and behaviors. Among the 959 passenger trips, the median trip duration was 10 minutes; the 95th percentile was 52 minutes. Frames from the beginning, middle, and end of trips longer than 5 minutes in duration were extracted for coding, along with a middle frame from trips shorter than five minutes. Front-seat passenger characteristics, postures, and activities were coded in a total 2438 frames. In approximately 72% of frames coded, the passenger was male and 77% of the passengers were estimated to be less than 30 years of age. In 33% of frames, the passenger did not wear the seatbelt. The most common passenger activity was talking (57%); phone interactions were observed in 10% of frames. Passengers were most often looking out the windshield (57%), followed by facing the passenger window (17%), their lap (14%), or the driver (10%). The passenger’s torso was rotated away from a neutral posture in more than 25% of frames, including pitched forward (17%), rotated left (6%), or rotated right (4%). The seat back was recorded as reclined beyond normal in 13% of frames, but very reclined in only 1.3% of frames.Toyota Collaborative Safety Research Centerhttps://deepblue.lib.umich.edu/bitstream/2027.42/154028/1/Reed Passenger Behavior Pilot UMTRI-2019-20.pd

Characterizing Child Head Motions Relative to Vehicle Rear Seat Compartment in Motor Vehicle Crashes

Technical Report FinalImproved padding or other countermeasures in vehicle rear compartments could reduce the incidence of head trauma for child occupants. However, knowledge of likely child head impact locations for a range of crash scenarios is needed to determine which areas and structures should be padded and where a side curtain should be deployed to protect child occupants. The objective of this study is to use a scalable MAthematical DYnamic MOdels (MADYMO) model of a child occupant to estimate the distributions of possible head impact locations as a function of crash type, vehicle interior characteristics, and child size. To achieve this goal, a series of simulations using a scalable MADYMO child-ATD model was conducted. The geometries of the second-row compartment from 5 vehicles were recorded using a laser scanner to provide high-resolution data for assessing probable head contact zones. Distributions of lateral and longitudinal delta V were calculated as a function of PDOF using the NASS-CDS dataset to provide proper simulation conditions based on real-world crashes. Simulations of crashes ranging from pure frontal to pure side impact (9 o’clock to 3 o’clock) with child ATDs with and without backless boosters were conducted using UMTRI’s parametric child ATD model in MADYMO, UMTRI's child ATD positioning procedure, and UMTRI's automated belt-fit and crash simulation system. The simulation results were used to create a model of the spatial distribution of head trajectories based on child body size and crash direction. By combining the head motion model and the vehicle second-row geometry models, the likely head contact zones with respect to interior components were identified. The findings of this study provide a reference for future vehicle rear compartment design to reduce head injuries for older children.National Highway Traffic Safety Administrationhttps://deepblue.lib.umich.edu/bitstream/2027.42/154006/1/UMTRI-2012-20.pd

Child Posture and Belt Fit in Second-Row Vehicle Seats

Technical ReportPosture and belt fit were measured for 40 children ages 5 to 12 years across two phases of testing involving six vehicles and six boosters, including one integrated booster. The three-dimensional locations of landmarks on the children, belt, and seat were recorded in each condition. Belt anchorage locations and other vehicle dimensions were recorded to characterize the seating environments. Lap belt fit was quantified by the location of the edge of the belt relative to the anterior-superior iliac spine landmark on the pelvis. Shoulder belt fit was measured as the lateral distance of the belt from the occupant centerline at the height of the suprasternale landmark. Lap belt fit without a booster was generally poor, with the belt lying fully above the pelvis for most children in most conditions. Belt positioning boosters improved lap belt fit in all conditions and improved shoulder belt fit for many combinations of children and vehicle. Taller children generally experienced better belt fit, but the effects were small compared to the benefits of using a booster. Belt fit scores were correlated with predictions based on previous laboratory studies using child stature and vehicle geometry as inputs. Mean belt fit scores were well correlated across conditions with predictions based on ATD measurements.National Highway Traffic Safety Administrationhttps://deepblue.lib.umich.edu/bitstream/2027.42/149102/1/UMTRI-2015-35.pdfDescription of UMTRI-2015-35.pdf : Technical Repor