Occupant Response Research Articles

Far-side occupant responses based on current US side-impact protocol using finite element human body models

Most of the applied vehicle side-impact occupant protection research to date has concentrated on near-side occupants. Currently, no regulation exists in North America for the far-side occupant protection. Real-world crash data has shown that occupants seated on the non-struck side, defined as 'far-side' occupants, are still subjected to a risk of injuries. The objective of this study is to investigate body responses for the far-side occupant using current US side impact protocols. Current side impact protocol in the USA is designed to meet side Moving Deformable Barrier (MDB) and fixed oblique pole impact. Two seating cases are addressed; the first case consisted of a far-side occupant in the first row (single occupant) to evaluate the interaction of the occupant to the structure. The second case, a near-side occupant, was added to the far-side occupant (two occupants in a row) to study the interaction of the occupant-to-occupant. A finite element human body model (50th male) was used as a far-side and near-side occupant. Simulation results indicated that the LINCAP barrier could potentially produce the significant head rotational acceleration and thoracic rib deflection if the far-side occupant was included in the existing near-side crash protocols.

Occupant response to transitions across indoor thermal environments in two different workspaces

To understand how transition across different thermal zones in a building impacts the thermal perception of occupants, the current work examines occupant feedback in two work environments — nursing staff in hospital wards and the workers in an office. Both studies used a mix of subjective surveys and objective measurements. A total of 96 responses were collected from the hospital wards while 142 were collected from the office. The thermal environment in the hospital wards was perceived as slightly warm on the ASHRAE thermal sensation scale (mean TSV = 1.2), while the office workers rated their environment on the cool side (mean TSV = −0.15). The results also show that when the transitions were across temperature differences within ±2 °C, the thermal perception was not impacted by the magnitude of the temperature difference — as reflected in occupant thermal sensation and thermal comfort/thermal acceptability vote. This would imply that the effect of temperature steps on thermal perception, if any, within these boundaries, was extremely short lived. These findings go towards establishing the feasibility of heterogeneous indoor thermal environments and thermal zoning of workspaces for human comfort.

Occupant response to different correlated colour temperatures of white LED lighting

Correlated Colour Temperature (CCT) of lighting may affect not only occupant visual perception, but also other indoor environment perceptions, such as perceptions of the thermal environment or the air quality. This study aimed at quantifying the association between CCT of white LED lighting and subjective perceptions and performance at operative temperatures at the upper and lower borders and in the middle of the comfort range.Higher CCT was significantly associated with decreasing thermal sensation, but only at the thermally neutral condition. Female subjects responded stronger to changes in CCT than male subjects. Under all temperature conditions, CCT was clearly associated with the perceived brightness of the light, and at 22 °C also with the perceived air quality and with subjectively assessed alertness. CCT had no effect on the measured performance of a d2 task.At 22 °C, the observed decrease in thermal sensation when CCT went from 2700 K to 6200 K was equivalent to a difference in operative temperature of 1.7 °C. With an assumed neutral CCT of 4500 K (middle of range), a decreased heating set point in an office building, corresponding to an equivalent shift in CCT from 4500 K to 2700 K, resulted in a reduction of around 8% of the building's total annual energy use. However, this assumes ideal conditions without influence from daylight, light from PC monitors, or coloured surfaces and other potentially disturbing factors.

Modeling and validation of a detailed FE viscoelastic lumbar spine model for vehicle occupant dummies

The dummies currently used for predicting vehicle occupant response during frontal crashes or whole-body vibration provide insufficient information about spinal loads. Although they aptly approximate upper-body rotations in different loading scenarios, they overlook spinal loads, which are crucial to injury assessment. This paper aims to develop a modified dummy finite element (FE) model with a detailed viscoelastic lumbar spine. This model has been developed and validated against in-vitro and in-silico data under different loading conditions, and its predicted ranges of motion (RoM) and intradiscal pressure (IDP) maintain close correspondence with the in-vitro data. The dominant frequency of the model was f = 8.92 Hz, which was close to previous results. In the relaxation test, a force reduction of up to 21% was obtained, showing high agreement in force relaxation during the in-vitro test. The FE lumbar spine model was placed in the HYBRID III test dummy and aligned in a seated position based on available MRI data. Under two impulsive acceleration loadings in flexion and lateral directions with a peak acceleration of 60 m/s2, flexion responses of the modified and original dummies were close (RoMs of 29.1° and 29.6°, respectively), though not in lateral bending (RoMs of 34.1° and 15.6°, respectively), where the modified dummy was more flexible than the original. By reconstructing a real frontal crash, it was found that the modified dummy provided a 10% reduction in the Head Injury Criterion (HIC). Other than the more realistic behavior of this modified dummy, its capability of approximating lumbar loads and risk of lumbar spine injuries in vehicle crashes or whole-body vibration is of great importance.

An open acceptance model for indoor environmental quality (IEQ)

Indoor environmental quality (IEQ) acceptance prediction is crucial to sustainable building development. A simple yet comprehensive IEQ modelling strategy that can genuinely reflect occupant's responses to environmental conditions is necessary. This study proposes an open acceptance model that uses frequency distribution functions of occupant's responses towards IEQ parameters to assess IEQ. The proposed model is not only flexible enough to encapsulate a diverse range of descriptive model parameters but also feasible for openly available IEQ acceptance data, offering the flexibility to add data incrementally to allow easy model updating as and when a new set of observations arrives, this model can be a solution to the existing problems and limitations encountered in IEQ modelling.

Crash safety concerns for out-of-position occupant postures: A look toward safety in highly automated vehicles

ABSTRACTObjective: Highly automated vehicle occupants will all be passengers and may be free to ride while in postures for which existing occupant safety systems such as seat belts and airbags were not originally designed. These occupants could therefore face increased risk of injury when a crash occurs. Given that current vehicles are capable of supporting a variety of occupant postures outside of the normal design position, such as reclined or turned passengers, an evaluation of current field data was performed to better understand the risks of being out of position.Methods: We investigated the frequency, demographics, and injury outcomes for out-of-position occupants using NASS-CDS. A matched analysis was performed to compare injury outcomes for out-of-position passengers with in-position drivers involved in similar crashes. Finally, case studies for out-of-position occupants were examined in the Crash Injury Research (CIREN) database.Results: Only 0.5% of occupants in NASS-CDS with a coded posture were out of position at the time of crash. Of the out-of-position occupants, being turned or seated sideways was almost as likely as being reclined. Out-of-position occupants were younger and less likely to be belted than their in-position counterparts. Analysis of the injury data indicated a trend that being out of position was associated with an elevated risk for serious injury. However, the number of out-of-position occupants was too small to provide a definitive or statistically significant conclusion on injury outcome.Conclusion: Though highly automated vehicles may eventually reduce the number of crashes and traffic fatalities in the future, there will be a transition period when these vehicles remain at risk from collisions with human-driven vehicles. These crashes could cause higher than anticipated rates of injury if occupants are less likely to be belted or tend to be in positions for which restraints are not optimized. This study highlights the need for future research on occupant response and countermeasure design for out-of-position occupants.

Influence of the chest compression measurement method on assessment of restraint performance in side-impact crash scenarios

Side impact crashes contribute a significant number of fatal injuries (25% of road fatalities in the USA in 2016), with severe thoracic injuries diagnosed in 58% of front near-side impact occupants. Epidemiological data indicate that thoracic-only side airbags (tSABs) are not as effective as laboratory testing has suggested, and one of the reasons for this may be the use of surrogate-specific injury assessment methods, which are not directly transferable between Anthropometric Test Devices (ATDs) and Post-Mortem Human Surrogates (PMHSs). This study examines the effect of the thorax deformation measurement location and method on the predicted performance of seatbelts and tSABs in a side impact using a Human Body Model (HBM). The HBM was integrated in a vehicle and subjected to a Moving Deformable Barrier (MDB) impact at 61 km/h, with four restraint configurations: belted and unbelted, with and without a tSAB. Occupant response was assessed through chest band (CB) deformation, and as a change in distance between markers on the ribs. Multiple measurement locations in the HBM enabled direct comparison between the methods. The CB method indicated a 35% increase of chest compression due to tSAB; the rib-deflection (RD) method was not sensitive to the tSAB. The RD method predicted a 20% reduction of chest compression due to the seatbelt, but the CB-measured change was negligible. This study highlights the importance of measurement method on the response outcome and demonstrates that different outcomes may be predicted using a HBM for the same impact scenario, depending on the measurement method.

Low-Speed Go-Kart Crash Tests and a Comparison to Activities of Daily Living

Abstract Go-karts are a common amusement park feature enjoyed by people of all ages. While intended for racing, contact between go-karts does occur. To investigate and quantify the accelerations and forces which result from contact, 44 low-speed impacts were conducted between a stationary (target) and a moving (bullet) go-kart. The occupant of the bullet go-kart was one of two human volunteers. The occupant of the target go-kart was a Hybrid III 50th percentile male anthropomorphic test device (ATD). Impact configurations consisted of rear-end impacts, frontal impacts, side impacts, and oblique impacts. Results demonstrated high repeatability for the vehicle performance and occupant response. Go-kart accelerations and speed changes increased with increased impact speed. Impact duration and restitution generally decreased with increased impact speed. All ATD acceleration, force, and moment values increased with increased impact speed. Common injury metrics such as the head injury criterion (HIC), Nij, and Nkm were calculated and were found to be below injury thresholds. Occupant response was also compared to published activities of daily living data.

Trunk muscle recruitment patterns in simulated precrash events

ABSTRACTObjectives: To quantify trunk muscle activation levels during whole body accelerations that simulate precrash events in multiple directions and to identify recruitment patterns for the development of active human body models.Methods: Four subjects (1 female, 3 males) were accelerated at 0.55 g (net Δv = 4.0 m/s) in 8 directions while seated on a sled-mounted car seat to simulate a precrash pulse. Electromyographic (EMG) activity in 4 trunk muscles was measured using wire electrodes inserted into the left rectus abdominis, internal oblique, iliocostalis, and multifidus muscles at the L2–L3 level. Muscle activity evoked by the perturbations was normalized by each muscle's isometric maximum voluntary contraction (MVC) activity. Spatial tuning curves were plotted at 150, 300, and 600 ms after acceleration onset.Results: EMG activity remained below 40% MVC for the three time points for most directions. At the 150- and 300 ms time points, the highest EMG amplitudes were observed during perturbations to the left (–90°) and left rearward (–135°). EMG activity diminished by 600 ms for the anterior muscles, but not for the posterior muscles.Conclusions: These preliminary results suggest that trunk muscle activity may be directionally tuned at the acceleration level tested here. Although data from more subjects are needed, these preliminary data support the development of modeled trunk muscle recruitment strategies in active human body models that predict occupant responses in precrash scenarios.

A Nonlinear Viscoelastic Model for Adipose Tissue Representing Tissue Response at a Wide Range of Strain Rates and High Strain Levels.

Finite element human body models (FEHBMs) are nowadays commonly used to simulate pre- and in-crash occupant response in order to develop advanced safety systems. In this study, a biofidelic model for adipose tissue is developed for this application. It is a nonlinear viscoelastic model based on the Reese et al.'s formulation. The model is formulated in a large strain framework and applied for finite element (FE) simulation of two types of experiments: rheological experiments and ramped-displacement experiments. The adipose tissue behavior in both experiments is represented well by this model. It indicates the capability of the model to be used in large deformation and wide range of strain rates for application in human body models.

Using GHBMC M50-O to assess the suitability of H-III and THOR for the SOI tests

The NHTSA frontal 90 kph 150 OMDB 35% offset test is a part of the new test protocol being proposed to simulate small overlap and oblique impact crashes in the field. An advanced crash test dummy, THOR, is proposed in the test protocol for injury risk assessment instead of the standard frontal impact dummy Hybrid III (H-III). An integrated vehicle finite element model with H-III, THOR and the GHBMC 50th male models is employed to compare the kinematics and injury differences. In this study, we evaluated the occupant response in the new frontal OMDB test using GHBMC models to quantify and qualify the potential injury pattern and risk in this type of crash. The vehicle model was validated with both a full frontal 35 mph rigid barrier test and the very first frontal OMDB test with the H-III 50th %ile male dummies is conducted. The differences in the measured responses of the H-III and THOR from simulations and tests, and the simulated responses of the GHBMC model, were compared. The additional tissue-level injuries predicted by the GMBMC model, which are beyond the capability of the H-III and THOR dummies, showed the potential injury pattern and risk of occupants in the OMDB test.

The vehicle frontal impact safety evaluation and design method based on the coupling effect between crash pulse and restraint system characteristic

This paper presents a new method to evaluate the design stiffness of vehicle structure and restraint system from the perspective of coupling effect, at the preliminary stage of safety design. The fast iteration algorithm is established to calculate occupant response database. Subsequently, the expressions about three indexes are derived to evaluate the crash pulse, the restraint system and the coupling effect between them. Based on the data from National Highway Traffic Safety Administration (NHTSA) frontal crash impact tests, the star-estimate map is established to estimate the star rating and design stiffness. Finally, a safety design example of M6 model is optimised to verify the validity of the proposed method, and the relative risk score (RRS) of design solution decreases by 43.6%. The proposed method can be used in the phase of conceptual design, greatly reduce the calculation amount of CAE analysis and shorten the product development cycle.

The vehicle frontal impact safety evaluation and design method based on the coupling effect between crash pulse and restraint system characteristic

This paper presents a new method to evaluate the design stiffness of vehicle structure and restraint system from the perspective of coupling effect, at the preliminary stage of safety design. The fast iteration algorithm is established to calculate occupant response database. Subsequently, the expressions about three indexes are derived to evaluate the crash pulse, the restraint system and the coupling effect between them. Based on the data from National Highway Traffic Safety Administration (NHTSA) frontal crash impact tests, the star-estimate map is established to estimate the star rating and design stiffness. Finally, a safety design example of M6 model is optimised to verify the validity of the proposed method, and the relative risk score (RRS) of design solution decreases by 43.6%. The proposed method can be used in the phase of conceptual design, greatly reduce the calculation amount of CAE analysis and shorten the product development cycle.

Promoting Energy Efficiency of HVAC Operation in Large Office Spaces with a Wi-Fi Probe enabled Markov Time Window Occupancy Detection Approach

In recent years, demand-based control in HVAC systems have achieved a great amount energy saving by providing precise services in according to actual demand. As the premise of determining actual demand, occupancy information has a significant impact on building heating, cooling and ventilation in building control and energy auditing. In this paper, a Wi-Fi probe based occupancy detection method is applied to detect the occupancy in typical office buildings. Given the Wi-Fi coverage and smart devices are widely used in modern buildings, Wi-Fi probe requires no initial investment and could scan the Internet connection request and response of occupants. Previous studies suggest time-series and stochastic characteristics of occupancy information, this research proposed a Time-Window based Markov Chain (TWMC) model to detect occupancy. An on-site experiment was conducted in this study to validate the proposed method. The results report an accuracy of over 80% (x-accuracy when x equals 4). Compared to actual occupancy profile, the proposed model shows over 88% of supply air amount reduction in energy simulation with an absolute deviation less than 20%. By integrating the proposed TWMC model based on Wi-Fi probe and demand-based control system, the energy consumption of HVAC system could be significantly reduced.

Adaptive approach of thermal comfort and correlation between experimental data and mathematical model in some schools and traditional buildings of Madagascar under natural ventilation

A good ventilation is important to improve indoor air in buildings. In Sub-Saharan Africa regions and other countries, both health and productivity are indeed elements depending on indoor comfort. The purpose of this research is to suggest a new thermal comfort approach based on subjective responses of occupants and mathematical models. There is a lack of data about indoor comfort in residential buildings in the tropical islands of Indian Ocean and the aim of the research is to propose guidelines for more comfortable constructions in Madagascar and other countries of the Indian Ocean. Experimental and subjective data were collected in 67 traditional habitats and 25 public and private schools, located in 25 districts of urban communes in the Northern Madagascar. Mathematical modelling was based on Rohles approach. At total of 992 questionnaires were collected and analysed during rainy and dry seasons. The results showed that traditional buildings were more comfortable than schools. Comfort temperature varied from 24.6 to 28.4 °C during both seasons in residences and schools. When the indoor air temperature varied in the 24.5–27.5 °C range, more than 80% of peoples were satisfied.

Comparing temperature and acoustic satisfaction in 60 radiant and all-air buildings

There is little knowledge from occupied buildings of the impact of radiant heating and cooling systems on indoor environmental quality aspects such as thermal comfort, indoor air quality, and acoustics. We present indoor environmental quality survey results from 3892 respondents in 60 office buildings located in North America; 34 of which used all-air systems and 26 of which used radiant systems as the primary conditioning system. In the current study, we present the survey results of 1645 occupants in buildings with radiant systems. To our knowledge, this is the largest dataset used in a comparison of occupant satisfaction in radiant buildings. We used an existing database to extract a subset of occupant responses from all-air buildings whose key characteristics match those radiant buildings. The results indicate that radiant and all-air spaces have equal indoor environmental quality, including acoustic satisfaction, with a tendency towards improved temperature satisfaction in radiant buildings.

Occupant responses in conventional and ABTS seats in high-speed rear sled tests

ABSTRACTObjective: This study compared biomechanical responses of a normally seated Hybrid III dummy on conventional and all belts to seat (ABTS) seats in 40.2 km/h (25 mph) rear sled tests. It determined the difference in performance with modern (≥2000 MY) seats compared to older (<2000 MY) seats and ABTS seats.Methods: The seats were fixed in a sled buck subjected to a 40.2 km/h (25 mph) rear sled test. The pulse was a 15 g double-peak acceleration with 150 ms duration. The 50th percentile Hybrid III was lap–shoulder belted in the FMVSS 208 design position. The testing included 11 <2000 MY, 8 ≥2000 MY, and 7 ABTS seats. The dummy was fully instrumented, including head accelerations, upper and lower neck 6-axis load cells, chest acceleration, thoracic and lumbar spine load cells, and pelvis accelerations. The peak responses were normalized by injury assessment reference values (IARVs) to assess injury risks. Statistical analysis was conducted using Student's t test. High-speed video documented occupant kinematics.Results: Biomechanical responses were lower with modern (≥2000 MY) seats than older (<2000 MY) designs. The lower neck extension moment was 32.5 ± 9.7% of IARV in modern seats compared to 62.8 ± 31.6% in older seats (P =.01). Overall, there was a 34% reduction in the comparable biomechanical responses with modern seats. Biomechanical responses were lower with modern seats than ABTS seats. The lower neck extension moment was 41.4 ± 7.8% with all MY ABTS seats compared to 32.5 ± 9.7% in modern seats (P =.07). Overall, the ABTS seats had 13% higher biomechanical responses than the modern seats.Conclusions: Modern (≥2000 MY) design seats have lower biomechanical responses in 40.2 km/h rear sled tests than older (<2000 MY) designs and ABTS designs. The improved performance is consistent with an increase in seat strength combined with improved occupant kinematics through pocketing of the occupant into the seatback, higher and more forward head restraint, and other design changes. The methods and data presented here provide a basis for standardized testing of seats. However, a complete understanding of seat safety requires consideration of out-of-position (OOP) occupants in high-speed impacts and consideration of the much more common, low-speed rear impacts.

Using Upper Extremity Skin Temperatures to Assess Thermal Comfort in Office Buildings in Changsha, China.

Existing thermal comfort field studies are mainly focused on the relationship between the indoor physical environment and the thermal comfort. In numerous chamber experiments, physiological parameters were adopted to assess thermal comfort, but the experiments’ conclusions may not represent a realistic thermal environment due to the highly controlled thermal environment and few occupants. This paper focuses on determining the relationships between upper extremity skin temperatures (i.e., finger, wrist, hand and forearm) and the indoor thermal comfort. Also, the applicability of predicting thermal comfort by using upper extremity skin temperatures was explored. Field studies were performed in office buildings equipped with split air-conditioning (SAC) located in the hot summer and cold winter (HSCW) climate zone of China during the summer of 2016. Psychological responses of occupants were recorded and physical and physiological factors were measured simultaneously. Standard effective temperature (SET*) was used to incorporate the effect of humidity and air velocity on thermal comfort. The results indicate that upper extremity skin temperatures are good indicators for predicting thermal sensation, and could be used to assess the thermal comfort in terms of physiological mechanism. In addition, the neutral temperature was 24.7 °C and the upper limit for 80% acceptability was 28.2 °C in SET*.

Occupants' perception of air movements and air quality in a simulated classroom with an intermittent air supply system

The study reported herein builds on occupant response to an intermittent air jet strategy (IAJS), which creates periodic airflow and non-isothermal conditions in the occupied zone. Previous research has highlighted benefits of IAJS for the thermal climate and energy saving potential in view of human thermal perception of the indoor environment. The study herein explores the occupant acceptability of air movements and perceived indoor air quality. Thirty-six participants were exposed to three room air temperatures (nominal: 22.5℃, 25.5℃ and 28.5℃) with each having four air speed conditions (nominal: &lt; 0.15 m/s under mixing ventilation (MV) and 0.4, 0.6 and 0.8 m/s under IAJS) measured at the breathing height (1.1 m). The results show that participants preferred low air movements at lower temperatures and high air movements at higher temperatures. A model to predict percentage satisfied with intermittent air movements was developed. The model predicts that 87% of occupants, in compliance with ASHRAE 55-2013 standard, will find intermittent air movements acceptable between 23.7℃ and 29.1℃ within an air speed range of 0.4 to 0.8 m/s. IAJS also improved participants' perception of air quality in conditions deemed poor under MV. The findings support the potential of IAJS as a primary ventilation system in high occupant spaces such as classrooms.

Differences in the kinematics of booster-seated pediatric occupants using two different car seats

ABSTRACTObjective: The objective of this article is to compare the performance of forward-facing child restraint systems (CRS) mounted on 2 different seats.Methods: Two different anthropomorphic test device (ATD) sizes (P3 and P6), using the same child restraint system (a non-ISOFIX high-back booster seat), were exposed to the ECE R44 regulatory deceleration pulse in a deceleration sled. Two different seats (seat A, seat B) were used. Three repetitions per ATD and mounting seat were done, resulting in a total of 12 sled crashes. Dummy sensors measured the head tri-axial acceleration and angular rate and the thorax tri-axial acceleration, all acquired at 10,000 Hz. A high-speed video camera recorded the impact at 1,000 frames per second. The 3D kinematics of the head and torso of the ATDs were captured using a high-speed motion capture system (1,000 Hz). A pair-matched statistical analysis compared the outcomes of the tests using the 2 different seats.Results: Statistically significant differences in the kinematic response of the ATDs associated with the type of seat were observed. The maximum 3 ms peak of the resultant head acceleration was higher on seat A for the P3 dummy (54.5 ± 1.9 g vs. 44.2 ± 0.5 g; P =.012) and for the P6 dummy (56.0 ± 0.8 g vs. 51.7 ± 1.2 g; P =.015). The peak belt force was higher on seat A than on seat B for the P3 dummy (5,488.0 ± 198.0 N vs. 4,160.6 ± 63.6 N; P =.008) and for the P6 dummy (7,014.0 ± 271.0 N vs. 5,719.3 ± 37.4 N; P =.015). The trajectory of the ATD head was different between the 2 seats in the sagittal, transverse, and frontal planes.Conclusion: The results suggest that the overall response of the booster-seated occupant exposed to the same impact conditions was different depending on the seat used regardless of the size of the ATD. The differences observed in the response of the occupants between the 2 seats can be attributed to the differences in cushion stiffness, seat pan geometry, and belt geometry. However, these results were obtained for 2 particular seat models and a specific CRS and therefore cannot be directly extrapolated to the generality of vehicle seats and CRS.