Vehicle Model Year Research Articles

Factors influencing side air curtain deployment in rollover motor vehicle accidents

Objective: Recent changes in FMVSS have led to the utilization of side air curtains to provide occupant retention during rollover events. However, the safety advantage provided by the air curtains relies on the vehicle system’s ability to detect the rollover event and deploy the curtains. The purpose of this study is to identify crash and vehicle characteristics in motor vehicle rollovers that influence side air curtain deployment and occupant outcomes. The current study aims to improve the understanding of rollover events and inspire more robust air curtain deployment strategies.Methods: Study data were extracted from rollover cases documented in the NASS-CDS data set from 2011 to 2015. Vehicle model years of 2011 or later with side air curtains installed were examined. The presence of a rollover sensor in each vehicle was determined from vehicle content data available on the Insurance Institute for Highway Safety’s crash rating website. The resulting data set contained 14,003 weighted cases of rollover accidents in which the side air curtain did not deploy (40 raw count) and 23,178 cases of deployment (80 raw count).Results: Several crash event and vehicle characteristics were similar for the nondeployed and deployed groups, including number of quarter turns, primary location of damage, initiating event for the rollover, and vehicle model year. However, the nondeployed group included significantly more passenger vehicle body types (vs. SUV or truck) and had a significantly lower rate of rollover sensor presence. Presence of a rollover sensor increased the odds air curtain deployment by a factor of 36.5 (95% confidence interval [CI], 5.06–265). Cases in which both side air curtains deployed resulted in a higher frequency of injured occupants (Maximum Abbreviated Injury Scale [MAIS] ≥ 3). However, rollover events resulting in these injuries were also associated with higher rates of impact with another object or vehicle and damage to the roof of the vehicle, suggesting a higher energy event.Conclusions: Nondeployment of the side curtain airbags in rollovers occurred more frequently in vehicles without dedicated rollover sensors, which were most frequently passenger vehicles.

Understanding the impact of road design characteristic on teen driver’s fatality

Objective: There is little research simultaneously examining both teen drivers’ characteristics and the driving environment. This study aimed to investigate how traffic engineering factors (road designs, traffic operations, and surface conditions) contribute to risks of teen driver’s fatality. Understanding the role of traffic engineering factors can further improve efforts to reduce teen diving-related fatal crashes.Methods: This study used the Fatality Analysis Reporting System and General Estimate System for years 2014 to 2015. We explored numerous engineering variables: horizontal/vertical alignment, intersections types, interchange areas, traffic ways types, posted speed limit, work zone areas, types of traffic control devices and road surface conditions. Traditional variables considered in this study included sex, age, presence of passengers in relation to age group, time of day, lighting condition, season, vehicle model year, vehicle type, seatbelt use, crash type and movement prior to a crash. We ran cross-tabulations and unadjusted analyses to report unadjusted odds ratios of teen driver’s fatality. A multiple logistic regression model was used to identify which variables related to road design and traffic operations remained significant after being adjusted by other variables.Results: For traditional factors, results corroborated prior findings. All the engineering factors, except work zone area, were significant in the unadjusted analyses; four variables – horizontal alignments, posted speed limit, traffic control device type, and traffic way type – remained statistically significant in the final model. The adjusted odds ratio (AOR) of curved high-speed segment was nearly seven times (6.94; 95% CI = 3.58, 13.46) that of a straight segment with a low posted speed limit (reference group). The AOR of no traffic control was four times (4.17; 95% CI = 2.95, 5.88) that of roads with traffic controls. The AOR of a two-way undivided road was almost three times (2.75, 95% CI = 1.43, 5.29) that of a two-way median barrier road (reference group).Conclusions: This study suggests teen driver education programs consider addressing road design characteristics. For example, incorporating focused lessons on traffic signs and traffic control types may better prepare young people for their driving experiences. Additionally, more supervised driving time is needed on various road types, especially those that present greater risks (e.g., roads with grades/curves, intersections with no traffic signal, undivided roads, and unpaved roads).

A machine learning approach capturing the effects of driving behaviour and driver characteristics on trip-level emissions

This study investigates the effects of different variables including meteorology, trip characteristics (such as time of day), driving characteristics (such as the frequency of extended idling), and driver characteristics (such as driving experience) on trip-level emission factors (EFs). Drivers in the Greater Toronto and Hamilton Area (GTHA) were recruited to collect in-vehicle GPS data over a one-week study period from March to July 2018. Data from 1113 driving trips were collected, including characteristics of the trips and the drivers (51 independent variables). Trip emissions were estimated in addition to a driving eco-score indicator (on a hundred point scale) based on log-transformed emissions of greenhouse gases (GHG) in CO2eq and fine particulate matter (PM2.5). A machine learning approach, the Extreme Gradient Boosting (XGBoost), was used to develop prediction models for CO2eq and PM2.5 emissions at a trip level. The coefficient of determination (R2) and root-mean-square-error (RMSE) of eco-score models were respectively 0.84 (std. dev. 0.05), and 10.26 (std. dev. 1.24) for CO2eq, and 0.85 (std. dev. 0.03), and 10.64 (std. dev. 0.79) for PM2.5. The novel Shapley additive explanation (SHAP) measures were employed to reveal the importance of various features affecting trip emissions. For CO2eq, driving behavior such as the frequency of extended idling was found to have the most significant impact on the trip emission intensity. Additionally, driving experience was the most significant discrete feature affecting the eco-score. For PM2.5, the most significant feature was driver age, which was highly correlated with vehicle model year. Finally, commuter drivers were found to have lower CO2eq and PM2.5 emission intensities, owing to their familiarity with route and traffic conditions.

A Comprehensive Analysis for the Heterogeneous Effects on Driver Injury Severity in Single-Vehicle Passenger Car and SUV Rollover Crashes

In road traffic crashes, although rollover crashes account for a relatively low proportion, those result in a high fatality rate. The present study performed random parameters ordered logit models to examine risk factors as well as their heterogeneous effects on driver injury severity in single-vehicle passenger car and SUV rollover crashes. Crash data for the empirical analysis were extracted from Texas Crash Record Information System (CRIS) database during the year 2016. Model estimation results show that six variables (male drivers, drivers’ age, airbag deployment, failure to drive in single lane, speed limit, and rural area) were found to produce normally distributed parameters in passenger car model, while nine parameters (male drivers, safety belt use, airbag deployment, drug or alcohol use, failure to drive in single lane, improper evasive action, vehicle model year, friday, and rural area) in SUV model were found to be normally distributed. Several other factors with fixed parameters were found to be associated with driver injury severity in single-vehicle passenger car or SUV rollover crashes, most notably: ejection or partial ejection, turning left, intersection, August, adverse weather conditions, and night with light. These variables were significant in both models; most variables have stronger effects on nonincapacitating injury and serious injury outcomes in SUV than in passenger car rollover crashes. These findings provide a deep insight into causality nature and factor involved in driver injury severity in single-vehicle passenger car and SUV rollover crashes and are also helpful for transport agencies to determine appropriate countermeasures aimed at mitigating injuries sustained by drivers in single-vehicle rollover crashes.

An analysis of real-world exhaust emission control deterioration in the California light-duty gasoline vehicle fleet

The understanding of vehicle exhaust emission control deterioration is important for developing accurate emission inventories and for evaluating emission reduction regulation effectiveness. We show that a common practice of conducting deterioration analysis for multiple-model-year groups may produce unrealistic deterioration rates, because the samples' model year constitution usually varies with age. As a more reliable approach, we analyze the deterioration for individual model years. We apply this approach to light-duty gasoline vehicle exhaust emission measurements conducted using remote sensing devices at a West Los Angeles location during seven campaigns between 1999 and 2015. Vehicles of 1985–1993 model years (termed herein as “pre-LEV” model years for predating California's Low-Emission Vehicle regulations), most of them older than 10 years when sampled, did not exhibit strong and consistent deterioration with age for carbon monoxide (CO) and hydrocarbon (HC) emissions, whereas their nitric oxide (NO) emissions appeared to deteriorate approximately linearly with age. The 1994–2003 model-year vehicles, subject to California's original Low-Emission Vehicle standards (LEV I standards) and up to about 20 years old when sampled, deteriorated approximately linearly with age for the three species. Our limited measurement records for the 2004–2014 model-year vehicles, subject to California's second-generation Low-Emission Vehicle standards (LEV II standards) and up to about 10 years old when sampled, did not exhibit consistent deterioration with age. Here we propose an empirical model to describe those deterioration patterns for the pre-LEV and LEV I vehicles.

Automobile injury trends in the contemporary fleet: Belted occupants in frontal collisions

Objective: As vehicle safety technologies and evaluation procedures advance, it is pertinent to periodically evaluate injury trends to identify continuing and emerging priorities for intervention. This study examined detailed injury distributions and injury risk trends in belted occupants in frontal automobile collisions (10 o’clock to 2 o’clock) using NASS-CDS (1998–2015).Methods: Injury distributions were examined by occupant age and vehicle model year (stratified at pre- and post-2009). Logistic regression models were developed to examine the effects of various factors on injury risk (by body region), controlling for delta-V, sex, age, height, body mass index (BMI), vehicle model year (again stratified at 2009).Results: Among other observations, these analyses indicate that newer model year vehicles (model year [MY] 2009 and later) carry less risk of Abbreviated Injury Scale (AIS) 2+ and AIS 3+ injury compared to older model year vehicles, with odds ratios of 0.69 (AIS 2+) and 0.45 (AIS 3+). The largest reductions in risk between newer model year vehicles and older model year vehicles occur in the lower extremities and in the risk of skull fracture. There is no statistically significant change in risk of AIS 3+ rib fracture or sternum injury between model year categories. Females are at greater risk of AIS 2+ and AIS 3+ injury compared to males, with increased risk across most injury types.Conclusions: For belted occupants in frontal collisions, substantial reductions in injury risk have been realized in many body regions in recent years. Risk reduction in the thorax has lagged other body regions, resulting in increasing prevalence among skeletal injuries in newer model year vehicles (especially in the elderly). Injuries also remain common in the arm and hand/wrist for all age ranges studied. These results provide insight into where advances in the field have made gains in occupant protection and what injury types remain to be addressed.

Factors contributing to serious and fatal injuries in belted rear seat occupants in frontal crashes

Objectives: Earlier research has shown that the rear row is safer for occupants in crashes than the front row, but there is evidence that improvements in front seat occupant protection in more recent vehicle model years have reduced the safety advantage of the rear seat versus the front seat. The study objective was to identify factors that contribute to serious and fatal injuries in belted rear seat occupants in frontal crashes in newer model year vehicles.Methods: A case series review of belted rear seat occupants who were seriously injured or killed in frontal crashes was conducted. Occupants in frontal crashes were eligible for inclusion if they were 6 years old or older and belted in the rear of a 2000 or newer model year passenger vehicle within 10 model years of the crash year. Crashes were identified using the 2004–2015 National Automotive Sampling System Crashworthiness Data System (NASS-CDS) and included all eligible occupants with at least one Abbreviated Injury Scale (AIS) 3 or greater injury. Using these same inclusion criteria but split into younger (6 to 12 years) and older (55+ years) cohorts, fatal crashes were identified in the 2014–2015 Fatality Analysis Reporting System (FARS) and then local police jurisdictions were contacted for complete crash records.Results: Detailed case series review was completed for 117 rear seat occupants: 36 with Maximum Abbreviated Injury Scale (MAIS) 3+ injuries in NASS-CDS and 81 fatalities identified in FARS. More than half of the injured and killed rear occupants were more severely injured than front seat occupants in the same crash. Serious chest injury, primarily caused by seat belt loading, was present in 22 of the injured occupants and 17 of the 37 fatalities with documented injuries. Nine injured occupants and 18 fatalities sustained serious head injury, primarily from contact with the vehicle interior or severe intrusion. For fatal cases, 12 crashes were considered unsurvivable due to a complete loss of occupant space. For cases considered survivable, intrusion was not a large contributor to fatality.Discussion: Rear seat occupants sustained serious and fatal injuries due to belt loading in crashes in which front seat occupants survived, suggesting a discrepancy in restraint performance between the front and rear rows. Restraint strategies that reduce loading to the chest should be considered, but there may be potential tradeoffs with increased head excursion, particularly in the absence of rear seat airbags. Any new restraint designs should consider the unique needs of the rear seat environment.

Exploring the factors contribute to the injury severities of vulnerable roadway user involved crashes

The vehicle to pedestrian (V2P) applications will enable safety, mobility, and environmental advancements for the vulnerable roadway user (VRU) that current technologies are unable to provide. The present research aims to explore the use of random parameters in logit models to examine factors that significantly influence injury severity of VRU involved crashes. Two types of logit models, the mixed generalized ordered logit (MGOL) models and mixed logit models are proposed to provide insights on reducing injury severities of pedestrian and bicyclist involved crashes and benefit amending current V2P applications to address the special safety needs and challenges of these VRUs. Based on 9180 pedestrian involved crashes and 1402 bicyclist involved crashes from the Fatality Analysis Reporting System (FARS), the measure of injury severities – time-to-death is considered as the independent variables to capture a more comprehensive picture of events after a crash occurs. By comparing to the ordered logit models and the multinomial logit models, the effectiveness and appropriateness of the proposed models are verified through two perspectives – goodness of fit and predictive power. The modelling results show that the injury severity of VRU involved crashes is significantly associated with involved non-motorist characteristics (age and police reported alcohol involvement), involved motorist characteristics (drunk drivers, previous recorded crashes, number of occupants), involved vehicle characteristics (vehicle body type, vehicle model year, travel speed), roadway characteristics (interstate, junction, roadway profile), and environmental characteristics (light and weather condition). Among these significant factors, the number of occupants, vehicle body type, interstate, and junction result in random parameters, which capture and reflect the unobserved heterogeneity across sampled observations. The analyses of under-researched aspects of VRU involved crashes, that is time-to-death, help us develop a deeper understanding of the consequences of injury and ultimately health and social costs. The findings indicate that the proposed MGOL models and mixed logit models can account for the heterogeneity issues in crash data due to the unobserved factors. In addition, the injury severity models that incorporate the random parameter features can reveal new insights and have superior goodness of fit.

A pedestrian serious injury risk prediction method based on posted speed limit

The purpose of this study was to develop a serious injury risk prediction algorithm for pedestrians, using data from the South Australian Traffic Accident Reporting System. Two algorithms were developed to estimate serious injury risk, using a logistic regression analysis of 6,868 vehicle-pedestrian crashes extracted from TARS data. In this study, an optimal model based on the best combination of risk factors according to the Akaike information criterion (AIC) was developed. Additionally, a secondary GPS model using only crash site characteristics that can be derived from GPS coordinates from the crash scene was also developed. The optimal model is based on site and environmental conditions that could be derived from GPS data (posted speed limit, distance from crash site, natural lighting conditions, road geometry, road horizontal alignment and road vertical alignment) as well as pedestrian age/gender, driver age/gender and vehicle model year. The second model only included features that could be derived from GPS data. The optimal model was reasonable in accuracy and gave an under-triage rate of 10% when the injury threshold was set to 15%, with a corresponding over-triage rate of around 60%. The GPS model, despite not being as accurate as the optimal model may be adequate in the absence of all the risk factors required for the optimal model, requiring an injury threshold of 20% to give an under-triage rate of 10%, with the corresponding over-triage rate being around 70%. Both models can potentially be used for serious injury risk prediction (SIRP) for pedestrians involved in a collision with a vehicle.

The gap between certified and real-world passenger vehicle fuel consumption in China measured using a mobile phone application data

The gap between certified and real-world passenger vehicle emissions is widening and has driven vehicle policy transitions in the US and in Europe, particularly in the wake of emissions measurement scandals. Since carbon dioxide emissions are highly correlated with fuel consumption (FC), fuel consumption regulation is a useful policy instrument to combat climate change. Although the Chinese government set fuel economy standards in 2004, like many countries it does not conduct testing to confirm real-world FC rates comply with the standards. This paper employs a dataset of real-world FC measurements self-reported by over 1 million vehicle owners in China between 2008 and 2017 through a dedicated mobile phone application. By comparing this user-generated FC data with FC certification, the study provides an indication of discrepancies of FC gap and its characteristics, including: vehicle model year, transmission type, segment, weight bin, and market share. The study finds that while average certified FC decreased by 15% between 2008 and 2017, real-world FC remained unchanged, resulting in FC gap increase from 12% to 30%. The paper concludes that use of a local test-cycle, authoritative data collection, and stronger enforcement, may be useful policy tools for reducing China's real-world vehicle energy consumption.

Nonlinear models of injury risk and implications in intervention targeting for thoracic injury mitigation

Objective: Field data analyses often use either parametric or nonparametric means to describe the relationship between risk and various predictor variables. This study sought to evaluate a hybrid approach using semiconstrained multivariate nonlinear spline-based analysis.Methods: Data were compiled from NASS-CDS years 1998–2015, selecting belted occupants age 16+ in collisions with a principal direction of force (PDOF) from 10 o’clock to 2 o’clock. Outcome measures included the incidence of Maximum Abbreviated Injury Scale (MAIS) 3+ injury in general and Abbreviated Injury Scale (AIS) 3+ rib fracture injury. Multivariate logistic regression models were fit controlling for PDOF, ΔV, vehicle model year, collision year, occupant age, occupant body mass index (BMI), and other select factors. Within the logistic regression models, each of the continuous variables was modeled with a 4-knot spline. These were compared to models treating ΔV and BMI linearly.Results: A total of 29,667 occupants were observed from the query, representing approximately 13,608,398 occupants when weighted. Sixty percent of the AIS 3+ rib fracture cases occurred at ΔVs at or below 40 km/h. The median age for cases without AIS 3+ rib fracture was 34 years old. The median age for cases with AIS 3+ rib fracture was 62 years old.When modeled via nonlinear spline, the risk of MAIS 3+ injury in general and AIS 3+ rib fracture injury specifically exhibited a relationship with ΔV similar in shape to that observed in the linear model. In both cases, the spline model exhibited greater risk prediction over ΔVs from 25 to 50 km/h compared to the linear model (20–33% greater risk at ΔVs below 40 km/h) and less risk than the linear model at greater ΔVs.BMI exhibited a nonlinear, nonmonotonic relationship with both injury types studied. The risk tended to be a minimum at BMIs of 22–24 kg/m2, with an increase in risk at both higher and lower BMIs. For AIS 3+ rib fracture, the risk for a person with a BMI of 18 was approximately equal to the risk for a person with a BMI of 30, both being approximately 40% greater than the risk associated with a BMI of 24.Conclusions: Nonlinear multivariate regression methods have the potential to convey information about the risk–predictor relationship that cannot be captured through traditional linear modeling. These results suggest that traditional linear logistic regression models may underestimate the risk of AIS 3+ rib fracture injury in the ΔV range where they most frequently occur (below 50 km/h). Due to its nonmonotonic effect, traditional linear models may underestimate injury risk at both high and low BMIs.

Epidemiology of injury patterns for 4- to 10-year-olds in side and oblique impacts

Objectives: With regard to the pediatric population involved in vehicle side impact collisions, epidemiologic data can be used to identify specific injury-producing conditions and offer possible safety technology effectiveness through population-based estimates. The objective of the current study was to perform a field data analysis to investigate injury patterns and sources of injury to 4- to 10-year-olds in side and oblique impacts to determine the potential effect of updated side impact regulations and airbag safety countermeasures.Methods: The NASS-CDS, years 1991 to 2014, was analyzed in the current study. The Abbreviated Injury Scale (AIS) 2005–Update 2008 was used to determine specific injuries and injury severities. Injury distributions were examined by body region as specified in the AIS dictionary and the Maximum AIS (MAIS). Children ages 4 to 10 were examined in this study. All occupant seating locations were investigated. Seating positions were designated by row and as either near side, middle, or far side. Side impacts with a principal direction of force (PDOF) between 2:00 and 4:00 as well as between 8:00 and 10:00 were included. Restraint use was documented only as restrained or unrestrained and not whether the restraint was being used properly. Injury distribution by MAIS, body region, and source of injury were documented. Analysis regarding occupant injury severity, body region injured, and injury source was performed by vehicle model year to determine the effect of updated side impact testing regulation and safety countermeasures. Because the aim of the study was to identify the most common injury patterns and sources, only unweighted data were analyzed.Results: Main results obtained from the current study with respect to 4- to 10-year-old child occupants in side impact were that a decrease was observed in frequency of MAIS 1–3 injuries; injuries to the head, face, and extremities; as well as injuries caused by child occupant interaction with the vehicle interior and seatback support structures in 1998 model year passenger cars and newer.Conclusions: Results from this study could be useful in design advances of pediatric anthropomorphic test devices, child restraints, as well as vehicles and their safety countermeasure systems.

Consumer safety complaints and organizational learning: evidence from the automotive industry

PurposeThe purpose of this paper is to investigate the value of information in consumer safety complaints for organizational learning.Design/methodology/approachEmpirical analysis of this study uses a novel secondary data set, which is formed by combining complaints data filed with the National Highway Traffic Safety Administration (NHTSA) for potential safety defects, and design change information from 2003 to 2011 model-year vehicles in the USA.FindingsFirst, the paper demonstrates the value of information embedded in complaints. Second, in the case of radical product redesigns, owing to the lack of direct applicability of consumer feedback based learning, the impact of learning on product safety is found to be muted, third, the results suggest that the safety complaint rates vary by vehicle classes/categories and, fourth, the findings differ from prior research conclusions on vehicle quality. Prior research finds the debuting car models have the lowest repair rates among all car models produced in a given year, but the current study finds the debuting models to have the highest rates of safety complaints.Originality/valueQuality management literature rarely examines the safety complaints data (which, unlike other consumer feedbacks, focuses exclusively on the safety hazards due to flaws that result in accidents). This paper fills the gap in literature by linking safety complaints with future product quality and organizational learning.

Rollover injury in vehicles with high-strength-to-weight ratio (SWR) roofs, curtain and side airbags, and other safety improvements

Purpose: This study investigated trends in severe injury and ejection in rollover crashes involving lap–shoulder-belted drivers and right-front passengers. It was conducted because of changes in 2009 to consumer information programs and regulations related to rollover protection. The data are presented by model year (MY) of the vehicle in groups from 1995 to 2016. NASS-CDS cases with 2010–2016 MY vehicles were also evaluated to determine the crash circumstances and causes for severe injury of belted occupants in vehicles with a high strength-to-weight (SWR) roof, curtain, and side airbags and other safety improvements.Methods: 1997–2015 NASS-CDS data were evaluated for severe injury and ejection of lap–shoulder-belted front outboard occupants in light vehicles. Crashes were grouped by front, side, rear, and rollover. The injury and ejection data were grouped by vehicle MY: 1995–1999, 2000–2004, 2005–2009, and 2010–2016. Only drivers and right-front passengers were included if they were lap–shoulder belted and 15+ years old. Severely injured occupants were defined as those with Maximum Abbreviated Injury Scale (MAIS) 4–6 or fatality (MAIS 4 + F). National estimates were made with weighted data using the ratio weight in NASS-CDS. All NASS-CDS electronic cases were evaluated for belted occupants with MAIS 4 + F injury in rollovers involving 2010–2016 MY vehicles. The crash circumstances and injuries were studied. These vehicles had high-SWR roofs to meet Insurance Institute for Highway Safety (IIHS) ratings and FMVSS 216.Results: The 1997–2015 NASS-CDS included 2,083,776 belted front occupants in rollover crashes with 24,466 (1.17%) MAIS 4 + F injuries. The frequency of rollover crashes has decreased with modern vehicles (P < .0001). The 1995–1999 MY vehicles involved in a rollover accounted for 7.03% of all crashes (756,228/10,760,000). The corresponding proportion was 3.57% with 2010–2016 MY vehicles (81,406 vs. 2,282,062).The risk for MAIS 4 + F was 1.325 ± 0.347% in rollover crashes with 1995–1999 MY vehicles. It was 27.2% lower in 2010–2016 MY vehicles at 0.964 ± 0.331% (P < .001). There were 42,567 (2.002%) ejections of belted occupants in rollover crashes, irrespective of injury outcome. The risk for ejection was 3.042 ± 1.44% in rollover crashes with 1995–1999 MY vehicles. It was 43.6% lower in 2004–2009 MY vehicle at 1.715 ± 0.660% (P < .001) and 83.4% lower in 2010–2016 MY vehicle at 0.505 ± 0.336% (P < .001). There were 17 rollovers with MAIS 4 + F in 2010–2016 MY vehicles in NASS-CDS. Their roof strength was SWR =4.15 ± 1.05 based on 15 vehicles. Many of the collisions involved front or side impacts and then a rollover. Four cases involved 16- to 30-year-old drivers in extremely high-speed loss-of-control crashes resulting in >10-cm vertical roof deformation or substantial roof deformation based on photos. The roof strength (SWR) of 4.20 ± 1.0 was not sufficient to prevent roof deformation in these crashes.Conclusions: This study found a reduction in severe injury and ejection risk with modern vehicles. It indicates that vehicle safety has improved in response to IIHS and NHTSA efforts to expand the array of safety requirements and increase performance so that newer models are safer than earlier ones. There has been an incremental improvement in safety due to these advances.

Newer Model Years Are Associated with Reduced Risk of Motor Vehicle Crash Fatalities among Older Drivers

Older drivers are a growing and particularly vulnerable population. Advances in vehicle safety may reduce the risk of death in the event of a motor vehicle crash (MVC). Although previous studies have identified a relationship between increasing model years and decreased risk of death in MVC among adult drivers, this relationship has not been quantified among older drivers. The purpose of this study was to examine the relationship between vehicle model year and the risk of death among drivers aged 65 years and older who were involved in MVCs in the United States from 2010 to 2015. Data were from a census of all fatal MVCs and a representative sample of all police-reported crashes nationwide. Drivers were stratified into five age groups (65–69, 70–74, 75–79, 80–84, and 85+). Vehicles examined were cars, sport utility vehicles, pick-up trucks, and vans. Overall, older drivers driving vehicles older than model year 1990 were more than twice as likely to be killed in a crash as individuals driving vehicles of model years 2000 to 2009. Older drivers driving vehicles of model years 2010 and newer had 46% lower risk of MVC death than those driving vehicles of model year 2000 to 2009. The relationship between vehicle model year and risk of death in a crash varied by driver age and vehicle type, however, the same overall patterns were observed for all age groups and vehicle types examined. These findings suggest that older adults are responsive to improvements in vehicle safety.

The Effects of Voice System Design Components on Driver Workload

In-vehicle voice control systems are standard in most new vehicles. However, despite auditory-vocal interaction allowing drivers to keep their hands on the steering wheel and eyes on the forward roadway, recent findings indicate the potential for these systems to increase levels of workload and lead to lengthy interaction times. Although many studies have examined the distraction potential of interacting with in-vehicle voice control systems, more research is needed to understand the relationship between different system design components and workload. In this study, we investigate the role of system delay, system accuracy, and menu depth in determining the overall level of demand and interaction times on eight different 2017 model-year vehicles. Voice system accuracy was measured via playback of a pre-recorded sample of voice commands through a studio monitor mounted near the headrest. Menu depth and system delay were calculated by measuring, respectively, the number of interaction steps and total system processing time required to access common infotainment functions. These measures were validated through linear and multiple regression analyses with workload and task time collected in an on-road study. We found system delay and system accuracy to be significant predictors of task time and subjective measures of workload from the NASA Task Load Index and the Driving Activity Load Index. A In addition to providing valuable information on the role of separate voice control system design components on resulting levels of workload, these results extend past research by generalizing findings to multiple current auditory-vocal systems.

Effects of lane departure warning on police-reported crash rates

ObjectiveTo evaluate the effects of lane departure warning (LDW) on single-vehicle, sideswipe, and head-on crashes. MethodPolice-reported data for the relevant crash types were obtained from 25 U.S. states for the years 2009–2015. Observed counts of crashes with fatalities, injuries, and of all severities for vehicles with LDW were compared with expected counts based on crash involvement rates for the same passenger vehicles without LDW, with exposure by vehicle series, model year, and lighting system standardized between groups. For relevant crashes of all severities and those with injuries, Poisson regression was used to estimate the benefits of LDW while also controlling for demographic variables; fatal crashes were too infrequent to be modeled. ResultsWithout accounting for driver demographics, vehicles with LDW had significantly lower involvement rates in crashes of all severities (18%), in those with injuries (24%), and in those with fatalities (86%). Adding controls for driver demographics in the Poisson regression reduced the estimated benefit of LDW only modestly in crashes of all severities (11%, p < 0.05) and in crashes with injuries (21%, p < 0.07). ConclusionsLane departure warning is preventing the crash types it is designed to address, even after controlling for driver demographics. Results suggest that thousands of lives each year could be saved if every passenger vehicle in the United States were equipped with a lane departure warning system that performed like the study systems. Practical applicationsPurchase of LDW should be encouraged, and, because drivers do not always keep the systems turned on, future efforts should focus on designing systems to encourage greater use and educating consumers about the benefits of using the systems.

Detailed assessment of pedestrian ground contact injuries observed from in-depth accident data

Most pedestrians struck by vehicles receive injuries from contact with the vehicle and also from the subsequent ground contact. However, ground related pedestrian injuries have received little focus. This paper uses 1221 German pedestrian collision cases occurring between 2000 and 2015 to assess the distribution and risk factors for pedestrian ground related injuries. Results show that for MAIS 2, the ground accounted for 24% of cases, for MAIS 3 the ground accounted for 20% of cases and for MAIS 4–5, the ground accounted for 14% of cases. There were no AIS 6 ground related injuries, though there were several fatal cases where the ground was coded as the most serious injury. The head, thorax and spine dominate AIS 4–5 ground contact injuries. Vehicle impact speeds were higher for ground related AIS 4–5 compared to AIS 2 injury cases and the average impact speed for ground related injuries to the upper and lower extremities was lower than for body regions like head, thorax and spine. There was a significant age effect on pedestrian ground related injury outcome, with older pedestrians suffering more severe injuries and the median age for thorax injuries was higher than for all other body regions. There was no significant difference in the proportions of AIS 2+ head injuries produced by ground contact for more recent vehicles (model year since 2005) compared to older vehicles (model year before 2005). However, logistic regression analysis showed that the normalised bonnet leading-edge height is a risk factor for adult pedestrian AIS2+ ground related head injuries, and this provides empirical support for recent computational modelling predictions which implied a relationship between vehicle shape and pedestrian ground contact injuries. Considering the potential benefits of preventing pedestrian ground contact, for collisions below 40km/h two thirds of the injury costs would be eliminated if ground contact could be prevented, and even higher benefits are likely at lower speeds (20 and 30km/h). These data demonstrate the importance of ground related pedestrian injuries and show that vehicle shape influences pedestrian injury outcome in ground contact. The data therefore provides significant motivation for countermeasures to prevent or moderate pedestrian ground related injuries.

Seat strength in rear body block tests

ABSTRACTPurpose: This study collected and analyzed available testing of motor vehicle seat strength in rearward loading by a body block simulating the torso of an occupant. The data were grouped by single recliner, dual recliner, and all belts to seat (ABTS) seats.Methods: The strength of seats to rearward loading has been evaluated with body block testing from 1964 to 2008. The database of available tests includes 217 single recliner, 65 dual recliner, and 18 ABTS seats. The trends in seat strength were determined by linear regression and differences between seat types were evaluated by Student's t-test. The average peak moment and force supported by the seat was determined by decade of vehicle model year (MY).Results: Single recliner seats were used in motor vehicles in the 1960s to 1970s. The average strength was 918 ± 224 Nm (n = 26) in the 1960s and 1,069 ± 293 Nm (n = 65) in the 1980s. There has been a gradual increase in strength over time. Dual recliner seats started to phase into vehicles in the late 1980s. By the 2000s, the average strength of single recliner seats increased to 1,501 ± 335 Nm (n = 14) and dual recliner seats to 2,302 ± 699 Nm (n = 26). Dual recliner seats are significantly stronger than single recliner seats for each decade of comparison (P < .001). The average strength of ABTS seats was 4,395 ± 1,185 in-lb for 1989–2004 MY seats (n = 18). ABTS seats are significantly stronger than single or dual recliner seats (P < .001). The trend in ABTS strength is decreasing with time and converging toward that of dual recliner seats.Conclusions: Body block testing is an quantitative means of evaluating the strength of seats for occupant loading in rear impacts. There has been an increase in conventional seat strength over the past 50 years. By the 2000s, most seats are 1,700–3,400 Nm moment strength. However, the safety of a seat is more complex than its strength and depends on many other factors.

Integrated indicator to evaluate vehicle performance across: Safety, fuel efficiency and green domains

In general, car manufacturers face trade-offs between safety, efficiency and environmental performance when choosing between mass, length, engine power, and fuel efficiency. Moreover, the information available to the consumers makes difficult to assess all these components at once, especially when aiming to compare vehicles across different categories and/or to compare vehicles in the same category but across different model years. The main objective of this research was to develop an integrated tool able to assess vehicle’s performance simultaneously for safety and environmental domains, leading to the research output of a Safety, Fuel Efficiency and Green Emissions (SEG) indicator able to evaluate and rank vehicle’s performance across those three domains. For this purpose, crash data was gathered in Porto (Portugal) for the period 2006–2010 (N=1374). The crash database was analyzed and crash severity prediction models were developed using advanced logistic regression models. Following, the methodology for the SEG indicator was established combining the vehicle’s safety and the environmental evaluation into an integrated analysis. The obtained results for the SEG indicator do not show any trade-off between vehicle’s safety, fuel consumption and emissions. The best performance was achieved for newer gasoline passenger vehicles (<5year) with a smaller engine size (<1400cm3). According to the SEG indicator, a vehicle with these characteristics can be recommended for a safety-conscious profile user, as well as for a user more interested in fuel economy and/or in green performance. On the other hand, for larger engine size vehicles (>2000cm3) the combined score for safety user profile was in average more satisfactory than for vehicles in the smaller engine size group (<1400cm3), which suggests that in general, larger vehicles may offer extra protection. The achieved results demonstrate that the developed SEG integrated methodology can be a helpful tool for consumers to evaluate their vehicle selection through different domains (safety, fuel efficiency and green emissions). Furthermore, SEG indicator allows the comparison of vehicles across different categories and vehicle model years. Hence, this research is intended to support the decision-making process for transportation policy, safety and sustainable mobility, providing insights not only to policy makers, but also for general public guidance.