Vehicle front-end geometry and in-depth pedestrian injury outcomes

OBJECTIVE

Large passenger vehicles have consistently demonstrated an outsized injury risk to pedestrians they strike, particularly those with tall, blunt front ends. However, the specific injuries suffered by pedestrians in these crashes as well as the mechanics of those injuries remain unclear. The current study was conducted to explore how a variety of vehicle measurements affect pedestrian injury outcomes using crash reconstruction and detailed injury attribution.

METHODS

We analyzed 121 pedestrian crashes together with a set of vehicle measurements for each crash: hood leading edge height, bumper lead angle, hood length, hood angle, and windshield angle.

RESULTS

Consistent with past research, having a higher hood leading edge height increased pedestrian injury severity, especially among vehicles with blunt front ends. The poor crash outcomes associated with these vehicles stem from greater injury risk and severity to the torso and hip from these vehicles' front ends and a tendency for them to throw pedestrians forward after impact.

CONCLUSIONS

The combination of vehicle height and a steep bumper lead angle may explain the elevated pedestrian crash severity typically observed among large vehicles.

Frontal NCAP performance and field injury over 40 years

OBJECTIVES

Vehicle and occupant responses in 35 mph NCAP tests were determined for small-midsize passenger cars grouped around model year (MY) 1980, 1990, 2000, 2010 and 2020. A baseline was established with 1980 vehicles not designed for NCAP. The results of four decades of vehicles designed for NCAP were compared to the baseline. The study also determined the risk for serious injury (MAIS 3 + F) by vehicle model year (MY) using 1989-2015 NASS and 2017-2020 CISS. It explored safety trends in frontal crashes over 50 MYs of vehicles.

METHODS

The 1980 baseline group was established with 10 1979-1983 MY passenger cars weighing <1,500 kg. Four decades of vehicle crash tests from five manufacturers established trends in vehicle dynamics and dummy responses over four decades of vehicles designed for NCAP. Triaxial acceleration of the head and chest were reanalyzed for each test to have a consistent set of responses over five decades. The risk for serious injury (MAIS 3 + F) to the driver and front passenger was determined by vehicle MY using 1989-2015 NASS and 2017-2020 CISS with belted and unbelted drivers and right-front passengers. The data was sorted in four MY groups 1961-1989 MY, 1990-1999 MY, 2000-2009 MY and 2010 MY-2021 MY. The risk for MAIS 3 + F injury was determined with standard errors using weighted data.

RESULTS

The 1980 NCAP tests brought about changes in vehicle structures and occupant restraints by 1990; however, HIC15 and 3 ms chest acceleration have not changed much the past 20 years since the use of advanced airbags and seatbelts with pretensioner and load-limiters. For the driver, HIC15 dropped 40 ± 19% from the 1980 to 1990 NCAP tests and dropped further to 76 ± 32% in 2020. The percentage drops after 1990 were not statistically significant. The driver 3 ms chest acceleration dropped 18 ± 5% from 1980 to 1990 and plateaued with 22 ± 6% in 2020. For the front passenger, HIC15 dropped 68 ± 52% from the 1980 to 1990 NCAP tests and plateaued at 71 ± 49% in 2020. The passenger 3 ms chest acceleration dropped 13 ± 5% from 1980 to 1990 and has fluctuated with minimal change. Injury risks based on responses show the same initial drop in 1990 and have remained essentially constant. Nothing meaningful has changed in dummy responses in the past 20 years of NCAP testing. The field data found the belted driver MAIS 3 + F risk was 1.66 ± 0.37% in 1961-1989 MY vehicles and 1.39 ± 0.33% in 2010-2021 MY vehicles. For belted right-front passengers, the risk was 1.52 ± 0.39% in 1961-1989 MY vehicles and 1.42 ± 0.46% in 2010-2021 MY vehicles. The field data shows no meaningful change in injury risk in 50 MYs of vehicles. NCAP involves 35-40 mph delta-V, which represents a small fraction, 0.33%, of belted occupant exposure and only 8.6% of severe injury based on 1994-2015 NASS.

CONCLUSIONS

The NCAP test lacks field relevance. Manufacturers are merely "tuning" the restraint systems for star ratings without meaningful changes in field injury risks the past 20 years. There are disbenefits of "tuning" safety for a single, high-severity crash when most of the severe injury occurs in lower severity crashes. NHTSA should reevaluate plans to change the dummy to Thor and add BrIC injury criteria to assess NCAP responses. These changes would cause manufacturers to further "tune" structures, restraints and interiors without meaningful effects in real-world crashes.

Bicyclist crashes with cars and SUVs: Injury severity and risk factors

OBJECTIVE

The popularity of bicycle travel has increased in recent years alongside a comparable increase in the risk of injury or death for those cyclists. The current study was conducted to investigate the differences in injury outcomes between bicyclists struck by SUVs and those struck by cars and to uncover the mechanisms behind injury patterns that have been observed in past research.

METHODS

We analyzed 71 single-vehicle crashes from the Vulnerable Road User Injury Prevention Alliance pedestrian crash database, focusing on crashes involving an SUV or car. Each crash from this database included an in-depth analysis of police reports, bicyclist medical records, crash reconstructions, and injury attribution by a panel of experts.

RESULTS

Bicyclist injuries from crashes with SUVs were more severe than those from crashes with cars, particularly with respect to head injuries. The greater injury severity associated with SUVs was related to these vehicles' tendency to produce injuries from ground contact or from vehicle components near the ground. In contrast, cars were much less likely to produce ground injuries and instead tended to distribute less severe injuries across multiple vehicle components.

CONCLUSIONS

The pattern of results suggest that the size and shape of SUV front ends are responsible for the differences in bicyclist injury outcomes. In particular, we found that SUV crashes inflicted more severe head injuries compared with car crashes and that SUVs were disproportionately likely to throw bicyclists to the ground and run them over.

Fetal deaths and maternal injury in motor-vehicle crashes using NASS-CDS and CISS field data

OBJECTIVE

This study determined the risk for fetal death and maternal injury in the same sample of motor-vehicle crashes. The frequency and risk of serious injury (MAIS 3 + F) were also assessed by sex, pregnancy, seating position and crash type.

METHOD

The 2008-2015 NASS-CDS and 2017-2020 CISS are representative samples that were analyzed for the risk of fetal death and the risk of maternal injury grouped by MAIS 0-2, MAIS 3 + F and death (F) in 2000+ model year (MY) light vehicles. All electronic cases involving fetal mortality were reviewed for mechanism of injury. Separately, the 2000-2015 NASS-CDS and 2017-2020 CISS data was analyzed for the risk of serious injury for male, female and pregnant female occupants by seating position and crash type in 2000+ MY light vehicles. All calculations are made with weighted data. The significance of differences in risk was determined by the Rao-Scott chi-square test in SAS and z-test for differences in proportions.

RESULTS

There were 2,467 ± 1,407 fetal deaths in light vehicle crashes from 2008-2015 and 2016-2020 with an annual occurrence of 206/yr. The risk for fetal death was 1.25% ± 0.74% of exposed pregnant females. There were 127 ± 67 deaths of pregnant females, or 11/yr in the same sample. The fatality risk was 0.065% ± 0.035%. The difference in proportions was statistically significant (z = 46.1, p < 0.0001). Fetal deaths occurred 19.4-times more often than deaths of pregnant females. In 82.9% of the crashes with a fetal death, the pregnant female was not seriously injured (MAIS 3 + F). The most common mechanism of fetal death was a minor crash, in 80.1% of the weighted cases based on review of photos of the case vehicle and observing very minor structural damage to the vehicle. The minor crash involved either yaw of the occupant compartment with side loading of the pregnant female or her displacement into the restraint system and side interior in 71.7% of the crashes. A severe crash with intrusion at the seating position of the pregnant female occurred in only 11.5% of cases. It usually caused serious injury to the pregnant female and fetal death.

CONCLUSIONS

Fetal deaths occurred 19.4-times more often than deaths of pregnant females in a 12-year sample of motor-vehicle crashes. The most common mechanism was a minor crash that resulted in a fetal death without serious injury to the pregnant female and involved side or oblique loading of the pregnant female.

Mitigating fuel tank syndrome pelvic injuries - is there potential for rider worn protectors?

OBJECTIVE

The aim of this study was to investigate the feasibility of rider-worn pelvis protection for mitigating injury risk when contacting the motorcycle fuel tank in a crash.

METHODS

A newly developed test apparatus was designed and constructed to simulate the interaction between a rider's pelvis and the motorcycle fuel tank in a frontal crash. Impacts were performed at a velocity of 18 km/h into four motorcycle fuel tanks. Further testing used a rigid fuel tank surrogate and the pelvis surrogate in an unprotected condition and with a series of impact protector prototypes. A subset of prototype samples was also tested at varying tank angles (30°, 37.5°, 45°) and impact speeds (8.5 km/h, 13 km/h, 18 km/h). Analysis of variance was used to determine whether the protector prototypes reduced pelvis response compared to unprotected.

RESULTS

Resultant peak pelvis acceleration was reduced by three pelvis impact protector prototypes compared to an unprotected condition. The reduction in peak acceleration occurred without a significant change in the peak pelvis rotational velocity. The pattern of protector performance was consistent at varying fuel tank angles but only reduced the pelvis response at the highest impact speed tested of 18 km/h.

CONCLUSIONS

The results indicate that there may be potential for using pelvis impact protection to mitigate injury risk by absorbing and/or distributing impact energy that would otherwise be transmitted to the rider's pelvis. However, due to the current paucity in understanding of pelvis biomechanics to anteroposterior loading, it is unknown whether the pelvis acceleration reductions achieved would prevent injury.