The effect of Rear-End collisions on triaxial acceleration to occupant cervical and lumbar Spines: An analysis of IIHS data.

Rear-end impacts are the most frequent type of the more than seven million motor vehicle collisions (MVCs) occurring annually in the United States. The cervical and lumbar spine are the most commonly injured sites as a result of rear-end collisions. The direction and magnitude of accelerations and forces to the spine are considered primary indicators of injury. Yet, there is a dearth of research regarding the relation and quantification of vehicle to occupant accelerations, as well as triaxial acceleration components (and thus, forces) to occupant spines in rear-end impacts. Therefore, the current study utilizes the Insurance Institute of Highway Safety (IIHS) test database to examine the relative relations between vehicle and occupant accelerations, as well as between component accelerations experienced at the cervical and lumbar spines in rear-end collisions. Anthropometric test device (ATD) head and pelvis accelerometer data from IIHS sled testing are used as representative measures of acceleration experienced at the cervical and lumbar spine, respectively. Peak resultant acceleration is calculated at the head and pelvis, and peak directional components (x, y, and z) of acceleration are compared to resultants. This analysis revealed significantly higher occupant head than sled (2.17 ± 0.4 × Sled; p < 0.001) and pelvis than sled (1.24 ± 0.27 × Sled; p < 0.001) accelerations. There were also significant differences across triaxial acceleration components relative to resultant at the head (x = 0.99 ± 0.02, y = 0.11 ± 0.05, z = 0.34 ± 0.06; p < 0.001 for all comparisons) and pelvis (x = 0.94 ± 0.06, y = 0.12 ± 0.14, z = 0.35 ± 0.08; p < 0.001 for all comparisons). A secondary analysis examining differences in occupant dynamics by seat designs across vehicle type revealed significant differences only between the pelvis z component accelerations in the passenger vehicle and SUV groups (passenger vehicle:SUV = 1.07, p < 0.001). Due to the uniform nature of IIHS sled testing protocols, this analysis reflects similarities in seat properties rather than between vehicle types. These results may provide a simplistic approach to quantify the magnitude of directional accelerations and forces to occupant spines in rear-end collisions.

Analysis of bicycle helmet damage visibility for concussion-threshold impacts.

Any helmet involved in an accident should be replaced, regardless of appearance after impact. However, consumer compliance and interpretation of this recommendation is unclear, for which there is additional ambiguity for lesser impacts. This study aims to investigate the relation between helmet damage visibility and lesser impacts in line with concussion. As a preliminary model, a commercially available road-style helmet was chosen. Twelve helmets underwent impact attenuation testing; four were dropped from the standard testing height of 2 m, and eight from lower drop heights (0.34 and 0.42 m) associated with the production of linear accelerations (90 and 100 g, respectively) consistent with the production of concussion. Expanded polystyrene damage was assessed via flat punch penetration testing. American adults were then polled on helmet damage visibility based upon before and after photos. All helmets demonstrated damage to the expanded polystyrene liner in the form of altered material properties. Helmets dropped from 2 m displayed significant changes in elastic buckling (p < .01) and densification behavior (p < .01) as compared with lower drop height results. Adverse change in elastic buckling behavior was found to increase linearly with drop height (p < .001). Damage visibility was significant for helmets dropped from a 2-meter height, however, such a relation among the helmets impacted at the threshold for concussion was lacking. These findings suggest that for the chosen helmet model, consumers may be unable to distinguish between new helmets and helmets with diminished protective abilities.

A Proposed Algorithm to Assess Concussion Potential in Rear-End Motor Vehicle Collisions: A Meta-Analysis.

Concussions represent an increasing economic burden to society. Motor vehicle collisions (MVCs) are of the leading causes for sustaining a concussion, potentially due to high head accelerations. The change in velocity (i.e., delta-V) of a vehicle in a MVC is an established metric for impact severity. Accordingly, the purpose of this paper is to analyze findings from previous research to determine the relation between delta-V and linear head acceleration, including occupant parameters. Data was collected from previous research papers comprising both linear head acceleration and delta-V at the time of incident, head position of the occupant, awareness of the occupant prior to impact, as well as gender, age, height, and weight. Statistical analysis revealed the following significant power relation between delta-V and head acceleration: head acceleration = 0.465delta-V 1.3231 (R 2 = 0.5913, p < 0.001). Further analysis revealed that alongside delta-V, the occupant's gender and head position prior to impact were significant predictors of head acceleration (p = 0.022 and p = 0.001, respectively). The strongest model developed in this paper is considered physiologically implausible as the delta-V corresponding to a theoretical concussion threshold of 80 g exceeds the delta-V associated with probability of fatality. Future research should be aimed at providing a more thorough data set of the occupant head kinematics in MVCs to help develop a stronger predictive model for the relation between delta-V and head linear and angular acceleration.