Impact reconstruction from damage to pedal and motorcycle helmets

Abstract

Pedal and motorcycle helmets offer a high level of protection to the wearer's head. There is a need to review and assess the performance offered by helmets, so that helmet design and test standards can be optimized. One input into this process is crash reconstruction. Helmeted crash cases can be collected and examined, leading to insights into impact severity, helmet performance and injury outcomes. However, it is unclear to what extent residual helmet damage reflects the impact characteristics. This paper addresses this issue using controlled laboratory impact tests.Two pedal cycle and three motorcycle helmet models were tested with an 'M' size headform in impact energy attenuation tests from 1 m, 2 m and 2.5 m. Headform acceleration, impact force and post-impact deformation were measured. The dynamic deformations were measured with three methods: video, kinetic energy and an analytical approach using impact force and liner yield stress.All five models offered highly repeatable performance in terms of impact energy attenuation and acceleration management in radial impacts across the impact severities. The results showed that the Standards Australia certified helmets provided impact protection to the head in impacts that greatly exceeded the impact energy attenuation performance requirements of those standards.The residual and dynamic deformation measurements were correlated with drop height and headform acceleration for pedal cycle helmets. The results indicate that the residual deformation observed in a pedal cycle helmet collected from a crash can be used to estimate the impact severity and, after undertaking exemplar impact tests on the same model helmet, the head impact acceleration. However, the residual deformation measured on the three motorcycle helmets was not correlated with the drop height, which indicated that, within the limits of this study, estimating crash severity from motorcycle helmet damage is not reliable.

Angular Impact Mitigation system for bicycle helmets to reduce head acceleration and risk of traumatic brain injury

“…Preliminary tests in this laboratory have shown that angular acceleration levels for microshell helmets may be up to 20% lower than those for hard shell helmets. McIntosh et al (2012) reported an average linear acceleration of 207 g for microshell helmets dropped from 2 m, which is 26% lower than the CONTROL helmets in this study. Changes to the density and thickness of an EPS liner can also lead to improvements in impact performance.…”

Long term bicycle related head injury trends for New South Wales, Australia following mandatory helmet legislation

“…Moreover, when considering the biomechanical helmet padding system protecting the head, Newtonian laws of physics dictate that an impact force via the helmet to the head during a reasonable velocity crash (50-60 km/h or less) must reduce the magnitude of the blunt force imposed onto the rider's head, and thus the severity of the head injury. This is a given physical fact that can be readily proven both experimentally and from in-depth real world crash investigations (Dorsch et al, 1987;Benz et al, 1993;McIntosh et al, 1998McIntosh et al, , 2010Pang et al, 2009;Haworth et al, 2010;McIntosh and Patton, 2012). Thus, given that helmets dampen the impact force and subsequent injury severity, it is expected that evidence of helmets reducing head injuries would be evident in hospital admissions data and bicycle population surveys.…”

Head impact velocities in FIS World Cup snowboarders and freestyle skiers: Do real-life impacts exceed helmet testing standards?

“…This suggests that the helmets worn provided substantial protection to the head against moderate to severe TBI and might exceed the homologation requirements. Homologation requirements are minimum performance requirements; for example, McIntosh and Patton44 observed in two AS/NZS 2063-compliant bicycle helmets that the peak headform acceleration at a drop height of 2.5 m remained under the 250 g pass level for the 1.5 m requirement mandated in AS/NZS 2063 44. The helmet models, condition and impact damage in three of our four cases is unknown.…”