Severity of cyclist head injuries caused by impacts with vehicle structure and road surface

Abstract

For cyclist fatalities in 2014 in Japan, the head was the most frequently injured body region. In the present study, the authors analyzed the features of cyclist head injuries in real-world traffic accidents using the data of patients who were taken to the emergency room in Dokkyo Medical University Koshigaya Hospital in Japan, from 2011 to 2013. The results indicated that the percentage of skull fractures was the highest among cyclist head injuries. Assuming that a helmet can prevent head injuries sustained by cyclists in traffic accidents, the effect of wearing a helmet was investigated in impact tests against a vehicle and road pavement. In the tests, the severity of potential head injuries was determined from the Head Injury Criterion (HIC) obtained in an adult pedestrian head-form impactor with and without a helmet. The impact location selected for a vehicle was the A-pillar because the pillar had much higher stiffness than the vehicle bonnet or windshield. It was found that the HIC values for the head-form impactor wearing a helmet were much lower than the HIC values for the head-form impactor not wearing a helmet in both the head-versus-A-pillar impacts and head-versus-pavement impacts. The results suggest that wearing a helmet could reduce the possibility of skull fracture in cyclists.

Finite element analysis of the effectiveness of bicycle helmets in head impacts against roads

“…In particular, the reduction in the peak skull strain used to estimate the skull fracture (92%-97%) was much larger than that for other head injuries. A study reported that skull fracture (25%) was the most frequent head injury, followed by subarachnoid bleeding (16%), and subdural hematoma (12%) in cyclists involved in traffic accidents (Oikawa et al, 2016b). Bambach et al (2013) indicated that head injury risk reduction was significantly associated with helmet use, with a reduction up to 74% overall, including a 78% reduction in skull fracture, 72% reduction in intracranial injury, 74% reduction in concussive injury, and 80% reduction in open head wounds.…”

“…For example, pedestrian head protection performance tests for vehicle hoods have been evaluated by the HIC (Matsui, 2011). When Oikawa et al (2016b) conducted impact experiments against the A-pillar of a vehicle and a road using a headform impactor with and without a helmet, the helmeted cases resulted in a 60% HIC reduction for impacts against a vehicle and an 86% HIC reduction for impacts against the road. Considering the results obtained from this study, those reductions would correlate with skull fractures, not brain injuries.…”

“…An FE headform impactor model was developed to evaluate the FE bicycle helmet model by comparing with experimental tests performed with a helmet placed on a headform impactor (Oikawa et al, 2016b). A headform impactor weighing 4.5 kg (Matsui and Tanahashi, 2004) represents the head of an adult human.…”

“…5. The FE bicycle helmet model was validated by comparison with a drop experiment of the helmet against road pavement (Oikawa et al, 2016b). The FE headform impactor model was coupled with the helmet model to match the experiment.…”

Correlation between acute phase head injury to cyclists and consciousness disturbance: a case study in reconstruction of single-cyclist accident

“…The coefficient of friction between the head or helmet and the wall was set to 0.5, as was the friction coefficient between the head and helmet (Fahlstedt et al, 2016). The FE bicycle helmet model was validated by comparison with a drop experiment of the helmet against the pavement (Oikawa et al, 2016). The comparison yielded good agreement between the resultant accelerations in the simulation and the experiment.…”