Bicycle Helmets: Head Impact Dynamics in Helmeted and Unhelmeted Oblique Impact Tests

Abstract

Objective: To assess the factors, including helmet use, that contribute to head linear and angular acceleration in bicycle crash simulation tests.

Method: A series of laboratory tests was undertaken using an oblique impact rig. The impact rig included a drop assembly with a Hybrid III head and neck. The head struck a horizontally moving striker plate. Head linear and angular acceleration and striker plate force were measured. The Head Injury Criterion was derived. The following test parameters were varied: drop height to a maximum of 1.5 m, horizontal speed to a maximum of 25 km/h, helmet/no helmet, impact orientation/location, and restraint adjustment. Additional radial impacts were conducted on the same helmet models for comparison purposes. Descriptive statistics were derived and multiple regression was applied to examine the role of each parameter.

Results: Helmet use was the most significant factor in reducing the magnitude of all outcome variables. Linear acceleration and the Head Injury Criterion were influenced by the drop height, whereas angular acceleration tended to be influenced by the horizontal speed and impact orientation/location. The restraint adjustment influenced the outcome variables, with lower coefficients of variation observed with the tight restraint.

Conclusions: The study reinforces the benefits of wearing a bicycle helmet in a crash. The study also demonstrates that helmets do not increase angular head acceleration. The study assists in establishing the need for an agreed-upon international oblique helmet test as well as the boundary conditions for oblique helmet testing.

Supplemental materials are available for this article. Go to the publisher's online edition of Traffic Injury Prevention to view the supplemental file.

Keywords:

• helmet
• brain injury
• impact biomechanics
• test methods

Acknowledgments

This work was conducted at the Biomechanics and Gait Laboratory, School of Risk and Safety Sciences, UNSW, under funding by an Australian Research Council (ARC) Linkage Grant LP0669480 Pedal and Motor Cycle Helmet Performance Study. The project partners are the Commonwealth Department of Infrastructure and Transport, NSW Roads and Traffic Authority (NSW RTA, now known as Roads and Maritime Services), Transport Accident Commission Victoria, NRMA Motoring and Services, NRMA-ACT Road Safety Trust, and DVExperts International. The authors thank the Roads and Maritime Services Crashlab and its staff for their assistance. The authors thank Dr. George Rechnitzer, Ross DalNevo, Professor Raphael Grzebieta, and Dr. Toh Yen Pang for their involvement in the development of the oblique test rig.