Replicating Real-World Friction of Motorcycle Helmet Impacts and Its Effects on Head Injury Metrics

The purpose of this study was to determine the frictional properties between the exterior surface of a motorcycle helmet and ‘typical’ roadway surfaces. Motorcycle helmet impacts into asphalt and concrete surfaces were compared to abrasive papers currently recommended by government helmet safety standards and widely used by researchers in the field of oblique motorcycle helmet impact testing. A guided freefall test fixture was utilized to obtain nominal impact velocities of 5, 7 and 9 m/s. The impacting surfaces were mounted to an angled anvil to simulate an off-centered oblique collision. Helmeted Hybrid III ATD head accelerations and impact forces were measured for each test. The study was limited to a single helmet model and impact angle (30 degrees). Analysis of the normal and tangential forces imparted to the contact surface indicated that the frictional properties of abrasive papers differ from asphalt and concrete in magnitude, duration and onset. Reduction in head acceleration, both linear and angular, was observed when asphalt and concrete were used as the impact surface. Roofing shingle was determined to be a more suitable material to simulate ‘typical’ roadway surfaces; however, this may not be ideal for use in a controlled laboratory setting. In a laboratory setting concrete, a commonly used roadway material, is recommended as a best-fit material to simulate the surface of a roadway for use in oblique motorcycle helmet impacts.