Differences in Impact Performance of Bicycle Helmets During Oblique Impacts

Area of Science:

• Biomechanics
• Sports Medicine
• Product Safety Engineering

Background:

• Cycling is a major cause of sport-related head injuries in the U.S.
• Current bicycle helmet standards do not adequately assess protection against common, concussive-level, oblique impacts.
• Limited data exist on the comparative protective performance of different helmet models under real-world conditions.

Purpose of the Study:

• To investigate and compare the protective capabilities of ten bicycle helmet models under common real-world oblique impact scenarios.
• To evaluate differences in linear and rotational accelerations and their correlation with concussion risk.
• To identify helmet design parameters influencing protective performance.

Main Methods:

• Oblique impact drop tests were conducted on ten helmet models onto an angled anvil.
• Impacts were performed at velocities and locations representative of common cyclist head impacts.
• Linear and rotational accelerations were measured and analyzed to determine concussion risk and relate it to helmet design features.

Main Results:

• Significant variations in linear and rotational accelerations were observed across different helmet models, leading to concussion risk differences exceeding 50% in some configurations.
• Linear acceleration differences were more pronounced between models than rotational acceleration.
• Helmet design factors such as shell thickness, vent configuration, and radius of curvature influenced effective stiffness at the temporal location.
• Liner thickness varied at the frontal rim, a frequently impacted area, suggesting potential deficiencies in current testing standards.

Conclusions:

• Existing bicycle helmet standards may not fully address protection against common oblique impacts experienced by cyclists.
• Helmet design significantly impacts protective performance, particularly linear acceleration mitigation.
• Recommendations include optimizing helmet stiffness and expanding standards testing to include frequently impacted areas like the frontal rim to enhance cyclist head protection.