Development of the Impact Attenuation Standard for Public Order Helmets

Public Order (PO) events, such as riots, expose officers to significant head injury risk. Helmets in the UK conform to the Home Office standard ‘PSDB 21/04’, although head injuries remain common, and helmet designs have seen little innovation since the 1970s. This research aimed to improve situational and injury representation in helmet testing standards to better scrutinise helmet efficacy. There is little knowledge of the specific causes of head injury in PO conditions. Analysis of footage identified prevalent threats associated with, projectile bricks and stones (37% of weapon events), flat-faced wooden beams (24.5%), and circular metallic poles (16.3%). Falls from height, particularly involving mounted officers, were also a significant risk. Representative experiments quantified the mechanics of these scenarios, showing peak linear accelerations of 126–771 g, angular accelerations of 1.3–24.5 krad/s², and pulse durations under 5 ms. A test system was developed to recreate these with more repeatable methodology, such as is required in standard procedure. Testing revealed that a cradled headform without a neckform, as per current standard procedure, most accurately replicated realistic dynamics. Flat anvils, which are not a current requirement of the standard, produced significantly higher peak kinematics compared to curved surfaces (P = 0.03). These also exceeded the 250 g failure threshold at lower impact energies (-48 J). In addition, angular velocity-based metrics, such as BrIC, predicted lower injury severity compared to angular acceleration-based metrics. Key recommendations for adaptations to the standard include that although the current 120 J energy drop test is representative of severe loading mechanics in PO activity, incorporation of flat anvils and angular-based failure thresholds would better scrutinise headgear efficacy. Suggested thresholds are 250 g for linear acceleration and 6 krad/s² for angular acceleration, however further validation is needed to finalise these. This work provides a foundation for improved helmet efficacy in PO activity and therefore long-term potential for a reduction in sustained neurotraumatic injuries.