When a cyclist is involved in a real-world impact, the offending vehicle occasionally leaves the scene (e.g. hit and run). Often, there are no witnesses and the impacted cyclist has little or no recollection about the collision events. In these instances, a forensic investigation of the collision is required in order to determine whether a phantom vehicle has been involved or, alternately, whether the cyclist has simply fallen and impacted the ground surface.

A series of dynamic impact tests were conducted in order to forensically evaluate the performance of bicycle helmets when impacted in environments intended to replicate realworld collisions between cyclists and vehicles. The first series of tests involved dynamic drop tests of helmeted 5-7kg surrogate headforms dropped from heights of 5 metres to 15 metres (to simulate different impact speeds) onto protruding metal objects, as well as from a nominal riding height of 1.3 metres onto a gravel road at 20km/h, 30km/h and 40km/h. The second series of tests involved impacts to a helmeted semi-rigid inverted pendulum with a total system mass of 55kg to 65kg. The inverted pendulum assembly was subjected to two types of dynamic helmet impact tests: A) Rotational free-fall helmet impact with the ground surface from nominal riding height and B) Helmet impact with a vehicle side rear-view mirror assembly (with incremental vehicle impact speeds of 20km/h to 60km/h).

The helmet damage sustained in each test was documented and recorded photographically and videographically. The post-impact results were then compared to the helmet damage sustained in real-world cyclist collisions with alleged vehicle involvement. The test results enabled scientific investigators to accept or reject hypotheses presented regarding the alleged collision events.

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