The Oblique Impact Test

The oblique impact test is designed to measure the rotational acceleration of a helmet and head form caused by friction. The results of this test can be used to monitor the risk of brain or neck injury caused on impact with the road.

Within the current European legislation, there are two methods of testing oblique impacts. The differences between the two methods are numerous - they are based on different principles - but are intended to identify similar helmet performance. Research has recently been completed which evaluates both Methods (A and B) and determines their suitability. Previous research had determined that Method B was more stringent, but this was based on a number of approximations involving non-linear energy transfer and complex loading mechanisms which is too simplistic in nature. Indeed recent evidence suggests that Method A is more stringent than Method B for surface friction.

For oblique impact testing Method A, as described in UN-ECE Regulation 22.05, is being used. Method A more closely simulates real world accident dynamic loading conditions, and provides a numerical (non-binary) result, as opposed to a simple pass/fail. Method A has its foundations in British Standard BS 6658:1985 and prescribes a test based on the peak tangential forces resulting from an oblique impact between the helmet and abrasive surface.

The helmeted head form is guided onto an oblique rigid anvil at a velocity of 8.5m/s. UN ECE Regulation 22.05 compliant abrasive inclined anvil test apparatus is used to assess surface friction. For this assessment, tests will be carried out using a size J head form only, with the results being applied for all helmet sizes.

Surface friction may be determined at any point on the helmet shell but for consistency tests are performed on both sides of the helmet with the helmet facing forwards (wherever possible). Impact sites are as near as possible to those identified as point X within UN ECE Regulation 22.05. The impact velocity will be 8.5 m/s, with a tolerance of -0 / +0.15m/s.

Should an unusual or standard geometric feature or fitting be within the impact site and be deemed likely to influence the result, then the site may be redefined to a suitable area.