CRASH assesses and compares motorcycle helmets in terms of their ability to protect the wearer's head in a crash and how comfortable the helmet is to wear.
The helmet's crash protection performance is assessed using the following criteria:
The helmet must be able to reduce the impact of a crash and manage the acceleration of the head to minimise injury. To achieve this, the helmet must:
In all tests, a simulated head with many characteristics of the human head is used to facilitate the measurement of various forces in the crash test. The data gathered is then assessed using recognised protocols, and scores are determined for each specific test.
A helmet's ability to mitigate the effect of a blow to the head is assessed by dropping it onto a hard surface representative of the roadway, and a 'hard metal edge' such as a kerb, roadside barrier or corner of a vehicle.
These test surfaces (anvils) are termed 'flat', 'hemispherical' or 'kerb'. CRASH uses modified tests comprising high and low speed impacts (compared to AS/NZS 1698 requirements) using a flat surface and higher speed impact than UN/ECE Regulation 22* using a simulated kerb surface.
In tests where the helmet is dropped onto a flat surface, the helmet mounted on a simulated head is dropped from heights of 0.8 metres and 2.5 metres (AS/NZS 1698 uses a drop height of 1.83 metres). The helmets are evaluated in terms of their ability to reduce impact to the head, maintain the helmet structural integrity, and ensure the chin strap is still working properly after the test. The test matrix and impact locations are shown in the figure and table below.
|Energy reduction in high speed impact on flat surface – Impact 1||A|
|Energy reduction in high speed impact on flat surface – Impact 2||C|
|Energy reduction in low speed impact on flat surface – Impact 1||B|
|Energy reduction in low speed impact on flat surface – Impact 2||D|
|Energy reduction in high speed impact on kerb surface||E|
An ideal helmet should be able to absorb maximum impact energy with as little rebound as possible, while maintaining a tolerable acceleration level. In this program the helmet's ability to maximise impact energy reduction is assessed by calculating the ratio of speeds before and after an impact (coefficient of restitution).
Impact energy attenuation test using a flat surface (anvil)
Impact energy attenuation test using a simulated kerb (anvil)
Another factor necessary for a helmet to be effective during a crash is that it remains in place during the crash. The helmet should also remain in place for subsequent impacts. Helmets are assessed in terms of their ability to stay on the wearer's head and minimise the rotation of the helmet so it remains effective in protecting the most important parts of the skull. This is assessed by rolling the helmet off from the simulated head by applying an upward force to the rear of the helmet at its base.
The strength of the helmet's chin strap is also tested to ensure that the chin strap remains intact and does not stretch to a point where the helmet would come off during a crash. The chin strap is tested by dropping a 10kg weight from a height of 750mm, resulting in a force being applied directly to the strap. This test is derived from UN/ECE Regulation 22.