The HANS system, also known as head and neck support device, is the most important safety device for an F1 driver.
The HANS device works in a similar way to a road car airbag. The airbag, in a normal road car, prevents the head and neck from overstretching, apart from preventing impact with the dashboard and other objects.
The HANS device has two straps (indicated by no. 2 in figure) which are attached with the helmet. The bulk of the job is done by these two straps. In case of an accident, the driver’s head and neck are subjected to massive forces and overstretching of the neck can cause it to break just like a matchstick.
So, to prevent this overstretching, the HANS device is used. In case of an accident, the HANS device stops the head from overstretching forward, thus reducing the load on the neck muscles. Bulk of the force of impact is dissipated by the shoulder blades of the device, thus preventing strain on neck and head structure.
HANS reduces neck motion by about 46 percent and the force of impact by 86 percent. The HANS device is a mandatory feature in formula one and has saved lives of many racing drivers.