This is what we found on Wikipedia regarding the Hans:

A HANS device (head and neck support device) is a type of head restraint and a safety device in motorsports. Head restraints are mandatory when competing with most major motorsports sanctioning bodies. They reduce the likelihood of head or neck injuries, including basilar skull fracture, in the event of a crash. The devices are now mass produced and marketed by Simpson Performance Products. There are many such devices on the market today, like the Hutchens device now known as the Simpson Hybrid Device, but the HANS is the original and most commonly used name.