Motorcycle helmet

A protective helmet worn by a motorcycle rider or passenger to reduce head injury in a crash. It typically combines a hard outer shell, an energy-absorbing liner, and a retention system.

Expanded polystyrene: A lightweight foam plastic whose cellular structure absorbs energy by deforming under impact. It forms the crushable liner that dissipates impact energy inside many motorcycle helmets.
Helmet fit: How closely and securely a helmet sits on a particular person's head. A correctly sized, stable fit helps the helmet remain in place during a crash.
Bicycle helmet: A helmet designed primarily to protect a cyclist's head in a fall or collision. Its testing and coverage requirements differ from those for motorcycle helmets.
T. E. Lawrence: A British writer and military officer known as Lawrence of Arabia, who died after a 1935 motorcycle crash. His death helped prompt Hugh Cairns to investigate head injuries among motorcyclists.
Helmet shell: The rigid outer layer of a helmet, designed to resist penetration and spread impact loads. It distributes concentrated contact forces and protects the liner from abrasion.
DOT motorcycle helmet standard: The United States Federal Motor Vehicle Safety Standard 218, which sets requirements for motorcycle helmets. It defines the performance and labeling requirements for helmets sold for road use in the United States.
Motorcycle helmet laws: Rules requiring or regulating helmet use by motorcycle riders and passengers. Legal requirements vary by jurisdiction and determine who must wear a helmet.
Hugh Cairns: A British neurosurgeon who studied head injuries and advocated protective helmets for motorcyclists. His research after Lawrence's death helped establish the case for motorcycle helmet use.
Helmet retention system: The straps and fasteners that keep a helmet secured to its wearer's head. A helmet cannot protect effectively if impact forces dislodge it.
ECE 22.06: A United Nations regulation setting approval requirements for motorcycle helmets and visors. Its current test regime includes impacts at multiple speeds and oblique-impact assessment.

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