Motorcycle helmets are very important in keeping people alive. In fact, there is nothing that will help you more in a crash situation than wearing one. A motorcycle helmet protects the head, and is also used as a face shield, for ear protection, and for intercom purposes.

Modern helmets are made from plastics, and are often reinforced with Kevlar or a carbon fiber. For comfort and protection they generally have fabric and foam interiors. During a crash situation, a motorcycle helmet will break, which is what they are designed to do. In essence, the helmet will absorb the energy and impact of the fall instead of the rider’s skull. As a result, they don’t offer much protection after their first impact. An impact may come from other reasons outside of a crash situation, ie. dropping the helmet from a high place, which may not cause any external damage. As a rule, helmets should be replaced after any type of major impact. But, it’s a good idea to replace it after three to four years, regardless of whether it has sustained impact or not; it’s a good safeguard.

There are three types of motorcycle helmets; depending on how much protection you are looking for:

• Full-face helmet: covers the entire head, including the base of the skull. These helmets usually have a protective section that covers the chin as well. A plastic shield covers the eyes. The obvious benefit of a full-face helmet is its level of protection. The drawbacks are an increased level of heat and reduced level of hearing.

• 3/4 face helmet: covers the back of the skull, but doesn’t have chin protection. Some offer a visor, which blocks out bright sunlight or blinding headlights. A 3/4 face helmet provides similar rear protection as a full-face helmet, but not much protection for the face.

• 1/2 helmet: provides the least amount of coverage generally allowed by law in the US. All of these types of helmets are secured by a chin strap, which offers some level of protection by keeping the helmet on the head.

More popular since mandatory helmet legislation was passed are "beanies", which are not certified and are used to by riders to make it appear that they are complying with the law. Such helmets are smaller and lighter than others and usually have a cool, sleek appearance. They are not good for crash protection because they lack the foam layer that protects the rider’s brain.

A typical motorcycle helmet has two major protective mechanisms:

• An outer shell that is made of acrylonitrile butadiene styrene (ABS) plastic, fiberglass or Kevlar. It is usually fairly thin. The purpose of this hard outer shell is to prevent penetration of the helmet by a pointed object that could puncture the skull. It also provides structure to the inner liner so it does not disintegrate when it hits concrete, pavement or any other hard surface. The foams used on motorcycle helmets usually have very little resistance to penetration and abrasion.

• A thick, soft inner liner made of expanded polystyrene foam or expanded polypropylene foam. The purpose of the foam liner is to crush during impact, which increases the distance and time over which the helmet stops, reducing its acceleration.