In collaboration with the Insurance Institute for Highway Safety, we have rated 238 bike helmets using the STAR evaluation system. Our impact tests evaluate a helmet's ability to reduce linear acceleration and rotational velocity of the head resulting from a range of head impacts a cyclist might experience.

The lab has not tested every model on the market or included in our review, but many of the models listed above have been rated. In fact, our best overall road bike helmet, the Giro Aries Spherical, is the top-rated model for protection that they have tested to date.

Full-face helmets provide the most head coverage, followed by mountain bike and skate helmets. Road bike helmets offer the least overall protection, generally. Most of today's bike helmets are constructed with Expanded Polystyrene (EPS) foam that is only designed to withstand one significant impact.

Head coverage varies and affects protection in a crash. Some helmets we cover here protect more of the back of the head than others. Full-face helmets provide the most head coverage, followed by mountain bike and skate helmets. Road bike helmets offer the least overall protection, generally.