A DOT-compliant helmet:

Question

While some people believe that a helmet will limit their vision, this is not the case. Any U.S. Department of Transportation-approved helmet will allow the wearer to see as far as is needed for safe riding.

Accepted Answer

Allows you to see as far to the sides as is necessary for safe riding.

Answer

Severely limits your vision.

Answer

Can become a hazard to the rider.