Here is a link to USDF Dressage Tests.

SAFETY NOTICE

While all equestrian sports involve inherent dangerous risk and no helmet can protect against all foreseeable injuries, USEF strongly encourages all riders to wear protective headgear with harness secured which passes or surpasses ASTM (American Society for Testing and Materials) / SEI (Safety Equipment Institute) standards for equestrian use and carries the SEI tag.