Until the document regarding American National Standard for High-Visibility Safety Apparel (ANSI/ISEA 107-1999) was published, there was no authoritative guide for performance specifications, design, and use of high visibility and reflective apparel, which included vests, bib-jumpsuit coveralls, jackets, harnesses and trousers.  The many workers that need this protection are now assured of being seen, both day and night, when they wear apparel that conforms to these regulations.  These conspicuity classes of garments are based on wearer’s activities:
Class I:

• Occupations requiring full and undivided attention to approaching traffic, moving no faster than 25 mph.

• Non-complex work backgrounds.

• Working away from traffic.

• Examples: Sidewalk maintenance workers, parking lot attendants, roadside “right of way”, delivery vehicle drivers (if criteria is met for Class I), shopping cart retrievers, and workers in warehouses with equipment traffic.

Class I garments should have a visible background of 217 sq. inches, and visible reflective of 155 sq. inches.
Class II:

• Occupations for workers that need greater visibility in inclement weather, or have greater risks than Class I; whose activities are near roadways where traffic speeds exceed 25 mph but less than 50 mph.

• Complex work backgrounds.

• Diversion of traffic attention.

• Examples: Ship cargo handlers, roadway construction, airport baggage/ground crew, emergency response/law enforcement, forestry, railway workers, school crossing guards, trash collection and recycling, delivery vehicle drivers where criteria is met.

Class II garments should have a visible background of 755 sq. inches, and visible reflective of 201 sq. inches.
Class III:

• Occupations of workers who face serious hazards and have high task loads that require attention away from their work.  Garments should provide enhanced visibility to more of the body, such as arms and legs.  Workers in locations where traffic exceeds 50 mph, should have the highest level of conspicuity.

• Workers who are exposed to extreme weather conditions.

• High risk workers and limited sight distances jobs.

• Examples: Utility workers, roadway personnel, survey crews, emergency response, equipment operators, railway workers, accident side investigators.

Class III garments should have a visible background of 1240 sq. inches, and visible reflective of 310 sq. inches.

Always be sure that the label on the vests identifies the vest maker and that it meets ANSI/ISEA.  It should display a picture of the vest, class and brightness level, and garment care guide.
Source: ANSI, Occunomix