ANSI/ISEA 107-1999
American National Standard for High Visibility Safety Apparel

Class I –

Lower visibility requirements for workers well separated from traffic
Vehicle and equipment speeds – under 25 MPH
Background material - 217 square inches
Retroreflective material is 155 square inches

Class II -

Medium visibility requirements for workers who are on or near roadways
Vehicle and equipment speeds – 25-50 MPH
Background material - 775 square inches
Retroreflective material is 201 square inches

Class III -

Highest visibility requirements for workers in high-risk areas and situations, needing to be seen by traffic by minimum distance of 1,280 feet
Vehicle and equipment speeds – over 50 MPH
Background material – 1,240 square inches
Retroreflective material is 310 square inches