49 CFR Parts 37 & 38 - Department of Transportation (DOT) ADA Regulations

II. Color Contrast—Step Edges, Lift Platform Edges

The material used to provide contrast should contrast by at least 70%. Contrast in percent is determined by:

Contrast=[B−B)/B]×100

Where B=light reflectance value (LRV) of the lighter area

and B=light reflectance value (LRV) of the darker area.

Note that in any application both white and black are never absolute; thus, B never equals 100 and B is always greater than 0.