To limit the probability that persons will not be able to readily identify the leading edges of treads and landings, and the beginning and end of ramps, which could lead to difficulties in moving in an emergency situation, which could lead to delays in the evacuation or movement of persons to a safe place, which could lead to harm to persons.
To limit the probability that persons will not be able to readily identify the leading edges of treads and landings, and the beginning and end of ramps, which could lead to persons tripping or falling, which could lead to harm to persons.