To limit the probability of:
- insufficient tread depth,
- incompatibility between the height of risers and the
average user's stride,
- insufficient room to accommodate the length of user's
- excessively steep stairs.
This is to limit the probability of:
- persons misstepping or tripping, or
- persons misstepping or tripping in an emergency, which
could lead to delays in the evacuation or movement of persons to a
This is to limit the probability of harm to persons.