Sentence 9.8.4.5.(2)

Intent 1:

To limit the probability that a mix of rectangular and tapered treads in a flight will disrupt the gait of users, or force them to switch to the other side of the stair, which could lead to:

• persons misstepping and tripping, or
• persons misstepping and tripping in an emergency, which could lead to delays in the evacuation or movement of persons to a safe place.

This is to limit the probability of harm to persons.

Intent 2:

To supersede the requirement stated in Sentence 9.8.4.5.(1) regarding the uniformity of runs in a mixed-tread flight and permit the run of tapered treads to exceed the run of rectangular treads where the tapered treads are at the bottom of the flight.