More usable tread space than ship's ladders


CONVENTIONAL STAIR

Imagine walking down (or up) a conventional stair. Each foot
normally uses only about half
of each tread, stepping out and
over the unused section (shaded
red).
STEEP STAIR

On a steeper stair or ladder,
the unused half tread becomes
an obstacle, significantly
reducing the usable tread
depth of the tread directly
below. As the angle increases,
the problem becomes worse.
LAPEYRE STAIR

In contrast, the Lapeyre
stair removes the unused
half of each tread, allowing
the foot to reach the next
tread in a straight, direct
line, providing more usable
tread depth.