US federal building codes, the
maximum height for an access ramp is 30 inches.
To reach entrances that exceed this limit, lifts or an
elevator may be installed.
Most cars cannot climb hills that have a
slope of 30° (or rise about 1 foot for
every 1.7 feet horizontally).
Most local building codes describe a maximum
stair rise of 8-1/4 inches and a minimum tread
width of 9 inches.
More than nine
out of ten avalanches occur on slopes ranging
from 25° to 45°.
ratio for slope is independent of units.
Most black diamond
ski slopes are around 30°
to 35°, while a 40° slope would be
considered the low end of extreme mountaineering.
Parts of Tuckermans Ravine on Mt. Washington
have slopes of about 50°.
Slopes are rates
of change, a fundamental idea of calculus.
Another way to express a slope uses the
trigonometry notion of tangent.