1.1.4 Walk cross slope. Measure for overall cross slope (the direction perpendicular to the running slope) by establishing elevations at the outside edges of the walking surface at 10 ft (3 m) intervals beginning at one end of the walking surface. Calculate the cross slope at these locations using the horizontal walking surface width and difference between the measurement elevations at the edges of the walking surface (i.e. the rise over the run).
If an obvious change in cross slope occurs between measuring points (such as a steeper driveway crossing a sidewalk), measure a minimum of two cross slopes at the steeper portion, but in no case should the measurements be farther apart than 5 ft (1.5 m).
A simple method of establishing the relative elevations is to use a rotating laser level on a tripod and document the difference in height on a stiff metal tape measure or surveyor's rod. Alternately, a surveyor's transit or other electronic surveying tool may be used if it meets the accuracy requirements of 1.1.1. For walkways that are narrower than the length of a carpenter's level, the instrument may be placed level, resting on the high edge of the walk, and the distance from the level to the low edge of the walk may be measured to determine the difference in elevation.
The methods in 1.1.3 and 1.1.4 of establishing the running slope and cross slope is consistent with the requirements of ADA/ABA - AG, which limits the running slope and cross slope of walking surfaces to 1:20 and 1:48, respectively. Slopes greater than 1:20 are considered ramps and must conform to the requirements for ramps. Currently, these are the only ADA/ABA - AG standards related to running and cross slope that must be met.
In the draft guidelines for public rights - of - way (which are not yet final) an exception for slope is granted to sidewalks that follow the natural slope of the adjoining street or grade even though it may be steeper than 1:20.
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