Dimensional Tolerances in Construction and for Surface Accessibility

1.1.14 Flatness of ramp cross slope. For ramps, measure flatness of cross slope by placing a 24 - in. (600 mm) digital inclinometer perpendicular to the line of travel at 4 ft (1200 mm) intervals with not less than two measurements per ramp. For short ramps where only two measurements are made, measure cross slope at the top and bottom of the ramp. For ramps up to and including 5 ft (1525 mm) wide between the handrails, measure cross slope in the center of the ramp. See Fig. 6(a).

Because most exterior ramps will be 5 ft wide or less and the most common path of travel would be approximately in the middle of the path it seems reasonable to measure at the center of the ramp.

For ramps over 5 ft (1525 mm) wide between handrails, measure along both handrails with one end of the digital inclinometer placed at the line used to measure running slope. See Fig. 6(b). In addition to the measurement locations in 1.1.14, if a portion of the ramp appears to be steeper than 1:48 (approximately 2%) measure at that location as well.

As the ramp gets wider, users may tend to travel toward one side or the other, especially if the ramp is not a curb ramp and has handrails.