Figure 15 is a set of three line drawing perspectives illustrating 3 types of perpendicular curb
ramps. The first one is inset into the sidewalk and comprises a level landing at the top that is 36
inches--the minimum width of the curb ramp--and a minimum of 48 inches long (60 inches is
desirable). The landing slope in either direction may not exceed 1:48. The ramp run may not
exceed 1:12, which requires a total length of almost 8 feet where there are 6-inch curbs, since the
sidewalk cross slope of 1:48 will contribute additional height as the ramp rises. Flares for
ambulatory pedestrians may be as steep as 1:10, which will require a 5-foot-long taper from the
toe of the ramp back up to full curb height. The line of the toe of the ramp at the street must be
perpendicular to the ramp run so that both long sides of the ramp are equal in length. A diagonal
ramp is shown as a perpendicular ramp installed at the apex of the corner to serve two crossings
rather than one. A built-up ramp projects from the sidewalk at the curb face into the roadway and
has convex flares from the ramp down to the street surface. Extra width–at least 48 inches--is
preferred, since there is no edge protection from these flares. Built-up ramps are not permitted in
traffic lanes.
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