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1991 ADA Standards for Accessible Design

Note: This document, portion of document or referenced document was published prior to the 2010 ADA Standards, and is still applicable.

4.7 Curb Ramps.

4.7.1 Location.

Curb ramps complying with 4.7 shall be provided wherever an accessible route crosses a curb.

4.7.2 Slope.

Slopes of curb ramps shall comply with 4.8.2. The slope shall be measured as shown in Fig. 11. Transitions from ramps to walks, gutters, or streets shall be flush and free of abrupt changes. Maximum slopes of adjoining gutters, road surface immediately adjacent to the curb ramp, or accessible route shall not exceed 1:20.

The ramp slope is a ratio equal to the vertical rise (y) divided by the horizontal run (x). It is equal to the tangent of the angle that the plane of the ramp surface makes with a horizontal (level) plane. For a curb ramp, the adjoining slope at walk or street shall not exceed 1:20.

Fig. 11 Measurement of Curb Ramp Slopes

4.7.3 Width.

The minimum width of a curb ramp shall be 36 in (915 mm), exclusive of flared sides.

4.7.4 Surface.

Surfaces of curb ramps shall comply with 4.5.

4.7.5 Sides of Curb Ramps.

If a curb ramp is located where pedestrians must walk across the ramp, or where it is not protected by handrails or guardrails, it shall have flared sides; the maximum slope of the flare shall be 1:10 (see Fig. 12(a)). Curb ramps with returned curbs may be used where pedestrians would not normally walk across the ramp (see Fig. 12(b)).

This figure shows a typical curb ramp, cut into a walkway perpendicular to the curb face, with flared sides having a maximum slope of 1:10. The landing at the top, measured from the top of the ramp to the edge of the walkway or closest obstruction is denoted as "x". If x, the landing depth at the top of a curb ramp, is less than 48 inches, then the slope of the flared side shall not exceed 1:12.

Fig. 12 Sides of Curb Ramps

Where the curb ramp is completely contained within a planting strip or other non-walking surface, so that pedestrians would not normally cross the sides, the curb ramp sides can have steep sides including vertical returned curbs.

Fig. 12 Sides of Curb Ramps

4.7.6 Built-up Curb Ramps.

Built-up curb ramps shall be located so that they do not project into vehicular traffic lanes (see Fig. 13).

A built-up curb ramp extends outward from the curb and slopes to the ground surface. The sides must also be tapered from the ramp surface to the ground, with a maximum slope of 1:10, so that there are no drop-offs along the edges.

Fig. 13 Built-Up Curb Ramp

4.7.7 Detectable Warnings.

A curb ramp shall have a detectable warning complying with 4.29.2. The detectable warning shall extend the full width and depth of the curb ramp.

4.7.8 Obstructions.

Curb ramps shall be located or protected to prevent their obstruction by parked vehicles.

4.7.9 Location at Marked Crossings.

Curb ramps at marked crossings shall be wholly contained within the markings, excluding any flared sides (see Fig. 15).

Curb ramp shown at marked crossings
Curb Ramps at marked crossings with segment of straight curb

 

 

 

 

 

 

 

 

 

 

 

 

Curb Ramps at marked crossings with 48 inch landing at bottom of curb ramp
Curb Ramps at Marked Crossings

 

Fig. 15 Curb Ramps at Marked Crossings

4.7.10 Diagonal Curb Ramps.

If diagonal (or corner type) curb ramps have returned curbs or other well-defined edges, such edges shall be parallel to the direction of pedestrian flow. The bottom of diagonal curb ramps shall have 48 in (1220 mm) minimum clear space as shown in Fig. 15(c) and (d). If diagonal curb ramps are provided at marked crossings, the 48 in (1220 mm) clear space shall be within the markings (see Fig. 15(c) and (d)). If diagonal curb ramps have flared sides, they shall also have at least a 24 in (610 mm) long segment of straight curb located on each side of the curb ramp and within the marked crossing (see Fig. 15(c)).

Curb Ramps at marked crossings with 48 inch landing at bottom of curb ramp
Curb Ramps at Marked Crossings

 

Fig. 15 Curb Ramps at Marked Crossings

4.7.11 Islands.

Any raised islands in crossings shall be cut through level with the street or have curb ramps at both sides and a level area at least 48 in (1220 mm) long between the curb ramps in the part of the island intersected by the crossings (see Fig. 15(a) and (b)).

Curb ramp shown at marked crossings
Curb Ramps at marked crossings with segment of straight curb

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 15 Curb Ramps at Marked Crossings

 

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