11B-406 Curb ramps, blended transitions and islands

[2010 ADA Standards] 406 Curb Ramps

ETA Editor's Note

The differences between 2010 ADA Standards Section 406 and CBC Section 11B-406 are numerous, as indicated by the italicized text, which is used by DSA-AC to identify departures from ADA requirements. The CBC requirements in this section are more stringent. Parallel curb ramps and blended transitions, although permitted by 2010 ADA Standards, are not defined or given special attention. Islands are addressed at 2010 ADA Standards 406.7, almost identical to CBC, except for detectable warnings. See also U.S. Access Board's Note to Reader at Detectable Warnings.

11B-406.1 General.

Curb ramps, blended transitions and islands on accessible routes shall comply with Section 11B-406. Curb ramps may be perpendicular, parallel, or a combination of perpendicular and parallel.

[2010 ADA Standards] 406.1 General. Curb ramps on accessible routes shall comply with 406, 405.2 through 405.5, and 405.10.

11B-406.2.1 Slope.

Ramp runs shall have a running slope not steeper than 1:12.

11B-406.2.2 Sides of curb ramps.

Where provided, curb ramp flares shall not be steeper than 1:10.

In cross section, a curb ramp with a maximum slope of 1:12 adjoins a surface at the bottom that has a maximum counter slope of 1:20.

FIGURE 11B-406.2.2 SIDES OF CURB RAMPS ‡‡

11B-406.3 Parallel curb ramps.

Parallel curb ramps shall comply with Sections 11B-406.3 and 11B-406.5. A parallel curb ramp may be provided with one sloping segment or two opposing sloping segments.

11B-406.3.1 Slope.

The running slope of the curb ramp segments shall be in-line with the direction of sidewalk travel. Ramp runs shall have a running slope not steeper than 1:12.

11B-406.3.2 Turning space.

A turning space 48 inches (1219 mm) minimum by 48 inches (1219 mm) minimum shall be provided at the bottom of the curb ramp. The slope of the turning space in all directions shall be 1:48 maximum.

Line drawing of a parallel curb ramp that is 48" wide and a landing at the bottom, between the two runs of the curb ramp, that is 48" x 48"

FIGURE 11B-406.3.2 PARALLEL CURB RAMPS ‡‡

11B-406.4 Blended transitions.

Blended transitions shall comply with Sections 11B-406.4 and 11B-406.5.

11B-406.4.1 Slope.

Blended transitions shall have a running slope not steeper than 1:20.

11B-406.5 Common requirements.

Curb ramps and blended transitions shall comply with Section 11B-406.5.

11B-406.5.1 Location.

Curb ramps and the flared sides of curb ramps shall be located so that they do not project into vehicular traffic lanes, parking spaces, or parking access aisles. Curb ramps at marked crossings shall be wholly contained within the markings, excluding any flared sides.

Exception: Diagonal curb ramps shall comply with Section 11B-406.5.9.

11B-406.5.2 Width.

The clear width of curb ramp runs (excluding any flared sides), blended transitions, and turning spaces shall be 48 inches (1219 mm) minimum.

11B-406.5.3 Landings.

Landings shall be provided at the tops of curb ramps and blended transitions. The landing clear length shall be 48 inches (1219 mm) minimum. The landing clear width shall be at least as wide as the curb ramp, excluding any flared sides, or the blended transition leading to the landing. The slope of the landing in all directions shall be 1:48 maximum.

[2010 ADA Standards] 406.4 Landings. Landings shall be provided at the tops of curb ramps. The landing clear length shall be 36 inches (915 mm) minimum. The landing clear width shall be at least as wide as the curb ramp, excluding flared sides, leading to the landing.

Exception: Parallel curb ramps shall not be required to comply with Section 11B-406.5.3.

[2010 ADA Standards] EXCEPTION: In alterations, where there is no landing at the top of curb ramps, curb ramp flares shall be provided and shall not be steeper than 1:12.

Advisory 11B-406.5.3 Landings. A level landing, 48” deep and at least as wide as the curb ramp, is required at the top of a curb ramp. The landing provides an area for users to exit the curb ramp and proceed along the walking surface at the top of the curb ramp.

Some designs have been proposed that reduce or omit the level top landing by providing a curb ramp with flared sides of 1:12 or less. This design is not compliant with the building code and may result in a condition where a wheelchair user cannot safely turn and proceed along the intersecting walk. Section 11B-403.5.1.1, requires walks and sidewalks to be 48” wide minimum; Section 11B-403.3 requires walks and sidewalks to have a cross-slope of 1:48 or less. In this example, reducing or omitting the top landing of the curb ramp may result in a substandard walk width and/or a walk with a cross-slope in excess of 1:48. ◼

Plan view of a perpendicular curb ramp with detectable warnings and a landing at least 48" deep at the top of the curb ramp.

FIGURE 11B-406.5.3 LANDINGS AT THE TOP OF CURB RAMPS ‡‡

11B-406.5.4 Floor or ground surfaces.

Floor or ground surfaces of curb ramps and blended transitions shall comply with Section 11B-405.4.

11B-406.5.5 Wet conditions.

Curb ramps and blended transitions shall comply with Section 11B-405.10.

11B-406.5.6 Grade breaks.

Grade breaks at the top and bottom of curb ramp runs shall be perpendicular to the direction of the ramp run. Grade breaks shall not be permitted on the surface of ramp runs and turning spaces. Surface slopes that meet at grade breaks shall be flush.

11B-406.5.7 Cross slope.

The cross slope of curb ramps and blended transitions shall be 1:48 maximum.

11B-406.5.8 Counter slope.

Counter slopes of adjoining gutters and road surfaces immediately adjacent to and within 24 inches (610 mm) of the curb ramp shall not be steeper than 1:20. The adjacent surfaces at transitions at curb ramps to walks, gutters, and streets shall be at the same level.

[2010 ADA Standards] 406.2 Counter Slope. Counter slopes of adjoining gutters and road surfaces immediately adjacent to the curb ramp shall not be steeper than 1:20. The adjacent surfaces at transitions at curb ramps to walks, gutters, and streets shall be at the same level.

FIGURE 11B-406.5.8 COUNTER SLOPE OF SURFACES ADJACENT TO CURB RAMPS

11B-406.5.9 Clear space at diagonal curb ramps.

The bottom of diagonal curb ramps shall have a clear space 48 inches (1219 mm) minimum outside active traffic lanes of the roadway. Diagonal curb ramps provided at marked crossings shall provide the 48 inches (1219 mm) minimum clear space within the markings.

11B-406.5.10 Diagonal curb ramps.

Diagonal or corner type curb ramps are perpendicular or parallel curb ramps that are oriented diagonally at an intersection. Diagonal or corner type curb ramps with returned curbs or other well-defined edges shall have the edges parallel to the direction of pedestrian flow. Diagonal curb ramps with flared sides shall have a segment of curb 24 inches (610 mm) long minimum located on each side of the curb ramp and within the marked crossing.

[2010 ADA Standards] 406.6 Diagonal Curb Ramps. Diagonal or corner type curb ramps with returned curbs or other well-defined edges shall have the edges parallel to the direction of pedestrian flow. The bottom of diagonal curb ramps shall have a clear space 48 inches (1220 mm) minimum outside active traffic lanes of the roadway. Diagonal curb ramps provided at marked crossings shall provide the 48 inches (1220 mm) minimum clear space within the markings. Diagonal curb ramps with flared sides shall have a segment of curb 24 inches (610 mm) long minimum located on each side of the curb ramp and within the marked crossing.

A plan view of a diagonal curb ramp is shown at a marked crossing. A space 48 inches minimum, measured in the direction of the ramp run, is provided at the bottom of the ramp outside active traffic lanes and within the boundary of the marked pedestrian crossing. Sections of curb 24 inches minimum in length are shown beyond the flared sides and within the marked crossing.

FIGURE 11B-406.5.10 DIAGONAL OR CORNER TYPE CURB RAMPS ‡‡

11B-406.5.11 Reserved.

11B-406.5.12 Detectable warnings

Curb ramps and blended transitions shall have detectable warnings complying with Section 11B-705.

U.S. Access Board's Note to Reader:

The Department of Transportation's ADA Standards require detectable warnings on curb ramps:

[ADA Title II - Public Transportation] 406.8 Detectable Warnings. A curb ramp shall have a detectable warning complying with 705. The detectable warning shall extend the full width of the curb ramp (exclusive of flared sides) and shall extend either the full depth of the curb ramp or 24 inches (610 mm) deep minimum measured from the back of the curb on the ramp surface.

11B-406.6 Islands.

Raised islands in crossings shall be cut through level with the street or have curb ramps at both sides. The clear width of the accessible route at islands shall be 60 inches (1524 mm) wide minimum. Where curb ramps are provided, they shall comply with Section 11B-406. Landings complying with Section 11B-406.5.3 and the accessible route shall be permitted to overlap. Islands shall have detectable warnings complying with Section 11B-705.

[2010 ADA Standards] 406.7 Islands. Raised islands in crossings shall be cut through level with the street or have curb ramps at both sides. Each curb ramp shall have a level area 48 inches (1220 mm) long minimum by 36 inches (915 mm) wide minimum at the top of the curb ramp in the part of the island intersected by the crossings. Each 48 inch (1220 mm) minimum by 36 inch (915 mm) minimum area shall be oriented so that the 48 inch (1220 mm) minimum length is in the direction of the running slope of the curb ramp it serves. The 48 inch (1220 mm) minimum by 36 inch (915 mm) minimum areas and the accessible route shall be permitted to overlap.

Figure (a) is a plan view of a raised pedestrian island with a walkway cut through at the same level as the street crossing.

(a) cut through at island

Figure (b) is a plan view of a raised pedestrian island between two traffic lanes. Aligned curb ramps with side flares slope down on each side. The level space between the top of both ramps is 48 inches long minimum. The width of both ramp runs is 36 inches.

(b) curb ramp at island

FIGURE 11B-406.6 ISLANDS IN CROSSINGS ‡‡

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2019 California Standards for Accessible Design Guide (effective January 1, 2020 with July 1, 2021 amendments)