A detectable warning at a curb cut is a 24-inch deep, full-curb-cut-width truncated dome surface set at the back-of-curb where the ramp meets the gutter. ADA Standards 705.3 controls the placement; ADA Standards 405 and 406 control the curb ramp's running slope, cross slope, and transition geometry that the dome panel sits on. A correct curb-cut detectable warning is one where the dome surface, the ramp slope, the level landing at the top, and the gutter at the bottom all satisfy their respective ADA requirements simultaneously.
This guide focuses on the curb-cut application specifically: sidewalk-to-street transitions, parking-lot accessible-route curb cuts, corner ramps at intersections, and the variations each presents.
ADA Curb Ramp Anatomy
A compliant curb ramp under ADA 405 and 406 has five components, each controlled by a separate dimension or slope.
Running slope (ADA 405.2)
The running slope of the ramp surface itself runs parallel to the direction of pedestrian travel. The maximum is 8.33 percent (1:12). Steeper slopes fail ADA 405.2 even if every other component is compliant.
Cross slope (ADA 405.3)
The cross slope perpendicular to the direction of travel cannot exceed 2.083 percent (1:48). This applies to the ramp surface and the level landing at the top.
Level landing (ADA 406.4)
A level landing at the top of the ramp must be at least 36 inches by 36 inches and have a slope of 2 percent maximum in any direction. The level landing is where pedestrians stop to wait or change direction at the top of the ramp.
Counter slope (ADA 406.2)
The counter slope of the gutter or street pavement at the foot of the ramp cannot exceed 5 percent (1:20). The transition from the ramp into the gutter has to be flush enough that wheelchair users can negotiate it without the front casters catching.
Detectable warning (ADA 705.3 referenced from 406.13)
The 24-inch deep truncated dome surface at the back-of-curb signals the bottom of the ramp where the pedestrian transitions into the vehicular surface. ADA 406.13 explicitly requires detectable warnings on perpendicular and parallel curb ramps where pedestrians cross into a vehicular way.
Where Exactly Does the Dome Surface Go?
The dome surface placement depends on the curb-ramp type.
Perpendicular curb ramp
The most common configuration. A ramp drops from the sidewalk down to the gutter perpendicular to the direction of travel. The dome panel goes at the back-of-curb (the bottom of the ramp where the curb meets the gutter), 24 inches deep up the ramp, full ramp width across.
Parallel curb ramp
The ramp runs parallel to the direction of travel, with the pedestrian descending the ramp before turning to cross the street. The dome panel goes at the back-of-curb at the bottom of the ramp segment, NOT at the level landing where the pedestrian first arrives. Width is the full ramp width.
Diagonal corner ramp
A single ramp at a corner serving both directions of pedestrian travel. The dome panel conforms to the actual curb-cut geometry, which is often a curved or chamfered shape rather than a rectangle. Custom-cut panels are common.
Built-up curb ramp
A ramp that is built up from the gutter rather than cut into the sidewalk. The dome surface still goes at the back-of-curb, even when the back-of-curb is the foot of a built-up structure rather than the bottom of an excavated cut.
Blended transition
A flush transition between sidewalk and street with no curb at all (common at modern accessibility-focused intersections). The dome surface goes at the line where the pedestrian crosses into the vehicular surface, with the same 24-inch depth and full width.
Verification at Install
Verify all five ADA components together at install. Failing any one component compromises the curb cut as a whole.
| Component | Tool | Pass criteria |
|---|---|---|
| Ramp running slope | Smart level or digital level | At most 8.33 percent |
| Ramp cross slope | Smart level | At most 2.083 percent |
| Level landing dimensions | Tape measure | At least 36 by 36 inches |
| Level landing slope | Smart level | At most 2 percent in any direction |
| Counter slope | Smart level | At most 5 percent |
| Detectable warning depth | Tape measure | At least 24 inches |
| Detectable warning width | Tape measure | Full ramp width |
| Detectable warning leading edge | Tape measure | At back-of-curb (0 inches setback) |
| Dome geometry | Caliper | ADA 705.1 spec |
| Dome contrast | LRV meter | 70 percent differential |
Common Errors at Curb Cuts
Cojo retrofit jobs surface these placement and ramp errors most often.
Dome panel set back from curb edge
The leading edge of the dome panel is 4 to 12 inches back from the back-of-curb. The setback creates an unmarked transition zone between the curb and the dome that fails 705.3. Common cause: panel installed on a flat landing rather than on the ramp surface itself.
Dome panel does not span full ramp width
The panel is 24 inches by 24 inches set in a 36-inch-wide ramp, missing 6 inches on each side. The shoulders of the ramp lack tactile warning. Solution is a 24 by 36 panel or a custom-cut to fit.
Ramp running slope exceeds 8.33 percent
A correct dome panel installed on a ramp that is too steep (8.5 to 12 percent) creates a curb cut that fails ADA 405.2 even if 705.3 is satisfied. The ramp must be reconstructed to bring slope into compliance.
Counter slope mismatch at the gutter
The transition from the ramp to the gutter is steeper than 5 percent, often because the gutter pour pre-dates the ramp retrofit. Wheelchair front casters can catch on the lip. Even with a correct dome panel, the curb cut fails ADA 406.2.
Level landing missing or too small
A perpendicular ramp without a 36 by 36 inch level landing at the top fails ADA 406.4. The dome panel placement is correct but the curb cut as a whole is non-compliant.
Compliance Disclaimer
This article reflects ADA Standards for Accessible Design as of 2026-05-07 and product spec sheets current at publication. Always verify current dimensions, contrast thresholds, and placement requirements with your local jurisdiction and the U.S. Access Board before issuing a final spec. Federal guidance under 36 CFR Part 1191 controls when state or local rules conflict. Detectable warning placement does not satisfy ADA compliance on its own — ramp slope, cross slope, level landing, and counter slope must also pass.
Sources
- ADA Standards for Accessible Design, Section 405 Ramps and 406 Curb Ramps, U.S. Access Board, https://www.access-board.gov/ada/
- ADA Standards for Accessible Design, Section 705 Detectable Warnings, U.S. Access Board, https://www.access-board.gov/ada/
- 36 CFR Part 1191, Americans with Disabilities Act Accessibility Guidelines, https://www.ecfr.gov/current/title-36/chapter-XI/part-1191
- FHWA Accessibility Resource Library, https://highways.dot.gov/civil-rights/programs/ada/accessibility-resource-library
- Oregon Department of Transportation, ADA Curb Ramp Design Guide, https://www.oregon.gov/odot/engineering/pages/ada.aspx
From Cojo's Crew
On a 6-curb-cut Springfield retrofit in March 2026 we found that 4 of the existing curb cuts had compliant dome panels but failed ADA 405.2 ramp slope (running 9.4 to 11.2 percent). The original 2008 install had set the panels correctly but the ramp itself was too steep. We demolished and re-poured the 4 ramps to 7.8 percent running slope, then reinstalled new polymer-concrete panels at the back-of-curb to 24 inches depth and full ramp width. All 6 cuts now pass ADA 405.2, 406, and 705.3 together. The dome panel is part of a system, not a standalone product.