ADA Standards 705.3 defines where a detectable warning surface must be installed: 24 inches minimum in the direction of pedestrian travel, full width of the curb cut or hazard, set back at most 8 inches from the curb edge or platform edge. A panel that meets ADA 705.1 dome geometry and ADA 705.2 70 percent contrast can still fail compliance if it is placed in the wrong location.
This guide covers placement geometry at curb cuts, transit-platform edges, and parking-lot path-of-travel applications, the verification method at install, and the common errors that cause inspectors to flag a panel.
What Does ADA 705.3 Actually Require?
ADA Standards for Accessible Design, Section 705.3, addresses placement at curb ramps under the broader umbrella of accessible-route construction (ADA 406.13). The technical text and U.S. Access Board commentary establish three controlling dimensions.
Depth in direction of travel
The detectable warning surface must extend at least 24 inches in the direction of pedestrian travel from the curb edge or hazard. This 24-inch depth is the federal floor; some state and local codes require deeper (Oregon DOT uses 24 inches for most applications).
Width across the cut
The detectable warning surface must extend the full width of the curb cut, ramp, or hazard. There is no minimum width because width is determined by the geometry of the cut. There is a maximum of "full width" because the surface cannot extend beyond the curb cut into adjacent walking surface that is not a hazard.
Set-back from curb edge
The leading edge of the detectable warning surface must be at the back-of-curb (where the curb meets the gutter) or set back at most 8 inches from that edge for certain transit applications. Most parking-lot and sidewalk applications place the leading edge directly at the back-of-curb.
Placement at Different Application Types
Standard curb cut at sidewalk
The dome panel begins at the back-of-curb and extends 24 inches up the ramp toward the sidewalk. The panel is the full width of the curb cut. This is the dominant application in commercial parking lots and city sidewalks.
Transit platform edge
ADA 810.5.2 requires a 24-inch detectable warning along the full length of any transit-platform edge with vehicular drop-off, set 0 to 8 inches from the platform edge. This applies to bus stops, light-rail stations, and ferry terminals.
Parking-lot path of travel
The accessible route through a parking lot does not require detectable warnings unless the route crosses a vehicular drop-off or hazard. ADA-striped accessible spaces and access aisles do not require domes; the curb cut connecting the access aisle to the building entrance does.
Hazardous-vehicular-area transition
Where a pedestrian path transitions into a hazardous vehicular area without a curb (such as a flush transition between sidewalk and traffic lane), ADA 705.3 requires a detectable warning at the transition point. Width and depth are the same as for a curb cut.
Verification Method at Install
Three measurements verify ADA 705.3 placement, each completed in under 2 minutes per curb cut.
Tape measure depth
Measure from the back-of-curb to the trailing edge of the dome panel. The reading must be at least 24 inches. The U.S. Access Board's commentary tolerates depth up to 60 inches if the curb-ramp transition zone justifies a deeper warning surface.
Tape measure width
Measure the curb-cut width at the back-of-curb (where the dome panel begins) and the dome panel's actual installed width. The two should match within 0.5 inches.
Tape measure set-back
Measure from the back-of-curb to the leading edge of the dome panel. The reading should be 0 inches for sidewalk and parking-lot applications, or 0 to 8 inches for transit-platform applications.
Common ADA 705.3 Placement Errors
These are the placement failures Cojo crews see most often on retrofit jobs.
Panel set back from the curb
A panel installed 6 inches behind the back-of-curb on a sidewalk application fails 705.3 because the leading edge is not at the curb edge. The 6-inch concrete strip between the curb and the panel becomes a hazard zone with no tactile warning.
Panel too shallow
A 24-inch by 18-inch panel set in a 36-inch-wide curb cut fails 705.3 in two ways: the depth is only 18 inches (under the 24-inch floor) and the width is short of the full cut. Both have to be corrected for compliance.
Panel installed beyond the curb cut
Some retrofits install a panel that extends 4 to 8 inches past the curb cut into the surrounding sidewalk, on the theory that more is better. ADA 705.3 limits the panel to the curb cut itself; extending beyond can create a sidewalk-walking-surface contrast issue and is technically non-compliant.
Curb cut at unusual angle
A diagonal curb cut (corner ramp) or a side-loaded curb cut can have a non-rectangular geometry. The panel must conform to the cut's actual shape, not be a standard rectangle that misses the corners. Custom-cut panels or trim during install solves this.
Mid-platform placement on transit edge
Transit platform edges sometimes get a panel installed 18 to 24 inches in from the platform edge, set back to "protect" the dome surface from being struck by a transit vehicle. ADA 705.3 requires the leading edge at the platform edge or within 8 inches; setting back further fails 705.3.
Oregon-Specific Placement Considerations
Oregon DOT's ADA Curb Ramp Design Guide layers on top of federal ADA. Key Oregon-specific notes:
ODOT 24-inch standard
ODOT projects use 24-inch depth as the standard, matching the federal floor. ODOT does not require deeper panels for highway-adjacent applications.
Portland Title 33
Portland public-right-of-way curb-ramp work follows ODOT and federal placement, with additional documentation requirements at acceptance. Plan for full-grid measurement at inspection.
Salem Chapter 79
Salem public works requires the dome panel at the back-of-curb with no setback for sidewalk applications. Public-facility work in Salem sometimes requires a 30-inch deeper panel for high-traffic transit-stop applications.
TriMet and Lane Transit
Transit-agency-owned platform edges follow federal ADA 705.3 and 810.5.2. The Trade Standards published by each agency layer additional requirements (typically depth or color preferences).
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. Manufacturer-supplied panels do not guarantee placement compliance — install-time tape measurement is required.
Sources
- ADA Standards for Accessible Design, Section 705.3 Location, U.S. Access Board, https://www.access-board.gov/ada/
- 36 CFR Part 1191 Appendix D, Detectable Warnings, 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 Hillsboro retail center retrofit in April 2026, the original 2009-vintage curb-cut concrete had been poured 2 inches taller than the surrounding sidewalk so the existing dome panels were set 4 inches behind the back-of-curb on a chamfered transition. The placement failed ADA 705.3 even though the panels themselves cleared 705.1 and 705.2. We poured a new flush curb-cut landing and reinstalled new dome panels at the back-of-curb, dropping the failure mode entirely. Placement is geometry, not just product.