Braillito Maps · Accessibility guides
Truncated domes and tactile paving: what they mean and their sizes
Truncated domes are the rows of small flat-topped bumps at the bottom of curb ramps and along train platforms. They are a detectable warning: a surface a person can feel with their feet or a cane that says “hazard ahead”. Tactile paving is the wider family, which in some countries also includes surfaces that guide.
This guide summarizes the sources it cites; it is not legal advice. The official texts are the reference.
Dome size and spacing
| Element | Requirement | Section |
|---|---|---|
| Base diameter | 0.9 to 1.4 inches (23–36 mm) | 2010 ADA Standards, 705.1.1 |
| Top diameter | 50 % to 65 % of the base diameter | 2010 ADA Standards, 705.1.1 |
| Height | 0.2 inch (5.1 mm) | 2010 ADA Standards, 705.1.1 |
| Center-to-center spacing | 1.6 to 2.4 inches (41–61 mm) | 2010 ADA Standards, 705.1.2 |
| Base-to-base spacing | at least 0.65 inch (17 mm) | 2010 ADA Standards, 705.1.2 |
| Contrast | light-on-dark or dark-on-light against the walking surface | 2010 ADA Standards, 705.1.3 |
The Public Right-of-Way Accessibility Guidelines use the same dome size and spacing, in a square or radial grid (PROWAG, R305.1).
Where they are required in the US
- Rail platforms. The 2010 ADA Standards require detectable warnings along platform boarding edges not protected by screens or guards, 24 inches (610 mm) wide, along the full length of the public area (2010 ADA Standards, 810.5.2 and 705.2).
- Curb ramps and crossings. PROWAG, the U.S. Access Board’s guidelines for sidewalks and streets, requires them at curb ramps and blended transitions at crosswalks, at cut-through refuge islands and at pedestrian rail crossings, at least 24 inches (610 mm) deep in the direction of travel and across the full width of the ramp (PROWAG, R205 and R305.1.4). The rest of the curb ramp is in ADA curb ramp requirements.
The Access Board published PROWAG as a final rule on August 8, 2023. The guidelines become enforceable when agencies such as the Department of Justice and the Department of Transportation adopt them as standards; the Department of Transportation adopted them on December 18, 2024 for new construction and alterations of transit stops in the public right-of-way (PROWAG). The sidewalk itself, with its width, slopes and passing spaces, is in ADA sidewalk requirements.
Tactile paving in the UK
The UK Department for Transport describes six tactile paving surfaces, each with its own message (DfT tactile paving guidance). The three most common:
| Surface | Meaning | Profile |
|---|---|---|
| Blister | a pedestrian crossing point, where the footway meets the road | rows of flat-topped blisters 5 mm (± 0.5 mm) high; red at controlled crossings, usually buff at uncontrolled ones |
| Corduroy | “hazard, proceed with caution”: steps, level crossings, tram platform ramps, shared areas | rounded bars 6 mm (± 0.5 mm) high and 20 mm wide, 50 mm apart, across the direction of walking |
| Guidance path | a route to follow where there is no building line or curb to use | flat-topped bars 5.5 mm (± 0.5 mm) high and 35 mm wide, 45 mm apart, along the direction of walking |
The surfaces usually come in 400 mm by 400 mm modules (DfT tactile paving guidance).
How to read them underfoot
Domes or blisters say “stop and check”: the sidewalk ends and the street begins, or the platform edge is near. Bars running the way you walk say “follow me”; bars across your path say “caution, something changes here”.
People feel them through their shoes or with a white cane; guide dog handlers use them too. For the domes to work they have to contrast with the pavement and be where the hazard is, not scattered as decoration.
Common problems
- Domes worn flat, or painted the same color as the sidewalk so they no longer contrast.
- Warning surfaces at the top of a ramp that leads nowhere dangerous, which teaches people to ignore them.
- A missing warning at a curb ramp, so the ramp feels like a continuation of the sidewalk into the street.
- Tactile tiles lifted or cracked, which turns a warning into a trip hazard.
Frequently asked questions
What are truncated domes?
Small domes with flat tops, set in a grid, that form a detectable warning surface: a change people can feel underfoot or with a cane at a hazard such as a street or a platform edge (2010 ADA Standards, 705.1).
Are truncated domes required by the ADA?
The 2010 ADA Standards require them along unprotected rail platform edges; PROWAG requires them at curb ramps and blended transitions at crosswalks, and becomes enforceable as agencies adopt it (2010 ADA Standards, 810.5.2; PROWAG).
What size are ADA truncated domes?
A base diameter of 0.9 to 1.4 inches (23–36 mm), a height of 0.2 inch (5.1 mm) and a center-to-center spacing of 1.6 to 2.4 inches (41–61 mm) (2010 ADA Standards, 705.1).
Why is some tactile paving red?
In the UK, red blister paving marks a controlled crossing, such as one with traffic lights; at uncontrolled crossings it is usually buff (DfT tactile paving guidance).
What is the difference between blister and corduroy paving?
Blister paving marks a pedestrian crossing point; corduroy, with rounded bars across the path, warns of a hazard such as steps (DfT tactile paving guidance).
More accessibility guides
- The white cane: what it tells the person using it and the people around them, and White Cane Safety Day.
- Guide dogs: how they work, where they can go under the ADA, and how to act around one.
- ADA ramp slope: the 1:12 rule, width, landings, handrails and edge protection.
- ADA curb ramps: curb ramp slope, counter slope, width, flared sides, the top landing, diagonal ramps, islands and detectable warnings.
- ADA sidewalk requirements: clear width, passing spaces, grade, cross slope, surface, protruding objects and street furniture, on public sidewalks and on site.
- ADA compliance: a checklist for small businesses, with the 2010 Standards section behind each item.
- All accessibility guides
Sources
Every figure in this guide comes from one of these official texts, which we read in October 2026.
- 2010 ADA Standards for Accessible Design. U.S. Department of Justice, published September 15, 2010; required for new work since March 15, 2012.
- Public Right-of-Way Accessibility Guidelines (PROWAG). U.S. Access Board, final rule published August 8, 2023.
- Guidance on the use of tactile paving surfaces. Department for Transport (UK), December 2021, published January 10, 2022.
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