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Detectable Surfaces

Curb Ramps and Detectable Warning Surfaces (Chapter 4 Part 3)

When creating an ADA compliant outdoor hardscape, it is important to understand the engineering considerations to be included in the design.  In recent years, there has been a noticeable addition to the curb ramps that have been required since 1992.  The original Americans with Disabilities Act of 1973 had mandated that all crossing areas where an elevated sidewalk or pedestrian thoroughfare met a road surface, a curb ramp should be constructed to make the area accessible for persons with mobility challenges.  These curb ramps have gone a long way in improving accessibility for people in wheelchairs, or those walking with a cane or crutches.  For many people, even the elevation of a curb—just six or nine inches, causes a great deal of difficulty.  The wide-spread addition of curb ramps has provided them with greater accessibility, and consequently greater opportunity.  While the curb ramps have gone a long way to make things more accessible for the mobility challenged, is needed to be done to ensure the safety of visually impaired people.  The United States Access Board explains that after much testing, the solution that was recommended was the addition of detectable warning surfaces.

Using High-Contrast Color

The recommendation for detectable warning surfaces states that because the variance in levels of visual impairment are so great, the surface should be of a highly contrasting color.  This means that in the case of a white, concrete sidewalk, a red, blue or bright yellow would be desirable.  If the paved area is asphalt construction, blue or red is preferred.  In the case of a red, stamped asphalt, a black and white detectable warning surface might be advisable.

The Federal Highway Administration studied the use of detectable warning surfaces in 2005 and found that the use of neutral colors (tan, grey and black) was not advisable.  For people with visual impairments, these colors did not provide a discernable visual warning.  The FHWA report also went on to recommend the normalization of the use of certain colors (i.e. blue for handicap access, red or yellow for street crossings).

The Truncated-Dome Texture

Careful consideration was given to the texture of the detectable warning surface.  The prevailing “truncated dome” texture was chosen for a variety of reasons.  First, the texture is easily recognized by touch, even through most shoes.  Also, because of the open configuration, the texture is not easily affected by elements like snow, rain, dirt or sand.  Basically, it stays clear in most conditions.  Rather than completely round domes, which could be an unstable texture, the truncated design was incorporated.  Testing confirmed that the truncated domes provided enough surface variance to be sensed, but still offered a safe surface for crutches and canes to interact with.

In the past texturizing impressions had been acceptable for curb ramps, but the FHWA recommendations amended in 2016 make no note of such techniques, and strictly refer to the truncated dome type of surface. 

ADA Compliant Curb Warning
Tile footpath curb warning for visually impaired.

Placement Recommendations

Though the engineering recommendations by the FHWA have not yet been adopted as law, they have been adopted by the United States Access Board.  The recommended installation of detectable warning surfaces are as follows:

At edge of drop-offs and passenger platforms for in rail transportation, a warning should be installed at a depth of 24” from the edge

At all curb ramps at a depth of 24” from the gutter, for the entire width of the ramp surface

At any designated crossing point of flush-engineered or blended surface pedestrian areas

Working within the ADA

Many customers are frustrated with the ADA standards and do not understand the importance of such requirements.  East Coast Paving and Site Development reminds you that complying with ADA standards is meant to provide everyone with equal access, and by following the recommendations of the United States Access Board, you’re not only following the law, you’re respecting everyone.  Let us work with you to create a site plan that is efficient and accessible for everyone.

Help with ADA Standards

Serving clients in New Jersey, New York and Eastern Pennsylvania, the experienced professionals at East Coast Paving and Site Development are prepared to help you achieve the standards for ADA compliance.

For additional questions about ADA compliance, contact the paving experts at East Coast Paving and Site Development at 732-329-3600 or email


2850 Woodbridge Avenue, Unit F
Edison, NJ 08837

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