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Accessible Walkways

The following excerpt from BIA Technical Note 14 Paving Systems Using Clay Pavers provides the most current, authoritative information available on the use of clay "brick" pavers in accessible walkways. This information highlights pertinent text from the American Disabilities Act Accessibility Guidelines (July 23, 2004) and the Revised Draft Guidelines for Accessible Public Rights-of-Way (November 23, 2005) pertaining to using pavers in an accessible walkway. To view this information and the entire Technical Note in PDF form, go to Technical Note 14.

Accessibility
The Americans with Disabilities Act Accessibility Guidelines (ADAAG) [Ref. 1] establish minimum design requirements that cover access for people with disabilities to public and private buildings and facilities. The Public Rights-Of-Way Accessibility Guidelines (Draft PROWAG) [Ref. 13] in draft form cover disability access provisions for pedestrian areas along public rights-of-way. Research has documented that clay paving systems can comply with the accessible provisions within these guidelines [Ref. 12 and 15].

The ADAAG and Draft PROWAG mandate several surface profile requirements applicable to all pavement systems. The designer should be aware of maximum permissible gradients and other requirements that often are overlooked (see Photo 5).

In addition to planning and designing in accordance with these guidelines, it is important to implement regular maintenance programs to maintain these routes in a safe and serviceable condition. Specific requirements especially pertinent to clay pavers include surface, changes in level, joints and detectable warning surfaces.

Surface. The ADAAG and Draft PROWAG require an accessible surface to be firm, stable and slip-resistant. Smoothness also may be an important criterion, because a pedestrian in a wheelchair may be more sensitive to vibration or trip hazards. Properly designed, installed and maintained clay paver surfaces achieve these properties. Besides inadequate design, installation or maintenance, all pavement systems may be subject to heaving and settlement of underlying soils that result in changes in level. Research has shown that the vibration on clay paver surfaces is comparable to or less than that of poured concrete and other common paving materials [Refs. 12 and 15].

Photo 5
At Grade Street Crossing with ADA-Compliant Surface Texture Changes

Figure 3
Requirements for Making Changes in Elevation

Changes in Level. Both the ADAAG and Draft PROWAG allow a change in level (surface discontinuity) up to 1/4 in. (6.4 mm) (see Figure 3a). Both the ADAAG and Draft PROWAG allow a change in level between 1/4 in. (6.4 mm) minimum and 1/2 in. (12.7 mm) maximum. The ADAAG requires this change in level to be sloped (beveled) not steeper than 1:2 (see Figure 3b). The Draft PROWAG also requires a maximum slope (bevel) of 1:2 for this change in level, but further mandates that the slope (bevel) be applied across the entire change in level (see Figure 3c).

With respect to pavers, sudden changes in level (differences in elevation of the top surfaces of adjacent pavers) should be kept to a minimum through careful design and installation and should be maintained as part of a regular maintenance program. Changes in level can result from heaving or settling of the pavement; uneven joints or can occur at frames and manhole covers.

Joints. The ADAAG does not specifically cover joints, but it does have requirements for openings in gratings, which could be considered as being similar. The Draft PROWAG ADAAG has requirements for horizontal openings in walkway joints and gratings. Both guidelines allow openings up to 1/2 in. (12.7 mm) wide, more than twice the typical width of joints between pavers in pavements with sand and bituminous setting beds that are typically 1/16 in. (1.6 mm) to 3/16 in. (4.7 mm) wide. Joints between pavers in a mortar setting bed are generally 3/8 in. (9.4 mm) to 1/2 in. (12.7 mm) wide, but would not be considered an opening.

Detectable Warning Surfaces. Both the ADAAG and the Draft PROWAG require detectable warning surfaces consisting of truncated domes sized to have a base diameter of 0.9 in. (23 mm) minimum and 1.4 in. (36 mm) maximum, a top diameter of a minimum of 50 percent to a maximum of 65 percent of the base diameter, and a height of 0.2 in. (5.1 mm). Clay pavers can be made with truncated domes. The ADAAG requires truncated domes to be placed on a square grid with a center-to-center spacing of 1.6 in. (41 mm) minimum and 2.4 in. (61 mm) maximum, and a base-to-base spacing of 0.65 in. (17 mm) minimum, measured between the most adjacent domes. The Draft PROWAG requires truncated domes to be placed in either a square or a radial grid pattern meeting the same dimensional layout requirements as set forth in the ADAAG.

Both guidelines require detectable warning surfaces to extend 24 in. (610 mm) from rail platform boarding edges. The Draft PROWAG also covers curb ramps and blended transitions that are not covered in the ADAAG. Curb ramps and blended transitions require detectable warning surfaces to extend 24 in. (610 mm) minimum in the direction of travel for their full width. Flares of curb ramps are not required to have a detectable warning surface.