Q5.) What dimensions and conditions can practitioners reasonably consider to be compliant when the conditions, as constructed, do not meet the technical requirements exactly and there are no official, published, industry-developed tolerances?
A5.) This is the most difficult question and the most subject to varying opinions.
Sloped concrete and asphalt surfaces are an excellent example of this problem. To our knowledge, none of the industry associations have developed official tolerances for sloped concrete or asphalt surfaces except those laid down by large paving machines. Without official guidance but based on an analysis of the capabilities of the materials and processes, David Ballast generally recommends a tolerance of 0.5% in the cross slope direction and 1.0% in the direction of travel for concrete or asphalt ramps and curb ramps. In consent decrees, the Department of Justice has often ignored slopes in the direction of travel when no measurement on an accessible route exceeds 5.9% on sloped walking surfaces, 8.9% on ramps and curb ramps, and no more than 2.9% at any point for the cross slope on an accessible route. More information can be found in David Ballast’s book mentioned above and in the Access Board’s research study at http://www.access-board.gov/research/completed-research/dimensional-tolerances.
We will be posting more specific opinions about how to determine these tolerances in future months. Check back here for more information on a broader range of tolerances.
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