Current and proposed Americans with Disabilities Act (ADA) guidelines offer no specific guidance on acceptable maximum cross slopes where constraints of reconstruction prohibit meeting the 2% maximum cross-slope requirement for new construction. Two types of sidewalk test-section data across a sample of 50 individuals were collected, were combined with an earlier sample of 17 individuals, and were analyzed, with an emphasis on cross slopes. These tests examined heart-rate changes and user perception of discomfort levels, and they relied on a random-effects model and an ordered-probit model, respectively. Model estimates were used to deduce critical or unacceptable cross slopes for critical conditions and critical populations of persons with disabilities. Predicted values for the most severe or constrained cases ranged from 5.5% to 6% cross slope. These cases included 5% primary slope (main grade) and 45-ft-long sections; the sections were traversed by cane, crutch, or brace and manual wheelchair users who were up to 80 years old. When primary slopes were reduced to 0% in the perception estimates, the critical cross slopes for the critical case rose to 6%. For most other persons with disabilities, the critical cross slopes ranged from 6% to 9% or more. These values substantially exceed the ADA accessibility guidelines' 2% maximum cross-slope standard for public sidewalks.
Abstract