Passed in 1990, the Americans With Disabilities Act protects the civil rights of people with disabilities. Since then, several federal laws have been passed to make sidewalks and street crossings accessible to all pedestrians, regardless of ability or disability.
The goal is to incorporate principles of universal design to make walkways accessible for the greatest number of users. According to the Federal Highway Administration, this means balancing the varying needs of different users even when they seem to be in conflict with one another.
Both new construction and existing facilities must have curb ramps installed according to Title II of the Americans With Disabilities Act. Without them, it is difficult and dangerous for people who use wheelchairs to access the street from the sidewalk, if not completely impossible. Ramps should be four feet wide in new construction although three feet is permissible in restricted spaces. The grade should be no more than 8.3%, and there should not be a significant change of grade between the ramp and the gutter. Otherwise, the wheelchair may bottom out, causing the user to fall forward.
Though necessary to provide access to those who use wheelchairs, curb ramps make it difficult for people with visual impairments to determine where the sidewalk ends and the street begins. Detectable warnings mark the transition in a way that is perceivable by tactile rather than visual means. A detectable warning consists of a surface covered with a square grid pattern of truncated domes that a person with visual impairments can feel under his or her feet.
Detectable warnings meet standard size requirements. Their design allows them to alert pedestrians with visual impairments to the transition while sufficiently spaced to make it easier for wheelchair users to navigate.