With the passing of the Americans with Disabilities Act (ADA) in the 1990s, tactile warning systems have been mandatory in the United States. A large part of these ADA compliant installations are truncated domes, small domes, or tactile walking surface indicators (TWSI), with flat heads that can be felt through your shoes. These truncated domes quickly became a requirement in ADA compliant tiles and tactile paving across the country. This is largely in part due to their utility, and the benefits they provide to visually impaired persons. Truncated domes serve to alert the visually impaired when they reach a potentially unsafe edge or crossing. Their most common applications are curb ramps, pedestrian crossings, and transit platforms; they were originally developed because of curb ramps, which did not have a way to alert the visually impaired of the curb’s edge.

With the standardization and popularity of detectable warning pavers, new issues have arisen. One of these issues is truncated dome spacing. Engineers needed to test the optimal spacing size and pattern was for the truncated domes; taking into account factors such as visibility, and accessibility for strollers and wheelchairs. The first pattern of truncated dome spacing implemented an alternating dome pattern, made it difficult for strollers and wheelchairs to travel over the detectable warning pad. After a return to the drawing board, an inline or grid design was implemented for ADA compliant tiles. This new layout proved to be the optimal spacing pattern for the truncated domes, as it allowed wheelchairs and strollers to travel with ease.

Detectable warning pavers initially featured a spacing of 1.67 inches between truncated domes. More recently, several U.S municipalities have adopted a wider truncated dome spacing of 2.35 inches, which has become more commonplace. The wider spacing between truncated dome installations still alerts the public of an unsafe edge, but for some it is perceived as more accessible and easier to travel on.

Every one of Access^® Tile’s tactile paving features wider truncated dome spacing of 2.35″. Further, the surface of all of our TWSI is designed with superior anti-slip technology. The area between each truncated dome features a ‘pyramid with sides’ design that wears better than all other designs on the market. The tops of the domes also feature twice as many tactile elements when compared to other products currently on the market.

View our ADA Regulations page for a summary of the act’s most important points, or view the full official Truncated Domes ADA Requirements to learn more about truncated dome spacing.

Quick Reference:

• Truncated domes are domes with flat heads that serve to alert individuals when they approach an unsafe area.
• Common areas of truncated dome application are curb ramps and transit platforms.
• An inline or grid design pattern proved to be the most practical for wheelchairs and strollers traveling over the detectable warning paver.
• Required Spacing between truncated domes is 1.67″ to 2.35″.
• Access^® Tile utilizes the wider truncated dome spacing (2.35″)  in all tactile paving.
• Each ADA compliant tile features a “pyramid with sides” design between the domes, tested to wear better than any other design.