Back in 2002, the city of Portland installed truncated domes in a downtown area; it was a surface-applied plastic panel of truncated domes, which was heated with a torch and applied to hardened concrete. Portland was well aware of previous failures regarding this particular product to perform adequately. Maintenance staff previously stated truncated domes began failing relatively quickly after installation (within a couple years).
Apparently municipalities and contractors alike are in a weak position when they order a product without having long-term maintenance information available. Several studies have been performed in the last two decades on the subject of detectable warning surface durability. However, we should be emphasized that very little long-term performance information is available for all the products manufactured. On average, long-term performance issues fall into two general categories:
-Color retention is a concern because panel coloring can fade due to UV exposure, sediments, deicing salts, construction, and several other factors. When colors are not retained, the surface’s function is devalued.
-Domes from detectible warning surfaces can be damaged or removed, often from snow plowing or shoveling. This is a huge issue for colder regions, where regular maintenance can systematically strip truncated domes, thus removing their identity as a detectable warning surface.
-People in wheelchairs claim the sporadic dots cause more problems than good, mostly due to a front wheel catching a dome wrong and falling, breaking bones. Along those lines, it has been reported that truncated bumps trigger muscle spasms for some people with spinal cord injury.
-Panels of detectible warning surfaces have been known to crack, peel, lose screw(s) or screw heads (for panels fastened into underlying concrete sidewalk), etc. Anything that generally removes the structural integrity of the panels or creates a tripping hazard takes away from the purpose of the panels.