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Truncated Domes — To Use or Not To Use?

Janis Kent, FAIA CASp © March, 2015

Truncated domes, a form of detectable warnings, have been around for a while. It is one of those items which is not a great solution but there does not appear to be anything comparable. It is meant for people with a visual impairment to determine the boundary between a sidewalk and a street. It has been used to warn of hazards along a circulation path where there is no curb, although it can cause a problem for people with other types of disabilities and can even create a trip hazard for those who are able-bodied. Also, in new construction, there has been a trend to eliminate curbs so we have even a less of a separation between vehicles and pedestrians.

The intent of detectable warnings is to alert those with a visual impairment that they are about to enter or cross into a potentially hazardous area. The issue becomes – just what is a hazardous area and then how do we demarcate this transition. I am sure that we have all seen an over-use of these with the placement becoming somewhat murky in terms of what is being communicated. There is the ongoing discussion as well, as to whether an access aisle for an accessible parking stall is considered hazardous necessitating it to be demarcated.

Initially detectable warnings were required in the 1991 ADA. On April 12, 1994 DOJ temporarily suspended their use except on rail platforms and platform boarding edges, stating more study was necessary. This suspension was extended a number of times. The 2010 ADA Standards currently only includes the requirement for rail platforms and platform boarding edges. The intent has been that it will become part of the Public Right of Way Accessibility Guidelines (PROWAG) whenever that gets published.

The California Building Code (CBC), on the other hand, did not include detectable warnings on curb ramps and blended transitions until the 1993 Supplement came out and became effective April 1, 1994 – just 11 days before their use was temporarily suspended in the ADA. Currently the CBC requires detectable warnings at a number of defined hazardous areas including reflecting pools. In California, if a facility was built before April 1, 1994, there is no requirement for truncated domes unless there is an alteration which triggers this CBC path of travel requirement. Some even feel that since the CBC requires use of ‘only approved detectable warning products’ installed after January 1, 2001, that they can not actually be installed since none are nor have ever been approved. CA Division of the State Architect – Access Compliance, is tasked to select an independent not-for-profit entity to evaluate detectable warnings biennially which has not yet been done. This approval process was not in place between April 1, 1994 and January 1, 2001.

So, where does this actually leave us? For the most part, in a lot of confusion. Currently for ADA, there is no requirement for detectable warnings on curb ramps, and it does appear that when the PROWAG gets approved it will be in the public right of way only rather than on private property. Also per the 2010 ADA, there is no longer a requirement to provide detectable warnings as a Barrier Removal task at existing facilities.

In California it is much more nebulous. For buildings constructed before April 1, 1994 there is no requirement to provide detectable warnings unless there has been an alteration, in which case this could be part of the Proportional Spending for Path of Travel obligations. California currently requires detectable warning surfaces on all curb ramp surfaces or at the edge of shared landings for double curb ramps. Additionally, CBC has requirements for when there is no curb or railing along an accessible route separating pedestrians from vehicles when the path crosses or adjoins a vehicular way along with a few other locations, which then leads us back to the requirement of only using approved detectable warnings. So the question in California becomes, does this get specified or not – and for that, I do not have a good answer at this time. I would suggest, though, to put back the curbs or some other type of non-walkable surface to separate pedestrians from vehicles, since it does serve a purpose and then confirm that the owner understands the risks of going one way or the other.


Be aware that your local City or County may have additional requirements that are more restrictive than the State or Federal requirements. Also, this article is an interpretation and opinion of the writer. It is meant as a summary – current original regulations should always be reviewed when making any decisions.

© Janis Kent, Architect, CASp 2015