Detectable Warnings (Part Two): Codes

Erick Mikiten, AIA

Last month we discussed Detectable Warnings and how the code’s vague phrase “Hazardous Vehicular Area” creates uncertainty. The code defines “Vehicular Way,” but leaves architects, plan checkers and site inspectors to decide what is “hazardous.”


These little yellow bumps were developed to serve people who are blind or low-sighted. The bright color is intended to be visible to people with limited vision, and the texture is detectable by a blind person’s cane. Many people don’t realize that the code also requires the surface to have “resiliency,” which means it needs to sound different from adjoining surfaces when tapped or swept with a cane. This is tremendously subjective, and architects don’t have guidance on which products achieve this.

Unintended Consequences

Visibility and cane-detectability are great, but there are unintended consequences. If you’ve ever tried rolling over these bumps with a manual wheelchair with hard plastic front casters, you know that they come close to loosening a tooth or two. In order to make the shape of each little derby hat detectable to a cane, they are too abrupt for many wheelchairs to cross comfortably. For people with walkers and weak ankles, the uneven surface can be a problem.

And there’s more. Take a look around and you’ll see that these plastic and rubber materials don’t hold up well. Here’s one in front of a 7-Eleven in Berkeley that gets a lot of hand truck traffic:

At this point, I’d argue that the jagged and lifted broken edge is more of a hazard than a help, especially for someone who is using a mobility aid, such as a cane or a walker, AND has limited sight.

When Bumps Lose Their Meaning

People who are newly blind who are learning to navigate with a cane are told not to rely on detectable warnings since they are installed so haphazardly as to become almost meaningless. The warnings are also absent from many hazardous places, so people are taught to rely on other clues, such as building edges, traffic sounds and changes in slope.

We see strips that have lost their color, like this one in Sacramento, made by one of the biggest manufacturers of rubber tiles:

We see others arranged in a meaningless collage. Here’s a driveway at a Kaiser facility that’s blocked by bollards, yet there are detectable warnings on the sidewalk.

I’ve crossed here dozens of times. Not once has there been a vehicle entering or exiting the driveway. If there was, it would be a slow process of someone stopping, getting out, removing the bollard, pulling in, getting out, and replacing it. Is that sort of traffic “hazardous”? I think not. And during the remaining 99.9% of the time, these are communicating to a blind person that they are at the street corner. Wrong.

Meanwhile, the four corners of the intersection beyond this driveway have no less than three different detectable warning treatments!

Parking lots can get even sillier, like this newly striped lot at a lumber store:

The token 3’x4’ panel covers only half the access aisle, so even if you think the choice to put it here is right, why not have it be full width? But it’s questionable whether this placement is necessary at all. The striped path of travel leads to the left, to a much busier drive aisle where big lumber trucks and contractors drive through; hurrying to pick up their orders…but there’s no detectable warning there.

Here’s another confusing application. The designer must have owned stock in the detectable warnings company, because every possible location is covered.

One edge of the blue space is completely lined even though it’s not a crossing or adjacent to a drive aisle. Given the slipperiness of these rubber domes, this is introducing a hazard for someone getting out of a car parked on a rainy day. Remember this is the blue space, frequently used by elderly people. And finally, the detectable warnings run all the way to the storefront wall, dividing the pedestrian walkway in two. Not only unnecessary, but how confusing would that be to a person who’s blind and encounters it – coming OR going?

Changes in the Code

In recognition of the confusion, the 2010 update of the ADA removed detectable warnings from every location except at curb ramps and transit platform edges.

But in the California Building Code we still have them. For now. They must be yellow at transit boarding platform edges, bus stops, hazardous vehicular areas, reflecting pools, and rail track crossings. On streets they don’t have to be yellow if they provide 70 percent contrast with surrounding surfaces. But that’s hard to achieve between a light grey sidewalk an asphalt street.

Design Advice

Until we have a better, more durable, non-slip option, or until California follows the ADA in limiting the required use, my suggestion is to avoid splattering detectable warnings everywhere. Don’t cry “wolf!” constantly, or your message will be meaningless. A more conservative approach in placement might actually enhance safety.

When you have complex vehicular and pedestrian overlaps, try to put yourself in the shoes of someone navigating with a cane. Put detectable warnings where you would stop and check for vehicles. In the planning phase, think about your parking lots and walkways early, and try to create a logical, readable environment that minimizes conflicts between people and cars. Ironically, that might mean more curbs and less flush transitions. This might seem counter to a wheelchair rider’s desire to have a flat environment, but as long as there are sufficient curb ramps and a logical pedestrian flow, curbs in parking areas can be much more detectable by everyone. And they can also be safer than a crumbling, faded, peeling, slippery grid of yellow domes.

Kerwin’s Comments: Erick has cited some great examples of misguided designs and applications in the attempt to comply with the code. From these it is clear that the code does not provide enough guidance to the designer or the building inspectors in creating and applying the code to meet the intent. The use and placement is one of the biggest mysteries and when the code is vague and interpreted in so many different ways, we end up with elements that are questionable in providing for the disabled. Providing for the visually and hearing impaired is a very difficult task. Perhaps the future may bring new technology to help the visually impaired be more cognizant of their environment. Imagine yourself being visually impaired and trying to maneuver the world on a daily basis.

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