Color contrast requirement for ADA detectable warning surfaces 1

[ACtrafficengr]

I'm working on crosswalks for intersections between HMA shared use paths and HMA roadways. We prefer the cast iron detectable warning surfaces for durability reasons, but when weathered, they will not have the required contrast against the HMA. They do sell powder-coated ones, but the first time a snowplow driver swings a bit wide, the wing plow will scrape the color off all the truncated domes. Both Neenah Foundry and E J Co recommend the natural finish.

Given that the cast iron DWSs have to be set into PCC anyway, I could make the slab large enough to provide a white border around the dark iron. My question is, how large would this border need to be?

I've sent an inquiry to the Access Board's technical assistance office, but I haven't received an answer yet.

 

[Ron]

My thought would be 4 to 6 inches wide. This is in keeping with parking delineation stripes and other pavement markings.

 

[DMBK]

@ACtrafficengr

Can you provide a sketch for your solution? The DWS has to be the full width of the corridor and transition, minus ay flare. If you are just widening the slab to add in a 'frame', it is my understanding that that would not be true to those requirements.

If you've heard back from the Access Board, I'd be interested in hearing how they responded.

 

[ACtrafficengr]

DMBK, this is what they sent me:

Mr. Mearkle,

A border of light concrete separating the dark cast iron plates from the asphalt would probably be acceptable. The border should be as wide as the detectable warning panel.

Disclaimer: Technical assistance provided in this email is intended solely as informal guidance; it is neither a determination of your legal rights or responsibilities, nor a statement of the official views of the U.S. Access Board or any other federal agency. Any links to non-federal websites are provided as a courtesy and do not represent an endorsement of the linked information, products, or services.

I guess I wasn't as clear as I needed to be. I was thinking about the length of the concrete, measured in the direction of pedestrian travel. For now, I'm specifying 1/2 ft of concrete between the road edge of pavement and the DWS, and 2 1/2 ft between the DWS and the path pavement, for a total width of 5 ft. The main reason I picked 5 ft is concrete crews are probably used to it since it's standard sidewalk width.

 

[ACtrafficengr]

I just got another reply from them. They said 6" of concrete should be sufficient, with the same disclaimer as above.