There has not been an empirical study of warning area signage installed for people who are blind, deaf, or deaf-blind. We have only professional opinion and tangential evidence. Specialists who work with people who are deaf-blind have found that some citizens have requested the installation of warning signs. One individual in Maryland who is deaf-blind requested signs be installed (Figure 1) stating that they "help drivers to be aware that deaf-blind people live in the area. I walk across the street and they will stop for me" (Ann Black, personal communication, January 3, 2011).
The authors then identified two similar nearby streets (Fordham Ave. and Martin Ave.) which did not have the warning plaques installed. All three crossings had white painted crosswalks with the same traffic control, a diamond-shaped pedestrian crosswalk sign, with either a diagonal arrow or a DEAF / BLIND PEDESTRIANS warning plaque placed on the pole below the crosswalk sign (Figures 1 and 2). The three sites were at streets with similar widths, with one lane for moving traffic in each direction (Figure 3), and each had the same speed limit of 25 mph. According to the Table of Speed and Stopping Distance (James Madison University, 2011), cars travelling 25-30 miles per hour would need 85-109 feet to stop for pedestrians, which we averaged to 97 feet for this study. At each site, landmarks were chosen that were 97 feet to the left and to the right of the crosswalk. The drivers’ line of sight for the pedestrian was at least 97 feet in all trials used to collect data.
| Yield | No Yield | Total | |
| No DB plaque | 38 | 4 | 42 |
| DB plaque | 24 | 3 | 27 |
| Total | 62 | 7 | 69 |