U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
202-366-4000
Figure 1. Graph. Overhead Sign Results for an SUV. This graph shows two families of curves. One family of curves shows how the legend luminance of different retroreflective sheeting materials changes as a SUV driver approaches a typical overhead guide sign. The second family of curves shows how much legend luminance is needed for the sign to be legible for various levels of accommodation (ranging from 50 percent to 95 percent). On the X-axis is the log of the luminance in candela per meters squared from 0.1 to 100, and on the Y-axis is the distance from the sign starting at 1000 ft and stopping at 200 ft. The graph also includes a legibility zone defined by a maximum legibility threshold of 640 ft and a last look limit of 200 ft. Within the legibility zone, the two families of curves show how the performance of retroreflective sheeting materials differs.
Figure 2. Graph. Overhead Sign Results for a Heavy Vehicle. This graph shows two families of curves. One family of curves shows how the legend luminance of different retroreflective sheeting materials changes as a heavy vehicle driver approaches a typical overhead guide sign. The second family of curves shows how much legend luminance is needed for the sign to be legible for various levels of accommodation (ranging from 50 percent to 95 percent). On the X-axis is the log of the luminance in candela per meters squared from 0.1 to 100, and on the Y-axis is the distance from the sign starting at 1000 ft and stopping at 200 ft. The graph also includes a legibility zone defined by a maximum legibility threshold of 640 ft and a last look limit of 200 ft. Within the legibility zone, the two families of curves show how the performance of retroreflective sheeting materials differs.