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Publication Number: FHWA-HRT-04-133
Date: December 2005

Enhanced Night Visibility, Volume II: Overview of Phase I and Development of Phase II

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Figure 1. Diagram. TCD evaluation intervals. This shows a vertically oriented bird’s-eye view of a section of two-lane road with left and right edge lines and a solid center line next to a broken center line. There is a vehicle in the right lane at the bottom of the diagram facing toward the top. A scale shows measurement interval along the right side of the diagram, starting with 0 at the vehicle’s nose, going to 8, and ending with n at the top of the diagram. Four arrows extend from the nose of the vehicle to various roadway infrastructure elements: road surface markings (the center and edge lines), overhead signs (shown at the top of the diagram), and roadside signs (off the right edge of the road). Back to Figure 1.

Figure 2. Equation. Luminance contrast. Luminance contrast equals the difference of maximum luminance minus minimum luminance, that difference divided by maximum luminance. Back to Figure 2.

Figure 3. Diagram. Smart Road pavement marking plan. The illustration is titled “Smart Road Pavement Marking Plan Enhanced Night Visibility Project.” It shows a horizontally oriented bird’s-eye view of a section of the two-lane Smart Road. A distance scale running along the bottom edge of the road goes from 0 feet to 7,550 feet (left-to-right). At 4,921 feet, the road is divided into two segments: darker gray, representing asphalt, and lighter gray, representing concrete. Two rows of small dots run the length of the road, one on either side, labeled “Delineator posts spaced 100 feet O.C. (both sides).” The distance scale is divided into three segments, each showing the length of road that used a particular type of road marking (all used white edge lines and yellow center line): the segment from 0 feet to 2,292 feet (on the asphalt portion of the road) used conventional tape, the segment from 2,292 feet to 4,921 feet (still on the asphalt) used fluorescent thermoplastic, and the segment from 4,921 feet to 7,550 feet (on the concrete) used fluorescent paint. A 2,460-foot portion of the road spanning the asphalt and concrete sections is marked “All Weather Test Section (AWT) (3,440 feet to 5,900 feet).” There is a note that says “Note: 3 percent grade from 0 feet to 2,297 feet, 6 percent grade from 2,297 feet to 7,550 feet.” A pullout illustration shows a close-up of a section of road with pavement marking dimensions. The edge lines are 4 inches wide and 9.84 feet from the outer edges of the road. The center line skip marks are 4 inches wide, 12 feet from either edge line, 10 feet long, and 30 feet apart. Back to Figure 3.

Figure 4. Equation. Modulation contrast. Modulation contrast equals the difference of maximum luminance minus minimum luminance, that difference divided by the sum of maximum luminance plus minimum luminance. Back to Figure 4.

Figure 5. Equation. Luminous contrast. Luminous contrast equals the difference of maximum luminance minus minimum luminance, that difference divided by maximum luminance. Back to Figure 5.

Figure 6. Equation. Luminance ratio. Luminance ratio equals maximum luminance divided by minimum luminance. Back to Figure 6.

Figure 7. Diagram. Electromagnetic spectrum. A scale of wavelengths runs from the top to the bottom of the diagram, from 250 nanometers to 10,000 nanometers. The scale is divided into three different regions: ultraviolet from 400 nanometers and lower; visible region, which is subdivided into colors moving from violet at 400 nanometers to blue, green, yellow, orange, and red at 700 nanometers; and infrared from 700 nanometers and higher. Back to Figure 7.

Figure 8. Line graph. Characteristics of available and prototype vision enhancement systems. The graph is titled “Spectral Distribution of High Intensity Discharge (HID) and Halogen.” The X-axis is labeled “Wavelength (nanometers)” and ranges from 380 to about 735 nanometers. The Y-axis is labeled “Relative Energy (Watts).” The graph shows an almost straight line labeled “Halogen” increasing from the lower left up to the right starting at 0.00 relative spectral power at about 390 nanometers to just above 0.08 relative energy at about 735 nanometers. At about 650 nanometers, the line switches from a smooth, steady increase to a line that fluctuates slightly. The graph shows another line labeled “HID” with a series of large peaks at the following approximate values: 0.10 relative energy at 470 nanometers, 0.125 relative energy at 515 nanometers, 0.105 relative energy at 550 nanometers, 0.125 relative energy at 570 nanometers, and 0.115 relative energy at 590 nanometers. After approximately 600 nanometers, there is a downward trend with some small peaks. Back to Figure 8.

Figure 9. Photo. Smart Road testing facility. The photograph shows a paved road with a large turnaround at one end extending down into a valley at the other end. Back to Figure 9.

 

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