20.2 Visibility of Lane Markings

  • Motorists must be able to clearly see longitudinal lane markings to follow them. Lane markings are designed for a specific preview time, which is the amount of time motorists look ahead on the road. Both marking width and retroreflectivity influence preview time. Table 20.1 provides design guidelines for markings.
Table 20.1 Marking Design Guidelines
Factor Guideline
Preview Time
  • Recommended preview time is 5 seconds. The minimum time is 3 seconds.
Marking-Specific Luminance
  • Minimum dark luminance = 100 mcd/m²/lux
  • Minimum dark luminance (adjusted for dirt) = 121 mcd/m²/lux
Marking Width
  • 6 in. or 8 in. markings offer better visibility than 4 in. markings and are a good choice if there are visibility-related concerns.
  • Wider markings are detected more easily by a motorist’s peripheral vision. Their use can improve motorist comfort and performance.

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Chris VanDyke

Research Scientist | Program Manager

chrisvandyke@uky.edu