Road signs are typically placed either by the roadside or above roads. They provide important information for guiding, warning, or regulating the behaviors drivers in order to make driving safer and easier. The difficulty in recognizing road signs is largely due to the following reasons:
- The colors of road signs, particularly red, may fade after long exposure to the sun. Moreover, paint may even flake or peel off.
- Air pollution and weather conditions (e.g., rain, fog, shadows, and clouds) may decrease the visibility of road signs.
- Outdoor lighting conditions varying from day to night may affect the colors of road signs.
- Obstacles, such as vehicles, pedestrians, and othe rroad signs, may partially occulde road signs.
- Video images of road signs will have motion blur if the camcorder is mounted on a moving vehicle due to vehicle vibration as well as motion.