| For safe driving in foggy condition it is important that driver recognize warning signs. The authors tested effects of retro-reflecting performance for signs by driving under foggy condition. The tests were conducted on a road in service under four visibility conditions: daytime clear、 daytime dense fog、 nighttime clear、 and nighttime dense fog. Two types、 incorporating wide-angle prism retro-reflective and encapsulated-lens retro-reflective materials are used for testing visibility targets. Drivers drove a test car under free-flow condition and cued an experimenter in the back seat upon recognizing the warning sign and again upon determining its meaning. Visibility and legibility distances in daytime dense fog and nighttime dense fog tended to be greater for the signs incorporating wide-angle prism retro-reflective material than for signs incorporating encapsulated-lens retro-reflective material. The findings demonstrate that installing traffic signs with high retroreflectivity can contribute to driving safety by improving visibility and legibility under fog. |
