Methodology for Determining Optimum Letter Spacing for Highway Signs Based on Driver's Legibility Performance

The purpose of this study is to determine the economical standard for road signs by verifying the difference in driver's legibility time with respect to the spacing of letters on the road signs. Laboratory simulations were conducted to confirm the difference in legibility time for six target signs of different spacing. Also, a binary logit model was used to find the main factors, which could lower the rate of misreading. This model involves not only a simple enlargement of signs but also a suitable match of letters and signs along with the optimal spacing of the text letters on the road signs to increase the legibility of the sign. The result of this study verified the importance of spacing in road signs and proved itself to be an effective method to determine the future standard for the road signs.