Determination of sign letter size requirements for night legibility by computer simulation. Paper presented at the 50th Annual Meeting of the Highway Research Board HRB, Washington, D.C., January 1971.

A computer simulation program was used to examine the adequacy of letter sizes on existing signing along a 20-mile stretch of interstate highway. A total of 63 signs were analyzed in detail for minimum required legibility under three various conditions which are respectively daylight, high-beam illumination, and low-beam illumination.