Evaluating the Clearview Typeface System for Negative Contrast Signs

The development of Clearview typeface began in response to a Federal Highway Administration (FHWA) study that recommended a 20 percent increase in sign letter height to provide greater reading distances for aging drivers. The original Clearview studies showed that it was possible to obtain significant improvements in guide sign reading distances for older drivers without increasing letter height by using mixed-case Clearview typefaces in place of all-uppercase Standard Highway Alphabets. Furthermore, the positive contrast (i.e., lighter letters on darker background) mixed case Clearview typefaces were found to be significantly more legible than the mixed case Standard Highway Series E(M) in several independent studies. This body of research led to the 2004 interim approval of Clearview on positive contrast guide signs by the FHWA. Clearview was specifically designed to improve guide sign readability at night for older drivers when used with high brightness sign materials by reducing or eliminating the negative effects of halation and overglow. However, the Clearview Typeface System also includes negative contrast versions to be used on regulatory and warning signs. The difference between positive contrast versions of Clearview and negative contrast versions are limited to stroke width; with negative contrast being heavier to counter-balance the halation effect of the lighter background when viewed at a distance and with high brightness retroreflective materials. While the research discussed above led to the development of guidelines and approval for the use of Clearview in positive contrast, definitive studies have not been conducted for negative contrast applications. Without this research, Clearview's approval will remain restricted to positive contrast applications and full adoption will not take place. The objective of the proposed research is to compare the legibility distance of the negative contrast (i.e., darker letters on a lighter background) Clearview Typeface System with that of Standard Highway Alphabets on regulatory signs in the daytime and nighttime with older and younger motorists. The researchers will identify the legibility distances and evaluate the effects of letter spacing of sign legends using: mixed case Clearview (Clearview 2B, 3B, and 4B) and both mixed and all upper-case Standard Highway Alphabets (Series C, D, and E) on white signs with black legends.