Effects of Font Design on Highway Sign Legibility

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Virginia Tech


The Manual on Uniform Traffic Control Devices (MUTCD) set Standard Highway Alphabet, or Highway Gothic, as the standard font for all American roadway signs in 1966. Since then, that standard has not changed, with all signs following the norm. In the 1980s, new retro-reflective sheeting introduced on American roadways caused Highway Gothic to be more difficult to read, due to the light "halo" effect caused around the letters, or halation. Recently, more studies have been conducted to improve the overall legibility of Highway Gothic. One study found that its legibility could greatly improve if it's size was increased by 20%. This, however, is extremely unlikely, since increasing the font size would also entail an increase in the physical signs lining roadways. In the 1990s, a new font was created, Clearview, to help combat the negative effects of Standard Highway Alphabet. This font received interim approval in 2004, which was removed in 2016 due to ambiguous results from studies as to whether it was more beneficial than Highway Gothic. It was reinstated two years later, in 2018. Legibility has five different components: retro-reflectivity, irradiation, luminance, contrast, and font design. Understanding these five components, and the benefits of each, can lead to the betterment of the font design on highway signs. This study consisted of two web-based tests. In the first test, the "Letters Test", participants would see a character slowly increasing in size on the screen. Once they could decipher the character, they would click the screen and input the character shown. On the second test, the "Words Test", participants would follow the same instructions, albeit with words in place of characters. There were four fonts tested, on both a positive and negative contrasts. The positive contrast consisted of a green background with a white font, and the negative contrast was a white background with a black font. The four tested fonts were E Modified Base, Alpha Two FHWA E Narrow, Alpha Two FHWA D, and Alpha Two FHWA C, named Base, Narrow, D-Altered, and C-Altered respectively. Forty-two participants participated in both tests. For the "Letters Test", the smallest average font size was the narrow font, followed by the base and D-altered. For the "Words Test", the smallest average font size was the base font, followed by the narrow, D-altered, and C-altered fonts. Overall, the base and narrow fonts took up more space than the D-altered and C-altered fonts. It is recommended that field tests are conducted with these fonts, taking into account the space that they take up, not the font size. This analysis could help to determine whether or not the altered fonts are as legible, or even more legible, than the base and narrow fonts when occupying the same space.



Sign Legibility, Font Design, Typefaces, Transportation Safety, Standard Highway Gothic, Clearview