Digging some and I found Typeface and Font Politics on America’s Roads - https://www.lacar.com/reports/typeface-and-font-politics-on-americas-roads https://www

Digging some and I found Typeface and Font Politics on America’s Roads - https://www.lacar.com/reports/typeface-and-font-politics-on-americas-roads https://www.lacar.com/reports/typeface-and-font-politics-on-... which also gets into the "which is better" > Highway Gothic’s problems rested in the interstices (spaces) of its “a”, “e” and “u”, and when reading them at higher speed, these vowels would present more like an “o”. In addition, lower case letters like “i” and “l” were indistinguishable, with halation further heightened by the glare of headlights at night. > ... > But herein lies a mystery. In its Federal Register notice, the FHWA concluded that although Clearview worked well for white lettering on a dark background, it was ineffective on dark lettering on white background. Moreover, it determined that the “retroreflective” material used on freeway signs created more of a problem than did the font of choice when it came to nighttime readability. Finding no benefit that could be remedied by simply replacing older Highway Gothic font signage, the FHWA reversed course. and some more digging finds that research / testing: Penn State History Lesson: The Drama Behind The ‘New’ Highway Sign Font - https://onwardstate.com/2021/08/26/penn-state-history-lesson-the-drama-behind-the-new-highway-sign-font/ https://onwardstate.com/2021/08/26/penn-state-history-lesson...