Legibility test by Road Research Laboratory at RAF Benson airfield

"How road sign legibility used to be tested by men sitting in a field. Legibility at speed was the key aim. A wonderful photograph from the archive shows flat-capped men from the Road Research Laboratory sitting in an airfield as a car approaches, with a road sign for Oldham and Smethwick strapped to its roof. The idea was to ensure that the overall shape of the placename was legible from a far, rather than the individual letters needing to be identifiable. Calvert has always compared it to looking at a Rembrandt painting: 'If you’re close up it doesn’t make any sense, but it all comes together at the appropriate reading distance.'"— https://www.theguardian.com/artanddesign/2020/oct/23/doyenne-of-design-how-margaret-calvert