This is a great article on the work of Lock Kinneir and Margaret Calvert in the late 1950s, when the government hired them to design a new system of signs for British roads. Before then, there had been no consistent design in place for road signs, and instead drivers were faced with a random mix of different shapes, colours and typefaces of varying legibility:
The constraints for the project were set with two simple questions: what do you need to know while traveling at speed, and at what distance do you need to know it? In an essay published by the Design Museum, Calvert said: “‘Style never came into it.’” The signs had to display reduced forms that could impart information immediately. Certain advances, like the new reflective white material that would coat signs, would help, but Kinneir and Calvert had to design their own typeface. In an essay Calvert wrote for the occasion, she explains: “Important details, such as the curve on the end of the lowercase l…and the obliquely cut curved strokes of the letters a, c, e, f, g, j, s, t and y, were specifically designed to help retain the word shape of place names when slightly letter-spaced…This specific letterform, after two attempts, and in two weights, was officially named ‘Transport’.”
Kinneir and Calvert created rules for traffic signs that have endured to this day. Consider the wide gaps in letter spacing typically seen on roadside signs: That spacing is derived from research the designers conducted on how type should scale according to the speed of traffic and the amount of information on display. For Transport, the unit of measure for spacing is based on the width of the capital letter ‘I’—a consistency in form which, over time, helped foster a sense of familiarity in drivers.
There’s an exhibition on now at the Design Museum in London – 50 Years of British Road Signs.