I don't think that's a contradiction - I'd guess that sans serif is indeed much easier to read specifically on signs. When the UK designed its road/motorway si

I don't think that's a contradiction - I'd guess that sans serif is indeed much easier to read specifically on signs. When the UK designed its road/motorway signs they conducted all kinds of usability studies and ended up designing the Transport typeface; just about any country I've been to in Europe uses sans typefaces for roadsigns and station/tube/airport signs. The jury may well still be out for body text in books and other publications. That's not the problem Johnston was asked to solve though.