The font is called "Eurostile" (see also Tratex) btw. Others are the DIN 1541 and FHWA family fonts or similar ones which are utilized on USA/Canada or European highway signs. Eurostile is similar. They are selected as they are designed for high-readability. FYI, "Clearview" is to replace the current FHWA set of fonts.
As for using fonts designed specifically for high-readability, the point is to make things easier for yourself by making it easy to read from a distance.