Some aspects of road sign posting on motorways are dealt with: traffic control, perceptibility of sign boards, location of pre-warning sign borads, legibility, uniformity and marking, as well as continuity in information. Furthermore the problem of road sign posting on roads other than motorways and some general problems are discussed, such as the indication of mileage on boards, color, lettering, number of legends, location of sign boards and their lighting by using reflective material or internally lighted road signs.