The Netherlands Transport Research Centre (AVV) is preparing functional specifications for the universal variable message sign (VMS), which shall be used as traffic signalling. It is of major importance that traffic signs are presented uniformly. In order to draft well-founded requirements, research was needed on the recognition distance of traffic signs, the backing board dimensions, and the allowed colour differences and reflections. In a laboratory matrix signs were simulated with images of traffic signs in various resolutions and in normal and inverted (white symbols on a black background) conditions. With 12 observers the recognition distance was determined. Information from literature was used to draft proposals for the requirements for the backing board dimensions and the allowed colour differences and reflections. Some of the conclusions made are: In order to recognise traffic signs at a distance of 200 m on a matrix sign with optimal optical properties, the height of circular and triangular signs should be at least 133 and 148 m, respectively. Arrows should have a minimal lenght of 49 cm. For displaying these signs a matrix sign is needed with a size of 1.5 x 1.7 m (h x w) and a light point distance of maximal 32 mm. For an aesthetic image the light point should be no more than 16 mm; The required resolution of a matrix sign does not depend on the recognition of the displayed traffic sign, but on its aesthetic properties; Concerning recognition there is no restriction for the use of inverted signs; A backing board with a width of 50 cm, measured from the side of the display surface, ensures sufficient legibility and conspicuity. and distracting reflections in signs can be avoided by establishing requirements for diffuse and specular reflections, which can be measured according to standardised methods. For related work see C 23395 (ITRD E206643).
Abstract