A study of the available literature leads to the following conclusions. - the conspicuity of a colour is determined by the brightness- and colour-contrast with its environment. - by the application of a contrasting coloured surface having dimensions of at least 30 cm the conspicuity may be increased. The apparent shape of the vehicle must not be affected. - from the available data about reflection properties of the environment and the colour discrimination capacity of man, a computational basis is derived for attaching a conspicuity index to each colour, for the situation in heavy overcast and clear weather. - in dusk, with fog, and over a large distance the luminosity (remission coefficient) will have a dominating influence on conspicuity, colour is then of minor importance. At dusk and in fog the lighting system of the vehicle should be used. Although the premises on which the computation method is based have not all been experimentally verified, it appears from the literature data not likely that experiments will change the constructed conspicuity index drastically. It also follows that there is little advantage in carrying out a field experiment. The author advises that the formula for the conspicuity index should be checked by laboratory simulation.
Abstract