Abstract
The question is posed whether the application of a colour difference for the central line on the road is the best solution available for the coding of the categories of road. It has been proposed to apply yellow centre lines on roads with two-way traffic and white centre lines on roads with one-way traffic. When it is considered necessary to have a coding system by means of horizontal road markings in order to indicate the difference between one-way and two-way roads, the exclusive use of a colour difference for this coding should not be recommended because the difference will not be prominent under favourable conditions and would be hardly visible or not visible at all under unfavourable conditions.