The most important aspect of road markings is that they must be retroreflective. The minimum night-time visibility (retroreflectivity) (RL) for white and yellow road markings must be 100 mcd/m2/lx and 70 mcd/m2/lx respectively. There are also other important parameters to which road markings should conform, such as the day-time visibility (luminance) (Qd), colour and skid resistance. The South African Bureau of Standards (SABS) regulations on plastic road-marking materials are insufficient, and therefore road-marking applicators could be applying inferior quality plastic road-marking materials. Since the European specifications are widely adopted by many countries, the BS EN 2007 specification was used in conjunction with the available South African standards in this study to determine the performance of thermoplastic road-marking materials. Retroreflectivity testing is important in controlling the final road-marking product.
The objectives of this study were:
■ To determine the RL and Qd service lives of various road-marking paints and road-marking materials on asphalt and chip seal road surfaces.
■ To determine if there are significant differences in RL, Qd and the colour of the road markings when washed with liquid soap mixed with water and hard brooms.
■ To check if the colour and skid resistance of the applied road markings comply with the specification.
Based on the data obtained from the study, the following conclusions were drawn:
■ The RL and Qd service lives of various road-marking paints and road-marking materials on asphalt and chip seal road surfaces were determined as between 1 and 48 months, and 1 and 30 months respectively.
■ There was no significant increase in RL or colour compliance of the washed road markings, while there was generally an increase in Qd after washing the test markings.
■ White road markings generally complied with the colour specification, while yellow road markings did not comply with the specification.
■ The initial skid resistance of white and yellow 1.2 mm thermoplastic road markings complied with the specification, while all other road markings did not comply with the specification.