From a car riding over road compartments with various surface textures, filmed records have been made from visual test targets mounted on a vehicle driving in front. A truck combination, being part of the column, caused a spray of thrown up rain water. The purpose of this was to find out whether the filmed records could demonstrate the alleged favourable effect on visibility of the draining properties of open and extremely open asphaltric concrete. The targets were designed to enable a quantitative appraisal on each road compartment of the effective visual acuity and the required intensity for rear running lights to be just perceived. From the test results obtained from a group of subjects watching the filmed records, cannot be concluded that open surface coating improve visibility significantly. Through light measurements on the film material, an estimate has been obtained of the contrast attenuation caused by the thrown up water. Although this method appears to be very sensitive to changes in visibility, no reliable effect of surface coating can be demonstrated.
Abstract