DELINEATION OF CONCRETE SAFETY SHAPED BARRIERS

In this paper, the results of a study of five delineation treatments for concrete safety shaped barriers are presented. These treatments were tested along a lighted urban freeway in Houston, Texas. A low-light video camera and time-lapse video recorder were mounted above each treatment to record nighttime traffic next to the barrier before and after the treatments were installed. Nighttime subjective evaluations were conducted when the treatments were newly installed and also after the treatments had been in place for several months and had become dirty. Study researchers also measured the visibility distances of the treatments at periodic intervals after delineation installation. The results showed that the treatments had little effect on lane distributions and vehicle lateral distances from the barrier. Subjects rated the side-mounted cube-corner lenses at 50-ft spacings as the brightest and most effective treatment of those studied. However, lane straddling rates may have increased slightly next to this treatment. Visibility data showed that the cube-corner lenses lost less of their original visiblity over time than did reflective sheeting. Also, side-mounted delineation was found to become dirty and lose its visibility faster than top-mounted delineation. On the basis of the measurements taken, top-mounted cube-corner delineators at spacings no greater than 200 ft were recommended for delineating concrete safety shaped barriers.