ENGINEERING ECONOMY AND ENERGY CONSIDERATIONS SKID RESISTANT SURFACES

The alternative available to the engineer to correct slippery pavements are delineated, and the alternatives available to construct a pavement with high initial and prolonged skid numbers are discussed. The improvement of existing Portland cement concrete surfaces may be effected by either treating the existing surfaces or by overlays. The former approach could involve the following recommended treatments. (1) Longitudinal sawn grooves; grooves 1/8 inch by 1/8 inch at 3/4 inch or 1 inch centers sawn longitudinally in the pavement with diamond saws. This has reduced wet pavement accidents by 85 percent in California (2) Transverse sawn groves, randomly spaced, could prove effective in improving drainage beneath tires in the flat areas of sag vertical curves and the flat area of transition from crowned tangent to superelevated horizontal curves. (3) Some advantages may be realized with diamond pattern sawn grooves. Overlays for PCC surfaces offer a variety of options. These include Portland cement concrete overlay, chip seals, hot-mix asphalt concrete, asphaltic concrete with precoated ships, open-graded hot-mix, epoxy seal, and epoxy-modified hot-mix. Overlays for bituminous surfaces are essentially the same as overlays for rigid pavements, differing only in the preparations of the existing surfaces to receive the overlays. Appropriate materials must be selected to provide both good immediate and long-term friction. Both Macro and micro texture is needed in surfaces to provide adequate friction over the range of normal driving speeds. Desirable aggregates are described under a number of headings. Materials and mixtures must also be designed to provide adequate texture throught the design life of the surface. Details of mix design, construction operations, texturing, curing and materials are outlined.