Proposed Recommendations to Minimize Wet Surface Accidents

Road sections with same construction time, material and geometric design can have different skid resistance over time. The frictional properties of pavement surfaces play an important role in highway safety. Analysis of friction information indicates a relationship between variety of conditions including roadway geometry, AADT, polish stone value and Friction Number (formerly referred to as skid number (SN)), climate and economics. Because of these varieties that affect safety aspects, researchers believe that it is best qualified to determine the necessary level of friction in each given situation. According to the statistic reports, approximately 13.5-18% of fatal accidents and 24.3-25% of all accidents occur when pavements are wet. The following factors affect the friction levels of a wet pavement surface: Micro-texture and Macrotexture; Age of the road surface; Seasonal variation; Traffic intensity; Aggregate properties; Road geometry. High demand category surfaces (FN=45-55) will be able to maintain the design frictional characteristics through their service life. Wet Frictional characteristics are easily lost if: Water ponds on the road surface due to rutting, shoving or poor drainage; Pavement flushes and submerges the aggregate; The wrong type of aggregate was used. To determine surface properties as sufficient for pavement skid resistance, this procedure was suggested: Check if wet weather problem exists; Select target design friction level; predict potential reduction of wet accidents; Calculate Benefit/Cost ratio of design target; Evaluate effectiveness of design; Select surface mix with adequate Polish Value. The following are proposed recommendations to potentially minimize wet surface accidents: Monitoring wet surface accident sites and locations; Identifying sites with low skid resistance and dealt with quickly by a suitable remedial treatment or use "Slippery When Wet" signs; Measuring skid resistance for low FN (FN<40); Testing for PV annually; Implementing a skid resistance design policy to select a (design FN) and PV for anticipated maximum speeds; Establishing a three-year maintenance program to monitor and eliminate the reduction in skid accidents; Including skid resistance improvement. This paper aims to describe the recommended process in developing a design policy to improve pavement surface friction.

کلیدواژه ها:

Frictional Properties ، Safety ، Surface Texture ، Skid Number