Comparative analysis of skid resistance on pavement between full-length and intermittent coating of red anti-skid under wet and dry conditions

Insufficient pavement skid resistance is a major contributor to wet-weather crashes, particularly in monsoon regions such as Thailand. This paper investigates the effectiveness of red anti-skid material (cold plastic) in improving pavement skid resistance and, in particular, compares full-length and intermittent application patterns. Three scenarios were examined over a 1,000-m closed asphalt test section: (1) untreated pavement, (2) full-length coverage with red anti-skid material, and (3) an intermittent 80/20 pattern (80 cm coated followed by a 20 cm uncoated gap). Skid resistance was measured with a continuous-reading, fixed-slip Airport Surface Friction Tester (ASFT T-10) and averaged every 10 m (μ 10 ) under both dry and wet (1-mm water film) conditions, giving 400 samples per scenario. A two-sample Z-test at the 95% confidence level showed that both treatments raised skid resistance significantly above the untreated surface (mean μ 10 increased from about 0.207–0.215 to above 0.40). Under dry conditions, full-length coating gave significantly higher friction (μ 10 = 0.4346) than the intermittent pattern (0.4269), whereas under wet conditions the intermittent pattern performed significantly better (0.4169) than full-length coating (0.4069). The intermittent pattern therefore maintains—indeed slightly improves—wet-weather friction while reducing red anti-skid material use, and its associated cost, by about 20% (equivalent to about 20,644 USD per 3.5-m-lane-kilometre). These results indicate that full-length coating is preferable where dry-surface friction governs, while the intermittent pattern is an economical and safe alternative for rainfall-prone locations.