Abstract
This research was undertaken to study the problems of skidding, particularly during the wet season. Thirty-nine typical street sections of known service age and traffic were selected from the Muscat area for field investigation. Six age groups were used, ranging from ⩽0.5 to >10 years, with five to eight road sections in each group. Traffic-level categories were low, medium, and high. Field measurements of dry and wet friction coefficients were undertaken for 6 months using a pendulum skid tester and a motometer decelerometer mounted on a test car. Site measurements included surface temperature, length of skidding, texture depth, and assessment of pavement condition. Cored samples 100 mm in diameter were visually evaluated and laboratory tested. The experimental work included determination of asphalt mix content and gradation, Los Angeles abrasion, and acid-insoluble residue of the extracted aggregates. Various relationships between friction coefficient and the relevant independent variables were developed. A predictive relationship between the friction coefficient and the skid length was obtained. Minimum required values of friction coefficient were recommended for safe performance. On the basis of criteria such as those proposed in this study, recommendations were made to immediately maintain eight streets to increase their skid resistance followed by others with different maintenance priorities to improve skid resistance. Open-graded friction courses are strongly recommended to reduce wet-weather skidding. The results of this research will have a positive effect on constructing and maintaining roads to reduce skidding accidents.
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