Development of a Flexible Pavement Overlay Thickness Prediction Model Based on Benkelman Beam Deflection and Equivalent Standard Axle on the Malang Section of the Provincial Road

Abstract

This study aims to develop a regression-based approximation model for flexible pavement overlay thickness on the Malang provincial road section using Benkelman Beam deflection values and cumulative Equivalent Standard Axle (ESA), with a uniform 15-year design life applied only as the traffic-load projection period. This research utilized a quantitative approach with a correlational and predictive design, applying purposive sampling to historical data from the Department of Public Works and Highways across sixteen road segments. Data were analyzed using the standard Benkelman Beam deflection-based overlay design procedure (Pd T-05-2005-B) to determine the required overlay thickness for each segment, followed by Multiple Linear Regression to quantify the empirical relationship between deflection, cumulative ESA, and overlay thickness. The results show that representative deflection is the dominant and statistically significant predictor of overlay thickness (R² = 0.983; p < 0.001), while cumulative ESA contributes in the hypothesized positive direction. Required overlay thickness across the sixteen analyzed segments ranged from 3.21 cm (Jl. Ir. Soekarno) to 4.54 cm (Wonomulyo-Gubuk Klakah and Jl. Raya Tulungrejo Segmen I); for example, the KM.113+700 - KM.115+405 segment required a 3.87 cm overlay due to a representative deflection of 248.52 mm and cumulative traffic load exceeding 147 million ESA. The regression equation consistently approximated the overlay thickness values obtained from the standard deflection-based calculation across the sixteen analyzed segments. The resulting model should therefore be interpreted as a simplified estimation tool rather than an independently validated predictive model.