Enhancing the Philippine Pavement Management System: A Structural Assessment of Roxas Boulevard Using Falling Weight Deflectometer and Backcalculation Method

Abstract

Abstract – The Philippine Department of Public Works and Highways (DPWH) oversees national road
construction and maintenance. Under its Pavement Management System (PMS), the agency conducts visual
condition surveys and road inventories to support asset preservation and network development planning. Despite
regular road monitoring, reports of sudden pavement failures due to unforeseen poor subsurface conditions
persist. This research study aims to address the gap in the structural assessment of roads by employing Falling
Weight Deflectometer (FWD) and backcalculation method. The FWD measures deflection that is used to
backcalculate pavement layer’s elastic modulus or strength. As a preliminary analysis for this study, three
backcalculation programs—BAKFAA, CalBack, and ELMOD—were compared based on their software
characteristics and the consistency of their backcalculation results using deflection data from the Federal
Aviation Administration (FAA). ELMOD showed consistent and reasonable results, producing modulus values
for each pavement layer material within typical ranges, and was therefore chosen to assess the structural strength
of the rigid pavements along Roxas Boulevard, Metro Manila. Sensitivity analysis of the backcalculated modulus
values generally showed stable results across different seed values, particularly in trials using seed moduli that
align with typical values of pavement layers. The evaluated sections of Roxas Boulevard show a 0.955% to 37.2%
deterioration in structural capacity within 2-3 years following reconstruction, contrasting with the Visual
Condition Index (VCI) of above 70.1, which indicates good road condition with little to no maintenance required.
This discrepancy demonstrates that while the surface may appear satisfactory, the underlying structural integrity
is compromised. The research findings underscore the importance of integrating road structural condition
evaluation into the Philippine PMS.

Keywords: backcalculation, falling weight deflectometer, pavement nondestructive testing, pavement
management system