A Standardized Grade Point Average (sGPA) Framework for Urban Pavement Systems: A Scalable Index for Infrastructure Economics and GIS-Based City Evaluation

Abstract

Paul T E Cusack

Urban infrastructure condition is typically measured using engineering indices such as the ASTM D6433 Pavement Condition Index (PCI), which, while precise at the segment level, lacks interpretability and comparability at the city scale. This paper develops a standardized, bounded 4.3-point infrastructure grading system (sGPA) that transforms PCI into a unified scalar metric analogous to academic GPA systems. The proposed framework aggregates road condition using length- and function-weighted methods, producing a city-level index suitable for econometric modeling, GIS mapping, and capital planning. We demonstrate that the sGPA is compatible with nonlinear urban welfare functions and enables direct integration into urban productivity models. Conceptual application to mid-sized cities such as Saint John illustrates its utility for infrastructure benchmarking and spatial inequality measurement.

PDF