Development of pavement thermal area index (PTAI) for flexible pavement performance evaluation

Pavements are exposed to severe weather conditions and continuous mechanical loading, leading to both visible surface degradation and hidden subsurface damage. Among the various forms of distress, fatigue cracking—particularly alligator cracking—commonly progresses into potholes and accelerates structural deterioration. Traditional performance indicators such as the Pavement Condition Index (PCI), Present Serviceability Index (PSI), and International Roughness Index (IRI) are widely used in Pavement Management Systems (PMS), but they often fail to capture early-stage thermal anomalies associated with moisture infiltration. This study introduces the Pavement Thermal Area Index (PTAI), a novel performance metric that integrates thermal and optical image processing. Field data were collected from three campus pavement sites using thermal cameras and mobile devices. Blue-channel segmentation was applied to extract cold regions from thermal images, and Sobel edge detection was used to identify crack patterns. A climate impact coefficient (k) was incorporated to normalize thermal area values. The results show that PTAI successfully links apparent distress with underlying thermal anomalies and can guide maintenance strategies such as overlay, reconstruction, or slurry sealing. Overall, PTAI offers a low-cost, scalable, and non-destructive tool to complement existing pavement performance evaluation methods.