Prediction of pavement performance deterioration is crucial for effective transportation infrastructure management and maintenance planning. This study focuses on developing deterioration models for flexible pavements in the Pacific Northwest, leveraging the extensive data available in the InfoPave Long-Term Pavement Performance (LTPP) tool. Specifically, historical records of International Roughness Index (IRI) measurements are analyzed to understand the performance degradation patterns of flexible pavements over time. Utilizing Kaplan-Meier (K-M) survival time analysis (reliability analysis), we investigate the survival probabilities of flexible pavements based on IRI measures identified by the federal measures over varying time intervals. By analyzing these survival curves, we aim to derive deterioration models that accurately estimate the percentage of flexible pavements surviving within specified IRI thresholds over time and identify trends in deterioration patterns affected by parameters such as maintenance treatments, average annual daily truck traffic, number of freeze and thaw cycles, average temperature, and the presence of cracking. The developed models provide valuable understanding into the deterioration trends of the Pacific Northwest’s flexible pavements and offer predictive tools for infrastructure asset managers to optimize maintenance strategies and allocate resources efficiently on the network level. This research contributes to the advancement of pavement management practices by utilizing robust statistical methods to analyze large-scale longitudinal flexible pavement performance data to enhance the resilience and durability of transportation infrastructure.