This study examines the influence of the International Roughness Index (IRI) on Cost-Benefit Analysis (CBA) in the ex-ante evaluation of road construction projects. The research combines a comprehensive literature review with an empirical case study using data from the Long-Term Pavement Performance (LTPP) InfoPave™ database. Specifically, Section 48-5154 of Interstate 10 in Texas was analyzed to explore the relationship between IRI and critical influencing factors such as pavement age, precipitation, and maintenance interventions. Correlation analysis revealed that increases in IRI were strongly associated with pavement aging and the presence of longitudinal cracking and rutting, while rehabilitation interventions significantly reduced IRI values. Precipitation levels prior to measurement were also found to affect IRI outcomes. These findings highlight the role of IRI as a critical input for estimating road user costs and for strengthening CBA methodologies. The study concludes that integrating IRI into economic evaluation frameworks enhances decision-making in infrastructure planning, supporting more effective allocation of public resources.