Road collisions and traffic injuries are global concerns with significant societal and economic implications. The Highway Safety Manual (HSM) was used to estimate the safety performance of highways and guide transportation decision-making. However, its applicability to the European road network remains uncertain. This paper aims to assess the implementation of HSM in the European context, focusing on two major Greek highways: Ionia and Olympia Odos. The study begins with a comprehensive description of the freeways, including geometric profiles, traffic flow, and crash data. HSM is then applied, considering data requirements and availability. The assessment involves predicting crash frequencies using historical data and comparing them to actual crash frequencies. The findings indicate that data requirements align with European practices, but significant disparities exist between predicted and actual crash frequencies. These discrepancies cannot be solely attributed to the HSM methodology, as other factors like data quality may influence the results. Further research is necessary to determine the suitability of HSM for the European context.