This paper compares the risk-based methodologies on the structural assessment of highway bridges underlying two national guidance documents, namely the well-established UK Design Manual for Roads and Bridges and the recent Italian Ministry of Infrastructure and Transport's Guidelines. Both documents present risk-based methods for evaluating the need for a structural assessment, while exhibiting fundamental differences. For instance, the Italian methodology uses a qualitative approach combining hazard, vulnerability and exposure classes in order to determine whether a structural assessment is required, whereas the UK methodology uses a quantitative risk appraisal based on reliability and risk scores. Both methodologies are applied to the case study of two bridges, highlighting similarities and differences between the two methodologies. The comparison of these two risk-based approaches may allow for a better understanding of the governing factors and for potential improvement of guidelines. © 2024 The Author(s).