Reliable data on the number of serious road injuries is a prerequisite for monitoring and evaluation purposes. In January 2013, the High Level Group on Road Safety representing all EU Member States established the definition of serious injuries as in-patients with an injury level of MAIS3+ (Maximum Abbreviated Injury Scale). Since then it is recommended that all EU countries provide data of serious injuries. The High Level Group identified three main ways Member States can estimate the number of serious road traffic injuries: 1) by applying correction factors on police data, 2) by using hospital data and 3) by using linkage between police and hospital data. Quality of data and method differ between Member States. The impact of this heterogeneity on final estimations is unknown. We aim to analyse the impact of a) the criteria used to select hospital casualties, b) on the converter to derive MAIS, and c) on the method used on the reliability of the estimation and the comparability across countries.Methods Three sub-studies will be carried out:A cross-sectional study of Hospital Discharge Data. This study will define criteria for inclusion/exclusion based on codes of the classification of diseases/injuries used (ICD9, ICD10, and AIS).A sensitivity analysis to assess the impact of obtaining MAIS from different methods (codifying directly with AIS, or converting from ICD diagnosis with Icdpic (stata), ICDMAP-90, ECIP-Apollo, or EU-AAAM).Comparison of the three methods to estimate number of serious injured.Results The future results will help to report serious road traffic injuries by EU Member States with standard criteria that would allow comparisons.Conclusions It is expected to provide specific guidelines for reporting serious road traffic injuries and to allow comparability between countries.