This paper presents the methodology used to improve knowledge about vulnerable road users accidents and more specifically pedestrians or cyclists. This work is based on a complete analysis of real accidents from three different approaches: in-depth accident investigation, numerical simulation with multibody model and experimental reconstitution with PMHS subject. Accidents chosen from an in-depth multidisciplinary investigation are numerical modelled using a multibody software. Then, a parametric study focused for instance on car velocity and victim position at impact is performed in order to find the best correlations with all indications produced by the in-depth analysis. Finally, the retained configuration close to the presumed real accident conditions is reproduced experimentally by crash-test using cadavers. All results are finally compared in order to validate the real accident reconstruction. This methodology is applied on two real accidents involving one pedestrian or one cyclist.