DRAG (from un modele de la Demande Routiere, des Accidents et leur Gravite) is a complex computer model that simulates accident propensities under detailed conditions. The DRAG approach constitutes the largest road accident modelling effort ever undertaken. Gaudry is the creator and developer of DRAG and this work explains its nature, purpose and value. Such a model, which explains accidents for a whole region, province or country, has advantages in answering many questions asked about accidents (such as the role of the economic cycle, weather, prices, insurance etc.) that other models fail...