The Norwegian Public Roads Administration (PRA) have established road accident investigation teams in nine counties. Guidelines for the collection of data on vehicles, road conditions, and involved road users have been prepared by the PRA. The present document contains guidelines for analysing the data in order to identify probable or possible direct or indirect contributing factors to the accident. The focus of the method is on identifying discrepancies between available relevant information and the information as recognised and utilised by the road users. Lack of information due to visibility obstacles, perceptual limitations or knowledge limitations are determined. The description of the method is accompanied by sample reports from actual road accidents.