This book addresses systematically, and for the first time in Italy, the subject of the investigation of road accidents. A natural complement to the first volume «Principi ed applicazioni», this second «Le indagini» is proposed as a reference text for all those who deal with investigations in the sphere of road accidents, in either their institutional or professional capacity. Through the presentation of numerous examples, an in-depth description of the investigation techniques is offered, analysing the various types of data, their characteristics and significance, and their relevance in the subsequent reconstruction of the dynamic of the road accident. Road, vehicle and man interact to create a very complex system; the partial failure of even only one of the components can cause an accident. The reconstructing technician has to discover, a posteriori, who or what didn't work; the better the data he has to work with, the closer to the truth his conclusions will be. Through indications of both an operational and an interpretative kind, the book proposes to guide the investigator in his collection of data about the road, the vehicle and the human behaviour.