The investigator's basic responsibilities upon arrival at the scene of an accident are listed, as are about 30 items of equipment needed for taking measurements and later preparing a scale diagram of the scene. The sets of events involved in an accident and the basic terminology used in traffic accident investigators are defined. Three categories of evidence are identified: primary short-lived evidence, secondary short-lived evidence, and long-term evidence. Guidelines on measuring and recording information cover the preliminary field sketch, the field sketch, the use of reference points, methods of measuring, methods of recording measurements, possible sources of measurement errors, and the preparation of scale diagrams. Detailed explanations are also given for constructing angles, circles, and curves, and making horizontal and vertical measurements. Appendixes present metric conversion factors and extensive mathematical tables. An index and 13 references are included.