DISCUSSION BEGINS WITH CLARIFICATION OF THE NEED FOR DETERMINING PRESCENE AND ONSCENE SERIES OF EVENTS, FOR CONDUCTING A THOROUGH INVESTIGATION AND PRESERVING EVIDENCE PROPERLY, AND FOR DIFFERENTIATING BETWEEN REAL ACCIDENTS AND FRAUDS STAGED TO OBTAIN INSURANCE MONEY OR COVER UP OTHER CRIMES. FORMULAS FOR CALCULATING REACTION DISTANCES, CONSTANTS, AND SQUARE ROOTS PROVIDE THE MATHEMATICAL TOOLS NECESSARY TO RECONSTRUCT THE ACCIDENT. STEP-BY-STEP PROCEDURES OF THE ACCIDENT INVESTIGATION PROCESS ARE OUTLINED COVERING THE PERIOD FROM THE ACCIDENT CALL TO THE ONSCENE INVESTIGATION AND COMPLETION OF THE ACCIDENT ANALYSIS. INVESTIGATION TECHNIQUES ARE DELINEATED, INCLUDING METHODS FOR EXAMINING VEHICLES FOR DEFECTIVE PARTS, THE ROADWAY FOR OBSTRUCTIONS AND PHYSICAL DEFECTS, AND INVOLVED DRIVERS AND PEDESTRIANS FOR ALCOHOL AND OTHER DRUG USE. BASIC PHYSICS IS EXPLAINED TO PROVIDE AN UNDERSTANDING OF VEHICLE MECHANICS AND DYNAMICS. ALSO, METHODS FOR DETERMINING THE PRECRASH PATH AND SPEED OF ACCIDENT VEHICLES ARE DESCRIBED TO INCLUDE EXAMINATION OF HIGHWAY MARKS, HIGHWAY FIXTURES, AND VEHICLE DEBRIS. FINALLY, PROCEDURES ARE OUTLINED FOR INVESTIGATING HIT-AND-RUN ACCIDENTS, USING PHOTOGRAPHS, AND DRAWING ACCURATE FIELD SKETCHES AND SCALE DIAGRAMS. CHARTS, GRAPHS, TABLES, ILLUSTRATIONS, REFERENCES, A BIBLIOGRAPHY, AND INDEX ARE PROVIDED. (AUTHOR ABSTRACT MODIFIED--PRG)