One essential component to Motor Vehicle Accident Investigations is a reconstruction of the accident scene. Initially the accident investigator analyzes the accident site and inspects the vehicle, documenting both in writing and with photo evidence taken at appropriate angles and measurements based on years of experience and expertise in knowing the crucial elements to reconstructing an accident. Then, after locating witnesses and any additional evidence and interviewing all witnesses, the accident reconstruction process can begin. It is a complex process that requires physics and mathematics to determine the speeds of the vehicles and their relative positions throughout the entire accident sequence. Investigator reviews, at a minimum pre-and post-impact direction of travel, the length of skid marks, the post-impact distances moved, friction levels for the various surfaces of the road, point of impact, impact angles, weather conditions, traffic patterns and the specific size, condition and weights of the vehicles.