Computers have affected the way we do business, and the area of automobile accident reconstruction is no exception. The United States Department of Transportation has developed several computer programs for automobile




Figure 1

accident reconstruction. One of these computer programs is called Calspan Reconstruction of Accident Speeds on the Highway or CRASH for short. This computer program calculates the impact speeds and changes of vehicle velocity during an accident.

Figure 1 shows typical information that is fed to the computer. The scene information describes to the computer the locations of the vehicle rest position, the expected impact position and direction of rotation. Next information must be supplied to the computer concerning the characteristics of the vehicle (weight, stiffness, model) as well as measurements of vehicle crush. The crush depth along the damaged portion of the automobile is indicated by the variables C1 through C6. So in Figure 1, L indicates that the damage width is 65 inches while the crush depths vary from 33 inches to 44 inches. The photograph in Figure 1 shows typical measurement of crush depth. Finally, the last piece of information supplied to the computer describes the frictional properties of the road at the time of the accident.

Figure 2 is the computer printout of the accident reconstruction. Under the printout for vehicle number 1, the impact speed was 44 mph forward and 14.3 mph laterally or to the right. This indicates that vehicle number 1 was attempting to turn right to avoid the collision. The printout for vehicle number 2 shows a forward speed of -2.2 mph which means the vehicle is moving backwards at 2.2 mph and a lateral speed of 46 mph to the right, which means that vehicle number 2 was in a sideways skid at 46 mph at impact. The speed change calculations



Figure 2

indicate the severity of the crash and are often used in determination of the chances of occupant survival. The CRASH computer program is available from the National Technical Information Service and is also available from private software vendors.

The CRASH computer program is based on Newton's Laws of Motion and principles of conservation of energy. It contains diagnostics that warn the user of improper or unreasonable input data. The CRASH computer program is a useful tool for analyzing the complexities of automobile accidents.

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