A.D. Tupper & Associates Limited

When a vehicle loses support from the ground it is launched into the air. In accordance with Newton’s first law of motion, it continues to travel horizontally at the same horizontal speed as it had at launch, and falls to the ground under the constant force of gravity. The launch may start as an initial upward, level or downward movement, and can provide a good accurate assessment of the speed at the start of the launch.

A fall occurs when a vehicle is traveling forward, and is no longer supported by the surface over which it is moving.

A flip occurs when a sideways moving vehicle meets resistance, such as through striking the curb, and rises and moves through the air. It is thus contrasted with a rollover, which may occur without the wheels digging in.

A vault occurs when a car moving forward or rearward, meets resistance, digs in and flips end over end.

The following information can be used to calculate the speed at which the vehicle left the ground:

Accurate location of vehicle centre of gravity (CG) at the point of launch

Accurate location of vehicle CG at the first point of landing

Difference in elevation of the vehicle CG between the launch and landing points.

The angle of launch.

The launch analysis is based upon a ballistic arc and can produce very accurate speed assessments provided the relevant data are accurate. Good data are reasonably hard to come by without accurate scaled plan and elevation drawings of the site and the vehicles, and one must be careful not to be seduced to a sense of precision if the data are imprecise.

The family of launch formulae has the potential of producing an accurate evaluation of speed of a vehicle in a launch, call, flip, or vault. The analysis is very sensitive to such variables as the launch angle, which is exceedingly difficult to quantify, and is thus prone to bad answers, particularly when used by inexperienced or improperly trained analysts.

All interested parties, including analysts, insurance representatives, police, crown, defense counsel, and the court, should be prepared to test the assumptions and examine the particular application of this process of speed determination.