Tractor Trailer Rollover Reconstruction Factors

As a trial lawyer in Atlanta, Georgia, handling catastrophic truck accident cases, I often need to use accident reconstruction experts.  Following are some of the factors that the reconstruction expert may consider in such an analyis, as summarized by my Tennessee co-counsel Morgan Adams:

Center of mass formula. The formula to determine the center of mass location is: the total moments ÷ the total weight = the center of mass.

Datum used for accident reconstruction measurements (a datum is an imaginary plane from which all measurements are taken), arm (the distance that a weight is located from the datum), moment (the product of weight x its lever arm).

Track width – Measured to the center of the tire, or to the center of the dual wheels.

Rollover threshold – a ratio of vehicle center of mass-to-track width. This predicts at what lateral acceleration the vehicle or component will roll over.

Rollover threshold formula – the rollover threshold formula is: rollover threshold = track width ÷ height of the center of mass. RT = 1/2 TW/CM
If the rollover threshold exceeds the coefficient of friction of the road surface, there will be a spin out instead of a rollover.  If the rollover threshold is larger than the coefficient of friction, and the vehicle rolled over, there is a mistake somewhere in your calculations or measurements. Therefore, if the coefficient of friction of the road surface is .40, and the rollover threshold is .46, the vehicle should spin out.

Rollover velocity formula – the rollover velocity formula is: rollover velocity = √ radius of the curve x gravity x rollover threshold. As the combined center of mass displaces laterally, it is no longer perpendicular to the track width. The effective track width (TW1) should be determined by measuring the distance from the center of the dual wheels to a point perpendicular to the shifted location of the combined center of mass. This is done by subtracting x from TW. To see how much this would change the original result, subtract x from the track width and recalculate the velocity formula. By allowing for center of mass displacement, the speed is lowered by 5 miles per hour. Therefore, suspension displacement has to be accounted for in reconstructions.

The Shigley Law Firm  represents plaintiffs in wrongful death and catastrophic injury cases statewide in Georgia, and in other states subject to the multijurisdictional practice and pro hac vice rules in each state. Ken Shigley was designated as a “SuperLawyer” in Atlanta Magazine and one of the “Legal Elite” in Georgia Trend Magazine. He is a Certified Civil Trial Advocate of the National Board of Trial Advocacy, Chair of the Southeastern Motor Carrier Liability Institute and former chair of the Georgia Insurance Law Institute. He particularly focuses on cases arising from truck accidents.