Speed, angle of crash played big role

Earnhardt lost control of his Chevrolet when he was in front of a pack of cars approaching the last turn of the last lap of the Daytona 500. He swerved up the banking where Ken Schrader's Chevrolet ran into the passenger side of Earnhardt's car. According to Global Positioning Data used by SportVision, which had in-car telemetry in Earnhardt's machine, it helped investigators estimate the speed that he hit the wall was between 156-161mph.

But it was the angle of impact played a major role in the force that caused Earnhardt's body to shift in a way that caused the fatal injuries.

The front tyres of Earnhardt's car were at a trajectory of 15 degrees, while the rear wheels were at 12 degrees. By contrast, Schrader's front wheels were at 12 degrees and 10 degrees for the rear. A 2-3 degree change, according to experts, creates a 25 percent increase in the energy that must be dissipated during the barrier impact.

"That's quite a substantial difference," said Dr Dean Sicking of the University of Nebraska, part of NASCAR's investigation team.

Earnhardt's car suffered a crash pulse of approximately 80 milliseconds in duration, which meant a deceleration of approximately 80 milliseconds. That means Earnhardt's car suffered a change of velocity by approximately 42-44mph as a result of the wall impact.

"This was a severe hit," added Dr. Sicking.

The velocity change when it made the initial impact with Schrader's car was 9-11mph. The 42-44mph change in velocity when he hit the wall was similar to a parked passenger car getting hit in a head-on collision by a car travelling at 75-80mph