Suddenly NASCAR was circled by safety critics, reports CBS News Correspondent Mark Strassmann.
Tuesday afternoon, NASCAR finally responded. Dale Earnhardt's broken seat belt was one of many factors that contributed to the death of the auto racing great, NASCAR said Tuesday in releasing its report on the wreck.
"The conclusion is not the easiest conclusion to report," said Dr. James Raddin, one of the lead investigators. "We conclude that there were a number of factors in which the timing came together to produce this result."
In its report, NASCAR said it will install "black boxes," similar to flight-data recorders used on airplanes, beginning next season to help understand the forces during crashes and try to improve car safety.
However, NASCAR will not require drivers to wear head and neck restraints, although it said their use would be encouraged.
Earnhardt was not wearing a head and neck restraint when he was killed, but NASCAR said it was unclear whether the HANS device would have saved him. Use of the devices has dramatically increased since his crash; 41 of 43 drivers wore them in Sunday's race.
NASCAR also did not recommend making changes to the design of cars so they can better withstand wrecks, nor did it suggest installing softer barriers at tracks.
"We are still not going to react for the sake of reacting," NASCAR president Mike Helton said, repeating a phrase he used the day after Earnhardt died.
Raddin, a director with San Antonio-based Biodynamic Research Corp., was commissioned to determine what caused Earnhardt's fatal injuries.
Because of the angle of his head and the separation of the seat belt, Raddin found Earnhardt suffered a blow to the back of his skull when his car hit the turn 4 wall almost head-on.
The blow caused by the left side of his head hitting the steering wheel or, on rebound, hitting the inside of the car caused a basilar skull fracture that ultimately killed the seven-time Winston Cup champion.
But in finding that the fracture started with a blow to the back of the head, Raddin disagreed with a court-appointed, independent examiner who determined the fracture was caused by a violent head whip.
Helton said the stock car racing organization will commission a study on restraint systems for drivers to take a closer look at seat-belt strength. But NASCAR will not mandate the use of the head and neck restraints that are designed to reduce violent head whips in crashes.
"We are pleased that a majority of Winston Cup drivers now use them," Helton said. "But we are not completely satisfied. We have intensified our efforts with drivers, equipment manufacturers and outside experts with the goal of helping all drivers find a system in which they feel comfortable and safer."
As for the seat belt, Raddin ruled out that is was cut by rescue workers as they tried to remove Earnhardt from the battered car.
"The physical evidence is clear," said Raddin, who showed a blown up photo of Earnhardt's seat belt. "This was not a cutting of a belt afterward. This was a belt that separated under load."
Raddin attributed the break to a phenomenon called "dumping," which is when the webbing is pulled or moved to one side of the adjustment device through which the belt webbing travels.
When a dumped belt is under stress, it can separate and tear across the entire webbing.
Raddin concluded that the dumping was not caused by driver adjustment because the marks on the left lap belt showed it was tightened in a symmetrical fashion.
A second investigator, Dr. Dean Sicking of the University of Nebraska, found that the car was traveling between 157-160 mph when it hit the wall.
In mandating for next season the installation of "black boxes," which will only record data, NASCAR is following the example f CART and the Indy racing league.
Ford has been supplying the black-box technology to the two leagues for several years in an effort to better understand the forces in crashes. Until now, NASCAR had resisted using the boxes on its cars, in part because it feared teams would use the information for competitive advantages.
The investigation, which cost more than $1 million, has been the most far-reaching independent inquiry in NASCAR's 52-year history.
Helton and the two lead investigators met with the majority of the drivers at a North Carolina country club early Tuesday morning to present their findings. Earnhardt's eldest son, Kerry, and his daughter, Kelly, attended along with several members of Dale Earnhardt Inc.
Dale Earnhardt Jr. did not attend the presentation, but a NASCAR spokesman said Helton has privately gone over the report with him. Earnhardt Jr.'s spokesman said the driver would have no comment Tuesday.
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