Investigators said the bus driver thought he was getting on an HOV lane when he drove onto an elevated exit ramp, plowing through a stop sign at highway speed and hurtling from an overpass onto the interstate below.
The March 2 crash killed five members of Ohio's Bluffton University baseball team and injured 28 others.
NTSB investigator Dave Rayburn said Georgia officials changed the layout of the signs after having trouble with their mounting. The change deviated from federal guidance about placement of certain exit signs to make them more clear, he said, but the change did not amount to a violation of federal regulations, which allow for some exceptions. Rayburn said nine accidents have occurred at the site between 1997 and 2007, including three fatal collisions. The drivers in all of the crashes were from outside the Atlanta area.
NTSB Chairman Mark Rosenker called it "an accident that didn't have to happen."
"Had the appropriate investigation been done at the state level we might not be here today," he said.
Investigators also said the 65-year-old bus driver was partly at fault.
He had a good driving record and had been driving for only an hour before the early-morning crash, they said. But his required medical certificate, which is required by law, was expired, and he had several risk factors for sleep apnea.
Still, they found no evidence that medical problems contributed to the crash.
Instead, "he missed what route guidance was available," said investigator Deborah Bruce, noting that 20 million drivers have successfully navigated the exit over 10 years. "He didn't decrease his speed as he came up the exit ramp," despite two signs notifying drivers of a stop ahead.
Parents of several of the crash victims appeared at the meeting to call for stronger regulations on bus safety, including for more driver training, stronger roofs, shatterproof window glazing and mandatory seat belts. The NTSB has made similar recommendations dating back to 1968, but the recommendations have never made it into law.
John Betts, whose son, David, was killed in the crash, said if the NTSB's proposals had been adopted, "our sons would be alive today."
"That's not a wish. That's not a fantasy. That's a fact," he said. "The apathy has gone on too long. These recommendations were made 40 years ago."
