The massive oak that fell and killed a driver in Great Falls on Tuesday night was obviously decayed and destined to fall, according to a state arborist and other tree experts.

Albert Carl Roeth III, 64, of Great Falls was driving his 2008 Mercedes CL600 southbound on Georgetown Pike about 6:30 p.m. when the estimated 100-foot, 40-ton tree unexpectedly fell from the right side of the road and crushed his car, Fairfax County police said. They are unsure how fast his car was traveling or where he was going.

“The tree was decayed to the point where it was going to fall,” said Robert Burris, the Northern Virginia arborist for the Virginia Department of Transportation. “It was just random that it came down when it did.”

Burris said the signs of decay included canopy die back and rotting at the tree’s base and in its roots. He said it’s unclear whether the decay was the result of disease, age or a combination of both. Burris said he did not think the recent derecho storm weakened the tree.

Authorities said that they had not had any reports about the tree, which was more than 100 years old and stood near the busy roadway and a strip mall that gets a significant amount of traffic in the 9900 block of Georgetown Pike.

VDOT officials said the tree was in their right of way, but they had no record of receiving previous complaints about it. Fairfax officials also said they had no record of receiving complaints about the tree.

Robert Blakely, an arborist who lives in Great Falls and has 36 years of experience, said the tree had obvious signs of decay and “should have been taken down.”

“It was a tree that presents liability to anyone and everyone underneath it. It’s a high-traffic area,” Blakely said. “I’m surprised it wasn’t a priority.”

Joan Morris, a VDOT spokeswoman, said the department does not inspect every tree on its right of way because there are simply too many.

She said VDOT maintenance crews regularly scan for dead trees as they are making their rounds. The department also relies on the public to report problem trees using a hotline at 800-FOR-ROAD.

Morris and Burris said they could not recall another incident in which a tree in VDOT’s right of way fell and killed a person. Arborist Mark O’Dell said Roeth was in­cred­ibly unfortunate.

“It’s like an airplane falling out of the sky and hitting you,” O’Dell said.