“Sunroofs are getting bigger, and so that raises questions that perhaps those numbers are larger,” Mr. Levine said.

Ms. Hankins is among those whose lives were forever changed.

The sunroof in her 2000 Ford Expedition was fun when she first got the vehicle, but the novelty wore off and she usually kept it closed — just as it was when she crashed on the way to work in Yazoo City, Miss., in 2005.

“I didn’t think I would ever be thrown out of it,” she said in a telephone interview.

Ms. Hankins has no memory of the crash, but the evidence showed that the truck rolled over, the glass panel of the sunroof popped out and she was thrown through the opening.

“It put me in a wheelchair,” she said, adding, “It scarred my face really badly.”

In the suit against Ford, Ms. Hankins’s lawyers argued that the automaker should have used laminated safety glass, the kind used in windshields, and more securely anchored the panel. The lawyers said Ford had known for decades that laminated glass — which uses a layer of plastic film between two layers of glass — was safer, but used less-expensive tempered glass.

The automaker acknowledged that tempered glass, which is used in side windows, was less expensive. However, it said serious brain and neck injuries could occur when heads hit laminated glass, a danger it concluded was a greater threat to belted occupants than ejection. (Ford asserted that Ms. Hankins had not been wearing a seatbelt — a suggestion she denied.)

The N.H.T.S.A. considered regulating sunroof safety in 2011 when it established rules to prevent side-window ejections but ultimately opted against doing so. (To comply with the side-window rules, carmakers usually rely on curtain airbags that cover the windows.)