Marjorie Hill, 83, was left trapped by her seat belt in the vehicle after it crashed and overturned on the way home from a family day out to Cleethorpes.
Mrs Hill, who lived in Fairway, Ordsall, Retford, suffered multiple injuries and was pronounced dead at the scene following the collision on 27th December 2011.
Her son-in-law David Westthorpe, who was driving the car, told the inquest at Lincoln Cathedral Centre that he could not explain how he failed to take the right hand bend at Brickyard Corner on the A631 Thorndike Way on the outskirts of Gainsborough.
The hearing was told that the car hit a chevron and went through a hedge before rolling over and finishing up on its roof in a field.
Mr Westthorpe said: “I remember saying that it wouldn’t be long before we got back to Retford.
“I saw the chevron when it was about 50 metres away. My speed was no more than 40 mph.”
“All I can remember is running out of control. I can’t offer any explanation for going off the road.”
His wife Sandra Westthorpe, who was sitting behind her mother in the vehicle, added “I remember seeing the red and white advanced warning board. It was instant. Then the car hit a chevron board.”
“I remember careering across what seemed to be a field then an impact with a hedge and then the constant rolling of the car which I didn’t think was going to stop.
“It just rolled over and over and came to a halt on its roof.”
“There were no other vehicles using the road. I don’t have any recollection of the vehicle braking or swerving. I just remember screaming.”
Accident investigator PC Mark Brown of Lincolnshire Police said that the increased grip had been installed on the road surface at the bend.
He said police investigated the possibilities that Mr Westthorpe either suffered a medical episode or fell asleep but there was no evidence to support either situation.
“It would appear that after approaching the bend the vehicle has just gone straight on,” he added.
West Lincolnshire deputy coroner Paul Smith recorded a verdict of accidental death saying: “There were no signs of braking or swerving. Mr Westthorpe offers no explanation for the collision.”
“There is no suggestion of any difficulty with the highway and the vehicle was found to have no difficulties which contributed to the collision.”
“I am satisfied that the collision and the consequences were nothing more than a tragic accident.”