A mother may have been distracted by her children in the moments before a crash in which she and her six-year-old son were killed, an inquest has heard.
Laura Hopes, 32, from Saltash, and her son Alfie died in the pile-up on the A38 in Cornwall on 9 July 2017.
Her car was seen drifting across the middle of the road shortly before the fatal collision, a hearing was told.
The inquest in Truro heard the most likely cause was distraction from children in the back or another source.
Mrs Hopes was travelling with Alfie and her other son Tommy, four, when other drivers noticed her Audi A3 drift across the central line on the road between Tideford and Landrake.
It brushed the verge in the seconds before the multi-vehicle crash, the inquest was told.
A third victim, Tony Woodman, 53, from Plymouth, died after getting out of his car to inspect an animal on the side of the road.
He had crossed the two carriageways on foot fearing the animal – which turned out to be a dead badger – was a dog.
He was hit by one of the vehicles and thrown over a hedge into a field.
A Volvo driven by Mr Woodman’s fiancé Kim Gasson was parked on the opposite side of the busy road.
Collision investigator Sgt Simon Bishop said there were four distinct impacts, the first being when Mrs Hopes’ car hit the back of a Land Rover Freelander driven by Nigel Williams in front.
The impact caused Mr Williams to lose control and his car to roll and hit Mr Woodman.
Mrs Hopes’ Audi hit two other cars in the oncoming lane before coming to a rest.
Mr Woodman died from chest injuries while a post-mortem found Mrs Hopes and Alfie died from multiple injuries. All three died at the scene.
Sgt Bishop said the most likely reason for Mrs Hopes’ driving was distraction or inattention “be that from the children in the back or another source”.
Sgt Steve James said the CPS had decided not to charge Ms Gasson with causing death by careless driving.
Coroner Guy Davies concluded the accident occurred “significantly” as a result of the driving of Mrs Hopes who “inexplicably” drove into the back of the car in front.