A coroner has called for a review of the closure of hard shoulders after an inquest into a minibus crash on the M4 that killed three people.
The bus carrying students was struck by a lorry near Newbury where there was no hard shoulder due to roadworks on 11 October last year.
Three members of staff from Prior's Court School in Thatcham died.
Senior coroner for Berkshire Heidi Connor will now ask Highways England to look into its management of roadworks.
Passengers Jason Aleixo, 44, from Thatcham and Lorraine MacLellan, 60, from Farnborough, Hampshire, died from multiple injuries at the scene. Driver Catherine Gardiner, 52, from Reading died in hospital the next day.
Ms Connor recorded that the deaths were due to a road traffic collision, but said it "remains unclear" why the minibus abruptly stopped.
She added: "On balance a problem with the vehicle was more likely than driver input."
The lorry, which was travelling at about 52mph, had little time to avoid the minibus, the inquest heard.
At the hearing at Reading Town Hall on Thursday Mrs Connor said a hard shoulder "may have offered the minibus an opportunity to move out of harm's way".
Mrs Connor said she had heard no evidence that anyone at Highways England was responsible for minimising hard shoulder closures.
Highways England has been asked to respond to the coroner.