A horrific car crash in which a Christian blogger and her three children died may have been down to fatigue or distraction, an inquest has heard.

Zoe Powell, a talented artist who made and sold her own faith-based products, was killed along with daughter Amelia, four, Phoebe, eight, and son Simeon, six, when the silver Subaru she was driving collided with a HGV on the A40 near Oxford on October 12.

Daughter Penny, 18 months, was ejected from her baby seat but survived. Husband Josh also survived.

Lorry driver Adao Patricio, who was not uninjured in the collision, described how the Subaru "swerved violently" into his path. 

He said: "The car was less than one lorry's length away from me when it changed direction and crossed into my lane.. It came across very quickly, it came at me so fast I did not have time to break."

Senior coroner Darren Salter said he could not rule out the possibility that the head-on collision was a "deliberate act" but said he did not think this likely.

He said it was "more likely to be due to fatigue or distraction, or a combination of the two, and that the steering input was driver error."

"The cruise control was engaged and at the last moment the accelerator was pressed instead of the brake, which is a phenomenon sometimes seen in these circumstances," he said, adding that the mother and children died when the car "crashed on to the wrong side of the road and collided with an oncoming lorry."

In a statement read to the court, Mr Powell said he could not remember the crash and that his last memory prior to the accident was picking up their children from his parents' house.

The extended families said in a statement that the conclusion of the police investigation and coroner's inquest "bring closure to what has been a very difficult part of the wider family's lives."

"Whilst there is much that we will never fully understand about the crash, it is helpful to comprehend some of the potential explanations of what led to it," they said.

"We thank the police, coroner and crash investigators for their hard work and thoroughness in it all.

"The possibility that such a small distraction may have caused such a horrific accident should act as a painful reminder for everyone that roads are dangerous places; the actions of a single moment have wrecked an entire family and had a lasting impact on everyone around them.

"Whilst it may be unpleasant to conceive, there is not a single driver who has not been in a similar situation but by luck alone they have avoided a serious crash.

"Driving is not as safe as we sometimes wish it was. We all have a duty to always drive to the best of our abilities and ensure that we keep the roads as safe as possible.

"As a family we encourage the wider public to learn from our heartbreak and please make sure they make the right choices when driving on the road."

They added that their Christian faith and the support of many people were giving them strength to deal with their loss.

"We miss them all greatly but are very glad of the times we had together, and as Christians we find rest knowing that their experience in heaven with Christ surpass anything they knew on earth," they said.

"We have been touched by the depth of support and generosity that has been provided by friends, family, the church and wider community. This has carried us through some very difficult times."