Peugeot has not crash-tested one of its cars for any driver weighing more than 12 stone 4lb (78kg), an inquest heard today.
Judith Evans, a Peugeot 107 driver who weighed almost 16 stone, died in a head-on crash with a Vauxhall Vectra on her way home from work on January 20 last year.
Asked whether the car company had carried out crash tests on the Peugeot 107 model with dummies weighing more than 78kg, a Peugeot safety expert said it had not.
The driver of the Vectra only suffered fractures to her kneecap and internal bruising, the inquest at High Wycombe Magistrates' Court in Buckinghamshire has heard.
But 56-year-old mother-of-three Mrs Evans, a Chiltern Railways customer relations officer from Aylesbury, Buckinghamshire, received injuries deemed by experts to be "not typical of the outcomes usually seen in such collisions".
They found that she died in accident circumstances in which an "efficient restraint system" - including a properly functioning seatbelt, airbag and seat - is designed to provide good protection, the inquest has heard.
Lawyer Robert Horner, representing Mrs Evans's family, asked Peugeot safety expert Richard Zeitouni: "Have you tested with any dummies more than 78kg?"
Mr Zeitouni, giving evidence, replied that Peugeot had not.
Mr Horner: "So you have not tested with a weight of dummy that corresponds to 50% of the male population?"
Mr Zeitouni: "When we designed this car we found it was good, adequate protection for the majority of occupants.
"It's an official dummy, a regulation dummy."
Both women were driving at about 30mph when the accident occurred, according to the Vauxhall driver.
But when their vehicles crashed into each other, Mrs Evans did not receive the usual protection provided by the design of the seat, the seat belt and the airbag, the inquest heard.
She suffered multiple fractures, chest injuries and abdominal injuries.
Mr Horner suggested that any consumer weighing more than 12 stone buying a car may be "slightly surprised that Peugeot has not tested for heavier than their weight".
But Mr Zeitouni said an investigation into the crash indicated that Mrs Evans was sitting further forward in her seat than would normally be the case.
She would therefore have been very close to the steering wheel when the airbag inflated, he said.
Mr Horner argued that she was sitting in an appropriate position, with her back against the back of the seat and that she did not even have the seat as far forward as it would go.
He said: "My criticism of the car (is) that therefore if you sit in an appropriately adjusted seat with your back against the upper part of the seat, the design is such that you can collide with the steering wheel before the airbag is inflated."
Mr Zeitouni denied this was the case.
The inquest yesterday heard from Vehicle Safety Consultancy Ltd (VSC), which was asked by Thames Valley Police to consider the protection offered to Mrs Evans in the collision on Coldharbour Way, Aylesbury, after they noticed her injuries seemed unusually severe for the force of the impact.
Peter Gloyns, a mechanical engineer at VSC, said the car's restraint system did not appear to have worked in the way it would be expected to.
He said: "The accident raises a serious question over the stability of the response of the total restraint system for an occupant of this build and weight in an accident of this severity in which it would be hoped that good protection could be offered."
Dr Gloyns suggested improvements may be needed to ensure that larger drivers were provided the same protection as slimmer ones.
Barrister William Vandyck, representing Peugeot, pointed out that the Vauxhall was heavier than the Peugeot and suggested that a hard part of the Vauxhall hit a soft part of the Peugeot, causing greater crushing of the Peugeot.
The car's safety features are also in line with European regulations, Peugeot has argued.
The inquest has also heard that Mrs Evans, normally a cautious driver, was travelling on the wrong side of the road and may have suffered a medical accident before the collision.
A Peugeot spokesman said the company had no comment to make at this stage.