Once upon a time Australian parents had the option of hitting the road with their infants in hammocks suspended from the roofs of their cars.

Key points: Four Corners' report on car seats for children in 1970 sparked wider public interest in the devices

Four Corners' report on car seats for children in 1970 sparked wider public interest in the devices Graphic footage of a simulated crash in which a dummy was flung headfirst into a concrete wall never made it to air

Graphic footage of a simulated crash in which a dummy was flung headfirst into a concrete wall never made it to air Featured expert Michael Henderson went on to head up road safety in NSW

The year was 1970, baby hammocks were marketed as a children's car safety device, and most people did not know better.

Michael Henderson — a medical doctor with an interest in engineering and child safety — was an integral part of an episode of Four Corners the same year, examining just how safe the available child safety devices for cars really were.

"I've never seen a replay … that was incredible," Dr Henderson said, after watching the story on YouTube, 48 years later.

He had forgotten entirely about the baby hammock, and marvelled at his youthful appearance and "posh accent".

"I got the wife in, 'come and see this'," he said.

$2 car seats and child-sized dummies flying into walls

The episode, unearthed by RetroFocus, showed viewers the dangers of budget-friendly $2-3 restraints designed to hook onto the top of bench seats, car seats that doubled as picnic chairs, early versions of crash tests and safety data from the United States.

"Car crashes are the commonest cause of childhood injury," the young Dr Henderson told Four Corners.

"Children are particularly vulnerable in car crashes … they have a soft skull, they're very likely to [sustain] head injury and facial injuries.

"They often fly upwards in a crash, hit the roof with tremendous force."

Or worse. Dr Henderson recalled an experiment he set up at reporter John Penlington's request which saw a child-sized crash-test-dummy sailing through a car's front window, headfirst into a concrete wall and then over it.

The graphic footage — testing a model of child restraint which hooked over the top of the seat — never made it to air, he said.

However, the message still hit home for many viewers.

People approached him after the episode aired and said, "wow, never knew that," according to Dr Henderson, and "it became a matter of public interest".

After the show, he went on to become New South Wales' Traffic Accident Research Unit director, then the state's head of road safety, and developed a six-point restraint system that is still used in Formula One racing cars today, he said.