Airbags alone are not enough to safeguard against serious injury to car occupants in the case of an accident, say German experts.
"Only by wearing a seatbelt are driver and front-seat passenger protected against being thrown at the dashboard or the windscreen," said Christian Buric of Germany's largest car club, the ADAC.
Airbags often don't operate at low speeds of up to 30km/h, according to two sets of tests carried out by the club at 30km/h and 64km/h.
ADAC research shows that one in five fatally injured car occupants was not wearing a seatbelt. The majority of those killed would still be alive if they had been wearing a seatbelt, said the club. About 98 per cent of motorists in Germany regularly wear a seatbelt while driving.
"People who are not wearing a belt risk serious head, neck and upper body injuries even at speeds of 30km/h," said Buric.
The impact in such a collision is the equivalent of falling to the ground from a height of 4m, he added. "With a seatbelt on, the person usually gets off lightly."
In a modern car, properly belted-up drivers and passengers can survive a crash at 64km/h with minimal injury, according to the latest ADAC tests.
Those not wearing a belt face severe and in some cases permanent injury.
The ADAC expert said back seat passengers should also take the wearing of seat belts seriously since they would otherwise not only be putting their lives at risk but also those of other car occupants.
When a crash occurs, rear seat occupants could easily be propelled forward and strike the head of the driver or front seat passenger.