One of the early criticisms of air bags in passenger cars was that they were said to protect only people who aren't belted in, with nothing but potentially-injurious effects for anyone who is.
Does anyone know if that is still (or was ever) true?
I believe that was never true for vehicle occupants
in the typical ranges of height, weight, and age.
Failure to use seat-belts with earlier generations of airbags tended
to lead to unbelted occupants "submarining" under the opening airbag,
leading to lower body injuries, although the "submarining" jargon now
appears to be applied to situation where a lap belt is wore higher on
the abdomen rather than low on the hip bones, with the higher position
tending to lead to abdominal injuries.
With newer generations of airbag design and other tech such as
active seat belt pre-tensioners, I would be extremely surprised to
find any recommendations against wearing seatbelts, except perhaps
for the 1 in 100,000 cases - near-term pregnant women or persons
with recent abdominal surgery.
Air bags work far better when you're belted in. The seat belt slows the occupant down so the air bag has more time to inflate and has less of a blow to cushion.
Seat belts don't necessarily keep you from wanging your head on the steering column or dashboard. Their behavior while resisting the dozens of gees of a crash isn't the same as when you just tug on them normally. They stretch out and dissipate energy but you can still be moving at a good clip when you get to the hard bits up front, unless an air bag gets in the way.
There's a lot of misinformation about air bags out there. For reasons I don't really understand, some people find them to be extremely objectionable, and this results in a great deal of material which greatly exaggerates their dangers and downplays their benefits.
I know someone who was hit head on. The airbag deployed, but she also had a bruise on her shoulder from the seatbelt. I think they work well together. I advocate both.
I think part of the confusion might be in the US at least airbags are part of the "passive protection" which is designed to protect you if you do nothing (before airbags where afordable there were all manner of pretty bad automatic shoulder belts for cars provided the mandated protection.)
There are many other good points being made in this subthread, the one I'd like to make is that if a driver is wearing a seat belt as he should, if he doesn't have an air bag and has a >= 35 mph collision, his head is going to hit the steering wheel, with worse and worse effects as the speed increases.
And without other equipment that's not practical to put in civilian vehicles, that sort of give in the seat belt system is required to avoid other bad effects like snapping necks.
It's all a carefully engineered system of tradeoffs, modulo Takata skipping the careful engineering step....
Does anyone know if that is still (or was ever) true?