[simpleigh]

Are you sure the button becomes difficult to use? I might be very wrong here, but I'd at least hope that "release easily even when hanging upside down" might be a design requirement of the average safety belt buckle. Perhaps this is why aircraft belts have very different buckles than car belts? Can anyone provide more detail?

[tombrossman]

I'm not sure the claim is true. I only have one personal experience to base this on (fortunately) but I was in an accident as a passenger in a Jeep Wrangler which ended up upside-down on its roll-cage. Both the driver and I were hanging from our belts and had no problem undoing the buckles. We had to do it one-handed with our other hand trying to support ourselves so as not to drop on our heads after releasing the buckle. Click, release, just like normal.

[vt240]

I was in a severe single car accident in a 80s era truck, where I ended up rolling many times down into a ditch, and finally resting upside down. Seat belt did not release, the button was just solid, and I had to hold my body up to un-catch the strap ratchet so that it would relax, and I could wiggle out. In the whole event, the hardest part was kicking out the driver side window to get out of the cab.

The only part that saved my life was that I had stacked a bunch of HP servers right behind the driver seat, the rest of the cabin was completely crushed in ;-)

(Edit: I will never own a 4x4 or any high center of gravity vehicle which doesn't have a roll cage ever again. The day after the accident, I was sitting at the junk yard looking at the mashed ball of metal which used to be my truck, I couldn't believe I walked away without a scratch.)

[encoderer]

I'm only in my 30s so I don't have a strong recollection of it, but it seems that buckle design change pretty significantly in the 90s.