First off, adding an airbag is technically impossible. The bags and belt tensioners are a system and additional items can't be just scabbed on like extra driving lights.

As to the crash safety of the 126, it is an old car and is many generations removed from modern passenger protection. After all, it's more than just road hugging weight. A couple of years back, I looked (on-scene) at a very nice black '89 560SEL that failed to yield to the ambulance that hit it on the left a-pillar at 25mph. The car was so crushed that the firemen had to cut the roof off to extract the driver.

My own "little" 3500 lb W203 C320 has eight airbags and up until the W211 was introduced provided the best crash protection of all MB's up to that point. According to an MB document, BTW. That's what I want when I tangle with another car.

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Roger E.