I only ride with helmet and gloves as far as safety gear on the road bike.

I have some padded undershorts for mountain biking that has some padding on the hip bones, also some knee pads and elbow pads. I don't ride that on my road bike obviously and only occasionally put on the knee and elbow pads while mtn biking anymore.

They'd mostly help with bruising and scraping against gravel of pavement. Going down on gravel and dirt on a mtn bike WITH that padding is better than without, to that I can attest, but I believe in the event of a crash that was severe enough to break bones, they'd offer little protection. In fact, I can't think of any safety equipment that would prevent that.