I read an interesting article once about vehicle safety. It said that the average proportion of fatal accidents in cars has remained fairly steady over the years, despite incredible advances in safety features.

The theory was that there's an acceptable level of risk stuck in people's minds, and as cars get safer people just drive more recklessly.

The only example I can remember is anti-lock brakes: now folks just follow closer than they used to before antilock brakes.

It was an interesting article. I have no idea how to find it again.