What will happen when the world runs out of oil-based fuels?

I just finished reading an article that claims we’ll run out of crude oil by the mid-50s, and our reserves of oil-based fuels will be gone by the 60s.

From what I understand, most of Earth’s infrastructure revolves around petrol and diesel. The trucks that transport goods across America, Australia, etc run on diesel. Most ships run on diesel. Most cars run on petrol.

So my question is, What happens then? What will modern countries do when the supplies of these fuels run out?