The big 5 is a tool that safari operators continue to use. It does not make much sense as this term is a hunting term. The big 5 are the five most dangerous animals to hunt on foot.It is not impossible to encounter the big 5 on a single drive in the bush. I have done this on a few occasions. However, when you are in the bush it is worth taking your time.
Given the big 5 is to do with hunting on foot, I have been more interested in encounters on foot. Before my recent trip, I had encountered Rhino Buffalo and Lion on foot (I do not consider it as an encounter unless I am within about 10m of the animal).