The lone bull elephant must have come walking out of the bush just as the car was driving along - speed limit in our South African game parks is 40km on dirt & 50km on tar.
Visitors are advised to stay at least 30 metres away from these lone elephants. Donot drive towards them, donot hoot or flick your lights at them. I have encountered quite a few coming towards our vehicle and usually stop. If he keeps coming I slowly start reversing and usually they wander off the road back into the bush.