Can anyone tell me the fastest driving route and approximate travel time from the airport in Johannesburg to Orpen Gate?

Try this link:
http://www.sanparks.org/parks/kruger.../get_there.php

N4 to Belfast, R540 to Lydenburg via Dullstroom, R36 and R531 to Orpen via Ohrigstad, JG Strijdom Tunnel and Klaserie.

About 4.5-5 hours depending on how you drive. A nice drive but be sure to watch carefully for signs in the towns as they are not large. The approach to the tunnel is quite spectacular. Immediately after you pass thru the tunnel, be prepared to pull off on the left if you want to enjoy a view and view/purchase some souvenirs. There are also places to pull over before the tunnel. Be careful on the section after Ohrigstad approaching the tunnel as there is the potential for accidents, take it slow. The low point of our 7 month trip was there, we passed an car-bicycle accident and a young boy was dying before my eyes (I told my wife to look away). We couldn't stop to help as they were trying clear the route for emergency vehicles. I still see his face.

I must be a slow driver - I believe it took us about 6 hours. Granted, we were in a VW Chico. Just remember to allow plenty of time to get from the Orpen gate to your camp. The camps really do shut their gates at 6:00pm and I think it's even earlier in the winter.

bella28

what time are you leaving from JNB airport ? early morning or later ?

we will drive the same way, but our flight arrives in JNB at 6am.
Nevertheless I am considering to drive slowly and to enjoy the route towards Kruger Park. A good option is to see Blyde River Canyon and the potholes, the gorges, pilgrim's rest and around.
So this will drives us to overnight outside Kruger Park and to enter it the next early morning.
Depending on your travel time maybe it is not so necessary to drive fast and directly to Kruger !

then you also have to add the travel time from Orpen Gate to your camp where you have to be before the gate closes, 5:30pm in winter !

I believe it's about 480 km. The first section is highway and I will admit I drove like the locals and did over 100 km/hr for that section. I guess 6 hours is reasonable if you take it easy. We were trying to arrive before dark so we pushed a little.