Perhaps the most confusing part of the system concerns the “commuter service” and the intermediate stops. Each train consists of 4 coaches. Two serve the intermediate stops (the so-called commuter service) and 2 serve JNB. If you are travelling to or from JNB you must sit in the coaches marked with an aeroplane on their doors. If you wish to go to Marlboro or Rhodesfield you must sit in one of the other 2 coaches. At those stations only the doors of the commuter coaches will open. JNB pax are prevented from alighting anywhere except JNB and Sandton (and hence must pay R100 per journey as opposed to the much cheaper fares on the commuter service).

So even though it looks like 2 routes on the route map, they are in fact served by the same train! (I was very pleased to see that even though I was travelling off-peak the commuter services were also well patronised.)

BTW there's heaps of information on the Gautrain web site. It's sometimes hard to find what you want but a bit of browsing uncovers lots of useful stuff - like the bus routes on a Google map and GPS coordinates for the bus stops.