You must obey the speed limits for the road and for your vehicle. A speed limit is the maximum speed allowed. It does not mean that it is safe to drive at that speed - always take into account all the conditions prevailing at the time.
Never drive so fast that you cannot stop well within the distance which you can see as being clear. Go much more slowly if the road is wet or if there is fog or mist. Do not brake sharply except in an emergency.
The maximum speed on all roads is 50km/h unless 'speed limit' signs show otherwise.
Variable speed limit signs
How big should a gap be?
Leave a big enough gap between you and the vehicle in front - big enough for you to stop safely if the vehicle suddenly slows down or stops.
Continuously try to anticipate the situation on the road ahead and leave yourself room to work - room to recognise a developing situation and to act.
If you have to take panic action because you have insufficient room to act smoothly, you are either going too fast or driving too close to the vehicle in front.
On wet roads, or if your tyres, brakes, or even your health, are below par, the gap should be much bigger than normal. And when a vehicle overtakes you and moves into the gap ahead, drop back to regain your safe gap.
The safe rule is to leave your stopping distance between your vehicle and the one in front. On roads with faster traffic it becomes much more important to keep a safe gap. Your stopping distance is still the only really safe gap but a reasonable and practical rule to apply in good conditions is a two-second time gap - more if you are driving a heavy vehicle.
Note: km/h means kilometres per hour.