Safe Driving Behaviour, Speed and Following Distance
Speed and stopping distance
Speed limits are maxima, not targets. You must always be able to stop within the distance you can see to be clear. The classic rule of thumb is the two-second gap in dry conditions, doubled to four seconds in rain or poor visibility, and more on gravel or oil-slicked surfaces. Stopping distance = thinking distance plus braking distance; both grow with speed, and braking distance grows with the square of speed, so doubling speed roughly quadruples braking distance.
The driving plan
Use the system of car control: mirrors, signal, manoeuvre for routine moves, and observe–anticipate–decide–act continuously. Scan far ahead, check mirrors every few seconds, and cover the brake when approaching hazards. Maintain a safe following distance so you can see the road ahead past the vehicle in front; if you cannot see its mirrors, the driver cannot see you.
Speed in context
Adjust speed for rain, darkness, school zones, roadworks, pedestrians and unfamiliar roads. In residential areas and near schools, 30 km/h or less is often appropriate even where the limit is higher. Slow down before a bend, not during it, and accelerate gently out of it.
Traps in questions
The two-second rule is often misremembered as one second or as a fixed distance in metres. Questions may ask what to do when a tailgater closes up: the safe answer is to increase your own gap ahead so you can brake gently, not to brake sharply to warn them. Another trap is treating the speed limit as always safe - in heavy rain the correct answer is often well below the limit.
Worked example
You are following a car at 60 km/h on a wet road. Pick a fixed object ahead; when the car passes it, count "one thousand and one, one thousand and two" - that is one second. In rain you need four seconds, so wait until the car is four counts ahead before checking your own gap. If a tailgater appears, ease off and let the gap ahead grow to eight seconds so your braking stays gentle.