Safe driving techniques, following distance and speed management
Domain 4: Safe driving techniques, following distance and speed management
This domain tests the arithmetic of safety: how much road you need to stop, how far back to sit, and how to choose a speed that fits the conditions rather than the sign.
The two-second rule
Pick a fixed object ahead - a pole or road marking. When the vehicle in front passes it, count "one thousand and one, one thousand and two". If you reach the object before the count ends, you are too close. Two seconds is the minimum in good, dry conditions; use three seconds at night, in rain, behind a heavy vehicle that blocks your view, or when tired. At 60 km/h that is about 33 m; at 120 km/h about 67 m.
Stopping distance
Total stopping distance = thinking distance + braking distance. Thinking distance is roughly one second of travel; braking distance grows with the square of speed. Doubling speed from 60 to 120 km/h quadruples braking distance, not doubles it. A wet road can double it again.
Speed limits and conditions
General limits: 60 km/h in built-up areas, 100 km/h on rural roads outside towns, 120 km/h on freeways - always subject to a lower signposted limit and always overridden by conditions. The legal maximum is not a target: fog, rain, darkness, roadworks or a queue ahead all mean slowing down. Slow vehicles keep left and let faster traffic pass.
Worked example
At 120 km/h you cover 33 m every second, so a two-second gap is about 67 m - roughly sixteen car lengths. If the car ahead brakes hard at a hazard, those 67 m are all you have to react and stop; on a one-second gap you would have 33 m and would hit it.
Traps
Counting seconds only in good weather; assuming braking distance doubles when speed doubles; sitting at the limit in heavy rain; tailgating a truck to "save fuel".