Speed Limits and Safe Following Distance
This domain tests two ideas together: the maximum speed the law allows, and the speed that is actually safe for the conditions. The exam regularly sets a scenario where the correct answer is below the posted limit.
Limits
As a general rule, passenger cars are limited to 60 km/h in towns and built-up areas and 90 km/h outside them; posted signs override these figures in both directions. Trucks, buses and vehicles towing trailers carry lower limits. Limits are also reduced around schools, pedestrian crossings and roadworks, and you must always be able to stop within the distance you can see to be clear, whatever the sign says. In fog, heavy rain, snow or on ice, that visible distance is short, so your speed must fall with it.
Following distance
The two-second rule is the working standard. Pick a fixed object such as a lamp post, and count one-thousand-and-one, one-thousand-and-two as the vehicle ahead passes it. If you reach it before finishing, you are too close. Double the gap to four seconds in rain, snow or ice, at night, or when following a truck that blocks your view of the road ahead. ABS helps you steer while braking but does not shorten stopping distance on ice.
Worked example
You follow a car at 90 km/h on a dry road. Reasoning: 90 km/h is 25 metres per second, so a two-second gap is about 50 metres. If the surface turns to packed snow, the same speed requires roughly four seconds, so the gap becomes about 100 metres - and on ice even that may not be enough.
Traps that cost marks
Treating the limit as a target; keeping the same gap when speed doubles, although the gap in metres must double too; assuming winter tyres cancel the need for extra distance; and forgetting that overtaking does not license exceeding the limit.