Maintaining a safe following distance is one of the most important skills for safe driving. The examiner is constantly checking whether you leave enough space between your car and the vehicle ahead, and whether you adjust that space for speed, weather, and road conditions.
The two-second rule is the standard guide for dry conditions. Pick a fixed point that the car ahead passes, then count two seconds before you pass it. If you reach it before two seconds, you are too close. In wet conditions, double this to four seconds. In icy or foggy conditions, you may need ten seconds or more.
Tailgating (driving too close to the vehicle in front) is dangerous and illegal. It removes your reaction time and space, increases the risk of a collision, and intimidates the driver ahead. If you are being tailgated, do not brake suddenly. Instead, ease off the accelerator slightly to increase the gap in front of you, giving yourself more room to react if the traffic ahead slows.
Stopping distances increase dramatically with speed. At 20 mph, the thinking distance is 6 metres and the braking distance is 6 metres, giving a total of 12 metres. At 30 mph, the total is 23 metres. At 50 mph, it is 53 metres. At 70 mph, it is 96 metres. These figures are for dry conditions: wet, icy, or worn tyres can double or treble them.
Large vehicles such as lorries and buses need more stopping distance and have larger blind spots. Do not cut in front of them after overtaking: they may not be able to stop in time. Give them extra space and patience, especially on hills and at junctions.
In heavy traffic, resist the urge to close the gap. Stop-start traffic encourages drivers to bunch up, but this increases the risk of low-speed collisions and makes it harder to react to sudden changes. Maintain a safe gap even in queues, and be prepared for the vehicle ahead to brake unexpectedly.