Safe and correct following distances are difficult to establish. For this reason, the 2 second rule is used to gain a safe following distance at any speed. The rule is very simple and easy to understand by using the method below. Keeping a gap of at least 2 seconds from the vehicle in front will provide a safe gap between you and the car in front at any speed.
Using the 2 second rule provides not only a general safer way of driving, but can also help to save fuel, brake wear and paint damage as a result of stone chips occurring due to driving too close to the car in-front.
The 2 second rule only applies to dry weather conditions. If conditions are wet, the rule should be doubled to 4 seconds to allow for longer braking distances. For frosty or icy conditions, this needs to be extended to 20 seconds (YES 10 times the gap in normal conditions!).
2 second rule explained
Let's suppose you are driving along a relatively straight road at 30 mph for example. To estimate the minimum and safe following distance, allow the car in-front to pass a fixed object, such as a lamp post or road sign.
As the rear of the car in-front lines up with your chosen reference marker, count to 2 seconds. A good way to do this it to say "Only a fool breaks the two second rule!" which take about 2 seconds to say slowly.
If before you have reached 2 seconds your vehicle has passed the same reference marker, you will need to check your mirrors, ease of your speed and increase the gap and try again.
The 2 second rule isn't just for the car in-front. If a car is driving too close behind you (tailgating), you will also need to take their thinking distance into account by leaving a sufficient and safe distance between yourself and the car in-front. In such a situation increase the gap to the car in front to compensate. So if the car behind is 1 second back, increase the gap to the car in front to 3 seconds.
By following the 2 second rule, if the car in front of you brakes sharply, you will be able to slow down in good time, but also allow plenty of time for the car behind you to slow down. It's also essential to learn safe braking techniques such as progressive braking. Progressive braking once learnt allows for safer driving and less wear