It's very important to make sure you have a safe distance between you and the vehicle in front, so you will have enough time to stop if you need to stop suddenly.
Several seconds can pass from the time you see the hazard until you come to a complete stop. This is because you need time to react to the hazard and take action – putting your foot on the brake – as well as time for the brakes to slow the vehicle down.
The faster you are going, the longer it will take to stop. This means you must increase your following distance as you increase your speed.
Some people take longer to react to hazards than others.
If you're tired, or your reaction times are slower than normal, take this into account and increase your following distance.
A good way to make sure you always keep a safe following distance is to use the two-second rule or the four-second rule, which are explained below.
Under normal conditions, the two-second rule is an easy way to make sure you have left enough following distance between your vehicle and the vehicle in front, no matter what speed you're travelling at.
To check if you are travelling two seconds behind the vehicle in front:
The two-second rule
In bad weather, when the road is wet or slippery, or when you're towing a trailer, you need to increase your following distance to four seconds, because you'll take longer to stop if you need to.
To check that you are travelling four seconds behind the vehicle in front, follow the instructions above for the two second rule, but count 'one thousand and one, one thousand and two, one thousand and three, one thousand and four' instead.
When you're following another vehicle and you don't intend to overtake them, you must leave enough space in front of your vehicle for vehicles behind to pass you.