Stopping distances. Drive at a speed that will allow you to stop well within the distance you can see to be clear.
You should
leave enough space between you and the vehicle in front so that you can pull up safely if it suddenly slows down or stops. The safe rule is never to get closer than the overall stopping distance (see Typical Stopping Distances diagram)
allow at least a two-second gap between you and the vehicle in front on high-speed roads and in tunnels where visibility is reduced. The gap should be at least doubled on wet roads and up to ten times greater on icy roads
remember, large vehicles and motorcycles need a greater distance to stop. If driving a large vehicle in a tunnel, you should allow a four-second gap between you and the vehicle in front
If you have to stop in a tunnel, leave at least a 5-metre gap between you and the vehicle in front.
Tailgating is where the gap between you and the vehicle in front is too small for you to be able to stop safely if the vehicle in front suddenly brakes.
Tailgating is dangerous, intimidating and can cause collisions, especially when driving at speed. Keeping a safe distance from the vehicle in front gives you time to react and stop if necessary. Dangerous and careless driving offences, such as tailgating, are enforced by the police.