Follow the two or three second rule…

It is very important to avoid following another car too closely, as it gives you less time to react if the driver in front of you decides to brake or turn suddenly. For safety, drivers are advised to maintain a distance of two or three seconds of the car in front. The rule varies on the weight/mass of the vehicle given the same speed. The higher the mass, the longer the time.

The distance is measured in time rather than meter (or other units of measurement) as it can be difficult to judge distances while driving and what counts as a safe distance varies depending on speed.