How the two‑second rule can save lives on busy highways

We often head out on the road. Family trips contribute to increased road traffic, including highways and expressways. In such conditions, the two-second rule—and sometimes even the three-second rule—becomes crucial.

This rule remains difficult to follow despite efforts to enforce it through regulations on maintaining proper distance. This challenge partly arises because the rule does not apply during overtaking, which can confuse the roads. Experienced drivers, however, are well aware of the two-second rule, while older drivers often apply the three-second rule.

The rule is easy to remember: while driving, you should maintain a two-second gap from the vehicle in front of you. In practice, this means that when passing a post that the car in front of you has just passed, you should pass it after two, preferably three seconds.

Research from the Massachusetts Institute of Technology confirms the effectiveness of this rule. The studies aimed to analyze drivers' abilities in the context of autonomous driving systems. The study found that drivers over 55 needed an average of 403 milliseconds to notice a danger and 605 milliseconds to decide. In comparison, drivers aged 20 to 25 recorded these times at 220 and 388 milliseconds, respectively.

This means that younger drivers have a reaction time of 0.6 seconds, including an extra 0.1-0.2 seconds for response. On the other hand, older drivers need about 1.5 seconds for a full response. Additionally, activating the braking system takes about another 0.3 seconds.

As stated in the Road Traffic Law, the time-based rule is easier to apply than maintaining a specific distance in meters. Regulations require maintaining a distance equal to half the current speed (at 75 mph, which is about 197 feet). Watching the milestone posts and counting the time they pass is much more convenient.

This issue is particularly important because failing to maintain proper distance is the fourth most common cause of road accidents. Accidents outside built-up areas are the most tragic—one in five involve a fatality, whereas in built-up areas, it is one in fifteen.