A number of people have asked me whether to follow the 2 seconds rules as recommended in UK and parts of Europe or the 3 seconds rules as suggested in America. Which one is correct? I have not come across the reasons for this difference, but possibly in US where cars are bigger, the 3 seconds gap is appropriate given the formula for momentum (mass x velocity). Thus bigger cars need longer time to stop. In contrast cars in Europe are smaller on average. In reality though, the minium distance ought to be at least 2 seconds but 3 seconds is even better and safer.
Video13: Lane discipline and overtaking