Too many people were taught, and still teach, the “two car’s length” rule. Which is awful. 2 to 3 seconds is much better and intuitive to figure out.
You say 3, which is great, but I’d settle for 2. Most people on the highways around me leave more like 0.5; I sincerely think the vast majority of people greatly overestimate the amount of space in front of them to the next car.
Two car lengths is ridiculously close. The average car is approx. 4.5m in length. Two car lengths is 9m. The average human reaction speed to visual stimuli is approx 250 milliseconds. At 100 km/h (28 m/s) you would travel 7 metres in that time, and that’s just the time for you to notice the stimulus and react, not to choose an appropriate action. If you’re 2 car lengths behind and the car in front of you brakes hard, you’re going to hit it.
2 seconds behind is 56 metres behind, or 12.5 car lengths. 3 seconds is 18.5 car lengths. Even 0.5 seconds is 3 car lengths. Not enough to safely react to the car in front of you doing something unexpected, but not the tailgating that 2 car lengths implies.
Too many people were taught, and still teach, the “two car’s length” rule. Which is awful. 2 to 3 seconds is much better and intuitive to figure out.
You say 3, which is great, but I’d settle for 2. Most people on the highways around me leave more like 0.5; I sincerely think the vast majority of people greatly overestimate the amount of space in front of them to the next car.
Two car lengths is ridiculously close. The average car is approx. 4.5m in length. Two car lengths is 9m. The average human reaction speed to visual stimuli is approx 250 milliseconds. At 100 km/h (28 m/s) you would travel 7 metres in that time, and that’s just the time for you to notice the stimulus and react, not to choose an appropriate action. If you’re 2 car lengths behind and the car in front of you brakes hard, you’re going to hit it.
2 seconds behind is 56 metres behind, or 12.5 car lengths. 3 seconds is 18.5 car lengths. Even 0.5 seconds is 3 car lengths. Not enough to safely react to the car in front of you doing something unexpected, but not the tailgating that 2 car lengths implies.