two-second rule
gap of two seconds between the rear bumper of the vehicle in front and the front bumper of the vehicle following in the same lane, regardless of the vehicles' speed(s)
en-US/ˈtu - ˈsɛkənd ˈɹul/
gap of two seconds between the rear bumper of the vehicle in front and the front bumper of the vehicle following in the same lane, regardless of the vehicles' speed(s)