How can you count following distance?

Look for a moving object and count the seconds it takes for you to pass it after the car you are following has passed it.

Look for the stripes on the road and count them as you pass by.

Look for the rear wheels of the car in front and count the number of rotations.

Look for a stationary object and count the seconds it takes for you to pass it after the car you are following has passed it.

All of the above methods can be used to count following distance. The key is to choose a reference point and measure the time or distance it takes for your vehicle to pass that point after the car in front of you has passed it.