Maybe you have experienced it: you are right on the speed limit of 70 miles an hour and you come over the top of a hill to find a big traffic backup right in front of you! Traffic is backed up in both lanes! Stopppp!!! You come down hard on the brake. It looks iffy! Are you going to stop in time?
I interrupt this scary moment for some information. When Lynn took driver's education in high school way back in former times, she was told to leave a car length for each ten miles an hour of speed. 70? Leave 7 car lengths. I searched the question on Google just now and found, when dealing in miles and not kilometers,
take the lead digit of the speed, 7 in this case, and square it. 49 and then add a zero, 490. Finally, divide the figure in half, 245 feet.
We have a major highway on the south edge of town. The speed limit is reasonable for steady traffic but the many businesses along the road make it easy for someone to slow down to make a turn into a parking lot. That leads to jerky, inconsistent speeds. Under those conditions, it is easy to find traffic speeding up, only to need to slow right down again when a car among several ahead is turning into a business. It is hard to maintain adequate stopping distance under those conditions.
