I have a theory about cars.
I've noticed this over the weeks as I've been jogging in the mornings. You see, the roads near our house are windy, with little to no shoulder. At 6 am (I know, I know) it's less of a big deal than, say, at 5 pm.
My theory? The Car Clump Theory, or CCT. The basic principle behind CCT is that where no shoulder or sidewalk is present and a pedestrian is sharing the road, all cars will travel in clumps of two, three, four or more cars. The pedestrian hears the cars coming up behind her, moves on to the uneven, often soggy grass. Thinking the car has passed, the pedestrian moves back onto what little shoulder is available, only to find herself in the midst of a car clump.
By the way, the inverse of CCT is true when you are the driver of a car waiting to make a left hand turn. Instead of traveling in clumps and thereby making it possible for you, the waiting driver to make your turn, the others cars will space themselves so perfectly that turning is impossible.
I believe CCT and its inverse should be submitted to the most reputable scientific journal available, don't you?