Thinking caps time, now. I’ve thought of writing Ask Marilyn with this one.
Have you ever noticed what happens when there is a puddle of water or spot of grease lying in a one-way lane? Cars will roll over the spot and pick up some of it, carry it around on the tire, and then “print” another spot about 6 ft away.
Or, at least, that’s what should happen. What actually does happen is that the spot gets printed, after many cars have passed, about one foot away. And then, after another foot, another print. And so on. I don’t have any pictures of this phenomenon but I see it all the time.
Next time you cross the road, look at the tar spots that have been picked up, and you’ll see. Note the distance from the first print to the source.
The obvious answer is that smaller tires will do that. But one-foot-in-circumference tires? How many tiny-tired things are rolling down the street?
There could be some sort of sophisticated transference between vehicles of varying tire sizes, picking up transferred spots and then laying them down in odd patterns. But it doesn’t explain how the initial print gets made a foot (or so) away.
Think I’m kidding? Check for yourself. You’ll never look at an expansion joint or a road kill the same way again.