[Doctor Stochastic]

The US has approximately 150,000,000 cars. Each car has approximately 4 tires of diameter 20 inches and width 5 inches. One eighth inch tread wears off each year from each tire under normal driving conditions. This leads to 150,000,000 * 2 Pi * 20 * 5 * 1/8 /1728 or about 6,800,000 cubic feet of tire dust deposited each year.

Why haven't people found the dust piles?

[Gumlegs]

Is that what that stuff under the bed is?

[exDemMom]

Why haven't people found the dust piles?

In my neighborhood, the street sweepers come by once a week and clean the streets. (It's obvious: the neanderthals had street sweepers.)