The Trucks

Around the clock, the trucks keep coming across the border.
The ones heading North are full of dirt and rocks.
The ones heading South are also full of dirt and rocks, but it’s different dirt and rocks.
We’re not sure why Canada and Mexico are sending all this stuff back and forth, but as long as their trucks keep paying the toll and buying our gas, we really don’t care.
They could haul more back and forth if they used freight trains, but some treaty requires that they use trucks.
So they are.
But why do it at all?
Strange.