Pipe Cleaners as Cargo for Toy Train

I observed my four-year-old play with his train and he cut up some pipe cleaners. I asked why. He said it's cargo so it's like he's delivering things on his train route.

So cute to see toddlers come up ideas using their own imagination and it doesn't require "actual toys", but pipe cleaners! He cut these strips himself, about 1.5 inches.