What was unusual about the conveyance used to pick up the children from the train depot?

What was unusual about the conveyance used to pick up the children from the train depot?
OK I'll bite. I don't see anything unusual about it. It's just a small pony cart pulled by a horse. What is it?

I think he's asking because he has to give the answer in essay form, as in homework. Unfortunately I don't know, I suppose to someone who gets a kick out of symbolism it must mean something.