When I was in my teens and early twenties, I’d sometimes run out to meet the Burlington Northern trains as they made their slow progress through the Colorado town of Fort Collins. Because the tracks ran down the center of a busy street, the train came through at a crawl. It was easy to swing aboard one of the freight cars and ride for a mile or two, then jump down on the edge of town where the engines dug in and the train accelerated.

If I mentioned the train to my friends, they thought my attraction had to do with that ride. They were wrong.