Travis Huggett thought of the subway as a means of getting from one place to another. Then he had a son on the autism spectrum.

To Orson, now 9, a train was something more than transportation. It was soothing, endlessly fascinating, more intriguing than any destination it might reach. At his school for children with autism, other boys shared the same passion. When Mr. Huggett started photographing some of them, asking them about their interest in trains, he discovered how many different ways they were drawn.

“Some were really interested in maps and timetables,” Mr. Huggett said. Some liked model trains more than the real thing. Some found crowded cars too stimulating, but one wanted even more stimulation: his idea was to ride the subway to Coney Island and then ride the Cyclone roller coaster. “It was incredible how different they all are,” he said. “I learned a lot about how diverse the community is.”