Ravi Greene can tell you how to get anywhere in New York City by transit — like the beach, on the 6 train.

“The 6 goes elevated from Whitlock Avenue to Pelham Bay Park,” he explains. “And at Pelham Bay Park, you can transfer for a Bx29 or a Bx12 — the Bx12 to Orchard Beach.”

Ravi has drafted elaborate proposals for expanded bus service in Brooklyn, and has memorized the exact date that the W train stopped running in 2010.

And he is only 5 years old.

Like many children with autism spectrum disorders, Ravi is fascinated by trains and buses, entranced by their motion and predictability. And for years, these children crowded the exhibitions of the modest New York Transit Museum, chattering about schedules and engine components and old subway maps.