My nephew who has Aspergers was always obsessed with thomas the train and then as he got older he became very interested in model train sets, miniature sets, etc...he still is fond of trains as an adult!
My DS who has Aspergers, he liked the thomas trains but never got obsessed about them. He was more obsessed with electronics, and still is to this day! My NT DD likes to play trains, but nothing I would lable obsessive. If there are out she will play with them.
I would worry more about the lack of speech and agree to have him assessed!
good luck!
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Dara, mom to my beautiful kids:
J- 8, diagnosed Aspergers and ADHD possible learning disability due to porcessing speed, born with a cleft lip and palate.
M- 5
M-, who would be 6 1/2, my forever angel baby
E- 1 year old!! !