I agree with PP about looking ot see if there is a Day Out with Thomas event in your area.
Also, have you taken your son to visit the local fire station? DH is a volunteer firefighter in our community and every so often a family will come by to just see the trucks and the station. The firefighters love that. They let the kids sit in the trucks and give them plasctic firefighter helmets and junior firefighter badges. You don't need an appointent to stop by as a family, but you might want to call ahead just to make sure that the crew and the rigs are there and not out on a call.
A couple of times a year our fire department has a community event with different activities like spraying the hose and finding you way out of a smoke-filled room (all very controlled activities). You might want to find out if your fire departmet does something similar.
Gena
DS, age 11 and always amazing
“Autistics are the ultimate square pegs, and the problem with pounding a square peg into a round hole is not that the hammering is hard work. It's that you're destroying the peg." - Paul Collins, Not Even Wrong