I'm not sure what aspect of road maps appeals to Archer's autistic mind. Roads come with numbers, labels, and categorizations, and those clearly delight him. He draws them on his Magnadoodle and adds road signs and exit structures.
What I wonder is whether the idea of maps holds any fascination for him. I suspect it does. When I drove the kids down to Little Rock last Thursday, I directed the kids to grab a book to read on the half-hour drive down. Archer brought his well-thumbed -- falling apart, actually -- Rand McNally road atlas. As we drove, he followed our progress with his finger, periodically calling existentially from the back seat "We're right here now, Mom," and anticipating the transition to the inset map of the city at the exact moment our position made this possible.
In his head, I imagine, he was riding through the map itself, the landscape outside his window replaced by the lines and colors and numbers and symbols traced by his finger. Perhaps he was filling in the spaces left blank by the atlas' relatively small scale, adding features too minor to show up on the printed page. Time to see what books on cartography are available at our local libraries.