Dreams
A fair number of the dreams that I can remember these days involve transportation networks. They’re mostly about rail, though highways and gadgetbahnen make occasional appearances.
My pet theory on dreams is that they’re narratives constructed out of concept nodes that are activated as a side-effect of processing and filing the day’s thoughts and memories. (See Susan Blackmore’s The Meme Machine for a treatment of conscious experience itself as a narrative strung together from sensory inputs.) Often I can take a seemingly-incomprehensible dream, figure out what concepts are at one remove from its literal elements, and discover that it’s really about something that’s actually been on my mind. (Well, it’s possible that I’m just experiencing overactive pattern recognition.)
Now, it’s true that I do think about transportation networks a decent amount, but I wonder if their frequent appearances are boringly literal, or whether they’re somehow helping me puzzle through problems.