The number 8
It looks like an infinity symbol. A friend of mine, Noel, said it was standing up. I like how that personfies an infinity symbol--like it's a person. Where does the infinity symbol work? Noel said a toll booth, because it stands up all day long.
To further expound upon the standing infinity symbol's significance:
* Toll booths are open 24 hours a day, 365 days a year. Eternally open.
* Illinois will always have toll booths. Yes, it's a sad world in Illinois.
* On a trip a car will go through the toll booth in one direction, then when coming home, they will come back through the other way... very much like how the infinity symbol operates.
* Sometimes toll booths are on an exit ramp that curves alot... like the shamrock interchanges that are in the shapes of infinity symbols.
* An idiosyncratic reason: The highway to my girlfriends is called Route 88.