Have you ever wondered how those big blue highway exit signs work?

If you’ve ever taken a road trip, you’ve likely seen those big blue exit signs advertising dining, lodging, bathrooms, gas stations and more along highway off-ramps. You’ve probably never thought much about the signs, other than to be grateful that fuel is ahead when your car is running on empty, or that there’s a McDonald’s at the next exit when your stomach is.

It turns out that there’s a lot that goes into determining which businesses are displayed on those signs.

Advertising doesn’t come cheap.

Although the cost of getting a specific sign varies by state, in general, businesses can expect to fork over between $500 and a couple thousand per year in order to get their logo on a sign. In addition to the cost to advertise, businesses are responsible for designing their logos to fit the specifications of the sign, which can add several hundred in additional fees. Businesses and states find the advertising profitable, though. For example, in Kentucky, the signs are managed through a state contract with Kentucky Logos, and the state received 35 percent of all logo sales, amounting to $618,904.91 in 2010, according to the Lexington Herald Leader. The report also notes that only 1 to 2 percent of businesses elect to discontinue advertising per year, indicating the signs are effective in bringing in business.

They come with a lot of rules and regulations.

Not just any business can get a coveted spot on the big blue signs. Again, regulations vary by state, but in general the business must offer a specific category of service like food, pharmacy or gas. From there, the rules become much more specific. For example, in New Jersey, gas stations must be within three miles of the highway and operate at least 16 hours per day, 7 days per week, 360 days per year, while restaurants must also be within three miles of the highway, have permits from all appropriate health departments and provide a public telephone, just to name a few of the regulations businesses must follow.

So there you go. Next time you’re cruising down the highway and a sign beckons you to crash for the night or grab a bite to eat, you’ll remember just what went into the placement of that sign.