Drive down any major interstate in the U.S. and you’ll see big blue signs decorated with business logos near most exits. A business must fall into one of these groups: attraction, pharmacy, camping, lodging, food and gas. States have various rules for the signs. For example, Michigan requires that any gas station on a specific service sign be within six miles of the highway, and be open at least 16 hours a day, seven days a week and 360 days a year. In addition, the gas station must offer water, gas, and oil for various types of vehicles, as well as public restrooms and a public telephone. The cost of getting on a specific service sign varies by state, but in general, it spans between about $500 and a couple grand per year. It's really quite interesting and prices may vary from state to state but you can read more about it here