Section 156 of Title 23, U.S. Code, applies to any disposal of real property that was acquired with the participation of Federal-aid highway funds. It has two basic requirements. First, States or other acquiring entities must charge fair market value for the sale or lease of any such property, unless it is used by a utility or for another Title 23 eligible project. Exceptions may also be granted if the property is used for social, environmental, or economic purposes. Second, the Federal share of net income derived from the sale or lease of such property must be used by the State for projects eligible under Title 23. Implementing regulations are set forth in 23 CFR part 710, subpart D.
An example of the application of the 23 U.S.C. 156 requirments is the lease of airspace.[443] The airspace above highways may be used for several purposes and States may charge for airspace use, depending on the purpose of the use. Some uses are for valuable public services, such as utilities, and may involve no direct charges or rent as a public service to the taxpayers.[444] Another use is for project mitigation activities that may be accommodated at low or no charge. Private uses for airspace over the Interstate that are appropriate and not harmful to highway operations also are types of uses, for which the States are required to charge market-based rents.[445]
Under 23 U.S.C.156, States may retain all of the income that they obtain from leasing airspace to private parties, so long as the percentage of income equivalent to the amount of the Federal share on the project is used for projects eligible under Title 23, United States Code. Appreciation in property values associated with a highway or transit improvement could be a potential source of revenue for private sector investors.