Most of the interstate highway system in the United Sates was planned and built as part of the Interstate Highway System under the National Interstate and Defense Highways Act of 1956. Today the Interstate System includes approximately 47,000 miles of roads representing an investment of $329 billion in 1996 dollars. In addition, there are approximately 21,000 miles of other non-Interstate roads that are limited access, divided highways. Eight percent, or 5,300 miles, of the total of 68,000 miles of limited access roads in the United States are tolled (Cox and Love, 1996).
Most of the roads that constitute the Interstate Highway System are non-tolled roads that were built and are maintained by gasoline taxes collected by state governments and the Federal government. There are, however, approximately 3,000 miles of toll roads that are also a part of the Interstate System that were financed and built by state and municipal governments and agencies. Examples include the Pennsylvania Turnpike, New Jersey Turnpike, Indiana Toll Road and the Chicago Skyway. There are only a very small number of toll roads in the US that have been developed, owned or operated by the private sector in the last hundred years.
Over the last several years there has been a movement in the US toward public-private partnerships in the transportation sector. The impetus behind this movement is the belief that the private sector can bring much needed capital and expertise to address the US growing transport infrastructure needs. One area in which the private sector has shown particular interest is existing toll roads, given what many believe are their attractive investment characteristics. This interest has been matched by the desire of some states and municipalities to monetize the future earnings of these toll roads to fund various operating and capital projects. The first two of these "monetizations" in the US were the Chicago Skyway and the Indiana Toll Road.