In more recent times the multilane expressways have often followed the abandoned rights-of-way of the old turnpikes. The opening (1940) of the first multilane superhighway, the Pennsylvania Turnpike, began a new era in tollroad construction. Since then every state has constructed at least one superhighway on either a toll or nontoll basis. Those that do charge tolls are most commonly located E of the Mississippi River.
The American superhighway network is commonly known as the Interstate Highway System (officially the Dwight D. Eisenhower National System of Interstate and Defense Highways). Authorized (1944) by an act of Congress, the interstate system is designed to provide an efficient national transportation system for ordinary use as well as in case of war or other emergency. Construction began in 1956 (although many previously constructed roads were absorbed into the system) and took thirty years to complete; it encompasses 42,796 mi (68,869 km) of roads, all but a few miles of which are completed. It is financed largely by the Federal Highway Trust Fund (established 1956), into which are paid the revenues from most highway-related federal taxes.
The states now also derive considerable income from various forms of road and motor-vehicle taxation, reducing the need for toll collection. Most of the larger roads that still charge tolls have been modernized with electronic toll-collection technology that eliminates the need for coins or tokens at the tollgate; sensors in the tollgate record a car passing through (if the car is equipped with the correct transponder, usually called a tag), and the toll is then charged to the tag's owner's account. In recent years an increasing number of toll roads have been built or operated by private companies
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.