The word freeway first surfaced in the mid-1930s in proposals for the improvement of the New York City parkway network. It is currently in regular use in the United States as well as parts of Canada and Australia. Other countries refer to a freeway as a grade-separated highwayFact: date=May 2007 or a superhighway.Fact: date=May 2007

In the United States, the term freeway is frequently used. In some regions of the U.S., other terms are also used, including Interstate, highway, expressway, and turnpike. While some people use these terms interchangeably, turnpikes and thruways have specific associations with toll roads and other limited access highways, such as the Pennsylvania Turnpike, West Virginia Turnpike, New Jersey Turnpike, Florida's Turnpike, and New York State Thruway;Fact: date=April 2007 consequently, the term freeway is often used in contrast to refer only to a toll-free roadAmerican Heritage Dictionary online at bartleby.com. as opposed to its original meaning – in which the component "free" implied freedom from traffic interference rather than "at no cost" – still used in other countries and in parts of the U.S.

General characteristics

The crossing of freeways by other routes is typically achieved with grade separation either in the form of underpasses or overpasses. In addition to sidewalks (footpaths) attached to roads that cross a freeway, specialized pedestrian bridges or tunnels may also be provided. These structures enable pedestrians and cyclists to cross the freeway at that point without a detour to the nearest road crossing.

Access to freeways is typically provided only at grade-separated interchanges, though lower-standard right-in/right-out access can be used for direct connections to side roads. In many cases, sophisticated interchanges allow for smooth, uninterrupted transitions between intersecting freeways and busy arterial roads. However, sometimes it is necessary to exit onto a surface road to transfer from one freeway to another. An example of this would be Interstate 70 in the town of Breezewood, Pennsylvania.

In the United States, mileposts start at the southern or westernmost point on the freeway (either its terminus or the state line). California, Ohio, and Nevada uses a postmile system where markers indicate mileage through the state's individual counties; however, Nevada and Ohio also use the standard milepost system concurrently with their respective postmile systems on freeways only. Until the 1980s, New York used reference markers which, like California, indicated mileage through individual counties. The New York State Department of Transportation has since supplemented their reference marker system with mileposts indicating a freeway's mileage through the state.Fact: date=April 2007