A freeway, highway\', superhighway, expressway (American English), or motorway' (British English) is a multi-lane road designed for high-speed travel by large numbers of vehicles. (In the western USA and in Australia, these are generally called freeways; in the eastern USA, roughly from Chicago eastwards, they are generally called expressways. In Quebec, they are called autoroutes, a French borrowing used by English speakers.)
Freeways have high speed limits, multiple lanes for travel in each direction, and a large separation (either through distance or high crash barriers) between the lanes travelling in opposite directions. Crossroads are bypassed using underpasses or overpasses, and entries and exits are limited in number and designed so as to ensure that vehicles do not disrupt the traffic as they enter or leave the freeway. Freeways do not usually have traffic lights.
Definitionally, as accepted by civil engineers in the United States, an expressway is any highway to which adjoining property owners do not have a legal right of access. A freeway is an expressway which is free-flowing; that is to say, there are no traffic conflicts on the main line of the highway which must be mediated by a traffic signal, stop signs, or related traffic controls. Many non-engineers misapprehend the "free" in "freeway" to mean that such a highway must be free of charge to use.
In the United States, many freeways are part of the Interstate Highway System, which superseded the largely at-grade United States highway system (though most of the latter highways are still in use). The first national freeway system was the German Autobahn. The concept of limited-access automobile highways dates back to the New York City area Parkway system, which began to be constructed in 1907 - 1908. On December 30, 1940 California opened its first freeway, the Arroyo Seco Parkway, now called the Pasadena Freeway, which connected Pasadena with Los Angeles.
The term has different definitions at different places even within the same country. In California, roads called 'expressways' can have crossroads and traffic lights at intersections, but freeways do not have any at-grade crossroads at all, and the only traffic lights are those at toll booths and ramp meters that control the flow of merging traffic. However, freeways should be distinguished from toll roads (or turnpikes), for which there is a fee for use, and which historically (before the advent of electronic toll collection) required users to stop to pay tolls. People in the northeastern U.S., unlike those in most of the country, do not use the word "freeway" except perhaps when speaking of highways in other parts of the country. The word "freeway" is also generally used in Australia.
Freeways have been constructed both between urban centres and within them, making common the style of suburban development found near most modern cities. As well as reducing travel times, the ease of driving on them reduces accident rates, though the speeds involved also tend to increase the severity and death rate of the crashes that do still happen.
Freeways come under heavy criticism from environmentalists, who argue that freeway expansion is self-defeating, the expansion will just generate more traffic. This is the debated induced demand hypothesis.
Progress has been made in making U.S. freeways and expressways more efficient however, adding high-occupancy vehicle lanes (HOV lanes) to discourage the typical no-passengers driving patterns, even building new roads with train tracks down the median (or overhead) instead of extra lanes. Intelligent transportation systems (ITS) are also increasingly used, with cameras to monitor and direct traffic, so that police, fire, ambulance, tow, HERO, or other assistance vehicles can be dispatched as soon as there is a problem, and to warn drivers via electronic message signs, radio, television. and the web to avoid problem areas. Research has been underway for many years on how to partly automate cars by making smart roads with such things as buried magnets to guide sensor-equipped vehicles, with on-board GPS to determine location, direction, and destination. While these systems may eventually be used on surface streets as well, they are most practical in a freeway setting.
A very few short privatized toll freeways have also been built by private companies with mixed success.
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