<P> Canada has no current national system for controlled - access highways . With the exception of the Trans Canada Highway, all highways, including the controlled - access ones, are under provincial jurisdiction . The largest networks in the country are in Ontario (400 - series highways) and Quebec (Autoroutes of Quebec). These roads are influenced by, and have influenced, US standards, but have design innovations and differences . The total length of dual - carriageways with controlled access in Canada is 6,350 kilometres (3,950 mi), of which 564 kilometres (350 mi) are in British Columbia, 642 kilometres (399 mi) in Alberta, 59 kilometres (37 mi) in Saskatchewan, 2,135 kilometres (1,327 mi) in Ontario, 1,941 kilometres (1,206 mi) in Quebec, and 1,000 kilometres (620 mi) in the Maritimes . </P> <P> The RN - 21 (East--West, Boulevard Monseñor Romero), is the very first freeway to be built in El Salvador and in Central America . The freeway passes the northern area of the city of Santa Tecla, La Libertad . It has a small portion serving Antiguo Cuscatlán, La Libertad, and merges with the RN - 5 (East--West, Boulevard de Los Proceres / Autopista del Aeropuerto) in San Salvador . The total length of the RN - 21 is 9.35 kilometres (5.81 mi) and is currently working as a traffic reliever in the metropolitan area . The RN - 21 was named in honor of the first mayor of San Salvador, Diego de Holguín, due to political reasons it was renamed Boulevard Monseñor Romero, in honor of Óscar Romero . The first phase of the highway was completed in 2009, and the second phase was completed and opened in November 2012 . </P> <P> In the United States, a freeway is defined by the federal government's Manual on Uniform Traffic Control Devices as a divided highway with full control of access . This means two things . First, adjoining property owners do not have a legal right of access, meaning that they cannot connect their lands to the highway by constructing driveways, although frontage roads provide access to properties adjacent to a freeway in many places . When an existing road is converted into a freeway, all existing driveways must be removed and access to adjacent private lands must be blocked with fences or walls . </P> <P> Second, traffic on a freeway is "free - flowing". All cross-traffic (and left - turning traffic) is relegated to overpasses or underpasses, so that there are no traffic conflicts on the main line of the highway, which must be regulated by traffic lights, stop signs, or other traffic control devices . Achieving such free flow requires the construction of many overpasses, underpasses, and ramp systems . The advantage of grade - separated interchanges is that freeway drivers can almost always maintain their speed at junctions since they do not need to yield to vehicles crossing perpendicular to mainline traffic . </P>

Whats the difference between a highway and a free way
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