Dual carriageway
A dual carriageway (BrE) or a divided highway (AmE) is a class of highway with carriageways for traffic travelling in opposite directions separated by a central reservation (BrE) or median (AmE). Roads with two or more carriageways which are designed to higher standards with controlled access are generally classed as motorways, freeways, etc., rather than dual carriageways.
"Divided highway" redirects here. For the Doobie Brothers album, see Divided Highway.A road without a central reservation is known as a single carriageway regardless of how many lanes there are. Dual carriageways have improved road traffic safety over the years and over single carriageways and typically have higher speed limits as a result. In some places, express lanes and local or collector lanes are used within a local-express-lane system to provide more capacity and to smooth out traffic flows for longer-distance travel.
History[edit]
A very early (perhaps the first) example of a dual carriageway was the Via Portuensis, built in the first century by the Roman emperor Claudius between Rome and its port Ostia at the mouth of the Tiber.
One claim for the first divided highway in the United States was Savery Avenue in Carver, Massachusetts, first built in 1860, where the two roadways were separated by a narrow strip of trees down the middle.[1] In 1907 the Long Island Motor Parkway opened, and roughly 20% of it featured a semi-dual-carriageway design. The New York City Belt Parkway system, which was built between 1907 and 1934, also pioneered the same design. However the majority of it featured concrete or brick railings as lane dividers instead of grass medians.
In the year of 1924 the first Italian autostrada was opened running 55 km (34 mi) from Milan to Varese. It featured a broad road bed and did not feature lane dividers except near cities and through the mountains.[2][3]
The London end of the Great West Road became Britain's first dual carriageway when it was opened in 1925 by King George V.[4]
In 1927 the Rome bypass was opened. It ran 92 km (57 mi) bypassing Rome to the east. Almost the entire length featured a dual-carriageway design. In the early 1930s, it was extended southward all the way to Naples and northward to Florence. Most of the original routing was destroyed by the Allies in World War II.
By 1930 several US and European cities had built dual-carriageway highways, mostly to control traffic jams and/or to provide bypass routes for traffic.
In 1932 the first German autobahn opened between Cologne and Bonn. It ran 21 km (13 mi) and became a precedent for future highways. Although it, like the first autostrada, did not feature a dual-carriageway design, it inspired the mass construction of future high-speed roadways.
During the 1930s, Germany, Italy, and the Soviet Union began construction of a network of dual carriageway expressways. By 1942, Germany had over 3,200 km (2,000 mi) of dual carriageway roads, Italy had nearly 1,300 km (810 mi), and the Soviet Union had 400 km (250 mi).
What may have been the world's first long-distance intercity dual carriageway/freeway was the Queen Elizabeth Way in Southern Ontario in Canada, initially linking the large cities of Toronto and Hamilton together by 1939, with construction on this stretch of the present-day Queen Elizabeth Way beginning in 1936 as "Middle Road". It was gradually upgraded to a freeway from the 1950s to 1970s.
Opened to traffic in 1940, the 160-mile-long (260 km) Pennsylvania Turnpike was the first rural dual carriageway built in the United States. By 1955 several states had built dual carriageway freeways and turnpikes and in 1957 the Interstate Highway System began. Completed in 1994, the major highway system links all the major cities of the United States.
