The Great Northern Highway is generally North-South highway which links
Perth with its most northern port of
Wyndham. It is 3,204 kilometres in length, with 3,144 kilometres being National Highway. It is constructed as a sealed, predominantly 2-lane single carriageway (excluding a number of single lane bridges in the
Kimberley).
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This highway is the longest intrastate highway in Australia and also the longest Australian highway in absolute terms. In parts, it is among the remotest sealed roads in the world. Some sections are several hundred kilometres in length without so much as a roadhouse. Economically, it is a vital link as it provides access to the resource rich regions of the
Pilbara and
Kimberley. In these areas, the key industries of mining, pastoral stations and tourism are all dependent on the highway.
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Prior to the 1960s, with the exception of several better quality sections in the wheatbelt area, Great Northern Highway was mostly a series of tracks linking
Perth to remote pastoral areas. However, several events occurred in the 1950s that moved the highway forwards. The federal government Beef roads scheme encouraged road building in the
Kimberley, which meant trucks were able to transport cattle to port, as against the historical but slow cattle drives. In the
Kimberley, a sealed single lane link between
Broome and
Derby was completed in the 1960s, as were a number of access roads to the port of
Wyndham.
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When iron ore was discovered in the
Pilbara, major improvements to the highway commenced in the 1960s and continued in the 1970s - the section between
Meekatharra and
Newman opened in 1978, having been upgraded and sealed to two lanes wide. Also in 1978, the road between
Halls Creek and
Wyndham was upgraded and sealed to two lanes wide, and was followed not long after in 1981 by the widened and sealed 476 km between
Port Hedland and
Broome, which runs parallel to
Eighty Mile Beach and past the western end of the Mandora Marsh.
Work accelerated in the 1980s as part of the Australian Bicentenary roadworks program. In 1986, the widened and sealed section between
Fitzroy Crossing and
Halls Creek was opened after 5 years of work. Between
Newman and
Port Hedland the Great Northern Highway was changed in the 1980s to a new route running to the west of the original. It had previously passed through
Nullagine and
Marble Bar. The new
Newman-
Port Hedland link was finished in 1989. This marked the completion of sealing the Great Northern Highway and also completion of the federally funded National Highway around Australia.
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Flooding can be a
hazard, as the
Kimberley and
Pilbara receive periods of torrential rainfall between November and May. The 'dry causeway' Willare Crossing of the
Fitzroy River is designed to withstand enormous floods. However, in the early 1980s, seasonal flooding washed away major sections of the 'causeway' several times. To alleviate the problem, two new bridges were built in 1985 to enable more water to flow through the crossing without overtopping the 'causeway'. Then, less than six months later, Cyclone Hector produced 70% more water than the crossing was designed to handle, and washed away 4 or 5 km of the newly rebuilt section and left one of the bridges without its abutments. It was again rebuilt, and although it has overtopped since, it has not again washed away as disastrously as in 1986.