Despite the provision of a completely sealed road, there was still much work to be done on the highway, with many older sections either worn out or not up to modern standards.
Narrow sections were widened to a full seven metres (23 ft), and repairs made to the road, shoulders, fencing, and line markings as required, with work carried out in sections and progressing along the length of the highway.
Four overtaking lanes were constructed between Mount Magnet and Cue in 1991; and between 1991 and 1993, there were eight contracts awarded to widen, reconstruct, and seal a combined total of more than 190 kilometres (120 mi) of the highway.

A range of projects were carried out across the length of the highway between 1996 and 2006.
By 1998, a 157-kilometre (98 mi) section between the Sandfire Roadhouse and Victoria Highway had been improved at a cost of $1.1 million, and another 42 kilometres (26 mi) north of Meekatharra was improved for $12 million in 1999.
Two bridges were constructed in the vicinity of Halls Creek in 2000, and another four in 2004/05, replacing floodways so that the highway would remain open during floods.
Similarly, 100 kilometres (62 mi) north of Halls Creek, the 240-metre-long (0.15 mi) Jarlalu Bridge over the Ord River was constructed to replace a single-lane floodway, and was opened in January 2003.
That same year, the bridges over the Fortescue and Gascoyne Rivers were strengthened to increase the highway's load capacity.
Modifications were made to the steep ascent of the Darling Scarp at Bindoon Hill between February 2002 and April 2003, and Great Northern Highway was realigned to bypass the Dalwallinu town centre.

Work on Great Northern Highway has been continuous.
From 2004 to 2010, the Muchea to Wubin section was upgraded, with parts reconstructed and realigned, and traffic lights installed at the intersection with Brand Highway.
In the Kimberley, five sections between Halls Creek and Victoria Highway were improved between 2008 and 2009 with regards to pavement strength, alignment, safety, and flood resistance.
From 2005 to 2010, the Perth section, through the Swan Valley, was upgraded, with the road widened, turning and overtaking lanes constructed, and street lighting improved.
Construction of a realignment around Port Hedland's Wedgefield industrial area, including a new parclo interchange at Wilson Street, began towards the end of 2012.
It was opened to traffic on 17 June 2014, and on 23 July 2014, Deputy Prime Minister Warren Truss, Federal Member for Durack Melissa Price, and Pilbara MLA Brendon Grylls officially opened the project.
It was finalised in August.
In October 2013, construction began on a project to straighten and widen Great Northern Highway's curves around Bindi Bindi.
The project was completed and opened to traffic on 27 February 2015, and allowed the speed limit to be raised from 80 to 110 km/h (50 to 70 mph).

A 21-kilometre-long (13 mi) section between Batty Bog Road (north of New Norcia) and Walebing was reconstructed between September 2014 and 2015.
Despite the provision of a completely sealed road, there was still much work to be done on the highway, with many older sections either worn out or not up to modern standards. Narrow sections were widened to a full seven metres (23 ft), and repairs made to the road, shoulders, fencing, and line markings as required, with work carried out in sections and progressing along the length of the highway. Four overtaking lanes were constructed between Mount Magnet and Cue in 1991; and between 1991 and 1993, there were eight contracts awarded to widen, reconstruct, and seal a combined total of more than 190 kilometres (120 mi) of the highway.
A range of projects were carried out across the length of the highway between 1996 and 2006. By 1998, a 157-kilometre (98 mi) section between the Sandfire Roadhouse and Victoria Highway had been improved at a cost of $1.1 million, and another 42 kilometres (26 mi) north of Meekatharra was improved for $12 million in 1999. Two bridges were constructed in the vicinity of Halls Creek in 2000, and another four in 2004/05, replacing floodways so that the highway would remain open during floods. Similarly, 100 kilometres (62 mi) north of Halls Creek, the 240-metre-long (0.15 mi) Jarlalu Bridge over the Ord River was constructed to replace a single-lane floodway, and was opened in January 2003. That same year, the bridges over the Fortescue and Gascoyne Rivers were strengthened to increase the highway's load capacity. Modifications were made to the steep ascent of the Darling Scarp at Bindoon Hill between February 2002 and April 2003, and Great Northern Highway was realigned to bypass the Dalwallinu town centre.
Work on Great Northern Highway has been continuous. From 2004 to 2010, the Muchea to Wubin section was upgraded, with parts reconstructed and realigned, and traffic lights installed at the intersection with Brand Highway. In the Kimberley, five sections between Halls Creek and Victoria Highway were improved between 2008 and 2009 with regards to pavement strength, alignment, safety, and flood resistance. From 2005 to 2010, the Perth section, through the Swan Valley, was upgraded, with the road widened, turning and overtaking lanes constructed, and street lighting improved. Construction of a realignment around Port Hedland's Wedgefield industrial area, including a new parclo interchange at Wilson Street, began towards the end of 2012. It was opened to traffic on 17 June 2014, and on 23 July 2014, Deputy Prime Minister Warren Truss, Federal Member for Durack Melissa Price, and Pilbara MLA Brendon Grylls officially opened the project. It was finalised in August. In October 2013, construction began on a project to straighten and widen Great Northern Highway's curves around Bindi Bindi. The project was completed and opened to traffic on 27 February 2015, and allowed the speed limit to be raised from 80 to 110 km/h (50 to 70 mph).
A 21-kilometre-long (13 mi) section between Batty Bog Road (north of New Norcia) and Walebing was reconstructed between September 2014 and 2015.
Great Northern Highway