Gilgandra and Walgett as National Route 55 in 1974, extending it to the border by 1983. This caused a major discrepancy for many years in that National Route 55 met the border at Mungindi but abruptly begun again over 100 kilometres (62 mi) west along the border at Hebel. The Queensland Road Department eventually changed this in 1997, diverting National Route 55 along its portion of Castlereagh Highway over the border south to Hebel; the former allocation between St George and Mungindi was then re-allocated National Route 46, however the New South Wales portion remained unallocated. With Queensland's conversion to the newer alphanumeric system in 2004, its route number was updated to route A7 between Rolleston and Roma (continuing north along Dawson and Gregory Highways to Emerald and Charters Towers), and A55 between Roma and St George; it is still allocated National Route 46 between St George and the border, and is still unallocated between the border and Moree. Roads of Strategic Importance upgrades The Roads of Strategic Importance initiative, last updated in March 2022, includes the following projects for Carnarvon Highway. Corridor upgrade A lead project to upgrade the Townsville to Roma corridor, including sections of Gregory, Dawson and Carnarvon Highways and surrounding state and council roads, at an estimated cost of $125 million, commenced construction of some work projects in 2020. Planning continues for other projects. Intersection upgrade Arcadia Valley Road A project to upgrade the intersection with Arcadia Valley Road at a cost of $925,000 was completed in January 2022. This project was targeted for "early works" by the Queensland Government. Intersection upgrade Castlereagh Highway A project to upgrade the intersection with Castlereagh Highway at a cost of $3.4 million is due for completion in mid-2022. This project is targeted for "early works" by the Queensland Government. Intersection upgrade Salmon Road A project to upgrade the intersection with Salmon Road at a cost of $4.8 million is due for completion in mid-2022. This project is targeted for "early works" by the Queensland Government. Orange Hill safety treatments A project to upgrade Carnarvon Highway near at a cost of $3.9 million was expected to finish in late 2021. This project was targeted for "early works" by the Queensland Government. Other upgrades Widen and seal A project to widen and seal a section of road north of Injune, at a cost of $5.22 million, started in May 2021. A