It is the main access road to the Carnarvon National Park, and serves as a strategic route to take B-doubles and other large vehicles (which cannot use Bruce Highway) to the Queensland ports north of Rockhampton.

It crosses the state border at Mungindi to eventually terminate at the intersection with Gwydir Highway in Moree, in New South Wales.

However, New South Wales had previously signed Castlereagh Highway between Gilgandra and Walgett as National Route 55 in 1974, extending it to the border by 1983.

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.

[16] A project to widen and seal a section of road east of St George, at a cost of $4.5 million, was completed in August 2021.

[19] The Queensland Inland Freight Route is a proposal to upgrade the existing highways from Charters Towers to Mungindi.