[1] The alphanumeric system, introduced in 2013 (at the same time as New South Wales), has effectively replaced the previous scheme across the territory.
The alphanumeric system, introduced in 2013 (at the same time as New South Wales switched to their own alphanumeric system, as they shared some route allocations), replaced the previous National Route and National Highway scheme across the territory.
It consists of alphanumeric routes, a two-digit number prefixed with a letter (M, A, or B) that denotes the grade and importance of the road, displayed on signs as yellow text on a green background with a white border; the ACT is now the only jurisdiction in Australia to use a border around allocations (NSW, previously the only other state that used them, removed them in 2020).
The system was prepared by COSRA (Conference of State Road Authorities), held between 1953 and 1954: once each state road authority agreed to the scheme, it was rolled out federally.
These new routes were symbolised by green shields with gold writing (the word "National" along the top of the shield, present in other states' National Highways, was excluded for those within the ACT).