The highest numbered A road in the UK, the A9013 comprises part of the former route of the A92 through Aberdeen city centre.
The road begins on Holburn Street at the very busy Garthdee roundabout on the A92 (formerly the A90 until the construction of the Aberdeen Western Peripheral Route), now home to a large superstore and various other retail outlets. The route heads north through several sets of traffic lights and roundabouts into the city centre, passing the B9077 Great Southern Road and the A93 Great Western Road, before arriving at a signal-controlled junction on Union Street, the "high street" of Aberdeen. The A9013 number then continues along the full length of Union Street, before twisting up to follow King Street as far as the crossroads with the A96 and A956. From there, King Street continues as the A956.
The A92 originally entered Aberdeen along the Stonehaven Road, the present A90. It then followed the route of the A9013 completely, along Holburn Street, Union Street and King Street, continuing along the present route of the A956.
At some point, the A92 was re-routed along what is now the B9077 Great Southern Road, rejoining the traditional route at the Holburn Street roundabout, instead of heading over the Bridge of Dee. It's possible the A9013 number was introduced then for the southern length of Holburn Street, but this author cannot confirm the validity of that statement.
For a brief period in the early 1990s, the A92 was re-routed again along Anderson Drive, before being renumbered A90 shortly afterwards. This author imagines that the rest of the A9013 (if not the entire route) came into being at that point.
Even today, there are still signs on the A9013 referring to the "A92 (A94)" route to Dundee and Perth. With the opening of the Aberdeen Western Peripheral Route in 2018, the A92 number has returned to Aberdeen, but continues to follow the Anderson Drive route rather than the traditional route now occupied by the A9013.
For many years through until around 1970 the A9013 was shown on OS 1:2500 and 1:10,000 / 10,560 scale mapping as the A9103. This is deemed to have been an error which was replicated across sheets and scales for a number of years before being identified.