Fullerton Road Interchange is junction 2A, formerly junction 1, of the M74.
For approximately 17 years after it opened in 1994, the Fullarton Road Interchange was the Glasgow terminus of the M74. The motorway flared out on the approach, following the lines of future sliproads to meet the flat roundabout. When the M74 was extended westwards to meet the M8 in 2011 this flaring allowed the mainline of the motorway to be constructed between the ready-built sliproads, and banked up to cross the roundabout on two overbridges. New west-facing sliproads were also constructed to provide a full-access junction. The other significant change at this junction brought about by the extension of the M74 was that it ceased to be Junction 1. In order to minimise the number of junction number changes down the road, the Scottish Government, or at least Transport Scotland, decided to add in a series of 'a' junctions, so Fullarton Road is now Junction 2a!
Besides the M74 slips, there are two further routes joining the roundabout. To the south the unclassified Fullarton Road heads into the Cambuslang Industrial Estate, while to the north it becomes a spur of the A74, leading up to the main A74, London Road. This junction, barely 200m away, was previously a roundabout, but has been remodelled and signalised to give priority to traffic moving from the M74 to the city bound A74 and vice-versa.
To further complicate matters, since the extension of the M74, there have been some signage and mapping changes which suggest that part, if not all, of the A74 is being renumbered as an extension of the A721. At present the few signs and road markings around this junction still seem to refer to the A74, but further into the city new signage has been erected in relation to the new A728 which suggests that the A74 is now the A721, a route which previously terminated near Uddingston to the east.