During the construction of the section around Cardiff in 1980, numbers were set aside for intermediate interchanges that were not built at the time. 33 had been set for the link road to the west (A4232), 32 for the A470, with 31 intended for the A469 to Caerphilly, and 30 for the great "Hook Road" - a plan which was later shelved. Junction 30 was later added to serve the link road in the east, which will eventually form a ring road from junctions 33 to 30, via Cardiff Bay. Number 31 remains unused as of 2006, and there are no immediate plans to build a junction with the A469.