 The A-55 runs parallel to the Autopista AP-9 for much of its length, and also connects with the Autovía A-52 at the town of O Porriño.Between Vigo and O Porriño, the autovía is an upgrade of the N-120 road, and between O Porriño and the Portuguese border it is an upgrade of the N-550.For the final 5 km (3 miles) of its length, from the end of the AP-9 north of Tui to the Portuguese border and the A3 autoestrada, the A-55 forms part of European route E01.