The A3 begins by proceeding ahead at a crossroads in Lisburn city centre, where the A1 veers to the left. It continues through the eastern suburbs of Lisburn before it comes to Junction 9 of the M1, where it intersects with the A26 travelling southwards from Antrim. The A3 carries the course of the A26 through the villages of Moira and Magheralin, before the A26 branches off again upon entering Lurgan, heading towards Banbridge.
