 The A78 begins in Greenock, Renfrewshire as a continuation of the A8 road at the Bull Ring roundabout, and runs in a southerly direction through the Spango Valley, Inverkip, Wemyss Bay, Largs, Seamill and then bypasses the major towns of Ardrossan, Irvine and Troon amongst others before terminating near Prestwick, Ayrshire, where it forms a junction with the A77.Much of the road is single carriageway - both for a short distance through Greenock and a 21-mile stretch between Inverkip and Ardrossan.The rest is dual carriageway - between the Eglinton and Warrix interchanges there are in fact 3 lanes in each direction, and the road is constructed to motorway standard (with full grade separation at junctions) save for a lack of hard shoulders.