NCN Route 73 is a cycle route which is far from complete. At present it runs from Kilmarnock to Ardrossan in Ayrshire, and then across Arran to Kintyre. However, it's current starting point in Kilmarnock is unlikely to be the easternmost limit of the route, which is probably intended to cross to NCN74 near Strathaven, or turn south along the A76 route to Dumfries.
At Present, however, it starts in Kilmarnock and heads west from the town centre, mostly following an old railway line to Irvine. It then follows the Annick Water and River Irvine through the town, before running between the railway and B779 to Kilwinning in a multiplex with NCN7. The two routes then split, and NCN73 follows a minor road under the A78 bypass to Stevenston, from where it follows first the railway, then a minor road along the coast to the ferry terminal at Ardrossan.