At present the A35 autoroute, which parallels the Rhine between Karlsruhe and Basel, and the A4 autoroute, which links Paris with Strasbourg, penetrate close to the centre of the city. The Grand contournement ouest (GCO) project, programmed since 1999, plans to construct a 24 km (15 mi) long highway connection between the junctions of the A4 and the A35 autoroutes in the north and of the A35 and A352 autoroutes in the south. This routes well to the west of the city and is meant to divest a significant portion of motorized traffic from the unité urbaine.