D51 connects A3 motorway Nova Gradiška interchange to Nova Gradiška and Požega. The road forms two junctions to D38 state road, one in Brestovac, where D38 branches off to Pakrac, and another 5 km (3.1 mi) further east, in Požega, where D38 branches off to Pleternica. Between those two junctions D51 and D38 are concurrent. The eastern terminus of the road is near Gradište, at a junction to D53 state road to Našice and Slavonski Brod. The road is 50.3 km (31.3 mi) long.

The A3 motorway is a major motorway in Croatia spanning 306.5 kilometres (190.5 mi). The motorway connects Zagreb, the nation's capital, to the Slavonia region and a number of cities along the Sava River. It represents a major east–west transportation corridor in Croatia and a significant part of the Pan-European Corridor X, serving as a transit route between the European Union states and the Balkans. Apart from Zagreb, where the A3 motorway comprises a considerable part of the Zagreb bypass, the motorway runs near a number of significant Croatian cities.