D3 is a state road in western parts of Croatia connecting Rijeka on the Adriatic coast to Zagreb, Karlovac and Varaždin, as well as to the Goričan border crossing to Hungary.
[2] The D3 state road is concurrent along parts of its route with other state roads, most notably the D1 between Zagreb and Karlovac, as well as some sections of the A4 (south of Popovec interchange) and the A3 (between Ivanja Reka and Lučko interchanges) motorways.
[1][2] The A3 and A4 motorway sections that are concurrent with the D3 state road are also a part of Zagreb bypass and are not tolled.
The road, as well as all other state roads in Croatia, is managed and maintained by Hrvatske ceste, a state-owned company.
[3] Traffic is regularly counted and reported by Hrvatske ceste, operator of the road.