North of Zagreb the D1 is mostly parallel to the
A2 motorway up to the Krapina interchange, connecting to a number of the A2 interchanges directly or via connector roads. It also runs parallel with railway tracks in some sections running through hilly terrain. A part of the D1 state road is concurrent with other routes: the A2 motorway between
Zaprešić and
Jankomir interchanges, the
A3 motorway between Jankomir and
Lučko interchanges, the
D3 state road between the A3 motorway Lučko interchange and
Karlovac, the
D6 state road in Karlovac, the
D33 state road in
Knin and the
D219 state road in
Sinj. The northern part of the D1 in Karlovac is actually a slightly lower road category because there are several intersections with traffic lights which slow the traffic down. Parts of the road in
Lika have
climbing lanes. The road, as well as all other state roads in Croatia are managed and maintained by
Hrvatske ceste, a state-owned company. == Traffic volume ==