It is a one-lane highway that spans from Macelj border crossing in the north via Krapina, Zagreb, Karlovac, Slunj, Gračac, Knin, Sinj, ending in Split.
[1] Before the A1 and A2 dual carriage motorways were completed in 2005 and 2007, respectively, the D1 was probably the busiest road during the summer in Croatia as it connected the northern border as well as the city of Zagreb with the tourist resorts on the Adriatic Sea.
Since then, the traffic has waned significantly, but the D1 remains relevant as an alternative to the tolled highways.
[4] Traffic is regularly counted and reported by Hrvatske ceste, operator of the road.
[5] The D1 AADT and ASDT (average summer daily traffic) figure variations observed south of Karlovac are attributed to tourist traffic to various regions of Adriatic Sea coast in Dalmatia region of Croatia.