D23 state road
Route information
Length	103.9 km (64.6 mi)
Major junctions
From	D3 in Duga Resa
Major intersections	D42 in Josipdol A1 in Brinje interchange A1 in Žuta Lokva interchange D50 near Žuta Lokva
To	D8 in Senj
Location
Country	Croatia
Counties	Karlovac, Lika-Senj
Major cities	Duga Resa, Josipdol, Senj
Highway system
Highways in Croatia

D23 state road, connects cities and towns of Duga Resa, Josipdol and Senj, to the state road network of Croatia, and most notably to A1 motorway in Žuta Lokva interchange,^{[1][maps 1]} as well as two major state roads - D3 and D8, located at the northern terminus and the southern terminus of the road respectively. The road is 103.9 km (64.6 mi) long.^[2] The route comprises a significant number of urban intersections, in segments of the road running through Duga Resa and Senj.

The D23 state road runs parallel to a section of the A1 motorway between Karlovac and Žuta Lokva interchanges, thus serving as an alternate or backup route for the motorway.^[3] Additionally, A7 motorway route is planned along the D23 road between Senj and Žuta Lokva. Once that motorway is completed, the D23 road shall run parallel to either A1 or A7 motorway along its entire length.^[4][5][6]

The road, as well as all other state roads in Croatia, is managed and maintained by Hrvatske ceste, a state-owned company.^[7]

Vratnik pass, currently a part of the D23 road, was already in use during Roman time as a salt road,^[8] and it became important for timber and other goods in the Middle Ages. However, the first well documented road built along the route was Via Josephina named after Joseph II, Holy Roman Emperor who commissioned its construction in 1775. Latin inscriptions carved in rock along the original Via Josephina route completed in 1779 testify that the Emperor travelled through the Vratnik pass on horseback when he realized that the route between Senj, as a major fortress on Adriatic coast, and the hinterland was nearly impassable. Legend has it that this happened when he fell from his horse near Vratnik Pass.^[9] Even though the incident is impossible to verify, the town of Josipdol to the east of the mountain pass is named after the Holy Roman Emperor.^[10]

In 1775, Joseph II indeed commissioned construction of the route, exactly 100 km (62 mi) long, from Vinko Struppi, a military engineer, and the road, named after the Emperor, was completed in 1779. The original route comprised very steep sections and 20% inclines were not uncommon. There was even one climb at a 30% grade. Because of this the road was modified and extended by 15 km (9.3 mi), in order to remove such steep sections. The first reconstruction was carried out as early as late 18th century, and another one between 1833 and 1845 managed by Field Marshal Josef Philipp Vukassovich (Croatian: Josip Filip Vukasović) and Josip Kajetan Knežić respectively. Subsequent modifications were not as significant. The road was paved in 1950, when the last minor modifications of the route were executed.^[11]

The route was distinguished by mile markers along the route, an obelisk in Karlovac marking the beginning of the road and a specially built gate in Senj marking its end. Most remarkably the original road included a stone bridge across three spans in Tounj, which was expanded during the reconstruction of 1845 and now has two levels. The upper level was destroyed during World War II, but it was rebuilt in the 1950s.

Traffic is regularly counted and reported by Hrvatske ceste, operator of the road.^[12] Substantial variations between annual (AADT) and summer (ASDT) traffic volumes are attributed to the fact that the road serves as a connection to A1 motorway and D8 state road carrying substantial tourist traffic.

D23 traffic volume
Road	Counting site	AADT	ASDT	Notes
D23	3008 Belavići	2,749	3,441	Adjacent to the Ž3176 junction.
D23	3013 Skradnik	1,782	2,209	Between the Ž2356 and Ž3255 junctions.
D23	3014 Munjava (Josipdol)	1,127	1,485	Adjacent to D42 junction.
D23	3028 Modruš	379	599	Adjacent to L34136 junction.
D23	4201 Brinje	912	1,299	Adjacent to Ž5110 junction.
D23	4101 Senj	3,417	7,555	Adjacent to D8 junction.

D23 major junctions/populated areas
Type	Slip roads/Notes
	Duga Resa D3 to Delnice (to the west) and Karlovac (to the east). Ž3182 to Belavići. The northern terminus of the road.
	Venac Mrežnički
	Donji Zvečaj
	Zvečaj Ž3183 to Gornje Bukovlje and Belavići
	Gornji Zvečaj
	Generalski Stol Ž3176 to Lešće and Orišje. Ž3185 to Perjasica and Barilović.
	Donje Dubrave
	Zdenac Ž3220 to Tounj. Ž3221 to Rebrovići.
	Ž3256 to Kamenica Skradnička, Gornje Primišlje and Slunj (D1).
	Skradnik Ž3255 to Oštarije (D42).
	Josipdol D42 to Ogulin (to the north). D23 and D42 are concurrent between Josipdol and Munjava for approximately 1.5 km (0.93 mi).
	Munjava D42 to Plaški (to the south). D23 and D42 are concurrent between Josipdol and Munjava for approximately 1.5 km (0.93 mi).
	Modruš
	Jezerane Ž5191 to Mrkopalj and Lokve (D3).
	Križpolje Ž5111 to Križ Kamenica. Ž5133 to Glibodol and Lička Jasenica (D42).
	A1 in Brinje interchange, to Zagreb (to the north) and to Zadar and Split (to the south).
	Brinje Ž5114 to Letinac.
	Prokike Ž5110 to Krivi Put and Klenovica (D8).
	A1 in Žuta Lokva interchange, to Zagreb (to the north) and to Zadar and Split (to the south).
	D50 to Gospić
	Melnice
	Vratnik
	Senj D8 to Rijeka (to the north) and Karlobag (to the south). The southern terminus of the road.

• Highways in Croatia
• Autocesta Rijeka - Zagreb
• Hrvatske autoceste