The A1 motorway (Croatian: Autocesta A1) is the longest motorway in Croatia spanning 454.5 kilometers (282.4 mi). As it connects Zagreb, the nation's capital, to Split, the second largest city in the country and the largest city Dalmatia, the motorway represents a major north–south transportation corridor in Croatia and a significant part of the Adriatic–Ionian motorway. Apart from Zagreb and Split, the A1 motorway runs near a number of major Croatian cities, provides either access to several national parks or nature parks and world heritage sites and numerous resorts, especially along the Adriatic Coast. The motorway is currently being extended south of Split to the port of Ploče and the city of Dubrovnik. National significance of the motorway is reflected through its positive economic impact on the cities and towns it connects as well as its importance to tourism in Croatia, however its genuine importance as a transit route shall be achieved upon completion of the Adriatic–Ionian motorway along the sections currently spanned just by the Adriatic Highway and two-lane roads in Slovenia and Albania connecting to the route.
The motorway consists of two traffic lanes and an emergency lane in each driving direction separated by a central reservation. All intersections of the A1 motorway are grade separated. As the route traverses rugged mountainous and coastal terrain the route completed as of 2010 required 351 bridges, viaducts, tunnels and other similar structures, including the two longest tunnels in Croatia and two bridges comprising spans of 200 metres (660 ft) or more. Currently there are 30 exits and 26 rest areas operating along the route. As the motorway is tolled using a ticket system and vehicle classification in Croatia, each exit includes a toll plaza.
A motorway connecting Zagreb and Split was originally designed in the early 1970s, and a public loan was started in order to collect sufficient funds for its construction. However, due to political upheavals in Croatia and Yugoslavia, construction of the motorway was labeled a "nationalist project" and cancelled in 1971. After Croatian independence and conclusion of the Croatian War of Independence, efforts to build the motorway were renewed and construction started in 2000. Zagreb–Split section of the route was completed by 2005, while the first sections between Split and Dubrovnik opened in 2007 and 2008. Construction costs incurred so far amount to 3 billion euro. The figure includes funds approved for construction work scheduled to be completed by 2013. On the other hand the amount does not include construction cost related to Lučko–Bosiljevo 2 section since that section was funded as a part of Rijeka–Zagreb motorway construction project through the privately owned Autocesta Rijeka–Zagreb, current operator of that sector. The remainder of the A1 motorway, i.e. the sections south of the Bosiljevo 2 interchange are operated by the state-owned Hrvatske autoceste.
The motorway is known for its scenic route, as it passes through many different geographic zones, such as the plains of inland Croatian, the Likan mountains, the coastal savannah around Zadar and the deep valleys of southern and central Dalmatia. It spans three very different climate zones in a short stretch of motorway, linking the sub-tropical coastal region and the mountain-climated Lika region at the Sveti Rok tunnel and then that region to the continental climate of inland croatia at the Mala Kapela tunnel.