The topic of this paper is the analysis of investment costs and profitability in the construction of a modern motorway network, as we have it today in the Republic of Croatia. For a comprehensive and correct valuation and analysis of the previous investment, development and management of the road network of motorways in the Republic of Croatia, it would be necessary to look at a longer period of time, namely the period of existence in the former state until 1990 and the period after independence, from 1991 to the present day. Such a comprehensive analysis would clearly show us exactly how the road infrastructure developed, at what speed and to what extent it met traffic demand, what the investment costs were in relation to the positive effects, and how these investment costs affected key economic indicators, GDP and the amount of public debt. Similar analyzes have been carried out from time to time in different time periods, in different segments and under various political influences. Strategies and programs for the sustainable development of the road sector are the key foundation for ensuring the efficient development and management of motorways and the execution of programs for the further construction and maintenance of the motorway network. Policies for the sustainable development of the motorway network imply a responsible and disciplined approach, which cannot be ensured without continuous planning and the adoption of planning documents (strategies, mid-term and long-term plans). Such plans and strategies are adopted at the level of the Government of the Republic of Croatia and at the level of macro and micro management in the road sector. Building transport infrastructure is one of the most important infrastructural and geopolitical goals of any developing country. The current network of motorways in the Republic of Croatia is at a very high level of completion, and is spatially branched and technically structured to very well connect the four macro-regional centers and centers of polarization in the Republic of Croatia (Pannonia Croatia, Adriatic Croatia, the capital city Zagreb and northern Croatia) Compared to the comprehensiveness in the past time periods, geopolitical statuses and data resulting coming from this and degrees of completion of construction by motorway routes, apropos macro/micro regional centers, the aim of this paper is to present an analysis of the justification of investment costs for the A1 Zagreb-Split-Dubrovnik route, the construction of which was one the most invested in the Republic of Croatia . The paper will analyze available statistical data on four counties within the A1 route - Lika-Senj County, Zadar County, Šibenik-Knin County and Split-Dalmatia County. Data on the costs of building the highway network will be used from publicly published financial reports and reports on the operations of Croatian motorways ltd., which is the public manager for the construction, maintenance and management of the A1 route, and is 100% state-owned.