According to the Infrastructure Ministry, the OECD's list will include the financial, technical, social and economic aspects of each model and possible risks they involve.

"A through analysis of risks, risks limitations and risk distribution among stakeholders plays an important role in the selecting of the model, which in turn will affect the future costs for the partners," the ministry has said.

After the most appropriate model is selected, Slovenia will start looking for a private investors to take part in the project, for which a construction permit is expected in 2016. According to the OECD, the process usually takes at least two years.

Slovenia also plans to carry out an international audit of the investment value, with results expected early in 2016. The draft investment plan puts the investment value at EUR 1.4bn.

Prior to that, the OECD will assess the country's plan to make a call for applications for the audit.

The project of upgrading the Koper-Divača section has already been subject to an external audit, which established its compliance with the construction act.