The Turkish company Cengiz Insaat would build the tube cheapest, EUR 89.3m, while Slovenian company Pomgrad together with Swiss group Marti would charge the most, EUR 140.3m.

In line with the rules governing the public call, DARS will further study the bids before selecting the contractor, the company told the STA.

Bids were also submitted by Implenia Österreich together with Implenia Switzerland and Slovenia's CGP Novo Mesto (EUR 114.8m) and Slovenia's Gorenjska Gradbena Družba in cooperation with Czech builder Metrostav (EUR 104.4m).

Slovenia's GH Holding is bidding in cooperation with Austria's Hochtief (EUR 118.6m) and Slovenia's Kolektor CGP together with Riko and Turkish firm Yapi Merkezijem (EUR 109.4m).

While Bosnia's Euroasfalt paired up with Slovenia's Cestno Podjetje Ptuj (EUR 106.3m), Greek J&P Avax would build the tube on its own for EUR 115m.

Italy's Astaldi would collaborate on the project with Slovenian partners Cipa and GIC Gradnje (EUR 117.5m).

The entire project involves the construction of a new, 3,546-metre motorway tube and a 620-metre motorway section to connect the existing motorway from the nearby tolling station with the new tube.

The investment is estimated at EUR 151.6m, VAT excluded, of which construction is budgeted at EUR 121.5m.

Works are expected to be launched this year and should be completed in five years.

As more than half of the planned tube is on the Austria side of the border, Austrian motorway operator Asfinag also published its tender last December.

According to the Slovenian business newspaper Finance, it has received seven bids for its part of the tube, with the prices ranging from EUR 89.8m to EUR 140.2m.

Once the second tube is completed, all traffic will be directed to it to allow for upgrading the old tube, which has been in use for 27 years.

To alleviate congestion and tackle safety concerns, Slovenia and Austria decided to build a second tube several years ago.