In line with the deal signed by Slovenia's DARS and Austria's Asfinag in Bruck an der Mur today, a second tube under the Karavanke (Karawanken) mountain range will be built by 2023, with the first tube then scheduled to be fully renovated.

While construction of the tube is due to begin in 2017, the Austrian press agency APA reported that Austria could start the first works on the project as early as this year, since a new bridge will first need to be built on the Austrian side.

The total value of the project is set at EUR 312m, with DARS assuming EUR 150m of the sum. Nearly 3.5 kilometres of the 7,864-metre tunnel passes on Slovenian territory.

The tunnel which links northern Gorenjsko region to the Austrian region of Carinthia has been a lifeline for traffic since it was opened in 1991, but increasing traffic in recent years prompted original plans for a two-tube tunnel to be revived on both sides of the border.

The tunnel was initially designed as a two-tube tunnel in the 1970s, but the countries later decided that a single two-way tube would suffice for traffic at the time.

Increasing use of the tunnel and related safety concerns as well as the need for repairs have in recent years seen the tunnel frequently limited to one-way traffic, causing congestions on the key road artery connecting central and SE Europe.

DARS chairman Matjaž Knez said the second tube would "primarily contribute to safety while also tackling a major bottleneck on the tenth pan-European transport corridor".