ANKARA

Turkey is planning a tender this year for a third underwater tunnel beneath Istanbul’s Bosphorus Strait, this one combining both road and railway passages, officials announced Tuesday.

The Grand Istanbul Tunnel contract will have the build-operate-transfer (BOT) model, said Cahit Turhan, Turkey’s transportation and infrastructure minister.

The three-level mega-project will integrate with the Yenikapi-Sefakoy subway line, he told an annual meeting in the capital Ankara.

After completion, the tunnel is set to be used by some 6.5 million people annually to travel between the Asian and European sides of Istanbul.

The 6.5-kilometer (4 mile) tunnel, which will include a rail system and highways together under the Bosphorus, aims to reduce traffic in the metropolis and save time.

The healthy operation of trade and transportation is indispensable for Turkey’s development, Turhan underlined.

The new tunnel is set to join the Eurasia Tunnel, a 5.4 km (3.4 mi) highway-only passage which opened in 2016, and the Marmaray, a 13.5-km (8.4 mi) commuter rail and train passage which opened in 2013, both beneath the Bosphorus.

*Writing and contributions by Gokhan Ergocun from Istanbul