The enormous Eurasia Tunnel Project linking Kazlicesme on Istanbul’s European side and Goztepe in Asia will reduce the city's notorious traffic levels and will have a total length of 14.6-kilometers (9 miles), 

The underwater section will be 3.34km long; drilling on this part of the project was completed earlier this week. 

Due to the intensive works, the project will be opened six months ahead of schedule, claimed a ministry source.

At its deepest point, the tunnel will be 106.4 meters underneath the Bosporus Strait.

Designed for light vehicles, such as cars and minibuses, vehicles will pass through the tunnel in 15 minutes. A toll will be levied at $4 for cars and $6 for minibuses.

The mega project will connect the city’s two sides with one railway and two land routes. It was contracted in 2009 with the cooperation of a Turkish-Korean joint venture, which was later named the Eurasian Tunnel Operation Construction and Investment -- ATAS -- in 2011.

According to the project, ATAS will be responsible for construction, operation and maintenance for a period of 25 years.

Istanbul is the second-worst European city after Moscow in terms of traffic congestion, according to 2012 data from Europe's biggest navigation systems company, TomTom.

In recent years, the city has persistently tried to tackle its traffic problems.

The Eurasia tunnel will be Turkey’s second underwater project in Istanbul after the Marmaray, a railway tunnel underneath the Bosphorus Strait which has already transported around 21 million passengers in the first six months following its inauguration in October 2013.