The two sides of the 5.4 kilometer long undersea motorway tunnel between the European and the Asian sides of Istanbul have successfully been connected on Saturday. The excavation work of the tunnel started on April 19 2014, with the attendance of Prime Minister Recep Tayyip Erdoğan, and finished on August 22, with a ceremony attended by Prime Minister Ahmet Davutoğlu and various high officials. The tunnel, which will be operational at the end of 2016, will connect the Kazlıçeşme neighborhood on the European side to Göztepe in Asia and will cut the travel time between the two congested areas to 15 minutes.The necessary expansion of current motorways and the building of the connecting roads will be completed next year. The entire project is 14.6 kilometers long, with the tunnel taking up 5.4 kilometers. The section directly under the sea will be 3.34 kilometers. The deepest section will be 106 meters under the sea level.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 traffic problems.In December 2006, Turkey's Transport and Communication Ministry tendered the project under the name of the Istanbul Bosporus Tube Crossing Project.The project was contracted in 2009 with the cooperation of a Turkish-Korean joint venture, which was later named as 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.The Eurasia tunnel will be Turkey's second underwater project in Istanbul after the Marmaray, a railway tunnel underneath the Bosporus Strait which has already transported around 21 million passengers in the first six months following its inauguration in October 2013.Last February, Turkish Prime Minister Ahmet Davutoğlu also announced an estimated $3.5 billion mega project for a three-storey sub-sea tunnel under Istanbul's Bosphorus Strait which will connect the city's two sides with one railway and two land routes, cutting travel times to 14 minutes.Davutoğlu had described the 6.5 km-long tunnel as the first of its kind in the world, as it is comprised of one rail system between two highways for motor vehicles 110 meters under the Bosporus Strait.Moreover, a third bridge over the Bosporus is currently in construction and is expected to be ready by the end of 2015. IC ICTAS Construction Company, which is building it, claims the structure will be the widest (59 meters), longest (1,048) and highest (320) bridge in the world.Despite being noticeable improvements, these projects have struggled to diminish traffic flow in the city.According to many transportation experts, Istanbul's traffic still needs a permanent solution-which is expanding the railways across the city.In fact, the city has plans to add more than 600 km of metro railway to its current 150km network by 2019.However, until then, Istanbulites may have to content themselves by honking their horns.