section_path: Transportation/Roads
section_name: Roads
paragraph_text: Roads
  
  Istanbul's motorways network are the O-1, O-2, O-3, O-4 and O-7. The total length of Istanbul Province's network of toll roads is 543 km (337 mi) (2024) and the state highways network (devlet yollari) is 353 km (219 mi) (2024), totaling 896 km (557 mi) of expressway roads (minimum 2x2 lanes), excluding secondary roads and urban streets. The density of expressway network is 16.8 km/100 km 2. The O-1 forms the city's inner ring road, traversing the Bosphorus Bridge, and the O-2 is the city's outer ring road, crossing the Fatih Sultan Mehmet Bridge. The O-2 continues west to Edirne and the O-4 continues east to Ankara. The O-2, O-3, and O-4 are part of European route E80 (the Trans-European Motorway) between Portugal and the Iran–Turkey border. In 2011, the first and second bridges on the Bosphorus carried 400,000 vehicles each day. The O-7 or Kuzey Marmara Otoyolu, is a motorway that bypass Istanbul to the north. The O-7 motorway from Kinali Gişeleri to Istanbul Park Service has 139.2 km (86.5 mi), with 8 lanes (4x4), and from Odayeri-K10 to Istanbul Atatürk Airport has 30.4 km (18.9 mi). The completed section of highway crosses the Bosporus via the Yavuz Sultan Selim (Third Bosphorus) Bridge, entered service on 26 August 2016. The O-7(Northen Beltway) 3.Beltway connects Istanbul Atatürk Airport with Istanbul Airport and Sabiha Gökçen Airport. Environmentalist groups worry that the third bridge will endanger the remaining green areas to the north of Istanbul. Apart from the three Bosphorus Bridges, the dual-deck, 14.6-kilometer (9.1 mi) Eurasia Tunnel (which entered service on 20 December 2016) under the Bosphorus strait also provides road crossings for motor vehicles between the Asian and European sides of Turkey. Road transport emits significant carbon dioxide, estimated at 7 million tons in 2021.