Otoyol in the context of "Otoyol 6"

Otoyol 3 (English: Motorway 3), also known as the European Motorway (Turkish: Avrupa Otoyolu) and abbreviated as the O-3 is a 245.1 km (152.3 mi) long otoyol in East Thrace, Turkey. The O-3 runs from Edirne to Istanbul and is the only motorway in Turkey located entirely in Europe. The motorway begins west of Edirne at "Edirne Batı K1" junction with the D.100 where it then continues as a beltway passing just north of Edirne. From there, the motorway passes through mostly rural farmland until it enters the Istanbul metropolis near Silivri. The eastern end of O-3 ends at the Istanbul Bağcılar "Mahmutbey Batı K20" Junction.

O-3 "Avrupa otoyolu" "Mahmutbey Batı K19" junction connects to O-7, E80, Istanbul Airport and Yavuz Sultan Selim Bridge in the north direction, to Ataturk Airport with the 2nd Beltway in the south direction. The last junction of the European motorway "Mahmutbey Doğu K20" connects to O-2 motorway (2nd Beltway) and Fatih Sultan Mehmet Bridge in the east direction, to 1st Beltway (O-1) with the O3-O1 connection road in the south direction. The motorway has six lanes, three in each direction, except for a 44.6 km (27.7 mi) section between Silivri and Esenyurt.

Otoyol 5 (English: Motorway 5), named the Kocaeli Gebze-Bursa-İzmir Motorway (Turkish: Kocaeli Gebze-Bursa-İzmir Otoyolu) and abbreviated as O-5, is a toll motorway in Turkey. Since being completed in 2019, it connects the Istanbul and Kocaeli metropolitan areas with İzmir, via Bursa and Balıkesir. The O-5 runs parallel to the D575 and the D565 for most of its length and is a major motorway in Turkey as it provides a direct connection between Kocaeli and its surrounding metropolis to the country's 3rd largest (İzmir) and 4th largest (Bursa) cities, bypassing the Gulf of İzmit via the Osman Gazi Bridge. The O-5 also makes up part of the International E-road network E881 thus making it one of the most extensive and expensive transport megaprojects.

The western part of the Bursa Beltway, which is part of the O-5, was completed during the 2000s. The rest of the O-5 has been under construction since the early 2010s, with the first portion opened from Altinova to Gemlik in April 2016. As of April 2017, the O-5 is open in two separate sections: the 105.5 km (65.6 mi) section from its northern terminus in Kocaeli, Gebze to Bursa, across the Osman Gazi Bridge along with a 18.2 km (11.3 mi) section from Kemalpaşa to its southern terminus in İzmir. The final section, Karacabey to Akhisar, opened on August 5, 2019.

Otoyol 4 (English: Motorway 4), named Anatolian Motorway (Turkish: Anadolu Otoyolu) and abbreviated as O-4, is a toll motorway connecting the northwestern Marmara region to the Central Anatolia Region in Turkey. It runs parallel to the D.100 for more than half of its length and then parallels the D750 for most of the eastern half. The O-4 is a major expressway in Turkey as it connects eastern Istanbul and the heavily urbanized northeastern shore of the Sea of Marmara to the nation's capital, Ankara. The O-4 also makes up part of the International E-road network E80 and E89 as well as the AH-1 of the Asian Highway Network.

The O-4 is the longest completed motorway in Turkey spanning 379 km (235 mi), just 14 km (8.7 mi) longer than the O-52. The partially-opened O-5 is expected to surpass the length of the O-4, when it is completed in 2019, with a total length of 407 km (253 mi). but nowadays the longest motorway in Turkey is Otoyol 21 with the opening Ankara-Niğde section. Construction of the O-4 began in 1984 and was widely completed in 1992 except for a short gap through the mountains west of Bolu. This gap was connected in 2006, with the opening of the Mount Bolu Tunnel.