Single carriageway in the context of "Strada statale 4 Via Salaria"

National Road 20 (Greek: Εθνική Οδός 20, abbreviated as EO20) is a single carriageway road in northwestern Greece. It links the cities of Ioannina and Kozani via Konitsa and Siatista. It passes through the Ioannina, Kastoria and the Kozani regional units. Since the opening of the A2 motorway (Egnatia Odos), it is no longer the fastest connection between Kozani and Ioannina. The section between Ioannina and Kalpaki is part of the European route E853.

Greek National Road 3 (Greek: Εθνική Οδός 3, abbreviated as EO3) is a single carriageway road in Greece. It connects Elefsina near Athens with the border of North Macedonia at Niki. It passes through Larissa and Florina. At Niki, it connects with the M5K motorway to Bitola. The section Kozani - Niki is also designated as the A27 motorway, part of which is operational as a 2-lane motorway.

Greek National Road 3 is one of the longest national roads in Greece and until the 1960s it served as the main route from Larissa to Thessaloniki. The A1 motorway now offers a faster connection to Thessaloniki. Most of the EO3, except the southernmost section between Eleusis and Bralos, is part of the E65.

National Road 48 (Greek: Εθνική Οδός 48, abbreviated as EO48) is a single carriageway road in central Greece. It connects the Greek National Road 5 at Antirrio with the town Livadeia, passing through Naupactus and Delphi. The section between Antirrio and Itea is part of European route E65. The GR-48 passes through the regional units Aetolia-Acarnania, Phocis and Boeotia.

National Road 38 (Greek: Εθνική Οδός 38, abbreviated as EO38) is a single carriageway road in western and central Greece. It connects Thermo with Lamia, via Agrinio and Karpenisi. It passes through the regional units Aetolia-Acarnania, Evrytania and Phthiotis. One section coincides with the European route E952. The E962 goes between Agrinio and Lamia.

Greek National Road 7 (Greek: Εθνική Οδός 7, abbreviated as EO7) is a single carriageway with at-grade intersections in the Peloponnese region in southern Greece. It connects the cities of Corinth and Kalamata, via Nemea, Argos, Tripoli and Megalopoli. It has been succeeded in importance by the A7 motorway (Corinth–Tripoli–Kalamata).

Greek National Road 2 (Greek: Εθνική Οδός 2, abbreviated as EO2) is a single carriageway with at-grade intersections, located in the regions of West Macedonia, Central Macedonia and East Macedonia and Thrace. It connects the Albanian border near Florina with the Turkish border near Alexandroupoli. Its section east of Thessaloniki has been replaced by the new A2 motorway (Egnatia Odos). The section between the Albanian border and Thessaloniki is part of European route E86.

A dual carriageway (BrE) or a divided highway (AmE) is a class of highway with carriageways for traffic travelling in opposite directions separated by a central reservation (BrE) or median (AmE). Roads with two or more carriageways which are designed to higher standards with controlled access are generally classed as motorways, freeways, etc., rather than dual carriageways.

A road without a central reservation is known as a single carriageway regardless of how many lanes there are. Dual carriageways have improved road traffic safety over the years and over single carriageways and typically have higher speed limits as a result. In some places, express lanes and local or collector lanes are used within a local-express-lane system to provide more capacity and to smooth out traffic flows for longer-distance travel.

Sturt Highway is an Australian national highway in New South Wales, Victoria, and South Australia. It is an important road link for the transport of passengers and freight between Sydney and Adelaide and the regions along the route.

Initially an amalgam of trunk routes, the Sturt Highway was proclaimed a state highway in NSW in 1933. In 1955, the route was allocated a National Route number (20). It was included in the National Highway system in 1992, forming the Sydney-Adelaide Link. Sturt Highway is allocated as route A20 for its entire length, the majority of which is a single carriageway, and freeway standard and 6-lane arterial road standard towards its western terminus in Gawler.

National Road 5 (Greek: Εθνική Οδός 5, abbreviated as EO5) is a single carriageway road in western Greece. It connects Antirrio, at the north end of the Rio-Antirrio bridge, with Ioannina in northwestern Greece, passing through Agrinio and Arta. The southern part, between Amfilochia and Antirrio, is part of the European route E55. The northern part, between Ioannina and Amfilochia, forms the European route E951. It passes on the east side of the Ambracian Gulf. In the future much of the traffic that used this road will be diverted to the new A5 motorway (Ionia Odos) motorway, which has already taken over parts of the road. Νear Arta there is a 200m. tunnel (Kleisoura tunnel) which opened in 1969

National Highway 01 or NH01, formally called the Ring Road (Pashto: د افغانستان حلقوي سړک; Dari: شاهراه حلقوی افغانستان), is a 2,200 km (1,400 mi) two-lane and four-lane road network circulating inside Afghanistan, connecting the following cities (clockwise): Kabul, Maidan Shar, Ghazni, Qalat, Kandahar, Delaram, Herat, Qala e Naw, Maymana, Andkhoy, Sheberghan, Mazar-i-Sharif, Puli Khumri, Charikar, and back to Kabul. It has extensions that connect Jalalabad, Bamyan, Khost, Spin Boldak, Lashkargah, Zaranj (Route 606), Farah, Islam Qala, Torghundi, Ymamnazar, Hairatan, Kunduz, and Fayzabad. The Ring Road is part of AH1, the longest route of the Asian Highway Network. National Highway 01 consists of four major sections, NH0101 to NH0104, linking the major economic centers.

Greek National Road 9 (Greek: Εθνική Οδός 9, abbreviated as EO9) is a single carriageway with at-grade intersections in the West Greece and Peloponnese regions. It runs along the west coast of the Peloponnese peninsula, from Patras to Methoni via Pyrgos. Its length is around 220 km (140 mi), making it the second-longest national highway of Greece.

The government of Greece plans to replace the road by a new motorway. This will be a southern extension of the A5 (Ionia Odos), which will connect the Albanian border near Ioannina with the A7 (Moreas) north of Kalamata. It is expected to be completed in 2015.

Greek National Road 33 (Greek: Εθνική Οδός 33, abbreviated as EO33) is a single carriageway road in southern Greece. It connects Patras with the Greek National Road 74 (Pyrgos - Tripoli) near Levidi, passing through the western and southern foothills of Mount Erymanthos.

Greek National Road 15 (Greek: Εθνική Οδός 15, abbreviated as EO15) is a single carriageway road in northern Greece. It connects Agios Germanos, near the border with North Macedonia, with the Greek National Road 6 near Kalampaka. It passes through Kastoria, Siatista and Grevena.

40°10′58″N 21°29′51″E / 40.1827°N 21.4975°E / 40.1827; 21.4975

The A470 (also named the Cardiff to Glan Conwy Trunk Road) is a trunk road in Wales. It is the country's longest road at 186 miles (299 km) and links the capital Cardiff on the south coast to Llandudno on the north coast. While previously one had to navigate the narrow roads of Llanidloes and Dolgellau, both these market towns are now bypassed due to extensive road modernisation. The 26 miles (42 km) from Cardiff Bay to Merthyr Tydfil are mainly dual carriageway, but most of the route from north of Merthyr to Llandudno is single carriageway.

South Carolina Highway 170 (SC 170) is a 49.010-mile (78.874 km) state highway, connecting northern Beaufort County with southern portions of Beaufort and Jasper counties. Due to increased population growth in both areas, the majority of the road is four lanes wide, with certain areas retaining the original two-lane configuration.