Beltway, orbital motorway, perimeter loop, beltline, and similar terms refer to an expressway/motorway/freeway style standard road that often originally enclosed the built up area and was later encroached upon by developed areas.
Ring road may sometimes refer to a beltway-style road, but more commonly indicates a road or series of roads within a city or town that have been joined together by town planners to form an orbital distributor style road, but where the standard of road could be anything from an ordinary city street up to an expressway level. The principal difference is that a ring road is an orbital distributor road system designed from already existing roads, as opposed to a beltway which is designed from new as such a road system. A ring road designation also implies a more inner-city road designed to route traffic around a city centre, as opposed to routing traffic around a larger conurbation.
Many beltway-style roads are part of a wider highway system; for example, in the United States, beltways are commonly a part of the Interstate Highway System. Using inner/outer directions is a common way of uniformly signing the directions of travel on beltways in America.
Geography can sometimes complicate the construction of a beltway. One example is Stockholm, where there is a semi-beltway (Essingeleden). To be completed, most of it will have to run in submarine tunnels.
Many cities and metropolitan areas deal with ring roads and beltways in unique ways, giving the roads recognizable differences. Some cities have elected to construct multiple ring roads and beltways.
Memphis has one completed freeway loop, I-240, and one under construction, I-269. In addition, Memphis has a parkway system forming an inner beltway around the downtown area – the South Parkway, East Parkway, and North Parkway – which was built in the early 20th century.
Raleigh, North Carolina has one completed beltway, known as the Capital Beltline or Interstate 440, which pioneered the Inner/outer directional system. The system, however, is being phased out to prevent confusion with the city's second beltway, known as the "Outer Loop" or Interstate 540, which is under construction.
Amsterdam has the A10 which circles Amsterdam through it's outer boroughs. It connects to the A1, A2, A4 and A8 motorways. The local S100 serves as the ring around central Amsterdam, and the southernmost section of the A9 connects the southern suburbs such as Osdorp, Amstelveen and Amsterdam Zuidoost.
Berlin is surrounded by Bundesautobahn 10 as its outer ring which mostly runs in the state of Brandenburg. It is approximately in length which makes it the longest beltway in Europe. An inner ring was planned, but only half was completed (Bundesautobahn 100).
Lisbon has the Circular Regional Interna de Lisboa and the Circular Regional Externa de Lisboa.
London has the London Inner Ring Road (which circles Central London), the North and South Circulars, at a greater distance from the centre (roughly at the Zone 3/4 boundary), and the larger M25 orbital motorway (which encircles Greater London).
Also, the half-loop M-45 runs between the M-40 and the M-50 at the east, where the two beltways are more separated; and there are plans to build a fourth full loop, the M-60, which would be over long and encompass the whole metropolitan area of Madrid. This proliferation of orbital motorways is partially due to the traditional high radiality of the Spanish highway network, which routed most cross-country traffic through Madrid.
Moscow Central Ring Road is a planned road which will consist of parts of Moscow Small Ring and Moscow Big Ring. Planned length is about , it will be opened in 2015.
The modern civic scheme of Beijing, China, is based on a number of ring roads, consecutively numbered from 2nd to the projected 7th. The innermost 2nd Ring Road was built on the site previously occupied by the moat of the Beijing city walls.
India's capital has two ring roads running around it.
The Chinese city of Shanghai gained its first ring road in the inter-war years in the form of the Zhongshan Road, a partial ring that enclosed the existing urban area, which was primarily made up of foreign concessions.
In the 1990s, an Inner Ring Road was constructed, mainly consisting of elevated roadways built on top of the Zhongshan Road, but which eventually made a complete circle around the urban core. A Middle Ring Road and an Outer Ring Road (the A20 Expressway) were later added.