The name "ring road" is used for the majority of metropolitan circumferential routes in the European Union, such as the Berliner Ring, the Brussels Ring, the Amsterdam Ring, the Boulevard Périphérique around Paris and the Leeds Inner and Outer ring roads. Australia and India also use the term ring road, as in Melbourne's Western Ring Road and Hyderabad's Outer Ring Road. In Canada the term is the most commonly used, with "orbital" also used to a much lesser extent.
In Europe, some ring roads, particularly those of motorway standard which are longer in length, are often known as "orbital motorways". Examples include the London Orbital (188 km), Rome Orbital (68 km) and Manchester Orbital (56 km).
In the United States, many ring roads are called beltlines, beltways, or loops, such as the Capital Beltway around Washington, D.C. Some ring roads, such as Washington's Capital Beltway, use "Inner Loop" and "Outer Loop" terminology for directions of travel, since cardinal (compass) directions cannot be signed uniformly around the entire loop. The term 'ring road' is occasionally – and inaccurately – used interchangeably with the term 'bypass'.
Bypasses around many large and small towns were built in many areas when many old roads were upgraded to four-lane status in the 1930s to 1950s, such as those along the Old National Road (now generally U.S. 40 or Interstate 70) in the United States, leaving the old road in place to serve the town or city, but allowing through travelers to continue on a wider, faster, and safer route.
Construction of fully circumferential ring roads has generally occurred more recently, beginning in the 1960s in many areas, when the U.S. Interstate Highway System and similar-quality roads elsewhere were designed. Ring roads have now been built around numerous cities and metropolitan areas, including cities with multiple ring roads, irregularly shaped ring roads, and ring roads made up of various other long-distance roads.
London has three ringroads (the London Orbital, the North and South Circular routes, and the Inner Ring Road). Other British cities have two (Birmingham, Leeds, Sheffield, Norwich and Glasgow). Columbus, Ohio, in the United States, also has two, while Houston, Texas will have three official ring roads (not including the downtown freeway loop). Some cities have far more—Beijing, for example, has six ring roads, simply numbered in increasing order from the city center (though skipping #1).
Geographical constraints can complicate or prohibit the construction of a complete ring road. For example, the Baltimore Beltway in Maryland crosses Baltimore Harbor on a high arch bridge, and much of the partially completed Stockholm Ring Road in Sweden runs through tunnels or over long bridges. However, some towns or cities on seacoasts or near rugged mountains cannot have a full ring road, such as Dublin's ring road; or, in the US, Interstate 287, mostly in New Jersey (bypassing New York City), or Interstate 495 around Boston, none of which completely circles these seaport cities.
Adjacency of international boundaries may also prohibit ring road completion in other cases. Construction of a true ring road around Detroit is effectively blocked by its location on the border with Canada; although constructing a route mostly or entirely outside city limits is technically feasible, a true ring around Detroit would necessarily pass through Canada, and so Interstate 275 and Interstate 696 together bypass but do not encircle the city. Sometimes, the presence of significant natural or historical areas limits route options, as for the long-proposed Outer Beltway around Washington, D.C., where options for a new western Potomac River crossing are limited by a nearly continuous corridor of heavily visited scenic, natural, and historical landscapes in the Potomac River Gorge and adjacent areas.
When referring to a road encircling a capital city, the term "beltway" can also have a political connotation, as in the American term "Inside the Beltway", derived metonymically from the Capital Beltway encircling Washington, D.C.
Examples of ring roads
Most orbital motorways (or beltways) are purpose-built major highways around a town or city, typically without either signals or road or railroad crossings. In the United States, beltways are commonly parts of the Interstate Highway System. Similar roads in the United Kingdom are often called "orbital motorways". Although the terms "ring road" and "orbital motorway" are sometimes used interchangeably, "ring road" often indicates a circumferential route formed from one or more existing roads within a city or town, with the standard of road being anything from an ordinary city street up to motorway level. An excellent example of this is London's North Circular/South Circular ring road.
In some cases, a circumferential route is formed by the combination of a major through highway and a similar-quality loop route that extends out from the parent road, later reconnecting with the same highway. Such loops not only function as a bypass for through traffic, but also to serve outlying suburbs. In the United States, an Interstate highway loop is usually designated by a three-digit number beginning with an even digit before the two-digit number of its parent interstate. Interstate spurs, on the other hand, generally have three-digit numbers beginning with an odd digit.
Circumferential highways are prominent features in or near many large cities in the United States. In many cases, such as Atlanta, Georgia, Interstate 285 (also known as the Perimeter) serves as a bypass while other highways pass directly through the city center. In other cases, a primary Interstate highway passes around a city on one side, with a connecting loop Interstate bypassing the city on the other side, together forming a circumferential route, as with I-93 and I-495 in the area of Lawrence, Massachusetts. However, if a primary Interstate passes through a city and a loop bypasses it on only one side (as in the Wilmington, Delaware, area), no fully circumferential route is provided.
Route numbering is challenging when a through highway and a loop bypass together form a circumferential ring road. Since neither of the highways involved is circumferential itself, either dual signage or two (or more) route numbers is needed. The history of signage on the Capital Beltway around Washington, D.C., is instructive here. Interstate 95, a major through highway along the U.S. East Coast, was originally planned as a through-the-city route there, with the Beltway encircling the city as I-495. The portion of I-95 entering the city from the south was soon completed (and so signed), primarily by adapting an existing major highway, but the planned extension of I-95 through residential areas northward to the Beltway was long delayed, and eventually abandoned, leaving the eastern portion of the Beltway as the best Interstate-quality route for through traffic.
This eastern portion of the Beltway was then redesignated from I-495 to I-95, leaving the I-495 designation only on the western portion, and the completed part of the planned Interstate inside the Beltway was redesignated as a spur, I-395. A few years later, the resulting confusion from different route numbers on the circumferential Beltway was resolved by restoring I-495 signage for the entire Beltway, with dual signage for I-95 for the highway's concurrent use as a through Interstate on its eastern portion.
The longest complete beltway in the United States is Interstate 275 (Ohio–Indiana–Kentucky), an 83.71-mile (134.72 km) loop in Ohio, Indiana, and Kentucky that forms a complete beltway around the Cincinnati, Ohio area. It is the only auxiliary interstate that enters three states, including one state that the parent route does not enter (Indiana), and it encloses an area of over 250,000 acres.
Other major US cities with such a beltway superhighway:
- Atlanta--Interstate 285
- Baltimore—Interstate 695 including the Francis Scott Key Bridge
- Charlotte--Interstate 485
- Cleveland--Interstate 480 (Ohio)
- Columbus, Ohio—Interstate 270
- Denver—Interstate 70, Colorado State Highway 470, and E-470
- El Paso, Texas – Loop 375
- Fort Worth, Texas—Interstate 20 and Interstate 820
- Houston—Interstate 610, Beltway 8 and the Grand Parkway.
- Indianapolis—Interstate 465
- Jacksonville—Interstate 295
- Kansas City, Kansas/Kansas City, Missouri—Interstate 435
- Memphis, Tennessee—Interstate 240 and Interstate 40 (Inner Beltway); Interstate 269 (Outer Beltway)
- Minneapolis/Saint Paul, Minnesota—Interstate 94, Interstate 494, and Interstate 694
- Central Nashville, Tennessee—Interstate 24, Interstate 40, and Interstate 65
- Norfolk, Virginia/Hampton Roads—Interstate 64 and Interstate 664
- Raleigh, North Carolina—Interstate 40 and Interstate 440 form an inner beltway, while Interstate 540/NC 540 will form an outer beltway when completed.
- St. Louis, Missouri—Interstate 255 and Interstate 270
- San Antonio—Downtown Circulator, Interstate 410, and Loop 1604
There are other US superhighway beltway systems that consist of multiple routes that require multiple interchanges and thus do not provide true ring routes. A designated example is the Capital Beltway around Harrisburg, Pennsylvania using Interstate 81, Interstate 83, and Pennsylvania Route 581.
Edmonton, Alberta has two ring-roads. The first is a loose conglomeration of four major arterial roads with an average distance of 6 km (4 mi) from the downtown core. Yellowhead Trail (Edmonton) forms the northern section, Wayne Gretzky Drive/75 Street, Edmonton forms the eastern section, Whitemud Drive forms the southern and longest section, and 170 Street, Edmonton forms the western and shortest section. Whitemud Drive is the only section that is a true Controlled-access highway, while Yellowhead Trail and Wayne Gretzky Drive have interchanges and intersections and are therefore both Limited-access roads. 170 Street and 75 Street are merely large arterial roads with intersections only. The second ring-road is known as Anthony Henday Drive and circles the city at an average distance of 12 km (7.5 mi) from the downtown core. It is a true Controlled-access highway for its entire 78 km (48 mi) length. It was built to reduce traffic inside of the ring-road itself, create a bypass route for the Yellowhead Trail, reduce travelling time for citizens on the outskirts of the city, and finally, to improve the movement of goods and services across Edmonton and the surrounding areas. It is currently under construction and named after Alberta explorer Anthony Henday. When complete in 2016, it will be the first free-flowing orbital road in Canada.
Most major cities in Western Europe are served by a ring road that either circles the inner core of the their metropolitan areas or the outer borders of the city proper or both. In major transit hubs, such as the Île-de-France region surrounding Paris and the Frankfurt area, major national highways converge just outside city limits before forming one of several routes of an urban network of roads circling the city. Unlike in United States, route numbering is not a challenge on Western European ring roads as routes merge to form the single designated road. However, exit and road junction access can be challenge due to the complexity of other routes branching from or into the ring road.
Major European cities that are served by a ring road or ring road system:
- Amsterdam – A10 motorway
- Barcelona – Ronda de Dalt and Ronda Litoral (inner city), B30 and B40 (metropolitan region)
- Berlin – Bundesautobahn 100 (inner city), Bundesautobahn 111 (city proper), Bundesautobahn 10 (inner metropolitan region)
- Brussels – Petite ceinture (inner city), Brussels Ring (city proper)
- Caen – Périphérique
- Cologne – Cologne Ring (inner city), Cologne Beltway (metropolitan region)
- Dublin - M50 motorway (Ireland)
- Frankfurt – Bundesautobahn 66 and Bundesautobahn 661 (city proper), Frankfurter Kreuz system (inner metropolitan region)
- Glasgow – Glasgow Inner Ring Road (inner city)
- Hamburg – Inner Ring (inner city)
- London – London Inner Ring Road (inner city), North Circular Road and South Circular Road (city proper), M25 motorway (metropolitan region)
- Lisbon - 2ª Circular (Inner City), IC17-CRIL (City Proper), IC18/A9-CREL (Metropolitan Region)
- Lyon – A7 autoroute and A46 autoroute (city proper)
- Madrid – M-30 (inner city), M-40 (inner metropolitan region)
- Manchester – M60 motorway (inner metropolitan region)
- Munich – Altstadtring (inner city), Bundesautobahn 99 (inner metropolitan region)
- Paris – Boulevard Périphérique (city proper), A86 autoroute (inner metropolitan region), Francilienne (tertiary ring road), Grand contournement de Paris (metropolitan region)
- Padua – GRAP
- Rennes - Rocade de Rennes (city proper)
- Rome – Grande Raccordo Anulare