Editing Roundabout (section)

=== Motorways ===
{{See also|Roundabout interchange}}
[[File:Opatovice nad Labem kruhový objezd from air K2 -1.jpg|thumb|Motorway junction with roundabout near [[Opatovice nad Labem]], Czech Republic]]

Roundabouts are generally not appropriate for placement on motorway or freeway mainlines because the purpose of such facilities is to provide for uninterrupted traffic flow. However, roundabouts are often used for the junction between the slip roads (called ''ramps'' in North America) and the intersecting road. A single roundabout, [[grade separation|grade separated]] from the mainlines, may be used to create a [[roundabout interchange]]. This type of junction is common in the UK and Ireland.

Alternatively, separate roundabouts also may be used at the slip road intersections of a [[diamond interchange]] to create what often is referred to as a "[[dumbbell interchange]]", which is increasingly common in both Europe and [[North America]] due to its reduced need for wide or multiple bridges. A variation of the dumbbell interchange, often called a "[[dogbone interchange]]", occurs when the roundabouts do not form a complete circle but are instead raindrop roundabouts (described [[#Raindrop roundabouts|above]]). This configuration reduces conflicts between vehicles entering the raindrop roundabouts from the ramps, reducing queueing and delays, compared with the dumbbell interchange.

Additional use of roundabouts for high-speed junctions is the [[roundabout interchange#Three-level stacked roundabout|3-level stacked roundabout]]—this is a [[roundabout interchange]] where ''both'' of the roadway mainlines are grade separated. In the United Kingdom, the [[M25 motorway|M25]]/[[A3 road|A3]], [[M8 motorway (Great Britain)|M8]]/[[M73 motorway|M73]] and [[A1 road (Great Britain)|A1(M)]]/[[M18 motorway (Great Britain)|M18]] interchanges are examples of this type. These junctions, however, have less capacity than a full [[free-flow interchange]]. A similar design to this is the [[three-level diamond interchange]].

Most junctions on [[Dublin]]'s M50 motorway C-road were built using a standard roundabout interchange. The traffic volume of several of these junctions increased to a level higher than the capacity such roundabouts can accommodate, and in turn, have been converted into partially or fully free-flowing interchanges. One example is the [[Red Cow interchange]]. In [[Northern Ireland]], the junction between the [[M1 motorway (Northern Ireland)|M1]] and [[M12 motorway|M12]] (Craigavon connector motorway) is via a standard roundabout with a raised centre, three onslips and three offslips, and two lanes.

In the city of [[Malmö]], Sweden, a roundabout connects two motorways, E22 from [[Lund]], and the [[Inre Ringvägen|Inner ring road]].

In the Netherlands, [[A6 motorway (Netherlands)|A6 motorway]] and [[A7 motorway (Netherlands)|A7 motorway]] used to cross near [[Joure]] using a roundabout until October 2017, when the junction was turned into a full [[Interchange (road)#Directional T interchange (Y-interchange)|Y-interchange]].<ref>{{Cite web|url=https://www.lc.nl/friesland/Video-Eerste-rit-over-het-nieuwe-knooppunt-Joure-22575041.html|title=Video: Eerste rit over het nieuwe knooppunt Joure|website=Leeuwarder Courant|date=13 October 2017 }}</ref> The junction between the [[A200 motorway (Netherlands)|A200]] and the [[A9 motorway (Netherlands)|A9]] uses a 3-level stacked roundabout. Near [[Eindhoven]] (the Leenderheide junction), the junction for the [[A2 motorway (Netherlands)|A2]] uses a roundabout. An overpass was built for the [[A67 motorway (Netherlands)|A67]] from Antwerp to Germany.

Near [[Liège]], Belgium, the Cheratte interchange between the [[A3 motorway (Belgium)|A3/E40]] and [[A25 road (Belgium)|A25/E25]] functions partially as a roundabout, with through traffic allowed to continue without entering the junction and traffic changing between motorways required to use the roundabout.

Rotary interchanges operate with [[traffic circle]]s rather than roundabouts. Rotary interchanges are common in [[New England]], particularly in the state of [[Massachusetts]], but a European example of a rotary interchange may be found in [[Hinwil]], Switzerland.