Dual carriageway

"Divided highway" redirects here. For the music album, seeDivided Highway (album).

Adual carriageway(BrE) or adivided highway(AmE) is a class of highway withcarriagewaysfor 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 asmotorways,freeways, etc., rather than dual carriageways.

A typical British dual carriageway with central barrier on theA63nearHull,England

Map by Cassius Ahenobarbus, zoomed in to show theVia Portuensis,with the dual carriageway splitting close to the city ofRome.This is a very early (perhaps the first) example of a dual carriageway.

Autostrada A20runs through the island ofSicilyinItalylinkingPalermotoMessina

Clara Barton Parkwayoutside Washington, D.C.

Jersey barriersmay be used to separate the carriageways where the space is narrow. See this example nearMálaga,Spain. There is also abus stopin the bottom-right corner of the picture; it would not exist in amotorway.

A road without a central reservation is known as asingle carriagewayregardless of how many lanes there are. Dual carriageways have improvedroad traffic safetyover the years and over single carriageways and typically have higherspeed limitsas a result. In some places, express lanes and local or collector lanes are used within alocal-express-lane systemto provide more capacity and to smooth out traffic flows for longer-distance travel.

History

A very early (perhaps the first) example of a dual carriageway was theVia Portuensis,built in the first century by the Roman emperorClaudiusbetween Rome and its harbor ofPortus.The route between the city and the port experienced a great deal of commercial and pedestrian traffic, as Portus served as the primary avenue for the grain shipments of theCura Annonaeinto Rome, as well as transporting the majority of goods imported from across theMediterranean world.This influx of road activity necessitated the construction of a dual thoroughfare as the road approached thePorta Portese,the corresponding gate in theAurelian Wallsof Rome for theVia Portuensis.

One claim for the first divided highway in the United States was Savery Avenue inCarver, Massachusetts,first built in 1860, where the two roadways were separated by a narrow strip of trees down the middle.In 1907 theLong Island Motor Parkwayopened, and roughly 20% of it featured a semi-dual-carriageway design. The New York CityBelt Parkwaysystem, which was built between 1907 and 1934, also pioneered the same design. However the majority of it featured concrete or brick railings as lane dividers instead of grass medians.

In the year of 1924 the first Italianautostradawas opened running 55 km (34 mi) fromMilantoVarese.It featured a broad road bed and did not feature lane dividers except near cities and through the mountains.

The London end of theGreat West Roadbecame Britain's first dual carriageway when it was opened in 1925 by KingGeorge V.

In 1927 the Rome bypass was opened. It ran 92 km (57 mi) bypassing Rome to the east. Almost the entire length featured a dual-carriageway design. In the early 1930s, it was extended southward all the way toNaplesand northward to Florence. Most of the original routing was destroyed by the Allies in World War II.

By 1930 several US and European cities had built dual-carriageway highways, mostly to control traffic jams and/or to provide bypass routes for traffic.

In 1932 the first Germanautobahnopened between Cologne and Bonn. It ran 21 km (13 mi) and became a precedent for future highways. Although it, like the firstautostrada,did not feature a dual-carriageway design, it inspired the mass construction of future high-speed roadways.

During the 1930s, Germany, Italy, andthe Soviet Unionbegan construction of a network of dual carriageway expressways. By 1942, Germany had over 3,200 km (2,000 mi) of dual carriageway roads, Italy had nearly 1,300 km (810 mi), and the Soviet Union had 400 km (250 mi).

What may have been the world's first long-distance intercity dual carriageway/freeway was theQueen Elizabeth WayinSouthern Ontarioin Canada, initially linking the large cities ofTorontoandHamiltontogether by 1939, with construction on this stretch of the present-day Queen Elizabeth Way beginning in 1936 as "Middle Road". It was gradually upgraded to a freeway from the 1950s to 1970s.

Opened to traffic in 1940, the 160-mile-long (260 km)Pennsylvania Turnpikewas the first rural dual carriageway built in the United States. By 1955 several states had built dual carriageway freeways and turnpikes and in 1957 theInterstate Highway Systembegan. Completed in 1994, the major highway system links all the major cities of the United States.

European implementations

Diagram of types of road in the UK

United Kingdom

In the UK, although the term "dual carriageway" applies to any road with physically separated lanes, it is frequently used as a descriptive term formajor routesbuilt in this style. Such major dual carriageways usually have two lanes of traffic in each direction, with the lane nearest the centre being reserved for overtaking.Occasionally dual carriageways have only one lane in each direction, or more than two lanes each way (sometimes to permit easier overtaking of slower uphill traffic). Different speed limits apply on dual carriageway sections from those that apply onsingle carriagewaysections of the same class of road, except in cities and built-up areas where the dual carriageway is more of a safety measure.

Sign informing motorists of an upcoming section of dual carriageway inSeacroft,Leeds

When first constructed, many dual carriageways—including the first motorways—had no crash- or other barriers in the central reservation. In the event of congestion, or if a driver missed their exit, some drivers made U-turns onto the opposite carriageway; many accidents were caused as a result of their misjudging the speed of approaching traffic on the other carriageway when doing so.

The majority of dual carriageway roads now have barriers. Some are heavy concrete obstructions which can bounce a vehicle back into the path of other traffic; others are made from steel ropes mounted on moderately weak posts, where the rope cuts into the vehicle body to slow the vehicle while keeping it against the barrier until it has stopped. Often on urban dual carriageways where the road has been converted from a four-lane single carriageway the central reservation will not be substantial: often just a small steel divider to save space.

Turning right (that is, across the line of traffic heading in the opposite direction) is usually permitted only at specific locations. Often the driver will be required to turn left (away from the dual carriageway) in order to loop around to an access road that permits crossing the major road.Roundaboutson dual carriageways are relatively common, especially in cities or where the cost of a grade-separated junction would be prohibitive. Where space is even more limited, intersections may be controlled by traffic lights. Smaller residential roads adjoining urban dual carriageways may be blocked off at one end to limit the number of junctions on the dual carriageway; often other roads will pass over or under the dual carriageway without an intersection.

A dual carriageway with grade-separated junctions and which meets other requirements may be upgraded tomotorwaystandard, denoted by an(M)added after the road number (e.g. "A1(M)"or"A38(M)"). Unlike in Ireland, there was no official terminology for 'high-quality dual carriageways' until April 2015, when in England a new standard was set to designate certain high-quality routes formally as" Expressways ".Many roads such as theA1,theA14,theA19and theA42are built to a high quality, with grade-separated junctions, full barriers at roadside and central reservations and, in some cases, three lanes of traffic. They may still fall short of motorway standard in terms of hard shoulders, the height of overpasses or the quality of intersecting junctions.

Speed limits

Thenational speed limitapplies on dual carriageways (unless it is in a 'built-up area', or a lower limit is posted), which is as follows:

National speed limits on dual carriageways in the UK

Type of vehicle	Speed limit
Car,motorcycleor a car-basedvanup to 2tonnes	70 mph (113 km/h)
Car withcaravanor trailer	60 mph (97 km/h)
Busorcoachup to 12 m long	60 mph (97 km/h)
Goods vehicle up to 7.5 t	60 mph (97 km/h)
Goods vehicle over 7.5 t	60 mph (97 km/h) (England and Wales) 50 mph (80 km/h) (Scotland and Northern Ireland)

A dual carriageway in a built up area will have a statutory speed limit of 30 mph (48 km/h) unless otherwise sign-posted. It is common for such urban dual carriageways to have an increased speed limit of 40 mph (64 km/h). A road deemed to be in a built up area is indicated by the presence of street lights; on lit dual carriageways that are not considered to be in a built-up area, the speed limit will be clarified with intermittent signs.

Ireland

A typical modern Irish dual carriageway (opened 2004) along theN11,south ofNewtownmountkennedy.On motorways, the yellow hard shoulder markings are unbroken.

An example of a 2+2 dual-carriageway in Ireland. This type is similar to many found in the UK.

Although in Ireland the term dual carriageway technically applies to any road with physically separated lanes, it is usually used only to refer to those route sections that do not have amotorwaydesignation. Most often it isnational roads(roads with a route number prefix ofN;e.g.N8) that are built as or upgraded to dual carriageway. A number of non-national roads (for example,regional roads) are dual carriageway, for example in urban areas near or in cities, or where the road was part of a national route.

Dual carriageways of this class differ from motorways in a number of ways. The hard shoulder is demarcated with a dashed yellow line (as opposed to an unbroken yellow line on motorways). The standard speed limit of 100 km/h (62 mph) for national routes usually applies (by default the limit is 80 km/h (50 mph) for non-national roads, even if dual carriageway). Local authorities have the power to apply a limit of up to 120 km/h (75 mph) as used on most motorways (TheHigh Quality Dual Carriagewaysection of theN1between the end of the M1 and the border withNorthern Irelandand the N25/N22 Ballincollig Bypass in Cork are the only route sections with such special limits).

Traffic lights and junctions are permitted at grade on dual carriageways. For older sections of dual carriageway, this has resulted in fewer flyover junctions. Newer dual carriageway sections are usually near motorway standard, with grade-separated junctions, but may not be designated as motorways due to the need to preserve access to adjoining property or to the absence of a non-motorway alternative route. Also, dual carriageways that are not motorway classified do not need to be equipped with emergency phones.

Motorway restrictions only apply to motorway sections, rather than all dual carriageway sections of national roads (these are signposted with theNprefix on the route number, rather thanM). Somenational secondary roads,andregional roadsin particular often have houses, schools and other developments fronting on to them. Less importantnational primary roads,and older sections not yet upgraded may also feature such developments built before the introduction the Irish Planning system in 1964. Today Irish planning policy prohibits such development on National Primary or National Secondary roads where the speed limit exceeds 60 km/h (37 mph).

This policy results from concerns expressed by the National Roads Authority. Alocal authorityis not obliged to implement this policy and can disregard this policy at its own discretion. This would usually only occur in exceptional circumstances or where planners are overruled by elected councillors using section 140 of the Local Government Act 2001. Accordingly,hard shouldersare included wherever feasible to provide for the resulting pedestrian and cyclist traffic, and are present on much of the national route network. These hard shoulders may also be used as running lanes by motorised traffic under certain conditions.

Until 2005, many motorways and dual carriageways in Ireland did not have crash barriers in the central reservation, the policy being to use a wider median instead. Crash barriers are now mandatory for such routes, and wire cabling or full crash barriers (depending on whether or not the route is a motorway, and median width) have been fitted to existing routes.

Between 2000 and 2010, three major types of dual carriageway were built on national road schemes in Ireland:

• High Quality Dual Carriageways(HQDC) – these were built mainly on the major inter-urban routes, to fullmotorwaystandard but without motorway regulations. The Roads Act, 2007 allows for these roads to be redesignated as motorways by ministerial order. Many of the sections of HQDC on the major inter-urban routes have been redesignated as motorways and full motorway regulations were applied when the redesignations came into effect.
• Standard dual carriageway of the traditional type was mainly used for schemes on theN11 road,theN18 roadand theN25 road.Plans for this type of dual carriageway on theN20 roadhave been superseded by newer plans to build a motorway, the M20, to replace most of this route. Traditionally this type of dual-carriageway had a mixture of at grade junctions (includingroundabouts), grade separated junctions, and median crossings. Nowadays they are similar to HQDCs, but minor at grade exits—generally left turn only—are allowed and the design speed (by Irish standards) is only 100 km/h. Median crossings and roundabouts are no longer generally found on these schemes. An example of a standard dual carriageway scheme, opened in 2006, is theEnnisbypass although this road has grade separated junctions and no median crossings. This route was upgraded to motorway status in 2009.
• 2+2 roads—officially these roads are designated asType 2dual carriageways by theNational Roads Authority(NRA). They were created by widening existing roads or building new roads, and have two lanes in each direction with a steelcable barrierin the middle but no hard shoulder. Most junctions areat-grade.With the exception of the restricted median width and the lack of lay-bys, this type of dual carriageway is similar to many dual carriageways found inthe UK.The first 2+2 scheme was the N4DromodRooskybypass, opened on 7 December 2007.
• 2+1 roads—officially these roads are designated asType 3dual carriageways by the NRA. They have two lanes in one direction and one lane in the other, alternating every few kilometres, and usually separated with a steel cable barrier. Sections of 2+1 road were built on the N20 and theN2.In July 2007, the NRA announced that it would no longer build 2+1 roads and 2+2 roads were built instead.

Germany

B6 nearHarlingerode

In Germany the termAutobahnähnliche Straße(motorway-like road) refers to roads that are similar to Germanautobahnin grade-separation and signage. Most of them are designated asKraftfahrstraßen(expressways), which means that the roads allow higher speed traffic than is common on other roads. This in turn requires them to have dual carriageways in most cases. An exception is the2+1 road systemin some rural areas; these roads are also referred to as expressways.

Autobahnähnliche Straßenmostly are colloquially referred to asgelbe Autobahn(yellow motorway) because they have the same technical standard as theAutobahnbut have black on yellow signs instead of the white on blue signs used on theAutobahnmotorway network. These are generally high-speed arterial roads in larger cities or important roads within a federal state that do not connect to major cities, so that they do not fall under the federal budget for theAutobahnnetwork. The federal roadBundesstraße 27is an example where about half of its length is upgraded to a high speed motorway standard. On the basis of their structure these roads have, comparable to the Germanautobahn,the legal foundation that no default speed limit exists (design speed 130 km/h), although the standard advisory speed limit (German:Richtgeschwindigkeit) still exists. Nevertheless, expressways are often given speed limit signs.

Exit signs.

At the moment some (blue) motorways have been taken out of theAutobahnnetwork programme but still have the blue signs (e. g. theB 59,formerlyA 540nearGrevenbroich); and on the other hand some former non-Autobahn(yellow) motorways have been added toAutobahnbudgeting but the signs have not been changed either (e. g. parts of theB 6,nowA 36in the north of theHarzhighland area in Saxony-Anhalt). Motorways that are neither in theautobahnnetwork nor in theBundesstraßenetwork are given black on white signs, following the same sign code as high-speed dual carriageways—this is mostly seen on urban trunk roads.

Italy

Main article:Roads in Italy

The stretch fromGrossetotoLivornoof theStrada statale 1 Via Aureliais classified asstrada extraurbana principale.

Via Cristoforo ColomboatPorta ArdeatinainRome,classified asstrada urbana di scorrimento.

Italian Highway Code (Codice della strada) divides dual carriageways into three different classifications:

• strada extraurbana principale(meaningmain highway) ortype-B road:a road with separate carriageways, at least two lanes for each direction, paved shoulder on the right and no cross-traffic. This type of road is quite similar to anautostradaortype-A road(Italian official name formotorwaysorfreeways), but its building standards are lower. Access limitations and drive behaviour on type-B roads are the same as the motorways (no pedestrians, bicycles and other slow vehicles), as well as the signage (except for the background color, that is blue instead of green). Speed limits on type-B roads are up to 110 km/h (70 mph). Type-B roads are always toll-free.
• strada extraurbana secondaria(meaningsecondary road) ortype-C road.This category contains all the roads in non-urban context that are neitherautostrada(type A) norstrada extraurbana principale(type B). This means that a dual carriageway that may not be classified as type-B road, since it does not meet such quality standards, belongs to this category. For type-C roads, there are neither special signage nor access restrictions, unless a specific sign is placed. The speed limit is 90 km/h (55 mph), on both single and dual carriageways.
• strada urbana di scorrimento(meaningurban expressway) ortype-D road:a road in urban context, with separate carriageways, and at least two lanes for each direction. At-level junctions with smaller roads, regulated by traffic lights, are allowed as well asroundabouts.Unless a prohibition sign is placed, there are not access restrictions. Speed limits on this type of road are up to 70 km/h (45 mph).

Italian type-B and type-C roads do not follow a specific numbering criterion. They may be numbered asStrade Statali(SS; "state roads" ),Strade Regionali(SR; "regional roads" ),Strade Provinciali(SP; "provincial roads" ) orStrade Comunali(SC; "municipal roads" ).

Spain

Theautovía A-5outsideMadrid.It is just a duplication of the old National Road 5.

Main article:Autovía

The Spanish word for dual carriageway isautovía(literallyautoway). All of them are government-owned and not tolled.

First-generation autovías, built in the 1980s and early 1990s, were just duplications in parallel of existing roads, as shown in the photograph. Modern autovías are two carriageways built from scratch, leaving the old road they replace as an alternative route for pedestrians, bicycles and other non-motorized vehicles.

Private properties may have direct access to an autovía, as well asbus stopsandgas stationsin the hard shoulders. Acontrolled-access highway(motorway) in Spain is referred to asautopista(literallyautotrack). They may be operated by private companies and be tolled. The two major accesses to Spain from France,AP-7intoCataloniaandAP-8into theBasque Country,are autopistas. In comparison, the prime road between Spain and Portugal is the photographedautovía A-5.In both autopistas and autovías, the genericspeed limitis 120 km/h (75 mph), minimum speed is 60 km/h (37 mph), driving backwards is strictly prohibited, and they shall not have at-grade junctions.

Croatia

Dual carriageways or expressways inCroatia(Croatian:brza cesta) are non-tolledroads with 2 or more lanes in each direction, but withoutemergency lanes.Themain motorways in Croatiaare also dual carriageways, but they have emergency lanes and tolls.

Many bypasses and beltways of smaller cities in Croatia have been recently constructed or planned as dual carriageways. All dual carriageways in Croatia house a central median, usually fitted with guardrails.

The most heavily used expressways in Croatia is theD10 road,connecting capitalZagrebtoVrbovecandKriževci.

See also:Highways in Croatia § List of expressways

Other regional implementations

United States

A divided highway (U.S. Route 52) in the state of Indiana

Savery Avenue inCarver, Massachusettswas the first divided highway in the U.S.

In the United States, this type of road may be called a divided highway, boulevard, parkway, expressway, freeway, or interstate, and has a grassy median orJersey barrierseparating the traffic directions. With few exceptions, all roads in the federally fundedInterstate Highway Systemare fully controlled access divided highways known asfreeways.A broader definition,expressways,includes both freeways and partial limited-access divided highways, and "expressway" is often used specifically to refer to the latter.

United States Numbered Highways,state highways and other locally maintained highways may also be divided.Speed limitson ruraldivided highwaysrange from 65 to 75 miles per hour (105 to 121 km/h), with some portions as high as 80 miles per hour (130 km/h). One privately run toll road in Texas, SH 130, has the highest speed limit in the United States at 85 miles per hour (137 km/h). Urban divided highways which areat gradeand typically have much lower speed limits are sometimes calledboulevards.

In keeping with theU.S. Department of Transportation'sManual on Uniform Traffic Control Devices(MUTCD), since the early 1970s all divided highways are striped by color to show the direction of traffic flow. Two-way undivided roads have an amber center line, with a broken line indicating passing zones and a solid line indicating no passing zones and solid white baseline shoulder stripes.

On undivided roads with more than one lane in each direction, the center is normally marked with a double solid line. The double solid stripe denotes that it is illegal topasson the other side of the center line. Multilane one-way carriageways use broken white lines between lanes; the median-side baseline is solid amber, and the right sideline is solid white.

Frequently in the U.S. the two carriageways are separated by some distance (wide medians with small forests or even hills in them), but drivers can always tell whether the roadway is two-way or one-way—and, if one-way, the direction in which the traffic flows—by looking at the striping coloration. For an example, see inset showingU.S. Route 52nearLafayette, Indiana.

Some divided highways have been turned into undivided highways by widening the lanes of an existing road (for example US Highway 33 betweenElkhartandGoshenin northern Indiana).

Canada

Highway 401,in Ontario, Canada, uses a divided highway,collector / express systemto separate local traffic from longer-distance travellers.

Like other countries, there are several types of divided highways; fully controlled-access divided routes with interchanges (commonly known as "freeways" in the United States, Australia, and regionally within Canada),expresswaysthat often include a mix of interchanges and traffic signals, and divided arterial roads that are almost entirely stop-controlled.Unlikesome other countries, divided dual carriageways in Canada are seldom equipped withtraffic circles,roundabouts, or rotaries as alternatives to stoplights.

In Canada, the term "divided highway" is used for this type of road, and the segment between the roadways is referred to as a "median". There may be gaps in the median strip of a partially controlled-access road to allow turning and crossing. More informally, a divided highway may be referred to as "twinned". This stems from the practice of "twinning" an existing two-lane highway and converting it into a divided highway. Such highways in southern Ontario, southern Quebec, and parts of Atlantic Canada usually feature full controlled-access with interchanges where robust federal and provincial funding has made such freeways possible. However, due to a lack of funding elsewhere, partial controlled-access "expressways" and limited-mobility divided arterial roads are more common in the western provinces where there are no specially numbered systems of freeways.

On some portions ofOntario's400-series highwaynetwork, the median may be either steelguardrailor anOntario tall-wallbarrier rather than an unpaved strip, particularly in urban areas.

Some partial limited-access divided highways such as theHanlon ParkwayandBlack Creek Drivehave stop-controlledat-grade intersectionsand private entrances, but have sufficient right-of-way to convert them to full freeways with interchanges if traffic warrants. There are alsoRIRO expressways,such asHighway 11and a portion ofHighway 35,which are not full freeways since they allow access to existing properties, but traffic speeds are faster than regular roads due to a median barrier preventing left turns (motorists have to use a"turnabout"overpass to access exits on the opposing direction).Speed limits in Canadaare usually 80 to 90 km/h on signalized divided highways and 100 to 120 km/h on freeways.

Australia

TheEastern Freeway,a typical dual carriageway inMelbourne,Australia

In Australia, dual carriageways are referred to in some regions as divided roads, though there is no official terminology. Each state's road agency has its own definition of what constitutes a 'motorway/freeway' standard divided road. Most states only declare a divided road as a 'motorway' or 'freeway' if access is completelycontrolled.Speed limits are usually 100 km/h or 110 km/h.

VicRoads,the agency responsible for highways in the state ofVictoria,has often declared rurallimited-accessdual carriageways as freeways.Furthermore, VicRoads applies theMdesignation to these roads in alpha-numeric route numbers, where most other states will only do so if access is completely controlled.

Dual carriageways exist in and around the major capital cities however there are currently several road projects under construction have now been completed, creating roughly 2,000 kilometres of continuous dual carriageway fromGeelongin Victoria toCurrainSouth East Queenslandexcept for one 14 kilometre section of thePacific HighwaythroughCoffs Harbour.

Since 2013, it has been possible to drive between Australia's two largest cities (SydneyandMelbourne) on a continuous dual carriageway. When it was completed, theHume Highwayduplication became the first major interstate duplicated motorway.

Brazil

Road system in Brazil, with divided highways highlighted in red.

The country has about 17,000 km (10,563 mi) of divided highways, 6,300 km (3,915 mi) only in theState of São Paulo.Currently it's possible to travel fromRio Grande,in the extreme south of the country, toBrasília(2,580 km (1,603 mi)) orCasimiro de Abreu,in the state ofRio de Janeiro(2,045 km (1,271 mi)), only on divided highways.

The first highway to be transformed into a divided highway in Brazil wasRodovia Presidente Dutra,which is part ofBR-116.In the stretch between the 2 largest cities in the country,São PauloandRio de Janeiro,the highway was duplicated in 1967.

• 
  BR-116in the state of São Paulo
• 
  BR-101in the state of Santa Catarina
• 
  BR-381in the state of Minas Gerais
• 
  BR-050in the state of São Paulo

Argentina

Duplicate Highways of Argentina, in red

Argentina has approximately 2,800 km of divided highways. It's 50 km on theRuta 1,which connectsBuenos AirestoLa Plata;157 km onRuta 3,between Buenos Aires/San Miguel del MonteandPuerto Madryn/Trelew;485 km on theRuta 7,which connects Buenos Aires toSantiago,Chile;700 km onRuta 9,which connects Buenos Aires,RosarioandCórdoba;and 589 km on theRuta 14,which connects Buenos Aires toPaso de los Libres,on the border with Brazil.

• 
  Ruta 9 / 14, in Zarate
• 
  Ruta 1 in Buenos Aires

Chile

Duplicate Highways of Chile, in red

Chile's main route isRoute 5(Pan-American Highway). FromPuerto MontttoCaldera(1,900 kilometres or 1,200 miles) it's a divided highway. Chile doesn't just expand the highway after the city of Caldera because in this part of the country, it enters theAtacama Desert,where there is low traffic of vehicles. TheRoute 68,(110 kilometres or 68 miles) connectingSantiagotoValparaíso,is also a divided highway. In 2020, Chile had 3,347 km (2,080 mi) of duplicated highways, the second largest network in South America, after Brazil.

• 
  Ruta 5 in Santiago
• 
  Ruta 68 going to Valparaiso

China

The best examples of dual carriageways inmainland Chinacan be seen on theChina National Highways.On some routes, such asChina National Highway 106,there is a central reservation.

Thailand

Most Highways in Thailand aresingle carriagewayswith ahard shoulder.Dual carriageways have frequentu-turnlanes and intersections slowing down traffic. Coupled with the increase in the number of vehicles and the demand for a limited-accessmotorway,the Thai Government issued a Cabinet resolution in 1997 detailing the motorway construction master plan.Some upgraded sections of highway are being turned into a "motorway", while other motorways are not being built from highway sections.

• 
  Thailand Route 12 single carriageway with a hard shoulder inPhetchabun
• 
  Thailand Route 22 dual carriageway with u-turn inSakhon Nakhon
• 
  AH1,AH2andThailand Route 32inAyutthaya

Turkey

Turkey has 28,986 km of dual carriageway as January 2023.Speed limit changes, but normally 110 km/h is the limit of state road (e.g.D 100). Turkey has 3,633 kmof motorways. The minimum speed limit on the Turkish motorways is 40 km/h and the maximum is 140 km/h. Almost all of the network is 6 lanes (3 in each direction) wide and illuminated. Some parts converted from uncontrolled access dual carriageways are 4 lanes (2 in each direction) wide. The motorway sign in Turkey is green and uses Highway Gothic typeface.

• 
  Turkish state road D 750 at Konya junction.Toros Mountainsin the background
• 
  Otoyol 2nearAli Sami Yen Stadium,Istanbul

India

India has many dual carriageways. Many of them are under the control ofNational Highways Authority of Indiaand some of them are under state and local authorities.National Highway (India)andState highways in Indiacomes under these type of roads, likeGolden Quadrilateraland major arterial roads.

• 
  Flyover in New Delhi Heading Towards Airport
• 
  Delhi Noida Direct Flyway

Pakistan

Hyderabad–Mirpurkhas Dual Carriageway was constructed in 2012 on which the work started in 2009. It was under the Special Directives of President Asif Ali Zardari and Chief Minister Sindh Syed Qaim Ali Shah the first dual carriageway constructed under the Public Private Plan it extends up to 60 km.

N-55 and N-5 are dual carriageways.

Philippines

PrincipalPhilippineExpressways,Metro ManilaRoads and Avenues inMetro Cebuare examples of dual carriageways in thePhilippines.STAR Tollway,NLEX,SCTEXandSLEXhave portions with central reservations. Some highways inside Metro Manila have underpasses, tunnels and flyovers.

• 
  A portion of theNorth Luzon ExpresswayinBulacan,Philippines,before the integration with SCTEX
• 
  A portion ofSubic–Clark–Tarlac ExpresswayinBataan

Singapore

ThePan Island ExpresswayinSingapore.

A high proportion of roads inSingaporeare dual carriageways with central reservations; examples include Clementi Road, Commonwealth Avenue and Holland Road. Often there might be railings erected on the central reservation to prevent pedestrians from dashing across the road. These usually have traffic lights along the way but flyovers and road tunnels (or 'underpasses') can be built to minimize the use of traffic lights; for example, at the Holland Road-Farrer Road-Queensway junction there are three levels of roads. Before the 1980s, roundabouts were popular, but since then many have been changed to traffic-light controlled junctions.

These dual carriageways are to be distinguished from motorways, known in Singapore as expressways such as thePan-Island Expressway(PIE) andAyer Rajah Expressway(AYE) where no traffic lights are used.

Malaysia

TheNorth–South Expresswayin the west coast ofPeninsular Malaysia

Known dual carriageways in Malaysia include theNorth–South Expressway(the main motorway system in PeninsularMalaysia), the East Coast Expressway (serving the Peninsular east coast), theFederal Highway(servingKuala Lumpur), theAMJ Highway(linkingMalaccaand theJohoreantownsMuarandBatu Pahat) and the under constructPan Borneo HighwayofSabahandSarawak.Some highways insideKlang Valleyhave underpasses, tunnels and flyovers e.g.SMART Tunnel(mostly tunnel section) andAmpang–Kuala Lumpur Elevated Highway(mostly elevated section). Apart from major motorways and expressways, treelined dual carriageways also pass through most urban areas.

See also

• 2+1 road
• Carriageway
• Controlled-access highway(also known asmotorway,freewayorexpressway)
• Limited-access road(also known asexpresswayorhigh-quality dual carriageway)
• Single carriageway

External links

• Department for Transport.Speed: Know your limits(PDF)