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{{About|a route, thoroughfare or way that supports travel by a means of conveyance|a place outside a port |
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a ship can lie at anchor|Roadstead|public roads|Highway|other routes|Thoroughfare|other uses|Road (disambiguation)}} |
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{{Public Infrastructure |image=]}} |
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A '''road''' is a ], route, or way on land between two ] that has been ] or otherwise improved to allow travel by foot or some form of ], including a ], cart, bicycle, or horse. |
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Roads consist of one or two ]s (]: carriageways), each with one or more ]s and any associated ]s (British English: pavement) and ]s. There is often a ]. Other names for roads include parkways, avenues, freeways, tollways, interstates, highways, or primary, secondary, and tertiary local roads. |
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==Definitions== |
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Historically many roads were simply recognizable routes without any formal construction or maintenance.<ref name="Ways_of_the_World "/> |
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The ] (OECD) defines a road as "a line of communication (travelled way) using a stabilized base other than rails or air strips open to public traffic, primarily for the use of road motor vehicles running on their own wheels", which includes "bridges, tunnels, supporting structures, junctions, crossings, interchanges, and toll roads, but not cycle paths".<ref> |
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{{cite web |url= http://stats.oecd.org/glossary/detail.asp?ID=4005 |publisher= OECD |title= Glossary of Statistical Terms |publication-date= 2004-02-26 |accessdate= 2007-07-17}}</ref> |
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The ], ] and ] ''Glossary for Transport Statistics Illustrated'' defines a road as a "Line of communication (travelled way) open to public traffic, primarily for the use of road motor vehicles, using a stabilized base other than rails or air strips. Included are paved roads and other roads with a stabilized base, e.g. gravel roads. Roads also cover streets, bridges, tunnels, supporting structures, junctions, crossings and interchanges. Toll roads are also included. Excluded are dedicated cycle lanes."<ref name="unece.org">http://www.unece.org/fileadmin/DAM/trans/main/wp6/pdfdocs/glossen4.pdf</ref> |
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The 1968 ] defines a road as the entire surface of any way or street open to public traffic.<ref>http://www.unece.org/fileadmin/DAM/trans/conventn/crt1968e.pdf</ref> |
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In urban areas roads may diverge through a city or village and be named as streets, serving a dual function as urban space ] and route.<ref Name="difference_between_road_and_street">{{cite web |title= What is the difference between a road and a street? |work= Word FAQ |publisher= Dictionary.com (Lexico Publishing Group, LLC) |year= 2007 |url= http://dictionary.reference.com/help/faq/language/d01.html |accessdate= 2007-03-24 }}</ref> Modern roads are normally smoothed, paved, or otherwise prepared to allow easy travel.<ref Name="RoadInfrastructureStrategicFrameworkforSouthAfrica">{{cite web |title=Road Infrastructure Strategic Framework for South Africa; A Discussion Document |publisher=National Department of Transport (South Africa) |url=http://www.transport.gov.za/library/docs/rifsa/infor.html |accessdate=2007-03-24 |deadurl=yes |archiveurl=https://web.archive.org/web/20070927063243/http://www.transport.gov.za/library/docs/rifsa/infor.html |archivedate=2007-09-27 |df= }}</ref> |
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===United Kingdom=== |
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In the United Kingdom '']'' details rules for "road users", but there is some ambiguity between the terms ''highway'' and ''road''.<ref>{{cite web|url=http://www.direct.gov.uk/en/TravelAndTransport/Highwaycode/DG_069869|title=The road user and the law}}</ref> For the purposes of the ], ], which covers ] but not ] or ], ''road'' is "any length of highway or of any other road to which the public has access, and includes bridges over which a road passes".<ref>{{cite web|url=http://www.legislation.gov.uk/ukpga/1984/27/section/142|title=Road Traffic Regulation Act 1984 – 142 General interpretation of Act |work=Legislation|quote="road" – (a) in England and Wales, means any length of highway or of any other road to which the public has access, and includes bridges over which a road passes, and (b) in Scotland, has the same meaning as in the Roads (Scotland) Act 1984}}</ref> This includes footpaths, bridleways and cycle tracks, and also road and driveways on private land and many car parks.<ref name=Direct>{{cite web|url=http://www.direct.gov.uk/en/TravelAndTransport/Highwaycode/DG_069869|title=The road user and the law|quote=Most of the provisions apply on all roads throughout Great Britain, although there are some exceptions.}}</ref> ], a ], is payable on some vehicles used on the public road.<ref name=Direct/> |
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The definition of a road depends on the definition of a highway; there is no formal definition for a highway in the relevant Act. A 1984 ruling said "the land over which a public right of way exists is known as a highway; and although most highways have been made up into roads, and most easements of way exist over footpaths, the presence or absence of a made road has nothing to do with the distinction.<ref>Reference listed says 1984, This description is used in several rules going back to at least 1975, The law of real property; Stevens, 1975; Authors – Robert Megarry, Sir Robert Edgar Megarry, Sir William Wade</ref><ref>{{cite web|url=http://www.hrothgar.co.uk/WebCases/hol/reports/07/44.htm|title=Judgment – Director of Public Prosecutions v. Jones and Another (On Appeal from a Divisional Court of the Queen's Bench Division)|quote=The land over which a public right of way exists is known as a highway; and although most highways have been made up into roads, and most easements of way exist over footpaths, the presence or absence of a made road has nothing to do with the distinction. There may be a highway over a footpath, while a well-made road may be subject only to an easement of way, or may exist only for the landowner's benefit and be subject to no easement at all|deadurl=yes|archiveurl=https://web.archive.org/web/20100403093123/http://www.hrothgar.co.uk/WebCases/hol/reports/07/44.htm|archivedate=2010-04-03|df=}}</ref> Another legal view is that while a highway historically included ]s, ]s, driftways, etc., it can now be used to mean those ways that allow the movement of motor-vehicles, and the term '']'' can be used to cover the wider usage.<ref>{{cite web|url=http://www.4-5.co.uk/practiceareas/index.cfm?id=486|title=Local government law – Highway law |quote=Historically, a highway comprehended any path in which members of the public had the right to pass and re-pass without let or hindrance. The term embraced footpaths, bridleways, driftways and so forth. The advent of the motor vehicle and its peculiar requirements has seen increasing distinctions between paths over which walkers and riders have a right of way and those ways that are predominantly used by motor vehicles. The former may be usefully termed "rights of way" (and are the subject of a separate entry in this web) and the latter may be termed "highways."}}</ref> |
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===United States=== |
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In the United States, laws distinguish between ''public roads'', which are open to public use, and ''private roads'', which are privately controlled.<ref>{{cite web|url=http://legal-dictionary.thefreedictionary.com/road|title=road|work=The Free Dictionary|quote=ROAD. A passage through the country for the use of the people. 3 Yeates, 421. 2. Roads are public or private. Public roads are laid out by public authority, or dedicated by individuals to public use. The public have the use of such roads, but the owner of the land over which they are made and the owners of land bounded on the highway, have, prima facie, a fee in such highway, ad medium filum viae, subject to the easement in favor of the public... Private roads are, such as are used for private individuals only, and are not wanted for the public generally. }}</ref> |
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==History== |
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{{Main|History of road transport}} |
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] called "the best road in the world" by ]<ref Name="TopGear">{{cite web |title= Top gear |publisher= BBC |year= 2010 |url= https://www.youtube.com/watch?v=pLxP_VHe0gg#t=34 |accessdate= 2010-09-08 }}</ref>]] |
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], with a ] surface and ]]] |
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]]] |
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], Sweden |
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]] |
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The assertion that the first pathways were the ]s made by animals has not been universally accepted; in many cases animals do not follow constant paths.<ref Name="Ways_of_the_World">{{cite book |last= Lay |first= Maxwell G |title= Ways of the World: A History of the World's Roads and of the Vehicles that Used Them |publisher= Rutgers University Press |year= 1992 |url= https://books.google.com/?id=flvS-nJga8QC&pg=PR3&lpg=PR3&dq=%22Ways+of+the+world%22+Rutgers+University+Press,+New+Brunswick |isbn= 0-8135-2691-4 }}</ref> Others believe that some roads originated from following animal trails.<ref>{{cite book |first1=D. |last1=Helbing |first2=P. |last2=Molnär |first3=I.J. |last3= Farkas |first4=K. |last4=Bolay |title= Environment and Planning B: Planning and Design 2001, volume 28 (Self-organizing pedestrian movement) |page= 376 |url= http://pedsim.elte.hu/pdf/envplanb.pdf |doi= 10.1068/b2697 |format=PDF}}</ref><ref Name="wheathampstead">{{cite web |title= Marshalls Heath Nature Reserve |work= History |publisher= wheathampstead.net |date= 24 February 2003 |url= http://www.wheathampstead.net/mh/history.htm |accessdate= 2007-04-28 }}</ref> The ] is given as an example of this type of road origination, where human and animal both selected the same natural line.<ref Name="Icknield">{{cite web |title= The Icknield Way Path |publisher= Icknield Way Association |year= 2004 |url= http://www.icknieldwaypath.co.uk/ |accessdate= 2007-04-29 }}</ref> By about 10,000 BC, rough roads/pathways were used by human travelers.<ref name="Ways_of_the_World"/> |
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* The world's oldest known paved road was constructed in Egypt some time between 2600 and 2200 BC.<ref> |
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{{cite news |url= https://www.nytimes.com/1994/05/08/world/world-s-oldest-paved-road-found-in-egypt.html |author= John Noble Wildord |title= World's Oldest Paved Road Found in Egypt |newspaper=] |publication-date= 1994-05-08 |accessdate= 2012-02-11}} |
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</ref> |
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* ]- paved streets are found in the city of ] in the Middle East dating back to 4000 BC<ref name="Ways_of_the_World"/> |
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* ] are found dating to 4000 BC in ], England.<ref name="Ways_of_the_World"/> |
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* The ], a ] causeway in England, is one of the oldest engineered roads discovered and the oldest timber trackway discovered in Northern Europe. Built in winter 3807 BC or spring 3806 BC, ] enabled very precise dating. It was claimed to be the oldest road in the world<ref Name="Current_Archaeology_172">{{cite web |title= The Somerset Levels (the oldest timber trackway discovered in Northern Europe) |work= Current Archaeology 172 |publisher= Current Archaeology |date=February 2001 |url= http://www.archaeology.co.uk/ca/issues/ca172/ca172.htm |accessdate= 2007-03-25 |archiveurl= https://web.archive.org/web/20070311003620/http://www.archaeology.co.uk/ca/issues/ca172/ca172.htm <!-- Bot retrieved archive --> |archivedate= 2007-03-11}}</ref><ref name="Highways:_The_Location"/> until the 2009 discovery of a 6,000-year-old trackway in ], London.<ref>{{cite web|url=http://archaeology.about.com/b/2009/08/15/oldest-trackway-found-in-plumstea.htm |title=Oldest Trackway found in Plumstead |publisher=Archaeology.about.com |date=2009-08-15 |accessdate=2013-08-14}}</ref><ref>{{cite web|url=http://www.eurekalert.org/pub_releases/2009-08/ucl-let081209.php |title=London's earliest timber structure found during Belmarsh prison dig |publisher=Eurekalert.org |date=2009-08-12 |accessdate=2013-08-14}}</ref> |
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* Brick-paved streets were used in India as early as 3000 BC.<ref name="Ways_of_the_World"/> |
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* In 500 BC, ] started an extensive road system for the ] (Persia), including the ], which was one of the finest highways of its time,<ref Name="RoyalRoad">{{cite web |last= Lendering |first= Jona |title= Royal Road |work= History of Iran |publisher= Iran Chamber of Society |url= http://www.iranchamber.com/history/achaemenids/royal_road.php |accessdate= 2007-04-09 }}</ref> connecting ] (the westernmost major city of the empire) to ]. The road remained in use after Roman times. The easternmost destinations of these road systems were in ] and ].<ref>{{cite book |first=John |last= Boederman|title=The Cambridge Ancient History|url=https://books.google.com/books?id=nNDpPqeDjo0C&pg=PA178|year=1997|publisher=Cambridge University Press|isbn=978-0-521-22804-6|page=178}}</ref> |
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* In ancient times, transport by river was far easier and faster than transport by road,<ref name="Highways:_The_Location"/> especially considering the cost of road construction and the difference in carrying capacity between ]s and river ]s. A hybrid of road transport and ship transport beginning in about 1740 is the ] in which the horse follows a cleared path along the river bank.<ref Name="horseboating">{{cite web |title= Horseboating |publisher= The Horseboating Society |url= http://www.horseboating.org.uk/ |accessdate= 2007-04-09 }}</ref><ref Name="HorseDrawnBoats">{{cite web |title= Horses and Canals 1760–1960 The people & the horses |work= Horse Drawn Boats |publisher= Canal Junction Ltd |url= http://www.canaljunction.com/craft/horsedrawn1.htm |accessdate= 2007-04-09 }}</ref> |
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* From about 312 BC, the ] built straight<ref name="Discovering_Roman_Technology"/> strong stone ]s throughout Europe and North Africa, in support of its military campaigns. At its peak the Roman Empire was connected by 29 major roads moving out from ] and covering 78,000 kilometers or 52,964 ]s of paved roads.<ref Name="Highways:_The_Location">{{cite book |last= O'Flaherty |first= Coleman A. |title= Highways: The Location, Design, Construction & Maintenance of Road Pavements |publisher= Elsevier |year= 2002 |url= https://books.google.com/?id=Ren4sWQ3jKkC&pg=PA1&lpg=PA1&dq=ancient+Egyptians+stone+paved+road++Great+Pyramid+in+about+3000+BC |isbn= 0-7506-5090-7 }}</ref> |
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* In the 8th century AD, many roads were built throughout the ]. The most sophisticated roads were those in ], which were paved with ]. Tar was derived from petroleum, accessed from ]s in the region, through the chemical process of ].<ref name=Ajram>{{cite book|author= Kasem Ajram|title=The Miracle of Islam Science|edition=2nd|publisher=Knowledge House Publishers|year=1992|isbn=0-911119-43-4}}</ref> |
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* The ] in Britain transferred responsibility for maintaining roads from government to local parishes.<ref name="Highways:_The_Location"/> This resulted in a poor and variable state of roads. To remedy this, the first of the "]" was established around 1706, to build good roads and collect tolls from passing vehicles. Eventually there were approximately 1,100 trusts in Britain and some 36,800 km (22,870 miles) of engineered roads.<ref name="Highways:_The_Location"/> The ] in Carmarthenshire and ] from 1839 to 1844 contributed to a ] that led to the demise of the system in 1844,<ref Name="Victorian_Powys">{{cite web |title= The Rebecca Riots |work= Rebecca and her daughters come to Rhayader |publisher= Victorian Powys for Schools |date= March 2002 |url= http://history.powys.org.uk/school1/rhayader/rebcmenu.shtml |accessdate= 2007-04-28 }}</ref> which coincided with the ]. |
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==Design== |
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Road design is part of ]. ] is designing a road for its environment in order to extend its longevity and reduce maintenance. The ] is used in many countries for the design of new asphalt roadsides. |
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==Road terminology== |
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;]: where a road slopes towards the outside of a bend, increasing the likelihood that vehicles travelling at speed will skid or topple. Usually only a temporary situation during road maintenance. |
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;]: the route of the road, defined as a series of horizontal tangents and curves. |
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;All-weather road: Unpaved road that is constructed of a material that does not create mud during rainfall. |
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;] |
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;]: A street that allows local vehicle traffic, but is prioritized for bicycles and other non-motorized travel |
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;]: an orange globe, lit at night, used to highlight a pedestrian crossing |
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;] |
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;]: Rigid posts that can be arranged in a line to close a road or path to vehicles above a certain width |
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;]: Highway over which the public have ] for vehicular and other kinds of traffic, but is used mainly as a footpath or bridleway |
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;]: Road that avoids or "bypasses" a built-up area, town, or village |
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;]: Section of a road with a carrying capacity substantially below that of other sections of the same road |
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;]: Non-reflective ] used on roads |
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;] (or crown): the slope of the ] downwards away from the centre of the road, so that surface water can flow freely to the edge of the carriageway, or on bends angling of the surface to lean traffic 'into the bend' reducing the chance of a skid. |
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;]: Another name for cross slope or camber |
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;]: Part of the road intended for the movement of road motor vehicles; the parts of the road which form a shoulder for the lower or upper layers of the road surface are not part of the roadway, nor are those parts of the road intended for the circulation of road vehicles which are not self-propelled or for the parking of vehicles.<ref name="unece.org"/> |
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;]: ] ] used on roads |
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;]: Sequence of tight serpentine curves (usually an S-shape curve or a bus stop) |
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;]: Road surface composed of a thin layer of crushed stone 'chips' and asphalt emulsion. It seals the surface and protects it from weather, but provides no structural strength. It is cheaper than ] or concrete. In the United States it is usually only used on low volume rural roads |
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;]: Road on the side of a cliff or mountain, with the ground rising on one side and falling away on the other |
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;]: The ] of the pavement, expressed as units of rise per unit of run, or as a percentage |
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;] (kerb): A raised edge at the side of the ]. |
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;]: (also kerb extension, bulb-out, nib, elephant ear, curb bulge and blister) ] measure, intended to slow the speed of traffic and increase driver awareness, particularly in built-up and residential ]. |
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;]: Part of a carriageway designated for cycles and distinguished from the rest of the carriageway by longitudinal road markings. Mopeds may also be allowed to use a cycle lane.<ref name="unece.org"/> |
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;]: Independent road or part of a road designated for cycles and sign-posted as such. A cycle track is separated from other roads or other parts of the same road by structural means. Mopeds may also be allowed to use the cycle track.<ref name="unece.org"/> |
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;]: cycling-friendly infrastructure integrated into the roadway or in its own right of way |
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;] |
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;]: a state road or county road that connects rural or agricultural areas to market towns. |
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;]: (literally "fork in the road") Type of ] where a road splits |
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;]: Longitudinal slope |
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;]: (UK) Unsurfaced road, may be so infrequently used that vegetation colonises freely, hence 'green'. Many green lanes are ancient routes that have existed for millennia. |
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;]: Prevents vehicles from veering off the road into oncoming traffic, crashing against solid objects or falling from a road. Also called a ] or ]. |
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;]: a drainage channel usually at the edge of the road or along a median. |
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;] (United States): System of Interstate and Defense Highways |
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;]: One of the longitudinal strips into which a carriageway is divisible, whether or not defined by longitudinal road markings, which is wide enough for one moving line of motor |
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vehicles other than motor cycles.<ref name="unece.org"/> |
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;] (Pullout, pull-off): A paved area beside a ] where ]s can stop temporarily to let another car pass. |
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;]: the hazard of stone chippings that have come loose |
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;]: On ] roads, including ]s, ]s and many ]s, the central reservation (]), median (]), median strip (North American English and ]), neutral ground or central nature strip (Australian English): Area that separates opposing ]s of traffic |
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;]: (Europe) (Freeways in the US, Special road in the UK) Road, specially designed and built for motor traffic, which does not serve properties bordering on it, with separate carriageways for traffic in two directions, with no crossings at the same level (road, railway, tramway track, or footpath) and sign-posted as a motorway and is reserved for specific categories of road motor vehicles.<ref name="unece.org"/> |
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;]: A relatively low level route through a range of mountains |
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;]: One of a series of numbered markers placed along a road, often at regular intervals, showing the distance to destinations. |
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;National Highway: Road built and maintained by a national authority. |
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;]: The road regarded as a geoconstruction. In the UK the term is ] and the pavement is a pedestrian walkway alongside the road. |
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;]: Designated point on a road where road marking or other means helps pedestrians cross safely |
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;]: (officially ''Pelicon crossing'') (UK) a PEdestrian LIght CONtrolled crossing. |
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;]: Highway owned and operated for profit by ] |
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;]: Road owned and maintained by a ], organization, or company rather than by a government |
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;]: the vertical alignment of a road, expressed as a series of grades, connected by parabolic curves. |
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;] |
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:A much safer design with a corner refuge island, a setback crossing of the pedestrians and ], generally between 1.5–7 metres of setback, a forward stop bar, which allows cyclists to stop for a ] well ahead of motor traffic who must stop behind the crosswalk. Separate signal staging or at least an advance green for cyclists and pedestrians is used to give cyclists and pedestrians no conflicts or a head start over traffic. The design makes a right turn on red, and sometimes left on red depending on the geometry of the intersection in question, possible in many cases, often without stopping.<ref>http://www.protectedintersection.com/wp-content/uploads/2014/02/Falbo_ProtectedIntersection_Transcript1.pdf</ref> |
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;]: Cyclists ideally have a protected bike lane on separated by a concrete median with splay ]s if possible, and have a protected bike lane width of at least 2 metres if possible (one way). In the Netherlands, most one way cycle paths are at least 2.5 metres wide.<ref name="bicycledutch.wordpress.com">https://bicycledutch.wordpress.com/2011/06/30/how-wide-is-a-dutch-cycle-path/</ref> |
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;]: Place where anyone has a right to come without being excluded because of ] conditions |
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;]: U.S. road that connects rural and agricultural areas to ]s |
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;]: Often assigned to identify a stretch of public roads – often dependent on the ], with numbers differentiating between ], motorways, ], etc. |
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;]: Process to reduce the harm (deaths, injuries, and property damage) that result from vehicle crashes on public roads |
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;]: Part or all of the road is occupied for work or maintenance |
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;]: Deviations from a true planar pavement surface, which affects vehicle suspension deflection, dynamic loading, ], surface drainage and winter operations. Roughness have wavelengths ranging from 500 mm up to some 40 m. The upper limit may be as high as 350 m when considering motion sickness aspects; motion sickness is generated by motion with down to 0.1 Hz frequency; in an ambulance car driving 35 m/s (126 km/h), waves with up to 350 m will excite motion sickness. |
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;]: a road junction where typically three or more roads are joined by a circular section of road. Traffic 'on the roundabout' has priority over traffic on approach roads, unless indicated otherwise. In countries where traffic drives on the left the roundabout is travelled in a clockwise direction. Also known as an ''island'' in parts of the UK. |
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;]: Cyclists ideally have a protected bike lane on separated by a concrete median with splay ]s if possible, and have a protected bike lane width of at least 2 metres if possible (one way). In the Netherlands, most one way cycle paths are at least 2.5 metres wide.<ref name="bicycledutch.wordpress.com"/> |
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;] (also hard shoulder): A clear, level area to the side of the roadway available for stopping if needed. |
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;]: Road numbered by the ], falling below numbered national highways (like ]) in the hierarchy ''or'' a road maintained by the state, including nationally numbered highways |
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;Traffic: Pedestrians, ridden or herded animals, vehicles, bicycles, and other conveyances using any road for purposes of travel.<ref>Laws of New York, Vehicle and Traffic Law § 152</ref> |
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;]: Deviations from a true planar pavement surface, which affects the interaction between road and tire. Microtexture have wavelengths below 0.5 mm, Macrotexture below 50 mm and Megatexture below 500 mm. |
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;]: Set of strategies used by ]s and ] to slow down or reduce motor vehicle traffic, thereby improving safety for pedestrians and ] and improving the environment for residents |
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;]: (UK) a small raised area used to help define the traffic flow, which may also act as a refuge for pedestrians crossing the carriageway or a location for signs, barriers or lights – a synonym for ] in some parts of the UK |
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;]: Also known as a traffic signal, stop light, stop-and-go lights – a signaling device at a road intersection, pedestrian crossing, or other location that assigns right of way to different approaches to an intersection |
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;] (UK): a pedestrian crossing marked by black and white stripes on the carriageway |
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==Construction== |
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]]] |
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] ]]] |
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] composed of cement-based material being applied during construction of the ] in ]]] |
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: ''"Roadbed" (from the 'related terms' ] & ]), as well as the term "Road building" redirects here.'' |
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<!-- Road building redirects here --> |
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{{See also|Macadam}} |
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'''Road construction''' requires the creation of an ] continuous right-of-way or '''roadbed''', overcoming geographic obstacles and having ] low enough to permit vehicle or ],<ref |
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Name="Kitsap_County_Road_Standards">{{cite web |title=Kitsap County Road Standards 2006 |publisher=Kitsap County, Washington |year=2006 |url=http://www.kitsapgov.com/PW/pdf/Revised%20Road%20Standards.doc |format=Doc |accessdate=2007-04-20 |deadurl=yes |archiveurl=https://web.archive.org/web/20060709203052/http://www.kitsapgov.com/pw/pdf/Revised%20Road%20Standards.doc |archivedate=July 9, 2006 }}</ref>{{rp|15}} and may be required to meet standards set by law<ref Name="MRSC_road_standards">{{cite web |title= Washington State County Road Standards |work= Chapter 35.78 RCW requires cities and counties to adopt uniform definitions and design standards for municipal streets and roads |publisher= Municipal Research & Services Center of Washington |year= 2005 |url= http://www.mrsc.org/subjects/Transpo/stand/CoRdStand.aspx |accessdate= 2007-04-20 |deadurl= yes |archiveurl= https://web.archive.org/web/20070927185007/http://www.mrsc.org/subjects/Transpo/stand/CoRdStand.aspx |archivedate= 2007-09-27 |df= }}</ref> or official guidelines.<ref Name="thelastfrontier">{{cite web|last=Shire of Wyndham East Kimberly |title=Guidelines for rural road design and construction technical specifications |publisher=Western Australia (The Last Frontier) |date=October 2006 |url=http://www.thelastfrontier.com.au/Publications/06K027005-061019-Rural%20Road%20Technical%20Specification%20complete%20(3).pdf |format=PDF |accessdate=2007-04-24 |archiveurl=https://web.archive.org/web/20070710022035/http://www.thelastfrontier.com.au/Publications/06K027005-061019-Rural%20Road%20Technical%20Specification%20complete%20%283%29.pdf |archivedate=2007-07-10 |deadurl=yes |df= }}</ref> The process is often begun with the removal of earth and rock by digging or blasting, construction of ], bridges and ], and removal of vegetation (this may involve ]) and followed by the laying of pavement material. A variety of ] is employed in road building.<ref Name="Caterpillar">{{cite web |title= Road Building Equipment |work= Constructing roads into forestry work areas |publisher= Caterpillar |year= 2007 |url= http://www.cat.com/cda/layout?m=62323&x=7 |accessdate= 2007-04-20 }}</ref><ref Name="Volvo">{{cite web|title=Volvo Construction Equipment (Europe) |work=Building the cities, towns, streets, highways and bridges in your neighborhood and in communities around the globe |publisher=Volvo |year=2007 |url=http://www.volvo.com/constructionequipment/europe/en-gb/work+solutions/government/introduction.htm |accessdate=2007-04-20 |archiveurl=https://web.archive.org/web/20061027082405/http://www.volvo.com/constructionequipment/europe/en-gb/work%2Bsolutions/government/introduction.htm |archivedate=2006-10-27 |deadurl=yes |df= }}</ref> |
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After design, ], ], legal and ] considerations have been addressed alignment of the road is set out by a ].<ref Name="Discovering_Roman_Technology">{{cite web |last= Hart-Davis |first= Adam |title= Roads and surveying |work= Discovering Roman Technology |publisher= BBC.CO.UK |date= 2001-06-01 |url= http://www.bbc.co.uk/history/ancient/romans/tech_02.shtml |accessdate= 2007-04-22 }}</ref> The ] and ] are designed and staked out to best suit the natural ground levels and minimize the amount of cut and fill.<ref name="thelastfrontier"/>{{rp|34}} Great care is taken to preserve reference ] <ref name="thelastfrontier"/>{{rp|59}} |
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Roads are designed and built for primary use by ] and pedestrian traffic. ]age and environmental considerations are a major concern. ] and ] controls are constructed to prevent detrimental effects. Drainage lines are laid with ] joints in the road easement with runoff ]s and characteristics adequate for the ] and storm water system. Drainage systems must be capable of carrying the ultimate design flow from the upstream catchment with approval for the outfall from the appropriate authority to a ], ], river or the sea for drainage discharge.<ref name="thelastfrontier"/>{{rp|38–40}} |
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A ] (source for obtaining fill, gravel, and rock) and a water source should be located near or in reasonable distance to the road construction site. Approval from ] may be required to ] or for working (crushing and screening) of materials for construction needs. The ] and vegetation is removed from the borrow pit and stockpiled for subsequent ] of the extraction area. Side slopes in the excavation area not steeper than one vertical to two horizontal for safety reasons.<ref name="thelastfrontier"/>{{rp|53–56 }} |
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<!-- Traffic considerations for work on existing roads are discussed beginning on p. 62 of the "thelastfrontier" reference. --> |
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Old road surfaces, fences, and buildings may need to be removed before construction can begin. Trees in the road construction area may be marked for retention. These protected trees should not have the topsoil within the area of the tree's drip line removed and the area should be kept clear of construction material and equipment. Compensation or replacement may be required if a protected tree is damaged. Much of the vegetation may be ] and put aside for use during reinstatement. The topsoil is usually stripped and stockpiled nearby for rehabilitation of newly constructed embankments along the road. Stumps and roots are removed and holes filled as required before the earthwork begins. Final rehabilitation after road construction is completed will include seeding, planting, watering and other activities to reinstate the area to be consistent with the untouched surrounding areas.<ref name="thelastfrontier"/>{{rp|66–67 }} |
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Processes during earthwork include excavation, removal of material to spoil, filling, compacting, construction and trimming. If rock or other unsuitable material is discovered it is removed, moisture content is managed and replaced with standard fill compacted to meet the design requirements (generally 90-95% relative compaction). ] is not frequently used to excavate the roadbed as the intact rock structure forms an ideal road base. When a depression must be filled to come up to the road grade the native bed is compacted after the topsoil has been removed. The fill is made by the "compacted layer method" where a layer of fill is spread then compacted to specifications, under saturated conditions. The process is repeated until the desired grade is reached.<ref name="thelastfrontier"/>{{rp|68–69}} |
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] |
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General ] should be free of ], meet minimum ] (CBR) results and have a low ]. The lower fill generally comprises sand or a sand-rich mixture with fine gravel, which acts as an inhibitor to the growth of plants or other vegetable matter. The compacted fill also serves as lower-stratum drainage. Select second fill (]d) should be composed of ], decomposed ] or ] below a specified ] and be free of large lumps of ]. ] fill may also be used. The roadbed must be "proof rolled" after each layer of fill is compacted. If a ] passes over an area without creating visible deformation or spring the section is deemed to comply.<ref name="thelastfrontier"/>{{rp|70–72}} |
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] such as ], ] and ] are frequently used in the various pavement layers to improve road quality. These materials and methods are used in low-traffic private roadways as well as public roads and highways.<ref name=Mainland> at www.mainlandaggregates.co.uk. Retrieved 25 Jan 2015</ref> Geosynthetics perform four main functions in roads: separation, reinforcement, filtration and drainage; which increase the pavement performance, reduce construction costs and decrease maintenance.<ref>Koerner, R. M. (2012) Designing with geosynthetics, 6th Edition, Xlibris Corporation, US</ref>{{Self-published inline|certain=yes|date=December 2017}} |
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The completed road way is finished by paving or left with a gravel or other ] surface. The ] surface is dependent on economic factors and expected usage. ] improvements such as ]s, ]s, ]s and other forms of ] are installed. |
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According to a May 2009 report by the American Association of State Highway and Transportation Officials (AASHTO) and TRIP – a national transportation research organization – driving on rough roads costs the average American motorist approximately $400 a year in extra vehicle operating costs. Drivers living in urban areas with populations more than 250,000 are paying upwards of $750 more annually because of accelerated vehicle deterioration, increased maintenance, additional fuel consumption, and tire wear caused by poor road conditions. |
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When a ] road is converted into dual carriageway by building a second separate carriageway alongside the first, it is usually referred to as ''duplication'',<ref> {{webarchive|url=https://www.webcitation.org/6GHx1Vq3c?url=http://www.neotrucks.com/pdf/glossary_abb_refer.pdf |date=2013-05-01 }} at The State of ]</ref> ''twinning'' or ''doubling''. The original carriageway is changed from two-way to become one-way, while the new carriageway is one-way in the opposite direction. In the same way as converting railway lines from ] to ], the new carriageway is not always constructed directly alongside the existing carriageway. |
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==Maintenance== |
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{{See also|Roadworks|Road_surface#Surface_deterioration}} |
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] |
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Like all structures, roads deteriorate over time. Deterioration is primarily due to accumulated damage from vehicles, however environmental effects such as ]s, thermal cracking and oxidation often contribute.<ref Name="frost">{{cite web |author= S.Kameyama, M. Kato, A. Kawamura, K. Himeno and A.Kasahara |title= ISAP 9th Conference Titles & Abstracts (#09044) |work= Effects of Frost Heave on the Longitudinal Profile of Asphalt Pavements in Cold Regions |publisher= International Society for Asphalt Pavements |date= August 2002 |url= http://www.asphalt.org/Pubs/9th_conf_abst.html |accessdate= 2007-05-13 |deadurl= yes |archiveurl= https://web.archive.org/web/20070813141736/http://www.asphalt.org/Pubs/9th_conf_abst.html |archivedate= 2007-08-13 |df= }}</ref> According to a series of experiments carried out in the late 1950s, called the ], it was empirically determined that the effective damage done to the road is roughly proportional to the ] of ].<ref Name="Motorway_Achievement_Pg252">{{cite book |author1=Ron Bridle |author2=John Porter |title= The Motorway Achievement: Frontiers of Knowledge and Practice |publisher= Thomas Telford |year= 2002 |page= 252 |url= https://books.google.com/?id=7Yqxyefv-VAC&pg=PA252&dq=4th+power+of+axle+weight |isbn= 0-7277-3197-1 }}</ref> A typical ] weighing 80,000 ] (36.287 ]) with 8,000 pounds (3.629 t) on the steer axle and 36,000 pounds (16.329 t) on both of the tandem axle groups is expected to do 7,800 times more damage than a passenger vehicle with 2,000 pounds (0.907 t) on each axle. ]s on roads are caused by rain damage and vehicle braking or related construction works. |
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] |
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] |
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] are designed for an expected ] or ]. In some parts of the United Kingdom the standard design life is 40 years for new ] and concrete pavement. Maintenance is considered in the whole life cost of the road with service at 10, 20 and 30 year milestones.<ref Name="Highways_The_Location">{{cite book |last= O'Flaherty |first= Coleman A. |title= Highways: The Location, Design, Construction & Maintenance of Road Pavements |publisher= Elsevier |year= 2002 |page= 252 <!-- different book different fact same page as ref Name="Motorway_Achievement_Pg252" --> |url= https://books.google.com/?id=Ren4sWQ3jKkC&pg=PA252&dq=Pavements+are+designed+for+an+expected+service+life |isbn= 0-7506-5090-7 }}</ref> Roads can be and are designed for a variety of lives (8-, 15-, 30-, and 60-year designs). When pavement lasts longer than its intended life, it may have been overbuilt, and the original costs may have been too high. When a pavement fails before its intended design life, the owner may have excessive repair and rehabilitation costs. Some ] pavements are designed as ''perpetual pavements'' with an expected structural life in excess of 50 years.<ref>{{cite book |last1= Newcomb |first1= David E. |last2= Willis |first2= Richard |last3= Timm |first3= David H. |title= Perpetual Asphalt Pavements: A Synthesis |publisher= Asphalt Pavement Alliance |date= 28 March 2010 |location= Lanham, Maryland |url= http://asphaltroads.org/images/documents/Perpetual_Pavement_Synthesis.pdf |accessdate= 2013-01-22}}</ref> |
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Many asphalt pavements built over 35 years ago, despite not being specifically designed as a perpetual pavement, have remained in good condition long past their design life.<ref>{{cite web |url= http://asphaltroads.org/perpetual-pavement/award-winners.html |title= Perpetual Pavement Award Winners |accessdate= 2013-01-22 |author= Asphalt Pavement Association}}</ref> Many concrete pavements built since the 1950s have significantly outlived their intended design lives.<ref Name="Map_Future">{{cite web |author1=Theodore R. Ferragut |author2=Dale Harrington |author3=Marcia Brink |last-author-amp=yes |title= Road Map to the Future |publisher= United States Department of Transportation – Federal Highway Administration |date= July–August 2002 |url= http://www.tfhrc.gov/pubrds/02jul/10.htm |accessdate= 2007-05-13 }}</ref> Some roads like ]'s "]", a major two-level viaduct in the downtown area, are being rebuilt with a designed service life of 100 years.<ref Name="Fly_Ash">{{cite web |last= ISG Resources, Inc |title= Fly Ash Concrete Design for Chicago's 100-Year Road Structure |work= Case Study |publisher= U.S. Environmental Protection Agency |date= December 2003 |url= http://www.epa.gov/epaoswer/osw/conserve/c2p2/cases/wacker-dr.pdf |format= PDF |accessdate= 2007-05-13 }}</ref> |
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Virtually all roads require some form of maintenance before they come to the end of their service life. Pro-active agencies use ] techniques to continually monitor road conditions and schedule preventive maintenance treatments as needed to prolong the lifespan of their roads. Technically advanced agencies monitor the road network surface condition with sophisticated equipment such as laser/inertial ]s. These measurements include road ], ], ], ], ] and ]. Software algorithms use this data to recommend maintenance or new construction. |
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Maintenance treatments for asphalt concrete generally include thin asphalt overlays, crack sealing, surface rejuvenating, fog sealingfo, ] or ] and ]. Thin surfacing preserves, protects and improves the functional condition of the road while reducing the need for routing maintenance, leading to extended service life without increasing structural capacity.<ref Name="Thin_Surfacing">{{cite web |first1=Ludomir |last1=Uzarowski |first2=Michael |last2=Maher |first3=Gary |last3=Farrington |author4= Golder Associates Ltd. |title= Thin Surfacing - Effective Way of Improving Road Safety within Scarce Road Maintenance Budget |work= Paper for presentation at the 2005 Annual Conference of the Transportation Association of Canada in Calgary, Alberta |publisher= Transportation Association of Canada |year= 2005 |url= http://www.tac-atc.ca/english/pdf/conf2005/s16/uzarowski2.pdf |format= PDF |accessdate= 2007-05-14 |archiveurl= https://web.archive.org/web/20080407011631/http://www.tac-atc.ca/english/pdf/conf2005/s16/uzarowski2.pdf <!-- Bot retrieved archive --> |archivedate= 2008-04-07}}</ref> |
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Older concrete pavements that develop faults can be repaired with a ], in which slots are cut in the pavement at each joint, and dowel bars are placed in the slots, which are then filled with concrete patching material. This can extend the life of the concrete pavement for 15 years.<ref>{{cite web|title=Dowel Bars for New and Existing Concrete Pavements|url=http://www.wsdot.wa.gov/NR/rdonlyres/43EF56B4-68AB-4465-87AC-A29826132144/0/DowelBarsfolio_Feb2013Final.pdf|publisher=Washington State Department of Transportation|accessdate=24 March 2014|date=February 2013}}</ref> |
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Failure to maintain roads properly can create significant costs to society, in a 2009 report released by the American Association of State Highway and Transportation Officials (US) about 50% of the roads in the US are in bad condition with urban areas worse. The report estimates that urban drivers pay an average of $746/year on vehicle repairs while the average US motorist pays about $335/year. In contrast, the average motorist pays about $171/year in road maintenance taxes (based on 600 gallons/year and $0.285/gallon tax). |
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===Slab stabilization=== |
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Distress and serviceability loss on concrete roads can be caused by loss of support due to voids beneath the concrete pavement slabs. The voids usually occur near cracks or joints due to surface water ]. The most common causes of voids are pumping, consolidation, subgrade failure and bridge approach failure. Slab stabilization is a non-destructive method of solving this problem and is usually employed with other Concrete Pavement Restoration ] methods including patching and diamond grinding. The technique restores support to concrete slabs by filing small voids that develop underneath the concrete slab at joints, cracks or the pavement edge. |
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The process consists of pumping a cementitous ] or ] mixture through holes drilled through the slab. The grout can fill small voids beneath the slab and/or sub-base. The grout also displaces free water and helps keep water from saturating and weakening support under the joints and slab edge after stabilization is complete. The three steps for this method after finding the voids are locating and drilling holes, grout injection and post-testing the stabilized slabs. |
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Slab stabilization does not correct depressions, increase the design structural capacity, stop erosion or eliminate faulting. It does, however, restore the slab support, therefore, decreasing deflections under the load. Stabilization should only be performed at joints and cracks where loss of support exists. Visual inspection is the simplest manner to find voids. Signs that repair is needed are transverse joint faulting, corner breaks and shoulder drop off and lines at or near joints and cracks. Deflection testing is another common procedure utilized to locate voids. It is recommended to do this testing at night as during cooler temperatures, joints open, aggregate interlock diminishes and load deflections are at their highest. |
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===Testing=== |
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Ground penetrating ] pulses electromagnetic waves into the pavement and measures and graphically displays the reflected signal. This can reveal voids and other defects. |
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The epoxy/core test, detects voids by visual and mechanical methods. It consists of drilling a 25 to 50 millimeter hole through the pavement into the sub-base with a dry-bit ]. Next, a two-part ] is poured into the hole – dyed for visual clarity. Once the epoxy hardens, technicians drill through the hole. If a void is present, the epoxy will stick to the core and provide physical evidence. |
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Common stabilization materials include ]-cement grout and polyurethane. The requirements for slab stabilization are strength and the ability to flow into or expand to fill small voids. Colloidal mixing equipment is necessary to use the pozzolan-cement grouts. The contractor must place the grout using a positive-displacement injection pump or a non-pulsing progressive cavity pump. A drill is also necessary but it must produce a clean hole with no surface ] or breakouts. The injection devices must include a grout packer capable of sealing the hole. The injection device must also have a return hose or a fast-control reverse switch, in case workers detect slab movement on the uplift gauge. The uplift beam helps to monitor the slab deflection and has to have sensitive dial gauges.<ref name="igga">{{cite web|url=http://www.igga.net/File/Minnesota-State-Aid-Concrete-Pavement-Rehabilitation-CPR-Best-Practices-Manual-_2006.pdf |title=Archived copy |accessdate=2013-05-13 |deadurl=yes |archiveurl=https://web.archive.org/web/20130809234355/http://www.igga.net/File/Minnesota-State-Aid-Concrete-Pavement-Rehabilitation-CPR-Best-Practices-Manual-_2006.pdf |archivedate=2013-08-09 |df= }} Minnesota DOT</ref><ref>Practical guidelines for CPR of Urban Roads: A compelling need for preserving city concrete streets led to the development of a methodology for scoping repairs and the undertaking of a comprehensive concrete pavement repair program in Grand Rapids, Michigan. June 2005. Better Roads.</ref> |
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===Joint sealing=== |
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Also called joint and crack repair, this method's purpose is to minimize infiltration of surface water and incompressible material into the joint system. Joint sealants are also used to reduce dowel bar corrosion in Concrete Pavement Restoration ] techniques. Successful resealing consists of old sealant removal, shaping and cleaning the reservoir, installing the backer rod and installing the sealant. Sawing, manual removal, plowing and cutting are methods used to remove the old sealant. Saws are used to shape the reservoir. When cleaning the reservoir, no dust, ] or traces of old sealant should remain. Thus, it is recommended to water wash, sand-blast and then air blow to remove any sand, dirt or dust. The backer rod installation requires a double-wheeled, steel roller to insert the rod to the desired depth. After inserting the backer rod, the sealant is placed into the joint. There are various materials to choose for this method including hot pour bituminous liquid, silicone and preformed compression seals.<ref name="igga" /><ref>{{cite web |url=http://www.igga.net/File/Minimize-Wheel-Slap-Keep-Your-Joints-Narrow-_2004.pdf |title=Archived copy |accessdate=2010-01-06 |deadurl=yes |archiveurl=https://web.archive.org/web/20110723154515/http://www.igga.net/File/Minimize-Wheel-Slap-Keep-Your-Joints-Narrow-_2004.pdf |archivedate=2011-07-23 |df= }} IGGA</ref><ref>How States Preserve Concrete Pavements: CPR pays off in extra pavement life. Better Roads. August 2005.</ref><ref>CPR brings dying pavement back to life: Georgia continues to be the leader in concrete pavement restoration, but as the word spreads other states are beginning to use this system to restore deteriorating pavements. April 1997, Roads & Bridges Magazine</ref> |
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==Safety considerations== |
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], line markings and ].]] |
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{{see also|Road traffic safety}} |
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Careful design and construction of roads can increase ] and reduce the harm (deaths, injuries, and property damage) on the highway system from traffic collisions. |
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On neighborhood roads ], ], pedestrian crossings and cycle lanes can help protect pedestrians, cyclists, and drivers. |
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Lane markers in some countries and states are marked with ] or |Botts dots, bright reflectors that do not fade like paint. Botts dots are not used where it is icy in the winter, because frost and snowplows can break the glue that holds them to the road, although they can be embedded in short, shallow trenches carved in the roadway, as is done in the mountainous regions of California. |
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For major roads risk can be reduced by providing ] from properties and local roads, ] and ] between opposite-direction traffic to reduce likelihood of head-on collisions. |
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The placement of energy attenuation devices (e.g. guardrails, wide grassy areas, sand barrels) is also common. Some ] such as road signs and ] are designed to collapse on impact. Light poles are designed to break at the base rather than violently stop a car that hits them. Highway authorities may also remove larger trees from the immediate vicinity of the road. During heavy rains, if the elevation of the road surface isn't higher than the surrounding landscape, it may result in flooding.<ref>{{cite book|last1=Neteler|first1=Markus|title=Open Source GIS: A GRASS GIS Approach|date=2007|page=149}}</ref> |
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] can improve road traffic safety and reduce the number of ] from ]. In their ''World report on road traffic injury prevention'' report, the ] identify speed control as one of various interventions likely to contribute to a reduction in road casualties. |
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==Environmental performance== |
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{{Main|Environmental impacts of roads}} |
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] |
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] section of ] connecting ] to ]]] |
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Careful design and construction of a road can reduce any negative environmental impacts. |
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] |
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Water management systems can be used to reduce the effect of pollutants from roads.<ref>{{Cite book|url=https://books.google.com/books?id=cdc3AQAAMAAJ&pg=PA293&dq=Drainage+systems+can+be+used+to+reduce+the+effect+of+pollutants+from+roads&hl=en&sa=X&ved=0ahUKEwj_5OHf0YTXAhWnllQKHe0QC8sQ6AEIKzAB#v=onepage&q=Drainage%20systems%20can%20be%20used%20to%20reduce%20the%20effect%20of%20pollutants%20from%20roads&f=false|title=Pittsburgh Light Rail Transit Reconstruction: Environmental Impact Statement|date=1979|publisher=The Administration|language=en}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=9o7rq6WnSXEC&pg=PA312&dq=Drainage+systems+can+be+used+to+reduce+the+effect+of+pollutants+from+roads&hl=en&sa=X&ved=0ahUKEwj_5OHf0YTXAhWnllQKHe0QC8sQ6AEIJjAA#v=onepage&q=Drainage%20systems%20can%20be%20used%20to%20reduce%20the%20effect%20of%20pollutants%20from%20roads&f=false|title=The Ecology of Transportation: Managing Mobility for the Environment|last=Davenport|first=John|last2=Davenport|first2=Julia L.|date=2006-06-30|publisher=Springer Science & Business Media|isbn=9781402045042|language=en}}</ref> ] and ] running off of roads tends to pick up gasoline, ], ], ] and other pollutants and result in ]. Road runoff is a major source of ], copper, ], ], lead and ]s (PAHs), which are created as ] byproducts of gasoline and other ]s.<ref>{{cite book |title=Stormwater Effects Handbook: A Toolbox for Watershed Managers, Scientists, and Engineers |publisher=CRC/Lewis Publishers |location=New York |year=2001 |isbn=0-87371-924-7 |url=http://unix.eng.ua.edu/~rpitt/Publications/BooksandReports/Stormwater%20Effects%20Handbook%20by%20%20Burton%20and%20Pitt%20book/MainEDFS_Book.html |first1=G. Allen, Jr. |last1= Burton |first2=Robert |last2= Pitt |chapter=2 }}</ref> |
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] chemicals and sand can run off into roadsides, contaminate ] and pollute ]s;<ref>Charles Seawell and Newland Agbenowosi (1998). {{webarchive |url=https://web.archive.org/web/20090521095505/http://www.cee.vt.edu/ewr/environmental/teach/gwprimer/roadsalt/roadsalt.html |date=2009-05-21 }} Virginia Polytechnic Institute, Department of Civil Engineering.</ref> and ]s can be toxic to sensitive plants and animals.<ref>University of Minnesota (2009). 2009-02-10.</ref> Sand applied to icy roads can be ground up by traffic into fine particulates and contribute to air pollution. |
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Roads are a chief source of ]. In the early 1970s it was recognized{{by whom|date=April 2018}} that design of roads can be conducted to influence and minimize noise generation.<ref>, ''Journal of Water, Air, & Soil Pollution'', Volume 2, Number 3, Biomedical and Life Sciences and Earth and Environmental Science Issue, pp. 387–92, September, 1973, Springer Verlag, Netherlands {{ISSN|0049-6979}}</ref> ]s can reduce noise pollution near built-up areas. Regulations can restrict the use of ]. |
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] contribute ]. Concentrations of air pollutants and adverse ] health effects are greater near the road than at some distance away from the road.<ref Name="carbonblack">{{cite web |title= Traffic-related Air Pollution near Busy Roads |publisher= American Journal of Respiratory and Critical Care Medicine Vol 170. pp. 520–26 |year= 2004 |url= http://ajrccm.atsjournals.org/cgi/content/full/170/5/520 }}</ref> ] kicked up by vehicles may trigger ] reactions.<ref> ''Science Daily,'' 1999-11-30.</ref> In addition, on-road transportation greenhouse gas emissions are the largest single cause of climate change, scientists say.<ref>{{cite journal|url=http://www.pnas.org/content/107/8/3382 |title=Attribution of climate forcing to economic sectors |accessdate=2013-08-14 |doi=10.1073/pnas.0906548107 |volume=107 |issue=8 |journal=Proceedings of the National Academy of Sciences |pages=3382–87|year=2010 |last1=Unger |first1=N |last2=Bond |first2=T. C |last3=Wang |first3=J. S |last4=Koch |first4=D. M |last5=Menon |first5=S |last6=Shindell |first6=D. T |last7=Bauer |first7=S |pmc=2816198 }}</ref> |
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] with ] near Summer Hill, ], England]] |
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]s in ], Russia]] |
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]s in the outskirts of ]]] |
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] going ]]] |
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], a route with a ] setup]] |
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] in the Philippines now called the Manila-Cavite Expressway]] |
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] |
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==Regulation== |
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] |
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===Right- and left-hand traffic=== |
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{{Main|Right- and left-hand traffic}} |
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Traffic flows on the right or on the left side of the road depending on the country.<ref Name="Why_In_Britain">{{cite web |author= Ray |title= Why In Britain Do We Drive On The Left? |publisher= 2Pass.co.uk |date= 2007 |url= http://www.2pass.co.uk/goodluck.htm |accessdate= 2007-03-24 }}</ref> In countries where traffic flows on the right, traffic signs are mostly on the right side of the road, ]s and ]s go counter-clockwise/anti-clockwise, and pedestrians crossing a two-way road should watch out for traffic from the left first.<ref Name="Rule_of_the_Road">{{cite book |last= Kincaid |first= Peter |title= The Rule of the Road: An International Guide to History and Practice |publisher= Greenwood Press |year= 1986 |isbn= 0-313-25249-1 }}</ref> In countries where traffic flows on the left, the reverse is true. |
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About 33% of the world by population drive on the left, and 67% keep right. By road distances, about 28% drive on the left, and 72% on the right,<ref name="brianlucas">{{cite web |last=Lucas |first=Brian |year=2005 |url=http://www.brianlucas.ca/roadside/ |title= Which side of the road do they drive on? |
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|accessdate=2006-08-03}}</ref> even though originally most traffic drove on the left worldwide.<ref>{{cite web |url=http://users.pandora.be/worldstandards/driving%20on%20the%20left.htm |title=Why do some countries drive on the right and others on the left? }}</ref> |
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==Economics== |
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{{Main|Transport economics}} |
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] with left-hand traffic]] |
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] is used to understand both the relationship between the transport system and the wider economy and the complex ]s when there are multiple paths and competing modes for both personal and freight (road/rail/air/ferry) and where ] can result in increased on decreased transport levels when road provision is increased by building new roads or decreased (for example California State Route 480). Roads are generally built and maintained by the ] using taxation although implementation may be through ] ]).<ref Name="Australia_CCG_2004">{{cite web |author= www.stat-usa.gov/ |title= International Market Research Reports |work= Australia CCG 2004 Update: Economic Trends and Outlook (E. Infrastructure ) |publisher= Industry Canada |date= 2006-02-28 |url= http://strategis.ic.gc.ca/epic/site/imr-ri.nsf/en/gr126748e.html |accessdate= 2007-04-17 |archiveurl= https://web.archive.org/web/20071114181049/http://strategis.ic.gc.ca/epic/site/imr-ri.nsf/en/gr126748e.html <!-- Bot retrieved archive --> |archivedate= 2007-11-14}}</ref><ref Name="ARTBA">{{cite web |title= State and Federal Gasoline Taxes |work= Maps, Reports and history of gas tax in the United States |publisher= American Road & Transportation Builders Association ("ARTBA") |url= http://www.artba.org/economics_research/current_issues/state_fed_gas_taxes.htm |accessdate= 2007-05-02 |archiveurl= https://web.archive.org/web/20070408082904/http://www.artba.org/economics_research/current_issues/state_fed_gas_taxes.htm <!-- Bot retrieved archive --> |archivedate= 2007-04-08}}</ref> or occasionally using ].<ref Name="IBTTA">{{cite web |title= International Bridge, Tunnel and Turnpike Association |date=April 16, 2007 |url= http://ibtta.org/ |accessdate= 2007-04-17 }}</ref> |
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] are a way for communities to address the rising cost by injecting private funds into the infrastructure. There are four main ones:<ref>{{cite journal|last=Cardno|first=Catherine|title=Infrastructure: New Report Examines the Potential of Public-Private Partnerships for Transportation Infrastructure|journal=Civil Engineering|year=2008|volume=78|issue=11|issn=0885-7024}}</ref> |
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* design/build |
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* design/build/operate/maintain |
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* design/build/finance/operate |
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* build/own/operate |
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Society depends heavily on efficient roads. In the ] 44% of all ] are moved by trucks over roads and 85% of all people are transported by cars, buses or coaches on roads.<ref Name="Road_Transport_(Europe)">{{cite web |title= Road Transport (Europe) |work= Overview |publisher= European Communities, Transportation |date= 2007-02-15 |url= http://ec.europa.eu/transport/road/index_en.htm |accessdate= 2007-03-24 |deadurl= yes |archiveurl= https://web.archive.org/web/20070315230823/http://ec.europa.eu/transport/road/index_en.htm |archivedate= 2007-03-15 |df= }}</ref> The term was also commonly used to refer to ]s, waterways that lent themselves to use by shipping. |
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===Construction costs=== |
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According to the New York State Thruway Authority,<ref> |
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{{cite web |title= Thruway Fact Book |publisher= New York State Thruway Authority |url= http://www.thruway.ny.gov/about/factbook/ |accessdate= 2011-05-05 |deadurl= yes |archiveurl= https://web.archive.org/web/20110502030241/http://www.thruway.ny.gov/about/factbook/ |archivedate= 2011-05-02 |df= }} |
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</ref> some sample per-mile costs to construct multi-lane roads in several US northeastern states were: |
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* Connecticut Turnpike – $3,449,000 per mile |
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* New Jersey Turnpike – $2,200,000 per mile |
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* Pennsylvania Turnpike (Delaware Extension) – $1,970,000 per mile |
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* Northern Indiana Toll Road – $1,790,000 per mile |
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* Garden State Parkway – $1,720,000 per mile |
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* Massachusetts Turnpike – $1,600,000 per mile |
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* Thruway, New York to Pennsylvania Line – $1,547,000 per mile |
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* Ohio Turnpike – $1,352,000 per mile |
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* Pennsylvania Turnpike (early construction) – $736,000 per mile |
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==Statistics== |
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The United States has the largest network of roads of any country with {{Convert|4050717|mi}} as of 2009.<ref></ref> The Republic of India has the second largest road system in the world with 4,689,842 kilometres (2,914,133 mi) of road (2013).<ref>{{cite web |url=http://164.100.47.134/intranet/NHDP.pdf |title=Archived copy |accessdate=2014-06-07 |deadurl=yes |archiveurl=https://web.archive.org/web/20140714152629/http://164.100.47.134/intranet/NHDP.pdf |archivedate=2014-07-14 |df= }}</ref> The People's Republic of China is third with {{Convert|3583715|km}} of road (2007). The Federative Republic of Brazil has the fourth largest road system in the world with {{Convert|1751868|km}} (2002). See ]. When looking only at ] the ] (NTHS) in China has a total length of {{Convert|45000|km}} at the end of 2006, and 60,300 km at the end of 2008, second only to the United States with {{Convert|90000|km}} in 2005. However, as of 2017 China has 130,000 km of Expressways.<ref></ref><ref>{{cite web|url=http://www.chinagate.com.cn/english/45626.htm|title=Expressways Being Built at Frenetic Pace|accessdate=10 January 2017|deadurl=yes|archiveurl=https://web.archive.org/web/20070701114053/http://www.chinagate.com.cn/english/45626.htm|archivedate=1 July 2007|df=}}</ref> |
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==Global connectivity== |
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{{Cleanup|section|reason=Cities list on the mainland not connected is either incomplete, America centric, or not formulated has examples.|date=September 2017}} |
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Eurasia, Africa, North America, South America, and Australia each have an extensive road network that connects most cities. |
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The North and South American road networks are separated by the ], the only interruption in the ]. Eurasia and Africa are connected by roads on the ]. The ] is connected to the ] by the ], and both have many connections to the mainland of Eurasia, including the bridges over the ]. ] has very few roads and no continent-bridging network, though there are a few ]s between bases, such as the ]. ] is the only ] to be connected to a continental network by road (the ] to Saudi Arabia). Even well-connected road networks are controlled by many different legal jurisdictions, and laws such as ] vary accordingly. |
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Many populated domestic islands are connected to the mainland by bridges. A very long example is the {{cvt|113|mi|adj=on}} ] connecting many of the ] with the continental United States. |
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Even on mainlands, some settlements have no roads connecting with the primary continental network, due to natural obstacles like mountains or wetlands, remoteness, or general expense. Unpaved roads or lack of roads are more common in ], and these can become impassible in wet conditions. As of 2014, only 43% of rural Africans have access to an all-season road.<ref>{{cite book |url=https://www.afdb.org/fileadmin/uploads/afdb/Documents/Publications/Tracking_Africa’s_Progress_in_Figures.pdf |title=Tracking Agrica's Progress in Figures |year=2014 |publisher=] |pages=71 |format=PDF}}</ref> Due to steepness, mud, snow, or fords, roads can sometimes be passable only to ] vehicles, those with ]s or ]s, or those capable of ] or ]. |
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Cities on the mainland of continents which do not have road access include: |
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* ], population 437,376 (2015) in the ] |
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* ], population 32,406 (2014) |
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* ], population 3,788 (2014) |
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* ], Nunavut, population 2,577 (2011) |
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* ], population 208 (2010) in the ] |
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Most disconnected settlements have local road networks connecting ports, buildings, and other points of interest. |
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Where demand for travel by road vehicle to a disconnected island or mainland settlement is high, ] ferries are commonly available if the journey is relatively short. For long-distance trips, passengers usually travel by air and ] upon arrival. If facilities are available, vehicles and cargo can also be shipped to many disconnected settlements by boat, or air transport at much greater expense. The island of Great Britain is connected to the European road network by ] - an example of a ] which is a service used in other parts of Europe to travel under mountains and over wetlands. |
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In polar areas, disconnected settlements are often more easily reached by ] or ] in cold weather, which can produce ] that blocks ports, and bad weather that prevents flying. For example, resupply aircraft are only flown to ] October to February, and many residents of coastal Alaska have bulk cargo shipped in only during the warmer months. Permanent darkness during the winter can also make long-distance travel more dangerous in polar areas. Continental road networks do reach into these areas, such as the ] to the North Slope of Alaska, the ] to ] in Russia, and many roads in Scandinavia (though due to ]s water transport is sometimes faster). Large areas of Alaska, Canada, Greenland, and ] are sparsely connected. For example, all 25 communities of ] are disconnected from each other and the main North American road network.<ref>{{cite web |url=http://nunavuttourism.com/planning-your-trip/how-to-get-here |work=Nunavut Tourism |title=How to Get Here |access-date=10 January 2017 |publisher=]}}</ref> |
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Road transport of people and cargo by may also be obstructed by ]s and travel restrictions. For example, travel from other parts of Asia to South Korea would require passage through the hostile country of North Korea. Moving between most countries in Africa and Eurasia would require passing through Egypt and Israel, which is a politically sensitive area. |
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Some places are intentionally ], and roads (if present) might be used by bicycles or pedestrians. |
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Roads are under construction to many remote places, such as the villages of the ], and a road was completed in 2013 to ]. Additional ] have been proposed, including a ] that would connect Eurasia-Africa and North America, a ] to the largest island of ] from Asia, and a ] to connect Europe and Africa directly. |
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==See also== |
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{{Portal|Roads}} |
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{{div col}} |
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* ] |
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* ] |
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* ] |
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* ] |
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* ] |
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* ] |
