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[[Image:Gotthard Alte Passstrasse.jpg|thumb|The [[St. Gotthard Pass]] road with [[hairpin turn]]s in the [[Swiss Alps]]]]
[[Image:Bangna-Bangpakong Road.jpg|thumb|Bangna-bangpakong road in Thailand]]
[[Image:I-80 Eastshore Fwy.jpg|thumb|[[Interstate 80]], the second-longest U.S. [[Interstate Highway System|Interstate highway]], runs from [[California]] to [[New Jersey]]]]
[[Image:Castle Roads-19th Century.jpg|thumb|[[Castle Roads, Bermuda|Castle Roads]], in [[Bermuda]]. An example of the maritime application of the word ''roads''.]]
A road is an identifiable [[Road number|route]], way or [[Trail|path]] between two or more [[Location (geography)|places]].<ref Name="Major_Roads_of_the_United_States">{{cite web
| title = Major Roads of the United States
| work = NationalAtlas.gov, Map Layer Info
| publisher = United States Department of the Interior
| date = [[March 13]], [[2006]]
| url = http://nationalatlas.gov/mld/roadtrl.html
| accessdate = 2007-03-24 }}</ref> Roads are typically smoothed, [[Pavement (material)|paved]], or otherwise prepared to allow easy [[travel]];<ref Name="RoadInfrastructureStrategicFrameworkforSouthAfrica">{{cite web
| title = Road Infrastructure Strategic Framework for South Africa
| work = A Discussion Document
| publisher = National Department of Transport (South Africa)
| date =
| url = http://www.transport.gov.za/library/docs/rifsa/infor.html
| accessdate = 2007-03-24 }}</ref> though they need not be, and historically many roads were simply recognizable routes without any formal [[construction]] or [[Maintenance, repair and operations|maintenance]].<ref name="Ways_of_the_World "/>
The term was also commonly used to refer to [[roadstead]]s, waterways that leant themselves to use by shipping. Notable examples being [[Hampton Roads]], in [[Virginia]], and [[Castle Roads, Bermuda|Castle Roads]], in [[Bermuda]] (also formerly in Virginia).{{Fact|date=February 2008}}
In [[urban area]]s roads may pass through a [[city]] or [[village]] and be named as [[street]]s, serving a dual function as urban space [[easement]] 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)
| date = 2007
| url = http://dictionary.reference.com/help/faq/language/d01.html
| accessdate = 2007-03-24 }}</ref> [[Economics]] and [[society]] depend heavily on efficient roads. In the [[European Union| European Union (EU)]] 44 % of all [[Good (economics and accounting)|goods]] are moved by [[truck]]s over roads and 85 % of all [[person]]s are transported by [[Automobile|car]]s, [[bus]]es 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 }}</ref>
The [[United States]] has the largest network of roadways of any single country in the world with 6,430,366 km (2005). [[India]] has the second largest road system in the world with 3,383,344 km (2002). [[People's Republic of China]] is third with 1,870,661 km of roadway (2004).<ref>https://www.cia.gov/library/publications/the-world-factbook/rankorder/2085rank.html, CIA World Factbook</ref> When looking only at [[expressways]] the [[National Trunk Highway System]] (NTHS) in [[People's Republic of China]] has a total length of 45,000 km at the end of 2006, second only to the United States with 90,000 km in 2005.<ref>[http://english.peopledaily.com.cn/200612/30/eng20061230_337130.html China to build more highways in 2007]</ref><ref>[http://www.chinagate.com.cn/english/45626.htm Expressways Being Built at Frenetic Pace]</ref>
==Usage and etymology==
{{see also|Usage of the terms railroad and railway|Street name}}
[[Image:Misty road.jpg|thumb|left|Misty road in Australia, entering into a township.]]
In original usage, a "road" was simply any [[Trail|pathway]] fit for [[equestrianism|riding]]. The word “[[street]],” whose origin is the [[Latin]] ''strata'', was kept for [[paved]] pathways that had been prepared to ease travel in some way. Thus, many "Roman Roads" have the word "street" as part of their name.<ref name="Highways:_The_Location"/><ref Name="Street">{{cite web | last = Harper | first = Douglas | title = Street | work = Online Etymology Dictionary | publisher = | date = November 2001 | url = http://www.etymonline.com/index.php?term=street | accessdate = 2007-03-25 }}</ref> Roads are a prerequisite for [[road transport]] of goods on [[wheel]]ed [[vehicle]]s<ref name="Highways:_The_Location"/>.
Words with related usage include, [[Avenue (archaeology)|Avenue]], [[Boulevard]], [[Cul-de-sac|Court]], [[Drive]], [[Freeway]], [[Highway]], [[Lane]], [[Parkway]], [[Trail|Path]], [[Street]], [[Turnpike]], and [[Right-of-way|Way]].
==History==
{{seealso|History of road transport}}
[[Image:PompeiiStreet.jpg|right|thumb|A [[cobblestone]] Roman road in [[Pompeii]].]]
That the first pathways were the [[trails]] made by animals has not been universally accepted, arguing that animals do not follow constant paths.<ref Name="Ways_of_the_World">{{cite book | last = Lay | first = Maxwell G | authorlink = | coauthors = | title = Ways of the World: A History of the World's Roads and of the Vehicles that Used Them | publisher = Rutgers University Press | date = 1992 | location = | pages = | url = http://books.google.com/books?vid=ISBN0813526914&id=flvS-nJga8QC&pg=PR3&lpg=PR3&ots=DvEHtwROGm&dq=%22Ways+of+the+world%22+Rutgers+University+Press,+New+Brunswick&sig=tK2dgY-CJ8S2DSeTaMJKKi82Uew#PPA6,M1 | doi = | id = 0813526914 }}</ref> Others believe that some roads originated from humans following animal trails.<ref>{{cite book | coauthors = D Helbing, P Molnär, I J Farkas, K Bolay | title = Environment and Planning B: Planning and Design 2001, volume 28 (Self-organizing pedestrian movement) | pages = Page 376 | url = http://pedsim.elte.hu/pdf/envplanb.pdf | doi = 10.1068/b2697 | id = |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 [[Icknield Way]] is given as an example of this type road origination, where man and animal both selected the same natural line.<ref Name="Icknield">{{cite web | title = The Icknield Way Path | publisher = Icknield Way Association | date = 2004 | url = http://www.icknieldwaypath.co.uk/ | accessdate = 2007-04-29 }}</ref> By about 10,000 BC, rough pathways were used by human travelers.<ref name="Ways_of_the_World"/>
=== Historical road construction dating to 4000 BC===
* [[Cobblestone|Stone]] [[Pavement (material)|paved]] streets are found in the city of [[Ur]] in the [[Middle East]] dating back to 4000 BC<ref name="Ways_of_the_World"/>
* [[Corduroy road|Corduroy roads (log roads)]] are found dating to 4,000 BC in [[Glastonbury, England]]<ref name="Ways_of_the_World"/>
* The [[timber trackway]]; [[Sweet Track]] [[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, [[Dendrochronology|tree-ring dating (Dendrochronology)]] enabled very precise dating. It has been 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 }}</ref><ref name="Highways:_The_Location"/>
* [[Brick]] paved streets were used in [[India]] as early as 3000 BC<ref name="Ways_of_the_World"/>
* In 500 BC, [[Darius I the Great]] started an extensive road system for [[Persia]] ([[Iran]]), including the famous [[Royal Road]] 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 | date = | url = http://www.iranchamber.com/history/achaemenids/royal_road.php | accessdate = 2007-04-09 }}</ref> The road remained in use after Roman times.
* 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 [[cart]]s and river [[barge]]s. A hybrid of road transport and ship transport beginning in about 1740 is the [[horse-drawn boat]] in which the horse follows a cleared path along the river bank.<ref Name="horseboating">{{cite web | title = Horseboating | work = | publisher = The Horseboating Society | date = | url = http://www.horseboating.org.uk/ | format = Web | doi = | 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 | date = | url = http://www.canaljunction.com/craft/horsedrawn1.htm | accessdate = 2007-04-09 }}</ref>
* From about 312 BC, the [[Roman Empire]] built straight<ref name="Discovering_Roman_Technology"/> strong stone [[Roman road]]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 [[Rome]] and covering 78,000 [[kilometer]]s or 52,964 [[Roman mile]]s of paved roads.<ref Name="Highways:_The_Location">{{cite book | last = O'Flaherty | first = Coleman A. | authorlink = | coauthors = | title = Highways: The Location, Design, Construction & Maintenance of Road Pavements | publisher = Elsevier | year = 2002 | location = | pages = | url = http://books.google.com/books?vid=ISBN0750650907&id=Ren4sWQ3jKkC&pg=PA1&lpg=PA1&dq=ancient+Egyptians+stone+paved+road++Great+Pyramid+in+about+3000+BC&sig=c1OaZDxjJjjOlWtkM-8h1m3niCo#PPA2,M1 | doi = | id = ISBN 0750650907 }}</ref>
* In the 1600s road construction and maintenance in Britain was traditionally done on a local parish basis.<ref name="Highways:_The_Location"/> This resulted in a poor and variable state of roads. To remedy this, the first of the "[[Turnpike trusts in the United Kingdom|Turnpike Trusts]]" 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 of engineered roads.<ref name="Highways:_The_Location"/> The [[Rebecca Riots]] in [[Carmarthenshire]] and [[Rhayader]] from 1839 to 1844 contributed to a [[Royal Commission]] leading 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>
== Road transport economics ==
{{main|Transport economics}}
'''Transport economics''' is a branch of [[economics]] that deals with the allocation of resources within the transport sector and has strong linkages with [[civil engineering]]. [[Transport]] economics differs from some other branches of economics in that the assumption of a spaceless, instantaneous [[economy]] does not hold. People and goods flow over networks at certain speeds. Demands peak. Advanced ticket purchase is often induced by lower fares. The networks themselves may or may not be [[competitive]]. A single trip (the final good from the point-of-view of the consumer) may require bundling the services provided by several firms, agencies and modes.
Although transport systems follow the same [[supply and demand]] theory as other industries, the complications of [[network effect]]s and choices between non-similar goods (e.g. car and bus travel) make estimating the demand for transportation facilities difficult. The development of models to estimate the likely choices between the non-similar goods involved in transport decisions "[[discrete choice]]" models led to the development of the important branch of [[econometrics]], and a [[Nobel Prize]] for [[Daniel McFadden]].<ref>{{cite web | title = The Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel 2000
| work = [[Daniel L. McFadden]] "for his development of theory and methods for analyzing discrete choice" | publisher = Nobel Foundation | date = 2000 | url = http://nobelprize.org/nobel_prizes/economics/laureates/2000/index.html | accessdate = 2007-05-02 }}</ref>
In transport, [[demand]] can be measured in numbers of journeys made or in total distance traveled across all journeys (e.g. passenger-kilometres for [[public transport]] or vehicle-kilometres of travel (VKT) for [[private transport]]). [[Supply]] is considered to be a measure of [[capacity]]. The [[price]] of the good (travel) is measured using the [[generalised cost]] of travel, which includes both [[money]] and [[time]] expenditure. The effect of increases in supply (capacity) are of particular interest in transport economics (see [[induced demand]]), as the potential environmental consequences are significant.
Road building and maintenance is an area of economic activity that remains dominated by the [[public sector]] (though often through [[private sector|private]] [[General contractor|contractor]]s).<ref Name="Australia_CCG_2004">{{cite web | last = 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 }}</ref> Roads (except those on private property that are not accessible to the general public) are typically paid for by [[tax]]es (often raised through levies on fuel),<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") | date = | url = http://www.artba.org/economics_research/current_issues/state_fed_gas_taxes.htm | accessdate = 2007-05-02 }}</ref> though some [[public road]]s, especially [[highway]]s are funded by [[toll road|toll]]s.<ref Name="IBTTA">{{cite web | title = International Bridge, Tunnel and Turnpike Association | work = | publisher = |date=[[April 16]], [[2007]] | url = http://ibtta.org/ | accessdate = 2007-04-17 }}</ref>
==Environmental aspects==
Motor vehicle traffic on roads generate [[noise pollution]] especially at higher operating speeds. Therefore, considerable [[noise health effects]] are expected from road systems used by large numbers of motor vehicles. [[Noise mitigation]] strategies exist to reduce sound levels at nearby [[sensitive receptors]]. The idea that road design could be influenced by acoustical engineering considerations first arose about 1973.<ref>[http://www.springerlink.com/content/x1707075n815g604/ C.Michael Hogan, '' Analysis of highway noise'', Journal of Water, Air, & Soil Pollution, Volume 2, Number 3, Biomedical and Life Sciences and Earth and Environmental Science Issue, Pages 387-392, September, 1973, Springer Verlag, Netherlands ISSN 0049-6979]</ref>
Motor vehicles operating on roads contribute [[air pollutant|emissions]], particularly for congested city street conditions and other low speed circumstances. Concentrations of air pollutants and adverse respiratory 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
| work =
| publisher = American Journal of Respiratory and Critical Care Medicine Vol 170. pp. 520-526
| date = 2004
| url = http://ajrccm.atsjournals.org/cgi/content/full/170/5/520
| accessdate = }}</ref>
==Driving on the right or the left==
{{main|Driving on the left or right}}
[[Image:drive on left in australia.jpg|thumb|left|A sign on [[Australia]]'s [[Great Ocean Road]] reminding foreign motorists to keep left.]]
[[Traffic]] flows on the right or on the left side of the road depending on the country.<ref Name="Why_In_Britain">{{cite web | last = | first = Ray | title = Why In Britain Do We Drive On The Left? | work = | publisher = 2Pass.co.uk | date = © 1996-2007 | url = http://www.2pass.co.uk/goodluck.htm | accessdate = 2007-03-24 }}</ref> In countries where traffic flows on the right, [[traffic sign]]s are mostly on the right side of the road, [[roundabout]]s and [[traffic circle]]s go counter-clockwise, and [[pedestrian]]s 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 | authorlink = | coauthors = | title = The Rule of the Road: An International Guide to History and Practice | publisher = Greenwood Press | date = 1986 | location = | pages = | url = http://www.amazon.com/Rule-Road-International-History-Practice/dp/0313252491 | doi = | id = ISBN 0-313-25249-1 }}</ref> In countries where traffic flows on the left, the reverse is true.
About 34% of the world by [[population]] drive on the left, and 66% keep right. By roadway 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?
|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>
==Construction==
[[Image:us land survey officer.jpg|thumb|Surveyor at work with a [[leveling instrument]].]]
[[Image:Road building-Hungary-1.jpg|thumb|right|Asphalt layer and roller]]
'''Road construction''' requires the creation of a continuous [[Right-of-way (transportation)|right-of-way]], overcoming geographic obstacles and having [[Grade (slope)|grades]] low enough to permit [[vehicle]] or [[walking|foot travel]].<ref Name="Kitsap_County_Road_Standards">{{cite web | title = Kitsap County Road Standards 2006 | work = | publisher = Kitsap County, Washington | date = 2006 | url = http://www.google.com/url?sa=t&ct=res&cd=4&url=http%3A%2F%2Fwww.kitsapgov.com%2FPW%2Fpdf%2FRevised%2520Road%2520Standards.doc&ei=CR4oRqeuCIuYgQOonvGyDQ&usg=AFrqEzc34dXvKRHE9kUtBqd8RfqzfNI2rA&sig2=nrd9wbiu_sCE4shhBWX6jw | format = Doc | doi = | accessdate = 2007-04-20 }}</ref> <sup>(pg15)</sup> 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 | date = 2005 | url = http://www.mrsc.org/subjects/Transpo/stand/CoRdStand.aspx | accessdate = 2007-04-20 }}</ref> or official guidelines.<ref Name="thelastfrontier">{{cite web | last = Shire of Wyndham East Kimberly | first = | title = Guidelines for rural road design and construction technical specifications | work = | 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 | doi = | accessdate = 2007-04-24 }}</ref> The process is often begun with the removal of earth and rock by digging or blasting, construction of [[Embankment (transportation)|embankment]]s, [[bridge]]s and [[tunnels]], and removal of vegetation (this may involve [[deforestation]]) and followed by the laying of [[pavement (material)|pavement material]]. A variety of [[heavy equipment|road building equipment]] is employed in road building.<ref Name="Caterpillar">{{cite web | title = Road Building Equipment | work = Constructing roads into forestry work areas | publisher = Caterpillar | date = 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 | date = 2007 | url = http://www.volvo.com/constructionequipment/europe/en-gb/work+solutions/government/introduction.htm | accessdate = 2007-04-20 }}</ref>
After [[design]], [[Approval rating|approval]], [[planning]], [[legal]] and [[Environmental policy|environmental]] considerations have been addressed alignment of the road is set out by a [[Surveying|surveyor]]. <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 [[Radius of curvature|Radii]] and [[Slope|gradient]] are designed and staked out to best suit the natural ground levels and minimize the amount of cut and fill.<ref name="thelastfrontier"/> <sup>(page34)</sup> Great care is taken to preserve reference [[Benchmark (surveying)|Benchmarks]] <ref name="thelastfrontier"/> <sup>(page59)</sup>
Roadways are designed and built for primary use by [[vehicular]] and [[pedestrian]] [[traffic]]. [[Storm drain]]age and environmental considerations are a major concern. [[Erosion]] and [[sediment]] controls are constructed to prevent detrimental effects. Drainage lines are laid with [[Seal (mechanical)|sealed]] joints in the [[easement|road easement]] with runoff [[coefficient]]s and characteristics adequate for the [[Zoning|land zoning]] 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 [[watercourse]], [[stream|creek]], [[river]] or the [[sea]] for drainage discharge. <ref name="thelastfrontier"/> <sup>(page38 to 40)</sup>
A [[Borrow pit]] (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 [[local authorities]] may be required to [[Water well|draw water]] or for [[Gravel|working (crushing and screening)]] of materials for construction needs. The [[top soil]] and [[vegetation]] is removed from the borrow pit and stockpiled for subsequent [[rehabilitation]] of the extraction area. Side slopes in the excavation area not steeper than one vertical to two horizontal for safety reasons. <ref name="thelastfrontier"/> <sup>(page 53 to 56 )</sup>
<!-- Traffic considerations for work on existing roads are discussed beginning on page 62 of the "thelastfrontier" reference. -->
Old road surfaces, fences, and buildings may need to be removed before construction can begin. [[Tree]]s 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 maybe [[mulched]] 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"/> <sup>(page 66 to 67 )</sup>
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 90% relative compaction. Generally [[blasting]] of rock is discouraged in the road bed. 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, the process is repeated until the desired grade is reached.<ref name="thelastfrontier"/> <sup>(page 68 to 69 )</sup>
[[Image:PavementStratum.JPG|thumb|right|Typical pavement stratum for a heavily traveled road]]
General [[Fill dirt|fill material]] should be free of [[organic compound|organic]]s, meet minimum [[California bearing ratio]] (CBR) results and have a low [[Atterberg limits#Plasticity index|plasticity index]]. Select fill ([[sieve]]d) should be composed of [[gravel]], decomposed [[Rock (geology)|rock]] or [[crushed rock|broken rock]] below a specified [[Particle size]] and be free of large lumps of [[clay]]. [[Loam|Sand clay]] fill may also be used. The road bed must be "proof rolled" after each layer of fill is compacted. If a [[Road roller|roller]] passes over an area without creating visible deformation or spring the section is deemed to comply. <ref name="thelastfrontier"/> <sup>(page 70 to 72 )</sup>
The completed road way is finished by [[Pavement (material)|paving]] or left with a gravel or other [[Dirt road|natural]] surface. The [[Types of road|type of road]] surface is dependent on economic factors and expected usage. [[Road-traffic safety|Safety]] improvements like [[Traffic sign]]s, [[Crash barrier]]s, [[Raised pavement marker]]s, and other forms of [[Road surface marking]] are installed.
===Duplication===
When a [[single carriageway]] road is converted into [[dual carriageway]] by building a second separate carriageway alongside the first, it is usually referred to as ''duplication''<ref>[http://www.dse.vic.gov.au/CA256F310024B628/0/49BEB2EFD9C65F56CA25723B0002618A/$File/GlossaryAbbRefer.pdf Glossary: Princes Highway, Traralgon Bypass - Planning Assessment Report] at The State of [[Victoria (Australia)|Victoria]] </ref> or ''twinning''. 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 [[Single track (rail)|single track]] to [[double track]], the new carriageway is not always constructed directly alongside the existing carriageway.
==Maintenance==
[[Image:Baustelle.svg|thumb]]
Like all structures, roads deteriorate over time. Deterioration is primarily due to accumulated damage from vehicles, however environmental effects such as [[frost heave]]s, thermal cracking and oxidation often contribute.<ref Name="frost">{{cite web | coauthors = 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 }}</ref> According to a series of experiments carried out in the late 1950s, called the [[AASHO Road Test]], it was empirically determined that the effective damage done to the road is roughly proportional to the 4th power of [[Gross axle weight rating|axle weight]] .<ref Name="Motorway_Achievement_Pg252">{{cite book | coauthors = Ron Bridle, John Porter | title = The Motorway Achievement: Frontiers of Knowledge and Practice | publisher = Thomas Telford | date = 2002 | location = | pages = Page 252 | url = http://books.google.com/books?id=7Yqxyefv-VAC&pg=PA252&ots=Yvl1puH55J&dq=4th+power+of+axle+weight&sig=qNz9nc_S0HgJDblEONAZXcS605g | id = ISBN 0727731971 }}</ref> A typical [[Semi-trailer truck|tractor-trailer]] weighing 80,000 [[Pound (mass)|pounds]] (36.287 [[Tonne|t]]) with 8,000 pounds (3.6287 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 [[Automobile|passenger vehicle]] with 2,000 pounds (0.907 t) on each axle.
[[pothole]]
Pavements are designed for an expected [[service life]] or [[design life]]. In some [[UK]] countries the standard design life is 40 years for new [[bitumen]] 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 | date = 2002 | pages = Page 252 <!-- different book different fact same page as ref Name="Motorway_Achievement_Pg252" --> | url = http://books.google.com/books?id=Ren4sWQ3jKkC&pg=PA252&ots=9b8s3lyHfg&dq=Pavements+are+designed+for+an+expected+service+life&sig=Wl0QDnn4_4vaXb-TQI8TiBarVAw | id = ISBN 0750650907 }}</ref> Roads can be and are designed for a variety of lives (8-, 15-, 30-, and 60-year designs). When pavement lasts longer then 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. Many concrete pavements built since the 1950s have significantly outlived their intended design lives. <ref Name="Map_Future">{{cite web | coauthors = Theodore R. Ferragut, Dale Harrington, and Marcia Brink | title = Road Map to the Future | work = | 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 [[Chicago, Illinois]]'s "[[Wacker Drive]]", a major two-level viaduct in 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>
Virtually all roads require some form of maintenance before they come to the end of their service life. Pro-active agencies continually monitor road conditions and apply preventive maintenance treatments as needed to prolong the lifespan of their roads. Technically advanced agencies monitior the road network surface condition with sophisticated equipment such as laser/inertial [[Profilometer]]s. These measurements include road [[curvature]], [[cross slope]], [[unevenness]], [[roughness]], [[rutting]] and [[texture (roads)]]. This data is fed into a [[pavement management system]], which recommends the best maintenance or construction treatment to correct the damage that has occurred.
Maintenance treatments for [[asphalt concrete]] generally include [[crack sealing]], [[surface rejuvenating]], [[Fogseal|fog sealing]], [[micro-mill]]ing and [[Chipseal|surface treatments]]. 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 | coauthors = Ludomir Uzarowski, Michael Maher and Gary Farrington, 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 | date = 2005 | url = http://www.tac-atc.ca/english/pdf/conf2005/s16/uzarowski2.pdf | format = PDF | accessdate = 2007-05-14 }}</ref>
==Terminology==
[[Image:068150 ba19047d.jpg|thumb|The [[A22 road|A22(T)]] near Summer Hill, [[East Sussex]], [[England]]]]
* [[Alignment (road)]] - Cross slope/Banking/Superelevation, horizontal and vertical curvature of a road.
* All-weather road - Unpaved road that is constructed of a material that does not create mud during rainfall. <!-- [[All-weather road]] redirects here, term is used freely in this contest on line, but note worthy references were not found -->
* [[Bollard#Roads|Bollard]] - Rigid posts that can be arranged in a line to close a road or path to vehicles above a certain width
* [[Byway (road)|Byway]] - Highway over which the public have [[Rights of way in England and Wales|a right to travel]] for vehicular and other kinds of traffic, but which is used mainly as footpaths and bridleways
* [[Bypass (road)|Bypass]] Road that avoids or "bypasses" a built-up area, town, or village
* [[Bottleneck (traffic)|Bottleneck]] - Section of a road with a carrying capacity substantially below that of other sections of the same road
* [[Botts' dots]] - Non reflective [[raised pavement marker]] used on roads
* [[Cat's eye (road)|Cat's eye]] - [[Reflection (physics)|reflective]] [[raised pavement marker]] used on roads
* [[Chicane]] - Sequence of tight serpentine curves (usually an S-shape curve or a bus stop) in a roadway
* [[Chipseal]] - 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 [[asphalt concrete]] or a [[concrete]], in the [[United States|U.S.]] it is usually only used on low volume rural roads
* [[Corniche]] - Road on the side of a [[cliff]] or [[mountain]], with the ground rising on one side and falling away on the other
* [[Curb (road)|Curb]] - Edge where a raised [[sidewalk|pavement/sidewalk/footpath]], [[road median]], or [[road shoulder]] meets an unraised [[street]] or other roadway.
* [[Curb extension]] - (or also kerb extension, bulb-out, nib, elephant ear, curb bulge and blister) [[Traffic calming]] measure, intended to slow the speed of traffic and increase driver awareness, particularly in built-up and residential [[neighborhoods]].
* [[Fork (road)|Fork]] - (literally "fork in the road") Type of [[Intersection (road)|intersection]] where a road splits
* [[Guard rail]] - Prevents vehicles from veering off the road into oncoming traffic, crashing against solid objects or falling from a road
* [[Green lane]] - ([[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, similar to a [[Byway (road)|Byway]]
* [[Interstate Highway System]] - [[United States]] System of Interstate and Defense Highways
* [[central reservation|Median]] - On divided roads, including [[expressway]]s, [[motorway]]s, or [[autobahn]]s, the central reservation [[British English|(British English)]], median [[North American English|(North American English)]], median strip (North American English and [[Australian English]]), neutral ground [Louisiana English] or central nature strip (Australian English) is the area which separates opposing [[lane]]s of [[traffic]]
* [[Mountain pass]] - Lower point that allows easier access through a range of mountains
* [[Milestone]] - One of a series of numbered markers placed along a road at regular intervals, showing the distance to destinations.
* [[Pavement]] - The road regarded as a geoconstruction.
* [[Pedestrian crossing]] - Designated point on a road at which some means are employed to assist pedestrians wishing to cross safely
* [[Private highway]] - Highway owned and operated for profit by [[private industry]]
* [[Private road]] - Road owned and maintained by a [[Person|private individual]], [[organization]], or [[company]] rather than by a [[government]]
* [[Public space]] - Place where anyone has a right to come without being excluded because of [[socioeconomics|economic or social]] conditions
* [[Ranch road]] - [[United States|U.S.]] road which serves to connect [[rural]] and [[agricultural]] areas to [[market town]]s
* [[Road number]] - Often assigned to a stretch of public roadway. The number chosen is often dependent on the [[types of road|type of road]], with numbers differentiating between [[interstate]]s, [[motorway]]s, [[Arterial road|arterial thoroughfare]]s, and so forth
* [[Road-traffic safety]] - Process to reduce the harm (deaths, injuries, and property damage) resulting from crashes of road vehicles traveling on public roads
* [[Roadworks]] - Part or all of the road has to be occupied for work or maintenance relating to the road
* [[Roughness]] - Deviations from a true planar pavement surface, which affects vehicle suspension deflection, dynamic loading, ride quality, 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.
* [[Shoulder (road)|Shoulder]] - Reserved area by the verge of a road, generally it is kept clear of all traffic
* [[State highway]] - Road numbered by the [[state]], falling below numbered national highways (like [[United States Numbered Highways|U.S. Routes]]) in the hierarchy ''OR'' A road maintained by the state, including nationally-numbered highways
* [[Texture (roads)]] - 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.
* [[Traffic calming]] - Set of strategies used by [[urban planner]]s and [[traffic engineering (transportation)|traffic engineer]]s which aim to slow down or reduce [[traffic]], thereby improving safety for [[pedestrian]]s and [[bicycle-friendly|bicyclist]]s as well as improving the environment for residents
* [[Traffic light]] - also known as a traffic signal, stop light, stop-and-go lights, robot or semaphore, is a signaling device positioned at a road intersection, [[pedestrian crossing]], or other location in order to indicate when it is safe to cross a road
==See also==
{{portal|Roads|Autoroute icone.svg}}
{{col-begin}}
{{col-2}}
* [[Corpse roads]]
* [[Design Manual for Roads and Bridges]]
* [[Habitat fragmentation]]
* [[Inca road system]]
* [[Line source]]
* [[List of roads and highways]]
* [[List of OECD countries by road network size]]
{{col-2}}
* [[Road movie]]
* [[Roadway air dispersion model]]
* [[Roadway noise]]
* [[Street]]
* [[Strip road]]
* [[Towing]]
* [[Trade route]]
{{col-end}}
==References==
{{reflist|2}}
==External links==
{{sisterlinks}}
*[http://www.euratlas.net/cartogra/Rocque/index.html The Post-Roads of Europe 1781 Map]
*[http://www.notolls.org.uk/index.htm National Alliance Against Tolls]
*[http://www.roadex.org The Roadex project]
{{Road types}}
{{Road junction types}}
[[Category:Streets and roads]]
[[Category:Road infrastructure]]
[[Category:Road transport]]
[[Category:Roads|Roads]]
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