Infrastructure

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Interstate 80, the second-longest U.S. Interstate highway, runs from California to New Jersey

Infrastructure can be defined as the basic physical and organizational structures needed for the operation of a society or enterprise [1], or the services and facilities necessary for an economy to function. [2] The term typically refers to the technical structures that support a society, such as roads, water supply, sewers, power grids, telecommunications, and so forth. Viewed functionally, infrastructure facilitates the production of goods and services; for example, roads enable the transport of raw materials to a factory, and also for the distribution of finished products to markets. In some contexts, the term may also include basic social services such as schools and hospitals [3]. In military parlance, the term refers to the buildings and permanent installations necessary for the support, redeployment, and operation of military forces [4].

In this article, infrastructure will be used in the sense of technical structures or physical networks that support society, unless specified otherwise.

Contents

[edit] History of the term

According to etymology online [5], the word infrastructure has been used in English since at least 1927 and meant: The installations that form the basis for any operation or system. Other sources, such as the Oxford English Dictionary, trace the word's origins to earlier usage, originally applied in a military sense. The word was imported from French, where it means subgrade, the native material underneath a constructed pavement or railway. The word is a combination of the Latin prefix "infra", meaning "below" and "structure". The military sense of the word was probably first used in France, and imported into English around the time of the First World War. The military use of the term achieved currency in the United States after the formation of NATO in the 1940s, and was then adopted by urban planners in its modern civilian sense by 1970. [6], .

The term came to prominence in the United States in the 1980s following the publication of America in Ruins (Choate and Walter, 1981)[1] , which initiated a public-policy discussion of the nation’s "infrastructure crisis", purported to be caused by decades of inadequate investment and poor maintenance of public works.

That public-policy discussion was hampered by lack of a precise definition for infrastructure. A U.S. National Research Council panel sought to clarify the situation by adopting the term "public works infrastructure", referring to:

"...both specific functional modes - highways, streets, roads, and bridges; mass transit; airports and airways; water supply and water resources; wastewater management; solid-waste treatment and disposal; electric power generation and transmission; telecommunications; and hazardous waste management - and the combined system these modal elements comprise. A comprehension of infrastructure spans not only these public works facilities, but also the operating procedures, management practices, and development policies that interact together with societal demand and the physical world to facilitate the transport of people and goods, provision of water for drinking and a variety of other uses, safe disposal of society's waste products, provision of energy where it is needed, and transmission of information within and between communities."[7]

In subsequent years, the word has grown in popularity and been applied with increasing generality to suggest the internal framework discernible in any technology system or business organization.

The 2009 report card produced by the American Society of Civil Engineers [2] gives America's Infrastructure a grade of "D".

[edit] Various uses of the term

[edit] Engineering and construction

Engineers generally limit the use of the term infrastructure to describe fixed assets that are in the form a large network. Recent efforts to devise more generic definitions of infrastructure have typically referred to the network aspects of most of the structures and to the accumulated value of investments in the networks as assets. One such effort defines infrastructure as the network of assets "where the system as a whole is intended to be maintained indefinitely at a specified standard of service by the continuing replacement and refurbishment of its components."[8] However, the principles that civil infrastructure is meant to have unlimited service life and always provide some specified minimum standard of service are neither inherent to the concept nor generally accepted by the societies served.

[edit] Civil defense and economic development

Civil defense planners and developmental economists may use a broad definition that includes public services such as schools and hospitals, emergency services such as police and fire fighting, and basic financial services.

[edit] Military

Military strategists use the term infrastructure to refer to all building and permanent installations necessary for the support of military forces, whether they are stationed in bases, being deployed or engaged in operations, such as barracks, headquarters, airfields, communications facilities, stores of military equipment, port installations, and maintenance stations [9].

[edit] Critical infrastructure

Main article: critical infrastructure

The term critical infrastructure has been widely adopted to distinguish those infrastructure elements that, if significantly damaged or destroyed, would cause serious disruption of the dependent system or organization. Storm, flood, or earthquake damage leading to loss of certain transportation routes in a city (for example, bridges crossing a river), could make it impossible for people to evacuate and for emergency services to operate; these routes would be deemed critical infrastructure. Similarly, an on-line booking system might be critical infrastructure for an airline.

[edit] Urban infrastructure

Urban or municipal infrastructure refers to systems generally owned and operated by municipalities, such as streets, water distribution, sewers, etc.

[edit] Other uses

In other applications, the term infrastructure may refer to information technology, informal and formal channels of communication, software development tools, political and social networks, or beliefs held by members of particular groups. Still underlying these more conceptual uses is the idea that infrastructure provides organizing structure and support for the system or organization it serves, whether it is a city, a nation, a corporation, or a collection of people with common interests. Examples: IT infrastructure, research infrastructure, terrorist infrastructure, tourism infrastructure.

[edit] Related concepts

The term infrastructure is often confused with the following overlapping or related concepts:

[edit] Land improvement and land development

Main articles: Land improvement and Land development

The terms land improvement and land development are a general terms that in some contexts may include infrastructure, but in the context of a discussion of infrastructure would refer only to smaller scale systems or works that are not included in infrastructure because they are typically limited to a single parcel of land, and are owned and operated by the land owner. For example, an irrigation canal that serves a region or district would be included with infrastructure, but the private irrigation systems on individual land parcels would be considered land improvements, not infrastructure. Service connections to municipal service and public utility networks would also be considered land improvements, not infrastructure. [10] [11]

[edit] Public works and public services

Main article: public works

The term public works includes government owned and operated infrastructure as well as public buildings such as schools and court houses. The term public works generally refers to physical assets needed to deliver public services.

Main article: public services

Public services include both infrastructure and services generally provided by government.

[edit] Typical attributes

Infrastructure generally has the following attributes:

[edit] Capital assets that provide services

  • They are physical assets that provide services;
  • The people employed in the infrastructure sector generally maintain, monitor and operate the assets, but do not offer services to the clients or users of the infrastructure. Interactions between workers and clients are generally limited to administrative tasks concerning ordering, scheduling or billing of services.

[edit] Large networks

  • They are large networks constructed over generations, and are not often replaced as a whole system.
  • The network provides services to a geographically defined area.
  • The system or network has a long life because its service capacity is maintained by continual refurbishment or replacement of components as they wear out.

[edit] Historicity and interdependence

  • The system or network tends to evolve over time as it is continuously modified, improved, enlarged, and as various components are re-built, decommissioned or adapted to other uses.
  • The system components are interdependent and not usually capable of subdivision or separate disposal, and consequently are not readily disposable within the commercial marketplace.
  • The system interdependency may limit a component life to a lesser period than the expected life of the component itself.

[edit] Natural monopoly

  • The systems tend to be natural monopolies, insofar that economies of scale means that multiple agencies providing a service are less efficient than would be the case if a single agency provided the service.
  • The assets have a high initial cost and a value that is difficult to determine.
  • Once most of the system is built, the marginal cost of servicing additional clients or users tends to be relatively inexpensive, and may be negligeable if there is no need to increase the peak capacity or the geographical extent of the network.

[edit] Types of infrastructure

The following list is limited to capital assets that serve the function of conveyance or channelling of people, vehicles, fluids, energy or information, and which take the form either of a network or of a critical node used by vehicles, or used for the transmission of electro-magnetic waves. Infrastructure systems include both the fixed assets and the control systems and software required to operate, manage and monitor the systems, as well as any accessory buildings, plants or vehicles that are an essential part of the system.

[edit] Transportation infrastructure

[edit] Energy infrastructure

[edit] Water management infrastructure

  • Drinking water supply, including the system of pipes, pumps, valves, filtration and treatment equipment and meters, including buildings and structures to house the equipment, used for the collection, treatment and distribution of drinking water
  • Sewage collection and disposal
  • Drainage systems (storm sewers, ditches, etc..)
  • Major irrigation systems (reservoirs, irrigation canals)
  • Major flood control systems (dikes, levees, major pumping stations and floodgates)

[edit] Communications infrastructure

  • Telephone networks (land lines) including switching systems
  • Mobile phone networks
  • Cable television networks including receiving stations and cable distribution networks
  • Internet backbone, including high-speed data cables, routers and servers as well as the protocols and other basic software required for the system to function
  • Communication satellites
  • Undersea cables
  • Major private, government or dedicated telecommunications networks, such as those used for internal communication and monitoring by major infrastructure companies, by governments, by the military or by emergency services
  • Pneumatic tube mail distribution networks

[edit] Waste management facilities

[edit] Geophysical monitoring networks

[edit] Other systems or networks

Note that certain systems or facilities that are similar to infrastructure are not included in this list because they are essentially services performed by people (commuter bus services, garbage collection services, emergency services) or they are facilities that are not necessarily part of or in the form of a network (parks, sports facilities), or they are essentially privately-owned industrial plants that do not necessarily depend on a fixed distribution network (oil refineries). However solid waste disposal facilities were included because they are often the critical nodal points of a network-like public service (garbage collection), and are usually publicly owned or heavily regulated. Telecommunication systems are included if their function is limited to the conveyance of information (telephone system), but not if their function includes supplying the content of that information (TV or radio networks).

[edit] Economics, Management and Engineering

[edit] Ownership and Financing

Infrastructure may be owned and managed by governments or by private companies, such as public utility or railway companies. Generally, most roads, major ports and airports, water distribution systems and sewage networks are publicly owned, whereas most energy and telecommunications networks are privately owned. Publicly owned infrastructure may be paid for from taxes, tolls or metered user fees, whereas private infrastructure is generally paid for by metered user fees. Major investment projects are generally financed by the issuance of long-term bonds.

Note that government owned and operated infrastructure may be developed and operated in the private sector or in public-private partnership in addition to in the public sector.

In the United States, public spending on infrastructure has varied between 2.3% and 3.6% of GDP since 1950. [12]

[edit] Planning and Management

Main article: Infrastructure Asset Management

The method of 'Infrastructure Asset Management' is based upon the definition of a Standard of Service (SoS) that describes how an asset will perform in objective and measurable terms. The SoS includes the definition of a minimum condition grade, which is established by considering the consequences of a failure of the infrastructure asset.

The key components of 'Infrastructure Asset Management' are:

[edit] Engineering

Main articles: engineering and project management

Most infrastructure is designed by civil engineers, except for telecommunications, electricity and monitoring networks, that are designed mainly by electrical engineers. In the case of urban infrastructure, the general layout of roads, sidewalks and public placed may sometimes be designed by urbanists or architects, although the detailed design will still be performed by civil engineers.

In terms of engineering tasks, the design and construction management process usually follows these steps:

  • Preliminary Studies:
    • Determine existing and future traffic loads, determine existing capacity, and estimate the existing and future standards of service;
    • Conduct a preliminary survey and obtain information from existing air photos, maps, plans, etc.
    • Identify possible conflicts with other assets or topographical features;
    • Perform environmental impact studies:
    • Given various time horizons, standards of service, environmental impacts and conflicts with existing structures or terrain, propose various preliminary designs;
    • Estimate the costs of the various designs, and make recommendations;
  • Detailed Survey:
    • Perform a detailed survey of the construction site;
    • Obtain As Built drawings of existing infrastructure;
    • Dig exploratory pits where required to survey underground infrastructure;
    • Perform soil sampling and testing to estimate nature, degree and extent of soil contamination;
  • Authorization:
    • Obtain authorization from environmental and other regulatory agencies;
    • Obtain authorization from any owners or operators of assets affected by the work;
    • Inform emergency services, and prepare contingency plans in case of emergencies;
  • Tendering:
    • Prepare administrative clauses and other tendering documents;
    • Organize and announce a Call for Tenders;
    • Answer contractor questions and issue addenda during the tendering process;
    • Receive and analyse tenders, and make a recommendation to the owner;
  • Construction Supervision:
    • Once the construction contract has been signed between the owner and the general contractor, once all authorisations have been obtained, and once all pre-construction submittals have been received from the general contractor, the construction supervisor issues an Order to Begin Construction;
    • Regularly schedule meetings and obtain contact information for the general contractor (GC) and all interested parties;
    • Obtain a detailed work schedule and list of subcontractors from the GC.
    • Obtain detailed traffic diversion and emergency plans from the GC;
    • Obtain proof of certification, insurance and bonds;
    • Examine shop drawings submitted by the GC;
    • Receive reports from the materials quality control lab;
    • When required, review Change requests from the GC, and issue Construction Directives and Change Orders;
    • Follow work progress and authorize partial payments;
    • When substatially completed, inspect the work and prepare a list of deficiencies;
    • Supervise testing and commissionning;
    • Verify that all operating and maintenance manuals, as well as warranties, are complete;
    • Prepare "As Built" drawings;
    • Make a final inspection, issue a certificate of final completion and authorize the final payment.

[edit] Impact on Economic Development

Main article: economic development

Investment in infrastructure is part of the capital accummulation required for economic development.

[edit] Use as Economic stimulus

During the Great Depression of the 1930s, many governments undertook public works projects in order to create jobs and stimulate the economy. The economist John Maynard Keynes provided a theoretical justification for this policy in the The General Theory of Employment, Interest and Money [13], published in 1936. Following the global financial crisis of 2008–2009, some are again proposing investing in infrastructure as a means of stimulating the economy (see the American Recovery and Reinvestment Act of 2009)

[edit] History

Main articles: History of road transport, Freeway#History, Canal#History, History of rail transport, Electric power transmission#History, Electrical telegraph#History, Telephone#History, and Public switched telephone network#Early history

[edit] Before 1700

Infrastructure before 1700 consisted mainly of roads and canals. Canals were used for transportation or for irrigation. Sea navigation was aided by ports and lighhouses. A few advanced cities had aqueducts that serviced public fountains and baths, and even fewer had sewers.

Roads:

The first roads were tracks that often followed game trails, such as the Natchez Trace.[14].

The first paved streets appear to have been built in Ur in 4000 BC. Corduroy roads were built in Glastonbury, England in 3300 BC[15] and brick-paved roads were built in the Indus Valley Civilization on the Indian subcontinent from around the same time. In 500 BC, Darius I the Great started an extensive road system for Persia (Iran), including the Royal Road.

With the advent of the Roman Empire, the Romans built roads using deep roadbeds of crushed stone as an underlying layer to ensure that they kept dry. On the more heavily traveled routes, there were additional layers that included six sided capstones, or pavers, that reduced the dust and reduced the drag from wheels.

In the medieval Islamic world, many roads were built throughout the Arab Empire. The most sophisticated roads were those of the Baghdad, Iraq, which were paved with tar in the 8th century.[16]

Canals and irrigation systems:

The oldest known canals were built in Mesopotamia circa 4000 BC, in what is now modern day Iraq and Syria. The Indus Valley Civilization in Pakistan and North India (from circa 2600 BC) had a sophisticated canal irrigation system.[17] In Egypt, canals date back to at least 2300 BC, when a canal was built to bypass the cataract on the Nile near Aswan.[18]

In ancient China, large canals for river transport were established as far back as the Warring States (481-221 BC).[19] By far the longest canal was the Grand Canal of China, still the longest canal in the world today at 1,794 kilometres (1,115 mi) long, and completed in 609.

In Europe, canal building began in the Middle Ages because of commercial expansion from the 12th century AD. Notable canals were the Stecknitz Canal in Germany in 1398, the Briare Canal connecting the Loire and Seine in France (1642) followed by the Canal du Midi (1683) connecting the Atlantic to the Mediterranean. Canal building progressed steadily in Germany in the 17th and 18th centuries with three great rivers, the Elbe, Oder and Weser being linked by canals.

[edit] 1700 to 1870

Roads:

As traffic levels increased in England and roads deteriorated. Toll roads were built by Turnpike Trusts, especially between 1730-1770. Turnpikes were also later built in the United States. They were usually built by private companies under a government franchise.

Water transport on rivers and canals carried many farm goods from the frontier U.S. (between the Appalachian mountains and Mississippi River) in the early 19th century, but the shorter route over the mountains had advantages.

In France, Pierre-Marie-Jérôme Trésaguet is widely credited with establishing the first scientific approach to road building about the year 1764. It involved a layer of large rocks, covered by a layer of smaller gravel. John Loudon McAdam (1756-1836) designed the first modern highways, and developed an inexpensive paving material of soil and stone aggregate (known as macadam).[20]

Canals:

In Europe, particularly Britain and Ireland, and then in the young United States and the Canadian colonies, inland canals preceded the development of railroads during the earliest phase of the Industrial Revolution. In Britain between 1760 and 1820 over one hundred canals were built.

In the United States, navigable canals reached into isolated areas and brought them in touch with the world beyond. By 1825 the Erie Canal, 363 miles (584 km) long with 82 locks, opened up a connection from the populated Northeast to the fertile Great Plains. During the 19th century, the length of canals grew from 100 miles (160 km) to over 4,000, with a complex network making the Great Lakes navigable, in conjunction with Canada, although some canals were later drained and used as railroad rights-of-way.

Railways:

The earliest railways were used in mines or to bypass waterfalls, and were pulled by horses or by people. In 1811 John Blenkinsop designed the first successful and practical railway locomotive [21], and a line was built connecting the Middleton Colliery to Leeds. The Liverpool and Manchester Railway,[22], considered to be the world's first "Inter City" line, opened in 1826. In the following years, railways spread throughout the United Kingdom and the world, and became the dominant means of land transport for nearly a century.

In the United States, the 1826 Granite Railway in Massachusetts was the first commercial railroad to evolve through continuous operations into a common carrier. The Baltimore and Ohio, opened in 1830, was the first to evolve into a major system. In 1869, the symbolically important transcontinental railroad was completed in the United States with the driving of a golden spike at Promontory, Utah.[23]

Telegraph service:

The first commercial electrical telegraph was first successfully demonstrated on 25 July 1837 between Euston and Camden Town in London. [24] It entered commercial use on the Great Western Railway over the 13 miles (21 km) from Paddington station to West Drayton on 9 April 1839.

In the United States, the telegraph was developed by Samuel Morse and Alfred Vail. On 24 May 1844, Morse made the first public demonstration of his telegraph by sending a message from the Supreme Court Chamber in the U.S. Capitol in Washington, D.C. to the B&O Railroad "outer depot" (now the B&O Railroad Museum) in Baltimore. The Morse/Vail telegraph was quickly deployed in the following two decades. On 24 October 1861, the first transcontinental telegraph system was established.

The first successful transatlantic telegraph cable was completed on 27 July 1866, allowing transatlantic telegraph communications for the first time. Within 29 years of its first installation at Euston Station, the telegraph network crossed the oceans to every continent but Antarctica, making instant global communication possible for the first time.

[edit] 1870 to 1920

Roads:

Tar-bound macadam (tarmac) was applied to macadam roads towards the end of the 19th century in cities such as Paris. In the early 20th century tarmac and concrete paving were extended into the countryside.

Canals:

Many notable sea canals were completed in this period: the Suez Canal (1869); the Kiel Canal (1897) - which carries tonnage many times that of most other canals; and the Panama Canal, opened in 1914.

Telephone service:

In 1876, Alexander Graham Bell achieved the first successful telephone transmission of clear speech. The first telephones had no network but were in private use, wired together in pairs. Users who wanted to talk to different people had as many telephones as necessary for the purpose. A user who wished to speak, whistled into the transmitter until the other party heard. Soon, however, a bell was added for signalling, and then a switchhook, and telephones took advantage of the exchange principle already employed in telegraph networks. Each telephone was wired to a local telephone exchange, and the exchanges were wired together with trunks. Networks were connected together in a hierarchical manner until they spanned cities, countries, continents and oceans.

Electricity:

At the Paris Exposition of 1878, electric arc lighting had been installed along the Avenue de l'Opera and the Place de l'Opera, using electric Yablochkov arc lamps, powered by Zénobe Gramme alternating current dynamos[25][26]. Yablochkov candles required high voltage, and it was not long before experimenters reported that the arc lights could be powered on a 7 mile circuit[27]. Within a decade scores of cities would have lighting systems using a central power plant that provided electricity to multiple customers via electrical transmission lines. These systems were in direct competition with the dominant gaslight utilities of the period.

The first electricity system supplying incandescent lights was built by Edison Illuminating Company in lower Manhattan eventually serving one square mile with 6 "jumbo dynamos" housed at Pearl Street Station.

The first transmission of three-phase alternating current using high voltage took place in 1891 during the international electricity exhibition in Frankfurt. A 25 kV transmission line, approximately 175 kilometers long, connected Lauffen on the Neckar and Frankfurt. Voltages used for electric power transmission increased throughout the 20th century. By 1914 fifty-five transmission systems operating at more than 70,000 V were in service, the highest voltage then used was 150,000 volts. [28]

Water distribution and sewers: This is a stub.

Subways: This is a stub.

[edit] Since 1920

Roads:

In 1925, Italy was the first country to build a freeway-like road, which linked Milan to Lake Como.[29] It is known in Italy as the Autostrada dei Laghi. In Germany, the autobahns formed the first limited-access, high-speed road network in the world, with the first section from Frankfurt am Main to Darmstadt opening in 1935. The first long-distance rural freeway in the United States is generally considered to be the Pennsylvania Turnpike, which opened on October 1, 1940.[30]. In the United States, the Interstate Highway System was authorized by the Federal-Aid Highway Act of 1956[31]. Most of the system was completed between 1960 and 1990.

Rural electrification: This is a stub.

Telecommunications: This is a stub.

[edit] See also

[edit] References

  1. ^ Infrastructure, Online Compact Oxford English Dictionary, http://www.askoxford.com/concise_oed/infrastructure (accessed January 17 2009)
  2. ^ Sullivan, arthur; Steven M. Sheffrin (2003). Economics: Principles in action. Upper Saddle River, New Jersey 07458: Pearson Prentice Hall. pp. 474. ISBN 0-13-063085-3. http://www.pearsonschool.com/index.cfm?locator=PSZ3R9&PMDbSiteId=2781&PMDbSolutionId=6724&PMDbCategoryId=&PMDbProgramId=12881&level=4. 
  3. ^ Infrastructure, American Heritage® Dictionary of the English Language, http://education.yahoo.com/reference/dictionary/entry/infrastructure (accessed January 17 2009)
  4. ^ Infrastructure, JP1-02, Department of Defense Dictionary of Military and Associated Terms, p. 260, 12 April 2001 (rev. 31 August 2005) http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA439918&Location=U2&doc=GetTRDoc.pdf(accessed January 17 2009)
  5. ^ Online Etymology Dictionary. Douglas Harper, Historian. http://dictionary.reference.com/browse/infrastructure (accessed: April 24, 2008)
  6. ^ The Etymology of Infrastructure and the Infrastructure of the Internet, Stephen Lewis on his blog Hag Pak Sak, posted September 22 2008. http://hakpaksak.wordpress.com/2008/09/22/the-etymology-of-infrastructure-and-the-infrastructure-of-the-internet/ (accessed: January 17, 2008)
  7. ^ Infrastructure for the 21st Century, Washington, D.C.: National Academy Press, 1987
  8. ^ Association of Local Government Engineers New Zealand: "Infrastructure Asset Management Manual", June 1998 - Edition 1.1
  9. ^ D.O.D. Dictionary of Military and Associated Terms, 2001 (rev. 2005)
  10. ^ Land improvement, Online BusinessDictionary.com, http://www.businessdictionary.com/definition/land-development.html (accessed January 31 2009)
  11. ^ Land development, Online BusinessDictionary.com, http://www.businessdictionary.com/definition/land-development.html (accessed January 31 2009)
  12. ^ "Money for Public Projects", The New York Times, November 19 2008 http://www.nytimes.com/imagepages/2008/11/19/business/economy/19leonhardt_graphic.ready.html (accessed January 26, 2009)
  13. ^ Keynes, John Maynard (2007) [1936]. The General Theory of Employment, Interest and Money. Basingstoke, Hampshire: Palgrave Macmillan. ISBN 0230004768 http://cepa.newschool.edu/het/essays/keynes/keynescont.htm.
  14. ^ Lay, M G (1992). Ways of the World. Sydney: Primavera Press. pp. 401. ISBN 1-875368-05-1.
  15. ^ Lay (1992)
  16. ^ Dr. Kasem Ajram (1992). The Miracle of Islam Science (2nd Edition ed.). Knowledge House Publishers. ISBN 0-911119-43-4. 
  17. ^ Rodda 2004, p. 161.
  18. ^ Hadfield 1986, p. 16.
  19. ^ Needham 1971, p. 269.
  20. ^ Lay (1992)
  21. ^ "John Blenkinsop". Encyclopedia Brittanica. http://www.britannica.com/eb/article-9001800. Retrieved on 2007-09-10. 
  22. ^ "Liverpool and Manchester". http://www.spartacus.schoolnet.co.uk/RAliverpool.htm. Retrieved on 2007-09-19. 
  23. ^ Ambrose, Stephen E. (2000). Nothing Like It In The World; The men who built the Transcontinental Railroad 1863-1869. Simon & Schuster. ISBN 0-684-84609-8. 
  24. ^ The electric telegraph, forerunner of the internet, celebrates 170 years BT Group Connected Earth Online Museum. Accessed July 2007
  25. ^ David Oakes Woodbury (1949). A Measure for Greatness: A Short Biography of Edward Weston. McGraw-Hill. p. 83. http://www.archive.org/stream/measureforgreatn001419mbp/measureforgreatn001419mbp_djvu.txt. Retrieved on 2009-01-04. 
  26. ^ John Patrick Barrett (1894). Electricity at the Columbian Exposition. R. R. Donnelley & sons company. p. 1. http://books.google.com/books?id=lF5KAAAAMAAJ&pg=PA3. Retrieved on 2009-01-04. 
  27. ^ "Notes on the Jablochkoff System of Electric Lighting". Journal of the Society of Telegraph Engineers IX (32): 143. 1880-3-24. http://books.google.com/books?id=lww4AAAAMAAJ&pg=PA143. Retrieved on 2009-01-07. 
  28. ^ Bureau of Census data reprinted in Hughes, pp. 282-283
  29. ^ Paul Hofmann, "Taking to the Highway in Italy", New York Times, 26 April 1987, 23.
  30. ^ Phil Patton, The Open Road: A Celebration of the American Highway (New York: Simon & Schuster, 1986), 77.
  31. ^ "The cracks are showing". The Economist. 2008-06-26. http://www.economist.com/world/unitedstates/displayStory.cfm?story_id=11636517. Retrieved on 2008-10-23. 

[edit] External links

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