Editing Road transport (section)

===Industrial civil engineering===
[[File:ThomasTelford.jpg|thumb|right|[[Thomas Telford]], the "Colossus of the Roads" in early 19th century Britain.]] 
By the late 18th and early 19th centuries, new methods of highway construction had been pioneered by the work of three British engineers, [[John Metcalf (civil engineer)|John Metcalf]], [[Thomas Telford]] and [[John Loudon McAdam]], and by the French road engineer [[Pierre-Marie-Jérôme Trésaguet]].

The first professional road builder to emerge during the [[Industrial Revolution]] was [[John Metcalf (civil engineer)|John Metcalf]], who constructed about {{convert|180|mi|km}} of [[turnpike trust|turnpike road]], mainly in the north of England, from 1765. He believed a good road should have good foundations, be well drained and have a smooth [[convex geometry|convex]] surface to allow [[Rain|rainwater]] to drain quickly into ditches at the side. He understood the importance of good drainage, knowing it was rain that caused most problems on the roads.

[[Pierre-Marie-Jérôme Trésaguet]] established the first [[scientific method|scientific approach]] to [[road building]] in France at the same time. He wrote a memorandum on his method in 1775, which became general practice in France. It involved a layer of large rocks, covered by a layer of smaller gravel.  The lower layer improved on Roman practice in that it was based on the understanding that the purpose of this layer (the sub-base or [[base course]]) is to transfer the weight of the road and its traffic to the ground, while protecting the ground from deformation by spreading the weight evenly. Therefore, the sub-base did not have to be a self-supporting structure. The upper running surface provided a smooth surface for vehicles while protecting the large stones of the sub-base.

The surveyor and engineer [[Thomas Telford]] also made substantial advances in the engineering of new roads and the construction of bridges. His method of road building involved the digging of a large trench in which a foundation of heavy rock was set. He also designed his roads so that they sloped downwards from the centre, allowing drainage to take place, a major improvement on the work of Trésaguet. The surface of his roads consisted of broken stone. He also improved on methods for the building of roads by improving the selection of stone based on thickness, taking into account traffic, alignment and slopes. During his later years, Telford was responsible for rebuilding sections of the [[Watling Street|London to Holyhead road]], a task completed by his assistant of ten years, [[John Benjamin Macneill|John MacNeill]].<ref>{{cite web|first=Mary|last=Bellis|title=Thomas Telford|work=About: inventors|publisher=About, Inc, [[New York Times]]|year=2007|url=http://inventors.about.com/od/tstartinventors/a/Thomas_Telford.htm|archive-url=https://archive.today/20120630042714/http://inventors.about.com/od/tstartinventors/a/Thomas_Telford.htm|url-status=dead|archive-date=June 30, 2012|access-date=2007-01-19}}</ref>

[[Image:Rakeman – First American Macadam Road.jpg|thumb|Construction of the first macadamized road in the United States (1823). In the foreground, workers are breaking stones "so as not to exceed 6 ounces in weight or to pass a two-inch ring".<ref name=rakemanPainting>[https://www.fhwa.dot.gov/rakeman/1823.htm "1823 - First American Macadam Road"]  ''(Painting - [[Carl Rakeman]])'' US Department of Transportation - Federal Highway Administration (Accessed 2008-10-10)</ref>]]
It was another Scottish engineer, [[John Loudon McAdam]], who designed the first modern roads. He developed an inexpensive paving material of soil and stone aggregate (known as [[macadam]]). His road building method was simpler than Telford's, yet more effective at protecting roadways: he discovered that massive foundations of rock upon rock were unnecessary, and asserted that native soil alone would support the road and traffic upon it, as long as it was covered by a road crust that would protect the soil underneath from water and wear.<ref name=ColossusofRoads>{{citation|author=Craig, David|title=The Colossus of Roads|work=Palimpsest|publisher=Strum.co.uk|url=http://www.strum.co.uk/palimps/macadam.htm|access-date=18 June 2010|archive-date=14 November 2020|archive-url=https://web.archive.org/web/20201114110349/http://www.strum.co.uk/palimps/macadam.htm|url-status=live}}</ref>

Also unlike Telford and other road builders, McAdam laid his roads as level as possible. His {{convert|30|ft|m|0|adj=mid|-wide}} road required only a rise of three inches from the edges to the center. Cambering and elevation of the road above the water table enabled rainwater to run off into ditches on either side.<ref name=McAdam1824p38>McAdam (1824), p.38</ref> Size of stones was central to the McAdam's road building theory. The lower {{convert|200|mm|in|0|adj=on}} road thickness was restricted to stones no larger than {{convert|75|mm|in}}. The upper {{convert|50|mm|in|0|adj=on}} layer of stones was limited to {{convert|20|mm|in|0}} size and stones were checked by supervisors who carried scales. A workman could check the stone size himself by seeing if the stone would fit into his mouth. The importance of the 20&nbsp;mm stone size was that the stones needed to be much smaller than the 100&nbsp;mm width of the iron [[carriage]] [[tyres]] that traveled on the road. Macadam roads were being built widely in the United States and Australia in the 1820s and in Europe in the 1830s and 1840s.{{sfn|Lay|1992|p=83}}