John Loudon McAdam: The Father of the Modern Road

John Loudon McAdam was a pioneering Scottish Engineer who single-handedly changed the way roads were built around the world. His innovative shallow camber, crushed compacted stone layered roads would become the standard for road building the world over.

His innovation was the biggest advancement in road building since the Roman Empire. If you are lucky you might still see some existing ones around the world today. The advent of motor vehicles has meant many of the original roads have now been resurfaced or replaced with a tar coating or Asphalt.

Before McAdam's roads, large "flat" rocks were laid together to approximate a level surface. Not only did John Loudon McAdam's design result in a smoother surface and carriage ride, but it was cheaper to build and lasted longer. This "new" roadway surface and construction process have since been immortalized with McAdam’s name, though with the Americanised spelling MacAdam or macadam.

McAdam's life was interesting in an of itself. Born into aristocracy, family problems would see him move to the U.S. just before the revolution. After the conclusion of the war, he and his family would return to the U.K. to restart their lives once again. An illustrious career in road building would see him invent one of the most important advancements in civil engineering to be seen for several thousand years. Needless to say, the world might look very different today if it wasn't for Mr. McAdam.

John McAdam's early life

John Loudon McAdam was born in Ayr, Scotland on the 23rd of September 1756. Some sources will state the 21st of September but this seems to be a point of contention amongst local historians. John was born to James McAdam, The Baron of Waterhead, and the niece of the 7th Earl of Dundonald, Susanna Chochrane. He was the youngest of 10 children and the second son of the Baron of Waterhead.

His elder brother, James, a Captain in the military, died when John was about 7 years old. It is not clear if he died of natural causes or from his services in the army. This tragic event left John as the only surviving male within the Waterhead family line.

Interestingly, his family name is thought to have changed from McGregor at some point in their ancestry. This is thought to have been changed to McAdam sometime during King James's VI's reign. The name change is claimed to be a direct reference to the descent of the family from the biblical Adam, "Son of Adam".

John Loudon McAdam's family stayed in the house he was born until 1760 when a new residence was built in Lagwyne. The Lagwyne Castle, now a ruin, is located on the outskirts of Carspairn in Scotland. This was part of the Waterhead Estate.

Shortly after moving in, the Castle actually burnt down. John's parents were actually away on business when the tragedy occurred. McAdam narrowly escaped the flames when he was rescued by the family nurse.

John's father decided not to rebuild the Castle and moved his family to, yes you've guessed it, another castle in Barquhan near Straiton. Whitefoord Castle has since been demolished and replaced with the currently standing Blaiguhan Castle.

John moves to America

John's father had somewhat of a less than ordered lifestyle and poorly managed his financial affairs. Almost inevitably James's financial "empire" collapsed. The resulting financial devastation forced James to sell his family's ancient Waterhead estate.

John's early life was about to change forever when his father, James, passed away when John was only 14. John moved to America in 1770 to be looked after by his uncle. William MacAdam, his uncle, was a very successful New York Merchant at the time.

John Loudon McAdam and his uncle also helped to found the New York Chamber of Commerce. Members included none other than one Samuel Adam and Paul Revere.

John McAdam, clearly inspired by his uncle, quickly became a merchant in his own right. His business prospered from Boston to Charleston. He even co-financed a Privateer ship, The General Matthew, which was engaged in the battle of Savannah Harbor during the revolutionary war. The vessel was heavily damaged during the conflict by secessionist forces.

John married Gloriana Nicoll who was the daughter of William Nicoll of Suffolk, New York. The couple inherited 1/3 of West Neck on Shelter Island and Blue Point Islip. When the American revolution gripped the 13 Colonies, John and his extended family declared their support for Loyalist Forces, sorry U.S. readers.

His uncle, Gilbert, later known as Gilbert McAdams of Merkland was "aide to Camp" to Richard Maitland, Adjutant General of the British forces in America. Richard Maitland later married Mary McAdam, sister of Gilbert and aunt to John.

John McAdam served in the British reserves during the revolution and also acted as a government contractor who engaged in the sale of prizes of war.

Yes, that was an official "job" at the time.

McAdam's life back in the UK

As you can imagine, once the revolutionary wars were concluded, John and his family were no longer welcome in America. John, his wife, and two children, swiftly relocated to Scotland in 1783. John's substantial assets in America were subsequently "appropriated" by the new American government. He did manage to take enough of his wealth with him to purchase an estate in Sauchrie, Ayrshire.

John Loudon McAdam took part in some local affairs in Ayrshire including operating the local Kaims Colliery. This coal mine supplied coal to the British Tar Company of Archibald Cochrane 9th Earl of Dundonald and Partners.

John's association with Admiral Lord Cochrane enabled him to acquire a controlling interest in the iron works and mills of the area that produced coal products, including tar.

The steel manufacturing processes, in particular, had a need for the coke byproducts from processing coal. At this time the flammability of coal gas was not recognized and sadly for the Earl, this was not capitalized on.

Cochrane had ambitions to sell the tar to the Royal Navy as a sealant for their ships hulls. Tests were conducted on a buoy which was very encouraging for both Cochrane and the Navy. The use of tar was, however, a direct competitor to copper hulling at the time. Conflicts of interest within the Navy and shipwright industries led to the patent expiring and the process being adopted by the Navy. Cochrane's investment had proved disastrous for him personally.

Adam had, unknowingly or not, built a strong knowledge base for his revolutionary invention in the future.

Laying the foundations for macadam roads

After his return to the UK, John began to experiment with road construction. One of his first tests was with road stones. He successfully built a road leading from the Alloway-Maybole highway to his newly acquired estate.

His road eventually became part of the highway and, interestingly, it was still in use right up to 1936.

in 1787, McAdam became a Trustee for the Ayrshire Turnpike. He found himself becoming increasing involved over time with the day to day maintenance and construction of roads over the next decade.

In 1974, John accepted his commission as a Major in the Royal Artillery Corp. John was particularly proud of this achievement, which incidentally, was one of the last to be personally signed by King George the 3rd. In 1798 he also received a Government appointment during the early stages of the Napoleonic War.

His role was as an agent providing logistical support for the Royal Navy in Falmouth, England. In 1801 he was recommended for a post as a surveyor at the Bristol Turnpike.

John Loudon McAdam accepted the position and this one decision that would change his life, and the world of roads, as we know it forever.

Roads would ever be the same again

After deciding to move to Bristol in 1802, he became a general surveyor for the Bristol Corporation in 1804. His experience with road construction over the last few years began to crystallize ideas for massive improvement in now middle-aged McAdam.

By this time he was a Trustee for no less than 34 Road Trusts.McAdam would put forward several cases for Parliamentary consideration on improving current infrastructure with a, then, novel solution. On three separate occasions in 1810, 1819 and 1823 he provided evidence for Parliamentary inquiries. He also penned two treatises in 1816 and 1819.

McAdam would put forward several cases for Parliamentary consideration on improving current infrastructure with a, then, novel solution. He also penned two treatises in 1816 and 1819.

McAdam starts to make waves

In his Remarks on the Present System of Road-Making and Practical Essay on the Scientific Repair and Preservation of Roads, he argued that roads should be raised above the surrounding ground. John also argued that they should have a composite structure of layered rocks and gravel laid in a systematic process.

At around this time, in 1816, John Loudon McAdam was appointed as the surveyor for the Bristol Turnpike Trust. Putting his "money where his mouth is" John began to remake the roads using crushed stone bound with gravel built on a firm base of foundation stones.

His new roads also had a camber which made them ever so slightly convex. This ensured rainwater could rapidly drain of the carriageway instead of pooling and penetrate the structure. This has been recognized as the greatest advance in road building since the Romans almost 2000 years before.

The process came to be known as Macadamisation or simply Macadam.

Macadam Roads are born

McAdam's new roads quickly became popular around the world. The National Road, completed in 1930, in the United States was the first Macadam Road in North America. His process quickly took Europe by storm with the vast majority of main roads undergoing Macadamisation by the end of the 19th Century.

McAdam was paid £5,000 for his work with the Bristol Turnpike Trust and was also made Surveyor-General of Metropolitan Roads in 1820. His inspired work on road building also made him many enemies. His new process and management work had exposed the corruption and abuse of existing road tolls at the time. Turnpike Trusts were revealed to the public as unscrupulous in nature with many running at a deliberate loss despite high toll takings.

This would cost John financially. His £5,000 (worth about $540,000 today) grant for expenses to the British Government to "just" £2,000 in 1827.

The Macadamisation process

McAdam's method for road building vastly simplified the process as well as improving the longevity of the completed infrastructure. John discovered that massive foundations of rock-on-rock were completely unnecessary.

He asserted that native soil alone should be enough to support the weight of the road and traffic so long as it was covered a "road crust" to prevent erosion of the underlying.

Macadam roads were laid as level as possible with a shallow camber across the structure. For example, on a 9.1-meter wide road, the surface would only need to be 7.6cm from the edges of the center line. The road structure was also elevated above the water table. This allowed for rainwater to run off into ditches on either side of the carriageway.

The size of stones was a critical element of McAdam's new roads. The lower 20-centimetres of the road thickness was restricted to stones no larger than 7.5 centimeters. The upper 5-centimeter layer of stones had to be around 2-centimeters. Each stone was checked by workers and supervisors before being laid.

John Loudon McAdam's designs dictated that no materials that could absorb water and damage the structure through freeze-thaw should be incorporated into the road. John was also determined that nothing should be laid on top of the road surface to "bind" them.

John Loudon McAdam's experience with road building had taught him that a layer of broken angular stones would act as a solid mass in their own right. This negated the need for a large stone layer previously used on roads. As the surface stones were also pretty small, at least smaller than commonly used tires at the time, they would provide a great running surface for traffic.

But what about Tresaguet and Telford?

There were some innovations made to road building prior to John Loudon McAdam. Pierre-Marie-Jérôme Trésaguet, for example, is considered to be the first person to improve road building since Roman times. Pierre was a French engineer.

He worked paving roads in Paris between 1757 and 1764. He also worked as the chief engineer for roads in Limoges, where he had the opportunity to find better and cheaper road-building techniques.

Tresaguet proposed a new method of building roads consisting of three layers of stones laid on a crowned subgrade with side ditches for drainage. The first two layers consisted of angular, hand-broken, aggregate of 7.6 cm size to about a depth of 20cm. The third layer was to consist of a 2.5cm aggregate size of around 5cm thick.

This top layer was meant to provide a smoother shape and carriages whilst protecting the larger stones underneath from iron wheels and horseshoes. Drainage problems were helped by adding a camber to the road and digging deep ditches either side of the carriageway.

As the entire structure was laid within a trench, this solution would be plagued with drainage problems.

Thomas Telford's Road

Thomas was a Scottish Engineer and surveyor who applied Tresaguet's and improved on them. He, however, put more emphasis on high-quality stone. Telford also noted that some of the problems the French were seeing with their roads could be avoided using cubical stone blocks.

Thomas used partially shaped paving stones, called pitchers, with a slightly flat face on the bottom instead of more amorphous hand broken aggregate, like Tresaguet's solution. Telford kept the natural formation level and used masons to camber the road surface on the upper surface of the blocks.

His solution placed a 15cm layer of stone no bigger than 6cm on top of the rock foundation. The road surface was finished using a mixture of gravel and broken stone. This came to be known as "Telford pitching". His roads depended on the resistant structure to prevent water from pooling and weakening the pavement structure. The carriageway was also above ground level whenever possible.

Where this was not possible, Telford's technique required the area around the road to be drained. Previously to Telford, road builders, especially in Britain, had ignored the need for drainage. Telford's "rediscovery" of this principle was a major breakthrough at the time and "paved" the way for McAdam's great achievements.

So what made macadam roads so innovative?

Although Tresaguet's designs had made some headway, they had significant issues with drainage. This had been partially improved with Telford's proposal but McAdam made drainage the primary consideration for his designs. McAdam required his pavements to be elevated above the surrounding ground. Primarily above the water table.

Telford's roads were pretty labor intensive during construction and maintenance, requiring highly skilled masons to be employed to work the foundation stone to provide the road camber. McAdam's solution provided a method by which the road surface would be compacted by traffic over time, a process that was more than adequate for the time. McAdam also put a strong emphasis on continuous maintenance, where required.

Although John Loudon McAdam had drawn on the failures and success of his predecessors, his complete reliance on broken aggregate rather than shaped stone blocks for structural strength was the biggest "paradigm shift" in road construction. McAdam’s success was also due to his efficient administration and his strong view that road managers needed skill and motivation.


Long after John Loudon McAdam's death in 1836, the advent of the motor car caused serious problems for the now very popular Macadam roads. As fast-moving cars moved over the road surface, it would create an area of low pressure. This would suck dust from the surface, creating large dust clouds and damage the road integrity.

In 1901 a Swiss Doctor, Ernest Guglielminetti, noted that if the surface could be coated with tar to solve this problem. Ernest came upon the idea of using tar from Monaco's Gasworks for binding the dust.

A little later, a mixture of coal tar and ironworks slag was patented by Edgar Purnell Hooley as tarmac.

The improved durability that this surfacing provided has meant that most stretches of Macadam roads have been resurfaced since the 1920's. So ubiquitous were Macadam roads across the world, especially in the U.S. that even modern roads are sometimes referred to as Macadam despite actually being asphalt or concrete.

This applies to Tarmac as well which can be colloquially used to describe asphalt roads or runways.

Death and legacy

John Loudon McAdam died on the 26th November 1836 in Moffat, Dumfriesshire, Scotland. He was returning to his home in Hoddesdon, Hertfordshire at the time. He had been enjoying a summer visit to Scotland at the time.

John's three sons and four grandsons would follow in their venerable ancestor's footsteps and assist future governments managing turnpike trusts across the UK. His second surviving son, James Nicoll McAdam, the "Colossus of Roads", was knighted for managing turnpike trusts: a knighthood, it is said, previously offered to his father but declined.

John Loudon McAdam contribution to engineering, more specifically Road building, changed the world forever. Although this process has been refined over time, the basic principle is still used today.

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