MACADAM – Advent of the macadam

 John Loudon McAdam (1756–1836)

John McAdam

John Loudon McAdam was born in AyrScotland in 1756. In 1787 he became a trustee of the Ayrshire Turnpike in the Scottish Lowlands and during the next seven years this hobby became an obsession. He moved to Bristol, England in 1802 and became a Commissioner for Paving in 1806. On 15th of January in 1816 he was elected Surveyor-General of roads for the Turnpike Trust, and was now responsible for 149 miles of road. McAdam first put his ideas about road construction into major practice, the first ‘macadamized’ stretch of road being Marsh Road at Ashton Gate, in Bristol.

McAdam’s methods

Photograph of Macadam Road, ca 1850s, Nicolaus, California

McAdam’s method was simpler, 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. McAdam laid his roads as level as possible. His 30-foot-wide (9.1 m) road required only a rise of 3 inches (7.6 cm) from the edges to the center. Cambering and elevation of the road above the water table enabled rain water to run off into ditches on either side.

The size of stones was essential to the McAdam’s road building theory. The lower 20-centimetre (7.9 in) road thickness was restricted to stones no larger than 7.5 centimeters (3.0 in). The upper 5-centimetre (2.0 in) layer of stones was limited to 2 centimeters (0.79 in) 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 2 cm stone size was that the stones needed to be much smaller than the 10 cm width of the iron carriage tires that travelled on the road.

McAdam believed that the “proper method” of breaking stones for utility and rapidity was accomplished by people sitting down and using small hammers, breaking the stones so that none of them was larger than six ounces in weight. Also, the quality of the road would depend on how carefully the stones were spread on the surface over a sizeable space, one shovelful at a time.

McAdam directed that no substance that would absorb water and affect the road by frost should be incorporated into the road. Neither was anything to be laid on the clean stone to bind the road. The action of the road traffic would cause the broken stone to combine with its own angles, merging into a level, solid surface that would withstand weather or traffic.

Through his road-building experience McAdam had learned that a layer of broken angular stones would act as a solid mass and would not require the large stone layer previously used to build roads. Keeping the surface stones smaller than the tire width made a good running surface for traffic. The small surface stones also provided low stress on the road, so long as it could be kept reasonably dry.

The first macadam in North America

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 [170 g] in weight or to pass a two-inch [5 cm] ring”.

The first macadam road built in the United States was constructed between Hagerstown and Boonsboro, Maryland and was named Boonsboro Turnpike Road. This was the last section of unimproved road between Baltimore on the Chesapeake Bay on to the Ohio River. Stagecoaches traveling the Hagerstown to Boonsboro road in the winter took 5 to 7 hours to cover the 10-mile (16 km) stretch. This road was completed in 1822, using McAdam’s road techniques, except that the finished road was compacted with a cast-iron roller instead of relying on road traffic for compaction. The second American road built using McAdam principles was the Cumberland Road which was 73 miles (117 km) long and was completed in 1830 after five years of work.

McAdam’s influence

McAdam’s renown is due to his effective and economical construction, which was a great improvement over the methods used by his generation. He emphasized that roads could be constructed for any kind of traffic, and he helped to alleviate the resentment travelers felt toward increasing traffic on the roads. His legacy lies in his advocacy of effective road maintenance and management. He advocated a central road authority and the trained professional official, who could be paid a salary that would keep him from corruption. This professional could give his entire time to his duties and be held responsible for his actions.

Water-bound macadam

McAdam’s road building technology was applied to roads by other engineers. One of these engineers was Richard Edgeworth, who filled the gaps between the surface stones with a mixture of stone dust and water, providing a smoother surface for the increased traffic using the roads. This basic method of construction is sometimes known as water-bound macadam.  Although this method required a great deal of manual labor, it resulted in a strong and free-draining pavement. Roads constructed in this manner were described as “macadamized.”

Tar-bound macadam

New Macadam Road construction at McRoberts, Kentucky: pouring tar, August 28, 1926.

With the advent of motor vehicles, dust became a serious problem on macadam roads. The area of low air pressure created under fast-moving vehicles sucked dust from the road surface, creating dust clouds and a gradual unraveling of the road material.[20] This problem was approached by spraying tar on the surface to create tar-bound macadam. On March 13, 1902 in Monaco, a Swiss doctor, Ernest Guglielminetti, came upon the idea of using tar from Monaco’s Gasworks for binding the dust. Later a mixture of coal tar and ironworks slag, patented by Edgar Purnell Hooley as tarmac, was introduced.

A more durable road surface (modern mixed asphalt pavement) sometimes referred to in the US as blacktop, was introduced in the 1920s. This pavement method mixed the aggregates into the asphalt with the binding material before they were laid. The macadam surface method laid the stone and sand aggregates on the road and then sprayed it with the binding material. While macadam roads have now been resurfaced in most developed countries, some are preserved along stretches of roads such as the United States‘ National Road.

Because of the historic use of macadam as a road surface, roads in some parts of the United States (as parts of Pennsylvania) are often referred to as macadam, even though they might be made of asphalt or concrete. Similarly, the term “tarmac” is sometimes colloquially misapplied to asphalt roads or aircraft runways.


Jump up^Lay, Maxwell G (1992), Ways of the World: A History of the World’s Roads and of the Vehicles That Used Them, New Brunswick, N.J.: Rutgers University Press, p. 73, ISBN 0-8135-1758-3, retrieved 18 June 2010 Paperback ISBN 0-8135-2691-4

  1. Jump up to:ab Lay (1992), p.73
  2. Jump up^Smiles, Samuel (1867). The Life of Thomas Telford, Civil Engineer. London: John Murray. p. 331. Retrieved 27 September 2011.
  3. Jump up to:ab Lay (1992), p.74, 75
  4. Jump up^British Museum, Engraving by Charles Turner
  5. Jump up to:ab c W. Skempton (2002). A Biographical Dictionary of Civil Engineers in Great Britain and Ireland: 1500-1830. p.416. Thomas Telford, 2002
  6. Jump up^McAdam, John Loudon (1824), Remarks on the Present System of Road Making; With Observations, Deduced from Practice and Experience (8th ed.), London: Longman, Hurst, Rees, Orme, and Brown, Paternobter Row, retrieved26 September 2011
  7. Jump up^Photograph of Macadam Road, Nicolaus (Calif.), ca. 1850sCalifornia Digital Library, retrieved 18 June 2010 Contributing institution: Sutter County Library
  8. Jump up^Craig, David, “The Colossus of Roads”, Palimpsest,, retrieved18 June 2010
  9. Jump up^McAdam (1824), p.38, 39-40 & 41
  10. Jump up^Lay (1992), pp.76-77
  11. Jump up^“1823 – First American Macadam Road” (Painting – Carl Rakeman) US Department of Transportation – Federal Highway Administration (Accessed 2008-10-10)
  12. Jump up to:ab c “John Loudon MacAdam”, Significant Scots,, retrieved 19 June 2010
  13. Jump up^O’Flaherty, Coleman A (2002), Highways: the Location, Design, Construction and Maintenance of Road Pavements (4th ed.), Woburn, MA: Butterworth-Heinemann, p. 228, ISBN 0-7506-5090-7, retrieved 18 June 2010
  14. Jump up to:ab John Loudon McAdam,, retrieved 18 June 2010
  15. Jump up^SI Neg. CCC-2777. Date: 8/28/1926 Consolidation Coal Company collection, National Museum of American History (Smithsonian Institution), Likely Public Domain–” about=”“> attributionURL “license ref=
  16. Jump up^Claudy, C.H. “The Right Road—and Why,” The Independent, New York, Volume 99, July, August, September 1919, 228. Retrieved on 2009-11-3.
  17. Jump up^“History of asphalt road construction – Tar road construction”. Retrieved31 July 2013.
  18. Jump up^Cavette, Chris, “Asphalt Paver”eNotes, retrieved 19 June 2010
  19. Jump up^Stephen T. Muench, Joe P. Mahoney, Linda M. Pierce et al., “History”, in .,WSDOT Pavement GuideWashington State Department of Transportation, p. 2 in Module 1: Welcome and Introduction, retrieved 19 June 2010

Eliminating Slip, Trip & Fall Hazards in Parking Lots

Each year, a large number of slip/trip and fall incidents occur in parking lots and adjacent walking surfaces that result in serious and, in some cases, fatal injuries.

Consider these statistics:

  • According to the Centers for Disease Control and Prevention (CDC), over one million Americans suffer a slip/trip and fall injury and over 17,000 people die in the U.S. annually because of these injuries.
  • Slip/trip and falls make up 15% of all work related injuries, which account for between 12% and 15% of all Workers’ Compensation expenses.
  • The CDC estimates that 20% to 30% of people who experience a slip and fall will suffer moderate to severe injuries such as bruises, hip fractures, or head injuries.
  • Slip and fall accidents are the common cause of traumatic brain injuries (TBI) and these account for 46% of fatal falls among older Americans.
  • Accident studies indicate that almost 80% of slips and falls due to snow and ice occur in parking lots or on sidewalks; more than 50% occur in the morning between 6:00 a.m. and noon.

In this article, we will review how parking lot/walking surface maintenance and response to weather conditions can prevent slip/trip and fall injuries in your workplace. 

Parking Lot/Walking Surface Maintenance
Establish a formal inspection program to identify current hazards and to plan for necessary maintenance, which should include at least the following:

  • Check regularly for cracks, depressions and uneven surfaces especially at the transition between asphalt and concrete walkways.  Sealing cracks can reduce frost heaves and extend the life of your lot.  Hazards such as potholes and broken walking surfaces are readily identifiable and should be corrected as quickly as possible before an incident occurs.
  • Inspect light bulbs and replace, if necessary.  It may often be dark when employees arrive and leave during the winter, and reduced visibility can increase risk.
  • Paint curbs, islands, ramps, wheel stops and other elevation changes with a contrasting color and slip resistant paint. If at all possible, Do Not use wheel stops (Bumper stops).
  • Provide curb cutouts that are slip resistant and meet ADA guidelines.
  • Ensure drain covers and utility grates are flush with walking surfaces with no openings in the grate greater than one inch.
  • Ensure that roof drains do not discharge across sidewalks or into parking areas.
  • Maintain awnings or canopies over stairs and entranceways.
  • Conduct thorough incident investigations and review of loss trends to discover the underlying causes of your slip/trip and falls in your workplace.  Eliminating the root causes will prevent recurrence.

Response to Weather Conditions
Slip/trip and falls can occur in parking lots at any time of year, but the winter months tend to have the highest frequency of these injuries because of rain, ice, and snow.  An effective response is removal of ice and snow completely before employees arrive for work and continued removal throughout the day.  A Snow and Ice Removal Program is the best way to achieve this objective.  Be sure that your program, at a minimum, allows for the following:

  • Assigning a Program Coordinator.  Ensure this person clearly understands all the responsibilities of the role.
  • Maintain a Snow Log showing the date, time, current weather conditions and what action was taken such as checking parking lot and sidewalk conditions, salting, shoveling, etc.
  • Clear parking lots of snow and ice before employees arrive.
  • Plow snow in parking lots when it reaches a depth of 3 inches.  Plow it to the low end of the lot or as close to drains as possible to reduce drainage, which can refreeze. Keep piles away from exits, which can obscure a driver’s view entering and exiting the lot.
  • Walkways, stairways and ramps should be completely cleared of snow and ice.
  • Entranceways need special attention because moisture can be tracked into facilities where tile and other surfaces can get slippery.  Provide extra walk-off mats during heavy snows.  Install wet floor signs to warn employees and visitors about the increased slip hazard.
  • Use deicers to treat icy pavements.  Salts, such as sodium chloride and calcium chloride, are the most common.
  • Use abrasives, such as sand, to provide traction for pedestrians and vehicles.
  • Pay particular attention to north facing sides of buildings, which receive less sunlight and tend to stay frozen much longer.
  • If outside contractors are used, the contract should be explicit about responsibilities, timing and priorities.
  • Require employees to wear slip resistant footwear.  Rubber soled shoes or boots are less likely to slip on icy surfaces than leather soled shoes or high heels.  Worn soles increase the likelihood of slipping.  Also, wide arrays of ice traction devices are available from suppliers, which are highly effective.