SAPEM Chapter 2 - Sanral

South African Pavement Engineering Manual
Chapter 2: Pavement Composition and Behaviour
2. HISTORY
This section looks at the history of roads, from their development, to the history of pavement design. The necessity
of roads is also discussed.
2.1 Development of Roads
An understanding of how pavement technology evolved requires a look back into the historical developments of
roads. In ancient times there was nothing more than a sparse network of tracks for humans to reach feeding and
drinking places. These tracks differed only slightly from the tracks made by the movement of foraging animals. The
primary difference was that obstacles, e.g., boulders, were removed from the more important routes and thorn
bushes were trimmed back by humans. More elaborate lines of communication than these simple tracks did not
appear until the number of humans in certain areas reached a stage where their social structures and networks
demanded more permanent contact between communities.
Roads thus appeared when groups of people started to interact with each other by travelling, doing business,
fighting, and socializing. This occurred around 3500 BC. At this time, the invention of the wheel and development of
chariots and wagons showed that the existing soil or subgrade on the interlinking routes was inadequate. Layers of
better quality material were required to protect the subgrade, giving rise to the pavement structure.
The earliest records of paved roads for wheeled traffic date from about 2200 BC in Babylonia (modern Iraq), in Crete
from about 1500 BC and in Egypt from about 540 BC. In Europe, the first substantial roads were built by the
Romans, with a network of more than 100 000 kilometres of road built between 400 BC and 400 AD. The Roman
roads were cambered to shed rainwater and were constructed on a foundation of large stones with a wearing course
of smaller stones and gravel, constrained between raised stone kerbs, as illustrated in Figure 1.
Figure 2.2. Typical
Roman Pavement
Figure 1. Typical Roman Pavement (McCauley, 1974)
The Romans were the best road builders of the remote ages. Conquests achieved through war games were one of
the reasons for this. The Romans needed a good network of roads to control their conquered subject-nations. The
army needed to be able to move fast to quell any revolting groups. The Roman roads were cobbled with a base
system that was dependent on the subgrade. They developed a three or four layer system, illustrated in Figure 2,
consisting of:
Top layer
Base, sometimes stabilised
Subbase
Subgrade
Section 2: History
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