20-03-2014, 04:17 PM
Introduction to Highway Engineering
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Overview
Road transport is one of the most common mode of transport. Roads in the form of trackways, human pathways
etc. were used even from the pre-historic times. Since then many experiments were going on to make the riding
safe and comfort. Thus road construction became an inseparable part of many civilizations and empires. In
this chapter we will see the different generations of road and their characteristic features. Also we will discuss
about the highway planning in India.
History of highway engineering
The history of highway enginnering gives us an idea about the roads of ancient times. Roads in Rome were
constructed in a large scale and it radiated in many directions helping them in military operations. Thus they
are considered to be pioneers in road construction. In this section we will see in detail about Ancient roads,
Roman roads, British roads, French roads etc.
Ancient Roads
The first mode of transport was by foot. These human pathways would have been developed for specific
purposes leading to camp sites, food, streams for drinking water etc. The next major mode of transport was the
use of animals for transporting both men and materials. Since these loaded animals required more horizontal
and vertical clearances than the walking man, track ways emerged. The invention of wheel in Mesopotamian
civilization led to the development of animal drawn vehicles. Then it became necessary that the road surface
should be capable of carrying greater loads. Thus roads with harder surfaces emerged. To provide adequate
strength to carry the wheels, the new ways tended to follow the sunny drier side of a path. These have led
to the development of foot-paths. After the invention of wheel, animal drawn vehicles were developed and the
need for hard surface road emerged. Traces of such hard roads were obtained from various ancient civilization
dated as old as 3500 BC. The earliest authentic record of road was found from Assyrian empire constructed
about 1900 BC.
British roads
The British government also gave importance to road construction. The British engineer John Macadam
introduced what can be considered as the first scientific road construction method. Stone size was an important
element of Macadam recipe. By empirical observation of many roads,he came to realize that 250 mm layers
of well compacted broken angular stone would provide the same strength and stiffness and a better running
surface than an expensive pavement founded on large stone blocks. Thus he introduced an economical method
of road construction.
The mechanical interlock between the individual stone pieces provided strength and stiffness to the course.
But the inter particle friction abraded the sharp interlocking faces and partly destroy the effectiveness of the
course. This effect was overcome by introducing good quality interstitial finer material to produce a well-graded
mix. Such mixes also proved less permeable and easier to compact. A typical cross section of British roads is
given in Figure 2:3.
Modern roads
The modern roads by and large follow Macadam’s construction method. Use of bituminous concrete and cement
concrete are the most important developments. Various advanced and cost-effective construction technologies
are used. Development of new equipments help in the faster construction of roads. Many easily and locally
available materials are tested in the laboratories and then implemented on roads for making economical and
durable pavements.
Highway planning in India
Excavations in the sites of Indus valley, Mohenjo-dero and Harappan civilizations revealed the existence of
planned roads in India as old as 2500-3500 BC. The Mauryan kings also built very good roads. Ancient books
like Arthashastra written by Kautilya, a great administrator of the Mauryan times, contained rules for regulating
traffic, depths of roads for various purposes, and punishments for obstructing traffic.
During the time of Mughal period, roads in India were greatly improved. Roads linking North-West and the
Eastern areas through gangetic plains were built during this time.
After the fall of the Mughals and at the beginning of British rule, many existing roads were improved. The
construction of Grand-Trunk road connecting North and South is a major contribution of the British. However,
the focus was later shifted to railways, except for feeder roads to important stations.