highway 1-27.docx

***Highway Engineering*** is an engineering discipline branching from civil engineering which involves the ***design**, **construction*** and ***maintenance*** of highway systems. Why are highways so important? Highways are vitally important to a country's economic development. The constructi...

***Highway Engineering*** is an engineering discipline branching from civil engineering which involves the ***design**, **construction*** and ***maintenance*** of highway systems. Why are highways so important? Highways are vitally important to a country's economic development. The construction of a high-quality road network directly increases a nation's economic output by reducing journey times and costs, making a region more attractive economically **History of highway engineering** *O*Road transport is one of the most common modes of transport. *O*Roads in the form of trackways, human pathways etc. were used even from the pre-historic times. *O*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. The history of highway engineering 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. 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 transportingbothmenandmaterials.Sincethese loaded animalsrequiremorehorizontal and vertical clearances than the walking man, *track ways emerged*. **Ancient Roads** 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. **Ancient Roads** After the invention of wheel, animal drawn vehicles were developed and the need for hard surface road emerged. **Ancient Roads** 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.*** **Roman roads Roman roads** The earliest large scale road construction is attributed to Romans who constructed an extensive system of roads radiating in many directions from Rome. They were a remarkable achievement and provided travel times across Europe, Asia Minor, and North Africa. **Roman roads** Romans recognized that the fundamentals of good road construction were to provide *good drainage*, *good material* and *good workmanship*. **Roman roads** Their roads were very durable, and some still exist. Roman roads were always constructed on a firm - formed subgrade strengthened where necessary with wooden piles. **Roman roads** The roads were bordered on both sides by longitudinal drains. The next step was the construction of the agger. This was a raised formation up to a *1 meter high* and *15 m wide* and was constructed with materials excavated during the side drain construction. **Roman roads** In the case of heavy traffic, a surface course of large 250 mm thick hexagonal flag stones were provided. **French roads French roads** During the 17th century, under the reign of ***Napoleon the Great***, France made a great stride on the road buildings. France made a great stride on road buildings. ***Pierre Tresaguet*** (1716-1796) the famous French Engineer introduced new methods of construction and maintenance of stone roads. **French roads** He improved the crown, the drainage, and the grade of the road Including the stone foundation by reducing the depth of broken stones to 25 centimeters. **French roads** The pavement used 200 mm pieces of quarried stone of a more compact form and shaped such that they had at least one flat side which was placed on a compact formation. **French roads** Smaller pieces of broken stones were then compacted into the spaces between larger stones to provide a level surface. Finally the running layer was made with a layer of 25 mm sized broken stone. **British roads 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. **British roads** 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. **British roads** 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. **Modern roads** The modern roads by and large follow Macadam\'s constructionmethod.Use of bituminous concrete and cement concrete are the most important developments. Various advanced and cost-effective construction technologies are used. Development of new equipment 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.