Module 3: Geometric design of highways

Lecture 11 Introduction to geometric design

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Roads classification criteria

Apart from the classification given by the different plans, roads were also classified based on some other criteria. They are given in detail below.

Based on usage

This classification is based on whether the roads can be used during different seasons of the year.

• All-weather roads: Those roads which are negotiable during all weathers, except at major river crossings where interruption of traffic is permissible up to a certain extent are called all weather roads.
• Fair-weather roads: Roads which are negotiable only during fair weather are called fair weather roads.

Based on carriage way

This classification is based on the type of the carriage way or the road pavement.

• Paved roads with hards surface : If they are provided with a hard pavement course such roads are called paved roads.(eg: stones, Water bound macadam (WBM), Bituminous macadam (BM), concrete roads)
• Unpaved roads: Roads which are not provided with a hard course of atleast a WBM layer they is called unpaved roads. Thus earth and gravel roads come under this category.