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Infrastructure Notes Transport, Water and Urban Development

By Archondo-Callao, Rodrigo S.

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Book Id: WPLBN0000204505
Format Type: PDF eBook
File Size: 0.1 MB
Reproduction Date: 2005
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Title: Infrastructure Notes Transport, Water and Urban Development  
Author: Archondo-Callao, Rodrigo S.
Language: English
Subject: Economics, Finance & business, World Bank.
Collections: Economics Publications Collection
Publication Date:
Publisher: The World Bank


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Archondo Callao, R. S. (n.d.). Infrastructure Notes Transport, Water and Urban Development. Retrieved from


Introduction: Roughness is irregularity of the road surface. It affects the operation of a vehicle ? safety, comfort and speed of travel ? and the rate of wear of vehicle parts. By extension, it impacts on vehicle operating costs, and hence on the economic evaluation of proposed road maintenance and upgrading expenditures. Roughness is measured using the International Roughness Index (IRI) which is a mathematically defined summary statistic of the longitudinal profile in the wheelpaths of a traveled road surface. The IRI describes a scale of roughness which is zero for a true planar surface, increasing to about 2 for paved roads in good condition, 6 for a moderately rough paved roads, 12 for a extremely rough On paved roads, roughness increases continuously over a year if maintenance is not applied. Roughness is generally measured with instruments, and one measurement on a paved road is sufficient to characterize the average annual roughness. On unpaved roads, however, roughness varies over a year as a function of the season, the changing location of the wheelpaths chosen by the vehicles, and the number and the effects of gradings and other maintenance activities. Therefore, a roughness measurement at a given point in time is not sufficient to characterize the average annual roughness of unpaved roads. The fragility of roughness measurement instruments makes them unsuitable for deployment on unpaved roads, hence road agencies are forced to define average annual road roughness of unpaved road by other means, for example by subjective methods.


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