1.1 Purpose and Scope of the Manual
The Ethiopian Roads Authority (ERA) has initiated a comprehensive program to
rehabilitate and upgrade the highway network in Ethiopia.
As the network of paved roads in Ethiopia evolves, it is likely that a gradual shift in
emphasis will occur, from new design and construction to maintenance and rehabilitation
of the existing paved network.
The design of new pavements is covered in the ERA Pavement Design Manual Volumes I
and II – 2002 (Ref. 1, 2). The purpose of this manual is to provide, as a complement, a
guide for the design of the most common rehabilitation solutions applicable to paved
roads, and for the selection of an appropriate rehabilitation alternative for a particular
This manual provides design procedures for the rehabilitation of both flexible and rigid
pavements. The procedures utilize data which are collected during desk studies as well as
by means of field work.
The data and their analysis are primarily directed towards a rehabilitation design on an
individual project basis, but are also meant to be used, on a more general basis, as inputs
to ERA’s Pavement Management System (PMS).
Several rehabilitation alternatives, including asphalt overlays, are usually available to the
design engineer from a technical viewpoint; the manual provides guidance regarding the
choices, practical and economical, between the various alternatives.
1.2 Organization of the Manual
The manual is organized in a manner designed to satisfy its purpose and scope as
identified above, and to guide its user along a natural progression following a
The procedure and the organization of the manual are illustrated in the flow diagram in
In Chapter 2, the user of the manual is taken through the steps required to collect an array
of data relevant to the rehabilitation project. This data includes various elements from
different sources (e.g. past road inventories, as-built pavement structures, unit prices,
etc.), essentially gathered as part of a desk study, and preferably prior to initiating the
collection of additional data in the field. Not the least important aspect of this task
consists of collecting relevant traffic data.
Pavement Rehabilitation and Asphalt Overlay Manual by Ethiopian Roads Authority