AN APPRAISAL OF THE GHANA HIGHWAY AUTHORITY ROAD DESIGN GUIDE

ABSTRACT
The Ghana Highway Authority Road Design Guide (GHA RDG) is over two decades old since it was published as a draft document in 1991. It was expected to be periodically updated and revised based on observations, comments, suggestions and criticisms from stakeholders as they utilised it. As of October 2015 however, no update or revision has been carried out. Increasingly, designers undertaking projects for the Ministry of Roads and Highways, in-house design engineers in the Ghana Highway Authority, consultants and other expatriate designers of projects in Ghana are resorting to the use of several other manuals as references for highway designs. As a result of this highway design in Ghana has become more laborious; it is difficult to ensure uniformity of design, consistency of designs across the trunk road network and also vetting of consultants’ design presentations has become very laborious. The aim of this study was to make an appraisal with a view to modifying the Guide. The specific objectives of this study were first to critically assess the suitability of the GHA RDG and its contents regarding capacity, safety and economy for the geometric design of elements for modern trunk and urban roads. Secondly, the study was also to make an assessment of commonly used sources and standards for road element design in Ghana over the last ten years and thirdly to provide a theoretical basis for inclusion or otherwise in the GHA RDG. In order to achieve the objectives of the study views of experienced highway designers regarding the suitability of the GHA RDG for current highway design were sought through the administration of questionnaire. The GHA RDG was also compared with some current highway design manuals in Africa and the United States of America for suitability. The results indicate that the GHA RDG does not meet several of the requirements for current highway design in Ghana. Because of its deficiencies, highway designers in Ghana are resorting to other standards including the Green Book, AASHTO’s A Policy on Geometric Design of Highways and Streets, and the Ugandan Geometric Design Manual, to mention a few, as references for geometric design. It is therefore necessary to revise several aspects of the Guide to ensure its suitability for modern highway designs in Ghana. Also, many areas would require revision and the inclusion of several topics which are not covered. A recommended table of contents for a revised GHA Road Design Guide has been proposed.


CHAPTER 1: INTRODUCTION
1.1      Background
The use of highway design standards, often presented as highway design guides or manuals, is to fulfil a number of objectives, key amongst which are:

1.   To ensure minimum levels of safety and comfort    of road users

2.      To arrive at an economic design

3.      To maintain uniformity in alignments, drainage and other road facilities

4.      To ensure sufficient capacity of road sections, intersections and other road related

facilities in order to cater for design traffic demand

In 1991 the Ghana Highway Authority (GHA), drawing from unwritten Ghanaian standards and some standards or guidelines for design in use in countries like Japan, Britain, USA and Malawi amongst others, put together a draft Road Design Guide (RDG) to be primarily used by road designers in GHA and also some local and foreign consultants. This was a period when most designs were carried out in-house. It was intended to also serve the needs of the Department of Feeder Roads and the Department of Urban Roads. The Road Design Guide was a draft document expected to be periodically updated and revised based on practice, observations, comments, suggestions and criticisms from all stakeholders (GHA, 1991). As at October 2015 however no update or revision had been carried out. Over two decades after its publication vehicle standards have improved, concepts for safe design roadways have seen tremendous improvement. Also, the use of computers has dramatically changed how designs are carried out and also the level of accuracy that can be achieved.

1.2      Problem Statement
In Ghana an urban area is defined as any settlement inhabited by 5,000 or more persons. Between the years 1948 and 2000 the number of urban areas has increased from 41 to 364 (UNEP et al., 2012). The vehicle population in 2005 was 767,067 and this increased to 1,127,986 in 2009 resulting in an annual average growth rate of 8.3% during that period (MRH et al., 2011).

In recent times, elevated highways, grade-separated intersections, multi-modal intersection designs, forgiving road environment and smoother alignments are being employed more for better traffic management and safety. This has resulted in the implementation of infrastructure projects such as the Tetteh Quarshie interchange (Accra), the George Walker Bush Highway (Accra), the Achimota – Ofankor multi-lane ‘segregated’ with varied access controls highway (Accra), the Sofoline Interchange (Kumasi), the Asokwa Interchange (Kumasi), the Nkawkaw by-pass, the Nsawam by-pass, and Suhum Interchange, to mention a few. There is therefore an increased need for designs to handle higher levels of traffic and traffic conflicts with a view to safety and economy. In other words there is the need to design roads which allow for greater mobility and speed without endangering the safety of pedestrians and other road users.

The GHA Road Design Guide provides some level of uniformity of design where designs fall within its scope. However, it is deficient in solutions such as roundabouts, grade-separated intersections and certain other aspects of geometric design like ‘broken-back’ alignment situations and number of curves per kilometre. These and others are reasons necessitating its revision.

Increasingly, in-house GHA highway geometric designers, and consultants undertaking designs for the Ministry of Roads and Highways are resorting to the use of several other manuals as references for highway designs in Ghana, and as a result:

i)                    Highway design in the Ghana has become more laborious for the designer

ii)                  It is difficult to ensure uniformity of design across the trunk road network

iii)                Vetting of  consultants’ designs has become very laborious for road agency staff

It is not even clear which manuals are most frequently utilised and for what purposes or elements of design. Should the GHA RDG be revised? What additional content might be necessary to be included and for what purposes or design elements? This study sought to find  answers to some of these searching questions by engaging stakeholders and undertaking a review of literature.

1.3      Study Justification
The results of the study would achieve the following:

i)                    Establish the strengths and deficiencies in the GHA Road Design Guide (1991).

ii)                  Improve upon the understanding of what manuals and guidelines are being used for designs in Ghana.

iii)                Recommend modifications to be considered in the revision of the GHA Road Design Guide (1991).

1.4      Study Objectives
The objectives of the study were:

i)                    Assess the suitability or otherwise of the GHA Road Design Guide (1991) for the geometric design of elements for modern trunk and urban roads.

ii)                  Make an assessment of commonly used sources and standards for road element design in the last ten years and provide a basis for inclusion or otherwise in the

GHA RDG.

iii)                Propose a detailed Table of Contents for a revised Manual, highlighting the main elements and requirements.

1.5      Scope of Study
The focus of the research was the geometric design of trunk and urban roads. The study therefore covered the following:

i)                    Theoretical assessment of geometric design criteria, controls and elements in the GHA Road Design Guide.

ii)                  Comparison between GHA Road Design Guide and other geometric design manuals.


iii)                Recommendations for inclusion with future revision of GHA Road Design Guide.

1.6      Study Limitation
The study was conducted within a relatively short period of time. Consultations with stakeholders, based on which analysis was done, was therefore conducted within limited time. Views and comments of a broad spectrum of stakeholders could therefore not be solicited. Hence although the findings, conclusions and recommendations of this study are a result of thorough analysis they may not be exhaustive.

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Item Type: Ghanaian Postgraduate Material  |  Attribute: 99 pages  |  Chapters: 1-5
Format: MS Word  |  Price: GH50  |  Delivery: Within 30Mins.
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