Rural Road Engineering

TRL has built up an unrivalled capability across a wide range of research and technical advisory activities in the field of highway and rural road engineering concerned with the planning, design and operation of roads in the tropics. Over 50 years experience has been accumulated in such diverse fields as:

• engineering geology and remote sensing
• evaluation and testing of bituminous and cementitious materials
• materials inventories
• use of indigenous road building materials
• construction in arid areas
• pavement and rehabilitation design
• non-destructive pavement evaluation methods
• pavement investigation
• road deterioration models
• improvements in maintenance techniques
• maintenance management and upgrading of gravel roads.

TRL's knowledge of the engineering characteristics of tropical gravel and conditions in road pavements in tropical environments has enabled us to develop more-suitable specifications for many local materials, and helped us in understanding road failure investigations where inappropriate materials have been used. Long-term assessment of the design and performance of both bitumen-surfaced and all-weather gravel and earth roads has improved our understanding of the way different road structures and surfacing materials behave under the extreme loadings and harsh climatic conditions in the tropics.

TRL offers specialist assistance in conducting evaluation studies to identify the causes of road failures and recommend appropriate rehabilitation measures. This draws on the methods developed in many countries in monitoring and analysing the behaviour of trial sections.

Low-volume Road Design and Construction

TRL has experience of increasing the cost-effective provision of low-volume roads using labour-based methods through reduced life-time costs and the application of appropriate standards. TRL has undertaken extensive research on low-volume roads throughout Africa, and particularly in Southern Africa. We managed the development of ‘A Guideline for Low Volume Sealed Roads for the Southern African Development Community (SADC)' which involved the active participation of most members of the SADC region.

TRL, in a major collaborative research initiative with ILO-ASIST, also developed the ‘Engineering Standards and Whole Life Costs for Labour-Based and Unpaved Roads' (published by ILO), with some of the research input being undertaken in Mozambique. TRL organised trials in Zambézia into the practicality and durability of a variety of low-cost seals and their construction using labour-based methods. These formed the basis for the 'Manual for Labour-based Construction of Bituminous Surfacings on Low-volume Roads'.

TRL has carried out trials on labour-based surfacing and developed documentation which includes a manual on labour-based surfacing ('Environmentally Optimised Design of Low Volume Sealed Roads'), exploring the importance of design aspects such as drainage, cross-section shape, the width of sealed shoulders and the selection of materials previously deemed to be marginal and unusable, and providing guidance material on design, material selection and appropriate surfacing techniques.

TRL is continuing its work in low-volume road design with a project supporting targeted interventions on low-volume roads in Mozambique, under AFCAP. The main theme of this and other proposed projects in Ethiopia and Kenya is using marginal, locally available materials to support sustainable rural roads and labour-based construction techniques, and providing sustainable engineering solutions to address access and mobility for the rural poor. TRL will develop standards to provide quality control on what materials can be used and how they should be applied and maintained in order to optimise the cost and performance of the road over its lifetime. Our capability includes the training element required to help achieve the mainstreaming of these standards.

Road Maintenance and Rehabilitation

TRL has been instrumental in conducting research on the planned and systematic maintenance of major capital infrastructure. We developed the earliest tools, such as the RTIM investment model for use in highway and maintenance planning, and were involved in the development of HDM-4, with specific reference to the technical relationships included in the program and the development of a global training and dissemination strategy.

In addition, we've been responsible for the development of user-friendly guidelines that are extensively applied in the design and implementation of many highway and bridge rehabilitation programmes. TRL staff have extensive experience of management of routine and periodic highway maintenance overseas, and in the evaluation of existing pavements and the design and specification of maintenance works including pavement rehabilitation and upgrading.

Socio-economic Impact of Rural Transport

TRL has extensive experience in assessing the socio-economic impact of transport interventions, drawing on community-based participatory research and perception studies. In recent years, TRL has primarily used sustainable livelihoods approaches to understand how interventions will impact on different parts of the community. Use may be made of such an approach to assess how the impact of road improvements may meet the transport needs of different social groups.

To undertake the approach, an analysis of both the external environment (e.g. national economic policy, donor interventions) and the local economic environment are carried out to identify the critical impacts on both the local community and their transport needs. Participatory approaches are adopted, disaggregating community accessibility needs by gender, age and income, and using sensitisation and consultation techniques to learn from the experiences of local communities.

TRL also has researchers specialised in conducting quantitative and qualitative surveys including participatory appraisal (PA), a consultative method combining visual mapping tools with group discussions and interviews.

TRL has worked extensively on transport and poverty research projects in developing and developed countries and provides advisory support on sustainable livelihood approaches and social inclusion, as well as gender and participatory rural appraisal methodologies.

Road Safety Engineering

TRL has extensive experience of road safety engineering in developing nations, including the development and application of manuals which relate to highway design and planning of roads in developing and emerging nations.

Perhaps the best-known highway design model for use throughout the developing world is 'Towards Safer Roads in Developing Countries' which was produced by TRL in the early 1990s, based on road safety work carried out in over half a dozen countries including Zimbabwe and Botswana. This is a practical design manual for planners and engineers which provides guidance on accident prevention and accident reduction. It highlights key safety reduction factors and explains how existing hazardous locations can be analysed and made safer by the introduction of low-cost counter-measures.

Recent research for the Department for International Development, carried out in five countries including India and Nepal, aimed to reduce road accidents by identifying cost and safety-efficient (CaSE) design principles for rural highways. It attempted to do so by: (i) identifying those aspects of highway planning and design where costs and safety can be optimised; (ii) identifying critical points of highway planning and design beyond which the provision for safety at minimal costs should not fall; and (iii) publishing a series of CaSE design notes on certain key engineering features to assist road designers in developing countries to balance the 'cost-conscious' and 'safety-conscious' approaches to design.

As well as carrying out research into safe road design, TRL has carried out work in many developing countries, designing and evaluating low-cost, appropriate road safety counter-measures designed to provide remedial action at sections of the road identified as accident blackspots. Improved enforcement measures have included police training, developing improved methods of data collection (Microcomputer Accident Analysis Package) and analysis of accident records.

TRL has also been involved in providing advice on road safety education and publicity, including the preparation of guidelines for promoting road safety education through community participation.