Pavement Design and Construction

The 5th update to one of the standard guides to designing pavements in tropical and sub tropical countries.

A large portion of the road network in developing countries in Africa consist of Low Volume Roads (LVRs). Funding for upgrading and maintenance of these roads pose a challenge for roads authorities as their limited budgets are mainly aimed at highways and major corridors. Isolated communities bear the burden of inaccessibility to markets, education and health facilities.
As part of a study that was launched by the Research for Community Access Partnership (ReCAP) an investigation into alternative surfacings to gravel roads was conducted in Ghana, Liberia and Sierra Leone. A stakeholder engagement process, designed around several workshops, was used to gain insight into the needs of the community. The local roads authorities, local engineers and technical pavement experts were involved in the selection of surfacing options which would be most suitable for implementation.
Several other aspects of the surfacing types were investigated such as the initial
construction cost, anticipated maintenance costs and life cycle cost. An exclusive
multicriteria analysis, which used the outputs from the different costing scenarios and the workshops was conducted, and a Monte Carlo simulation was completed to select the most appropriate surfacing solutions.

An excellent report on options for using cement concrete pavements the benefits they offer in a time of climate change. Covers a range of pavement types, and gives guidance on considerations for how to select the appropriate solution. But I'm biased ... I designed the project and helped the team!

This report examines the viability of using recycled plastics in asphalt and sprayed seals by Australian and New Zealand road authorities. The report presents the findings of a literature review, including case studies of local and overseas road trials. It finds that waste plastic can act as a partial aggregate replacement in bituminous mixes and a binder extender without having any significant influence on the properties of the asphalt mix. However, not all recycled plastics are suitable for bitumen modification at high temperatures. It also finds that while there may be environmental benefits associated with the use of recycled plastic, there are concerns regarding the potential health and safety hazards that road workers might be exposed to while handling these materials, sustainability impacts, and impacts on the surrounding environment.

The main purpose of these Guidelines are to provide practitioners with the requisite tools for undertaking an environmentally optimized approach to the design of LVRs in India that takes account of the many locally prevailing road environment factors that impact on the design of such roads. Such an approach is aimed at providing appropriate and cost-effective designs for LVRs, bearing in mind their practical implementability within the available resources and level of expertise in rural areas. To the extent possible, the use of locally available materials in their natural state, or after suitable processing, must be maximized to not only reduce construction costs but, also, to minimize adverse environmental impacts regarding the use of non-renewable resources (aggregate and gravel). The availability of plant and equipment for construction and maintenance, as well as the level of quality control that can be effectively exercised in the field should also be considered.

New Zealand pavement engineers, in collaboration with colleagues in South Africa and Australia, are recognised internationally as leaders in the use of stabilisation in highway, road, airport, port and industrial hardstand pavement applications. Stabilisation is used to rectify a deficiency in a soil, aggregate or surfacing material. Stabilised materials contribute to the strength and performance of pavements at all levels: subgrade; subbase; base and surfacing.  Applied research into and development of leading edge testing and design knowledge, coupled with significant improvements in the capacity and effectiveness of stabilisation construction plant and work site processes now offer the wider transport industry in New Zealand relatively safe, efficient and sustainable pavement construction, rehabilitation and maintenance options incorporating stabilisation.  This research was undertaken to bring together informed, current technical advice from a variety of sources to enable road controlling authorities, consultants and contractors in New Zealand to successfully investigate, design, construct, maintain and operate pavements with stabilised components

Short technical note describing geocell (Hyson cell) pavements and how they can make a big difference for low volume rural roads.

Report on how to undertake pavement designs using materials available in the Pacific Islands.

Report from India on the construction of geocell concrete pavements for low volume roads.

With the evolution of the road industry and growing traffic on roads, construction materials have also been evolved and more unconventional ingredients have been incorporated. The rationales was the scarcity of conventional natural materials and the jeopardized environment which have underpinned the tendency towards evaluation other materials resources to be incorporated in the road industry. The inclusion of such materials entails several secondary and tertiary materials. Several waste by-products and materials have been investigated, assessed, evaluated for utilizations and practiced in the field. Depending on the attributes of the characteristics of the recycled material, the inclusion varies. Some recycled material have been proven to possess preferable properties over the other and have performed satisfactorily in the field. However, there are numerous concerns regarding such incorporation based on both laboratory experimental, and field observations which have turned out to be of the essence for further in-depth studies. Reclaimed asphalt pavement, recycled concrete aggregates, plastic wastes, scrap tires, mine wastes, recycled crushed glass, foundry sand, coal combustion products as fly ash, bottom ash, and pond ash, steel slag, oil sand, oil shale sand, lateritic soil, are amidst the long list. It is believed that magnificent preservation of natural and precious resources would be attained from the inclusion of secondary and tertiary materials in road construction. Nonetheless, without rigorous cooperation between the academia and the industry and educating people who are in routinely interact with paving activities, several performance-related issues would not be resolved and would remain in existence. This paper present a literature review report on the most viable recycled materials currently in practice by the industry and it aims towards developing a noble idea on better inclusion of a recycled material in the road industry.

Detailed analysis of costs of road construction.

The current version of the Austroads sprayed seal design method was published in 2006 and has been in use for the last nine years. During recent times, a number of sprayed sealing practitioners have indicated that the basic voids factor for single/single seals in the current Austroads sprayed seal design method is too high for low volume roads. To address these concerns, a questionnaire was initially distributed to jurisdictions and local councils to determine the extent of the concerns. The results obtained during a literature review of the derivation of Austroads basic voids factor for single/single seals, and the equivalent factor in the New Zealand seal design method, were used as a basis to propose changes to the Austroads basic voids factor.

The responses to the questionnaire indicated that the main issue associated with the Austroads sprayed seal design method was that the basic voids factor for single/single seals was too high for low volume roads. The results obtained during the literature review indicated that the Austroads basic voids factor has developed empirically over time based on observations by sealing experts and practitioners, while the current New Zealand equivalent factor is based on quantitative measurements obtained during an extensive series of road trials. As the New Zealand equivalent of the basic voids factor was based on quantitative measurements, the New Zealand seal design approach was used to propose changes to the Austroads basic voids factor.

A new version of the Austroads basic voids factor has been proposed for single/single seals which will require lower basic voids factors to be used for low volume roads. The new version of the Austroads basic voids factor was compared with recent Australian seal data/observations in order to investigate whether its use would result in issues with sprayed seals. Based on these comparisons, it appears unlikely that use of the new version of the Austroads basic voids factor will result in issues with sprayed seals.

Report on the use of sand in road construction.

Guidelines for concrete pavement desgin for low volume roads with average daily traffic less than 450 Commercial Vehicles Per Day.  This document covers the design principles of rigid pavements of low volume roads 3.75 m wide (minimum 3 m wide in hills) made up of conventional concrete, roller compacted concrete and self-compacting concrete. 

Presentations from the World Bank session on Otta Seals.

Natural gravel materials have traditionally been used for upgrading earth to gravel roads or for regravelling  existing gravel roads. However, serious concerns have arisen regarding the continuous use of vast amounts of gravel - a non-renewable, finite resource - which is not only being rapidly depleted in many countries but is also unsustainable in the medium to long term. This has prompted road engineers to consider the use of low-cost bituminous surface treatments on these gravel roads as an alternative to regravelling. One type of surfacing that can provide an economic and practical alternative to traditional surfacings, such as the Chip seal, is the Otta seal. Unfortunately, lack of information regarding this relatively new type of bituminous surfacing has suppressed its more widespread use, despite its excellent performance in a number of countries.

 In view of the above, the first presentation provides state-of-the-art information on the provision of the Otta seal surfacing as an economic and practical alternative to the more traditional bituminous surface treatments. The presentation outlines the origin, properties, design and construction of the Otta seal and very briefly discusses its implementation impacts and the global use of the Otta seal.

 This type of bituminous seal was first introduced to Botswana in the late 1970s with design and construction being initially undertaken in-house and, subsequently, by the private sector. However, a somewhat haphazard approach to the transfer of this relatively new technology from the public to the private sector was largely responsible for initially suppressing the uptake of this innovative type of surfacing despite its eminent suitability for use with locally available, marginal quality aggregates. Many lessons have been learned from this experience which are likely to be useful to other countries where the introduction of the Otta seal is being contemplated.

 The second presentation highlights the critical importance of undertaking effective technology transfer to ensure the sustainability of any new type of technology, such as the Otta seal. The presentation considers the path from research to implementation of new technology, including the typical constraints and barriers that are faced in the African region. In the context of the Otta seal experience in Botswana then identifies typical barriers and constraints to its ready adoption by the private sector and proposes measures for overcoming them. The presentation concludes that a carefully crafted, pro-active approach to technology transfer is necessary to ensure the sustainability of the Otta seal in countries where it is being introduced for the first time.

 The Kingdom of Tonga’s road network, comprising approximately 640km of public roads, has had minimal road maintenance over the past decade. As a result, the road network is rapidly deteriorating. The World Bank funded Transport Sector Consolidation Project is supporting the Government of Tonga in implementing a road maintenance program to prolong the serviceability of the road network. However, due to the limited capacity of the local contracting industry, and a severe lack of quality road surfacing aggregate, traditional surfacing methods for periodic maintenance and road upgrading are not suitable. Innovative surfacing technologies, such as Otta Seals, were adopted to overcome the local limitations. The main objective of this presentation is to document the introduction of Otta Seals to Tonga and the experience to date. It will also briefly capture the applications, benefits and limitations of Otta Seals, and the reasons why they have been considered for Tonga. The paper provides a brief review of the local contracting industry and the availability of locally sourced aggregate in Tonga, and the effects that these have on the choice of pavement surfacing alternatives. The first trial sections were awarded to a local contractor in January 2012, and the works were started after the rainy season in July 2012. The process of introducing the new technology has to date been successful and progress of this project is being monitored by a number of other South Pacific countries that are faced with the similar constraints.

 This presentation covers the monitoring programme for several Otta Seal Trials in the South Pacific region.  In order for this technology to be accepted within the region, Otta Seal Trials were set up in order to a) introduce the technology to the region and b) to demonstrate the practicality and appropriateness of this technology within the geology, environment and traffic loading. A monitoring guideline that defines how to install a test section, and the protocol required to periodically monitor a test section, was developed.  The philosophy for these requirements was to develop procedures that required minimal training of assessors while at the same time would yield useful data that could be utilized for statistical analysis of the surface performance. The setting up of the Otta Seal Trials for the South Pacific Islands has confirmed a number of recommendations related to road performance experiments including:

· Clearly define the objectives for the trials with consideration for the region and the available resources (i.e., skilled labor, materials, equipment, etc.);

· Only collect the data needed to answer the objectives/questions; and,

· Trials should be designed within context of available resources for conducting the monitoring.

Through the on-going, Danida supported, Rural Transport Infrastructure (RTI) component of the U-Growth Programme, an initiative has been undertaken to develop low-cost seal (LCS) technology in Uganda. LCSs allow wide use to be made of locally available materials and provide a viable, cost-effective and sustainable alternative to natural gravel surfaces with more manageable maintenance requirements. Such seals may also be constructed by smallscale contractors using relatively low-capital, labour based methods and relatively small mechanised plant.

In anticipation of mainstreaming LCS technology, initially under the RTI program (300 km during the 4-year program period 2010-2013) and subsequently under the Government of Uganda’s (GoU) National Development Plan (10,000 km in the 5-year period 2010/112014/15), training modules were prepared by a consultant, MELTC staff were trained and a number of types of LCSs were constructed in early 2011 as a demonstration project.

Before a final commitment is made regarding the adoption of LCS technology a concrete justification for so doing is required by the Ministry of Works and Transport (MoWT) as a basis for developing a clear policy and strategy for adoption by GoU. To this end, an assessment of the various key aspects of LCS technology as proposed to be applied in Uganda was carried out.

Running over 1,100 pages, the manual comprises fourteen chapters covering a range of elements of pavement engineering. The chapters, inter alia, include the history of roads, the development of pavement engineering with time through the understanding of the behaviour of materials and their utilization, the influence of the environment and traffic, the interface between tyre and pavement, references to testing methods guiding the reader through the numerous tests to be conducted, and laboratory management. It explains relevant concepts, tells the reader of the do’s and don’ts, and also contains guidelines on the investigation of the road prism, the pavement and geology, and suggests the expertise required for carrying out geotechnical investigations.

This is a comprehensive guideline manual, not a policy manual. It is to be regarded as a best practice guideline, providing the sequence of steps for practitioners. Its benefits will manifest over time with its use, with the harmonization of designs and standards. It predominantly provides advice and guidance for the design of safe, state of the art, cost effective – taking into account the carbon footprint – pavements for motorists, thus reducing the cost of transport.

Application guide accompanying the Drainage Manual.

Comprehensive manual on drainage design for roads.

This study on Encouraging Private Sector Development in the Road Sector in Pacific Island Countries aims to capture the best practices in involving local firms and workers in road infrastructure project delivery and to inform next steps for increased participation. The report focuses on a review of experiences in seven Pacific Island Countries (Samoa, Solomon Islands, Timor-Leste, Tonga, Vanuatu, Kiribati and Papua New Guinea) through a combination of desk reviews and visits to the countries concerned1. The subsequent analysis of information has looked at the four key components of encouraging private sector development in the road sector: i) policies, guidance, controls and incentives, ii) models of local participation, iii) capacity building efforts and iv) contract and project structuring. This report presents the main findings of the study from the perspective of each of the countries covered, as well as from a regional perspective.

This guide is for those involved with the planning, design, construction or maintenance of low-volume rural roads in developing and emerging regions, primarily in the tropical and sub-tropical regions of Africa, Asia and, possibly, South America.

The guide provides information on a range of tried and tested road surfacing and paving techniques that are relatively low cost and offer sustainable solutions for road works. The techniques focus on the optimal use of local resources, in often challenging physical and operational environments.

Recent pavement research highlights the importance of locally-oriented solutions, based on available local resources and the local road environment, in developing local 'good practice' to support the development of affordable and sustainable rural road infrastructure.

The document deliberately avoids extensive technical detail, but provides reference to technical methodologies available for adaptation to local conditions and resources. An online strategy was adopted to increase flexibility and enable easier access to review and update information.

"Little Black Book 2010-2011" prepared by Mott MacDonald (UK); it presents benchmark costs for road construction and maintenance, including for many specific sub-categories of road works and road asset management activities.  This a very useful booklet which provides answers to those of us who are sometimes wondering if prices for specific contracts are high or low, or who would like to make rough cost estimates for projects. 

While the benchmark prices are given for the UK, there are "location adjustment factors" for many countries and regions around the world.

Report describing the introduction of Otta Seals to Tonga with detailed guidance and technical specifications.

Detailed technical specifications used on the World Bank financed Armenia Local Roads Improvement Project.

Guide to the design and construction of roller compacted concrete pavements.

Report describing different options for pavements on low volume roads. Good photos.

Introduction to design and construction of concrete block pavements.

An excellent resource site with information on all aspects of roller compacted concrete pavements - from design through construction to performance.

Materials specifications used in the Province of Ontario

Good summary of airfield pavement designs.

This study evaluated the performance and cost of commonly used dust palliatives using a mobile air sampling technique. Treatments of calcium chloride, magnesium chloride, and organic polymer-plus-binder were evaluated at standard application rates during the first year and at variable rates during the second year. The treatments were applied to a variety of subject roads that were located throughout Minnesota. Average daily traffic levels varied from 25 to 700 vehicles per day.

The overall data trend showed that treatments reduced dust levels and measurements showed that aggregate surface
moisture content was the best predictor of dust control efficiency. Positive relationships were measured between
dust control efficiency and other variables in the study, generally reinforcing the concept that higher application
rates may be more successful on gravels containing greater amounts of material passing the #200 sieve. A negative
relationship was measured between dust control efficiency and sand equivalency, showing that treatments on gravels containing more sand material were less effective. In addition to dust control, study participants observed a secondary benefit of surface stabilization, which lasted for a period of time. Treated sections that developed surface stabilization were able to reduce maintenance activities to intersection areas only.

The Otta seal is a low-cost seal option used in developed and developing countries for seal extension and resurfacing treatments. The technique is called ‘Otta seal’ because it was first developed and trialled in the Otta Valley in Norway, in 1963, as an inexpensive seal-extension treatment. After its initial success in the Norwegian trial, the use of the treatment spread throughout developing countries in Asia and Africa, and life cycles of up to 25 years are reported from South Africa.

This report describes a successful trial of the use of a simplified version of the Otta seal as a method for minimising dust emissions from gravel roads in New Zealand. It also compares the performance and cost effectiveness of the Otta seal with traditional dust minimisation techniques.

The idea of designing and building quieter pavements is not new, but in recent years there has been a groundswell of interest in making this a higher priority. Various State Highway Agencies and the Federal Highway Administration have responded accordingly with both research and implementation activities that both educate on the state-of-the-practice, and advance the state-of-the-art. The Little Book of Quieter Pavements was developed with this purpose in mind… to help educate the transportation industry, and in some cases the general public, about the numerous principles behind quieter pavements, and how they connect together.

The AUSTROADS document Pavement Design – A Guide to the Structural Design of Road Pavements does not specifically design for plastic deformation in the basecourse; however, both experiments and field observations demonstrate that, with sufficient traffic loading, plastic deformation accumulates in the basecourse, sub-base, and the subgrade. Furthermore, pavement design in New Zealand is critically dependent on subgrade strength, apparently neglecting the accumulation of plastic strain in the granular layers of the pavement.

This study, initiated in 2004, examines the design methodologies presented in AUSTROADS and evaluates them against available New Zealand research. Various subgrade strain criteria are examined for New Zealand conditions. The roughness model from HDM III has been used to generate a pavement design figure similar to ‘Figure 8.4’ of AUSTROADS. The figure indicates that for lower design traffic levels AUSTROADS is highly conservative; for high design traffic levels AUSTROADS is not conservative enough. The results for design traffic between 10^5 and 10^6 ESA might help explain the observation that lives greater than 50 years are being achieved in New Zealand since, assuming the modelling is correct, in effect, these roads have been over designed.

Prepared for the World Bank, this

publication has two main objectives:

 

• To summarise more than 25 years of experience with the global use of Otta seals and to provide technical evidence and economic justifications for its consideration for use

in all countries.

• to provide state-of-the-art information on the provision of the Otta seal surfacing as an economic and practical alternative to more traditional surface treatments.

 

The publication will provide the required guidance to a wide range of stakeholders including politicians, practitioners, consultants and contractors, as well as material suppliers, donors, road users and, importantly, Road Authority personnel - who may be considering the use of the Otta seal in their countries.

 

By promoting an innovative approach to the provision of bituminous surface treatments, this publication will undoubtedly lead to a more efficient use of available resources. This will result in direct benefits to many countries and will facilitate socio-economic growth and development and much needed poverty reduction. This publication also provides a useful list of references on the design, construction and maintenance of Otta seals.

These supervision and construction guidelines synthesize the accumulated substantial experience and knowledge and provide guidance on the range of trialed paving techniques, including:

• Explanation of key issues within the specifications

• A series of clear and concise step by step guides on construction • Key supervision issues

• Advice on supervision procedures

• Advice on in situ and laboratory control testing

• Advice on quality control

Supplement to the Austroads pavement design guide for use in New Zealand. This includes features like:

• Updated sub-layering scheme for unbound layers;
• Use of a full standard axle in the design model;
• Revised subgrade strain performance criterion; and,
• Incoporation of a Project Reliability factor to reflect appropriate levels of design risk.

Natural gravel materials have traditionally been used for upgrading earth to gravel roads or for regravelling existing gravel roads. However, serious concerns have arisen regarding the continuous use of vast amounts of gravel - a non-renewable, finite resource - which is not only being rapidly depleted in many countries but is also unsustainable in the medium to long term. This has prompted road engineers to consider the use of low-cost bituminous surface treatments on these gravel roads as an alternative to regravelling them in an unsustainable and
increasingly costly programme.

One type of surfacing that can provide an economic and practical alternative to traditional surfacings, such as the Chip seal, is the Otta seal. Unfortunately, lack of information regarding this relatively new type of bituminous surfacing has suppressed its more widespread use, despite its excellent performance in a number of countries.

This publication provides state-of-the-art information on the provision of the Otta seal surfacing as an economic and practical alternative to the more traditional bituminous surface treatments. The publication outlines the origin, properties, design and construction of the Otta seal and discusses its implementation impacts and the various factors that contribute to its sustainability. Finally, the paper provides information on the global use of the Otta seal, including two case histories relating to its introduction in eastern and southern Africa.

See here for another report on Otta Seals.

There is a great need for durable noise reducing pavements for highways. The concept for noise reduction is to create a pavement texture, with big cavities at the pavement surface in order to reduce the noise generated from air pumping, and ensuring a smooth surface so noise generated by vibration of the tyres will not be increased. Open textured pavements are open only at the upper part and are not expected to need special winter maintenance. European experiences with thin layers have been further developed. Four different pavement concepts are used: Open graded asphalt concrete (DAC-open), Stone Mastics Asphalt (SMA), a thin layer constructed as an UTLAC (Ultra Thin Layer Asphalt Concrete), and semi porous pavement (PAC). In 2006 10 optimized thin layers were laid on a Danish highway near Herning. Maximum aggregate sizes were in the range of 6 to 8 mm. Dense Asphalt Concrete with 11 mm maximum aggregate size is a reference pavement. The results from the first series of SPB noise measurements are presented in this paper.

This report presents the findings of a study of alternate pavement designs targeted at reducing the initial construction costs of concrete pavements without compromising pavement performance. Test sections were constructed with alternate dowel materials, reduced dowel placements, variable thickness concrete slabs and alternate surface and subsurface drainage details. Performance data was collected out to 5 and 7 years after construction.

The study results indicate that FRP composite dowels may not be a practical alternative to conventional epoxy coated steel dowels due to their reduced rigidity, which results in lower deflection load transfer capacities at transverse joints. Ride quality measures also indicate higher IRI values on sections constructed with FRP composite dowels. Study results for sections constructed with reduced placements of solid stainless steel dowels also indicate reduced load transfer capacity and increased IRI values as compared to similarly designed sections incorporating epoxy coated dowels. Reduced doweling in the driving lane wheel paths also is shown to be detrimental to performance for most constructed test sections. The performance of sections with reduced doweling in the passing lane wheel paths indicates that this alternate may be justifiable to maintain performance trends similar to those exhibited by the driving lane with standard dowel placements.

Performance data from sections constructed with variable slab geometry and drainage designs indicate that one-way surface and base drainage designs are performing as well or better than standard crowned pavements with two-way base drainage. The drainage capacity of the base layer, constructed with open graded number 1 stone, appears sufficient to handle all infiltrated water.

Chapters from UK road design manual

Paper discussing experiences with labour based bituminous surfaces for low volume roads.

Report detailing general description and technical specifications for low-technology/labour based bituminous surfacing options. Includes Penetration Macadam and Otta Seals.

This Guideline provides information, guidance and instructions on quality assurance procedures and specifications applicable for road works executed using labour-based methods. The text covers aspects relating to the uniqueness of labour-based technology including problems that make conventional approval methods inappropriate.

Report showing labour based paving options.

Paper comparing prime vs tack coats.

A Guide has been prepared that documents the available options for roadway surfacings, and provides a decision-making process to allow consideration of functionality, performance, durability, safety, life-cycle costs, as well as aesthetics and environmental impacts.

A comprehensive guide to all aspects of chip sealing, prepared by Transit New Zealand. There is no better single reference available.

In tropical and sub-tropical countries, the performance of Hot Mix Asphalt (HMA) has often been disappointing, with road surfaces sometimes failing within a few months of construction. Under the high temperature conditions experienced in these countries, bitumen, which is a visco-elastic material, can become very soft. Bitumen can also undergo relatively rapid chemical changes that cause many of the desirable properties of HMA to be degraded or lost altogether. Overseas Road Note 19, which is based on the experience of TRL and collaborating organisations throughout the world, provides a guide to the appropriate design of HMA, and accounts for these deficiencies. This experience has been gained in carrying out a comprehensive, co-ordinated and long-term series of research projects as part of the DFID ‘Knowledge and Research’ programme. The research showed that the behaviour of asphalt surfaces in tropical and sub-tropical environments was frequently contrary to expectations and has given rise to a paradigm shift in our understanding of road behaviour. This new Road Note is aimed at engineers responsible for roads and gives guidance on the design, manufacture and construction of HMA pavement materials in tropical and sub-tropical climates. The HMA requirements are described for different traffic loading categories, including severely loaded sites such as climbing lanes.

Minor roads in rural and urban areas are vital to the socio-economic well being of communities by providing access to schools, clinics, jobs, neighbouring communities and higher order roads. The provision of bituminous surfacings either as spot improvement measures or on longer lengths of road can greatly improve wet season passibility and reduce maintenance needs. In urban areas and villages there are also additional dry season benefits from dust reduction. Bituminous surfacings constructed by labour-based techniques are a cost effective method of improving accessibility whilst providing opportunities for increasing the skills base of emerging contractors. The paper reviews some labour-base surfacing techniques which increase opportunities for the development of communities and small-scale entrepreneurs.

The main purpose of the Guideline is to contribute to the social and economic enhancement of the rural and peri-urban poor by improving access and mobility through the cost-effective provision of bitumen surfaced roads. It highlights the potential benefits to be accrued from the implementation of research findings and innovation carried out in the region to provide appropriate local solutions for the provision of low-volume sealed roads.

This manual is a guide to the construction of new bituminous surfacings on unpaved low trafficked roads in tropical countries using labour-based methods. It is aimed at local government officials and their staff, and smallscale contractors who are responsible for carrying out the work employing mainly local labour.

To achieve the desired results it is essential that works supervisors be trained by means of short training courses and field trials to deliver the required standard of workmanship. This manual can also be used to assist with this training. Labour-based construction of bituminous surfacings can be very effective providing there is good roadside drainage and the underlying road surface is sufficiently stable and the workmanship is to a good standard. It is therefore stressed that the preparation of the existing road and materials used must meet the particular country and ministry design specifications before any sealing work is undertaken.

Road construction in rural areas is increasingly being focused on provision of access and poverty alleviation. When access is treated as a priority, it is likely that there will be an increased use of spot improvement techniques. The decision to surface a road with a bituminous seal may be made because the existing gravel pavement requires too much maintenance or because suitable regravelling materials are scarce and in some cases sealing roads, which carry traffic as low as 30 vpd, may be justified. The upgrading of short sections of road for which the use of conventional large road construction equipment is prohibitively expensive make the methods described here most suitable.

The techniques described in this manual, use low cost plant that can either be manufactured locally or be bought or hired by small local contractors. However, there are situations where traffic levels will be at the limit of the ‘low-volume’ category and in these cases the use of bitumen heating and spraying tanks if appropriate, should be used. Any additional equipment that may be required should be relatively cheap and within the range of the capital investment expected by small-scale contractors.

Presentation by International Labour Organisation on options for low cost surfaces

Excellent paper on issues related to using coral derived aggregates for road construction.

This Guideline captures best regional and international practice in all aspects of LVSR provision. It is not a prescriptive document but,rather, provides guidance to users so as to ensure that well-considered decisions are
made. The development of the Guideline has benefi ted from the close involvement of practitioners in the region.

The Guideline presents a major departure from traditional practice in all aspects of LVSR provision by examining procedures, practices and methods used in:

• planning, appraisal and environment
• construction and drainage
• geometric design and road safety
• maintenance
• pavement design, materials and surfacing

The Guideline promotes the use of a holistic approach to LVSR’s, which recognizes that criteria need to be satisfied in the different and often interacting dimensions of road provision.

Paper describing considerations in constructing pavements in tropical countries.

Research conducted by UK Dept of International Development, who commissioned TRL to develop a manual that would provide sound, research-based advice on the suitability of alternative bitumous surfacings. This involved trials in Mozambique.

Overseas Road Note 19. This Road Note is aimed at engineers responsible for roads and gives guidance on the design, manufacture and construction of HMA pavement materials in tropical and sub-tropical climates. The HMA requirements are described for different traffic loading categories, including severely loaded sites such as climbing lanes. The procedures take into account the fact that many countries have limited facilities for designing bituminous mixes and therefore need to use commonly available or inexpensive equipment. The Road Note complements and, in many parts, also updates Overseas Road Note 31 (TRL, 1993 which gives recommendations for the design and construction of new road pavements but which also includes chapters on the design of pavement layers).

Construction costs of the upper pavement layers (roadbase and sub-base) are typically about 30 to 40 per cent of the total road construction cost. The work reported here concentrates on granular pavement materials, although many of the principles developed and described are applicable to the materials used in the lower layers (subgrade and fill). The limiting criteria (compacted strength, plasticity and grading) set out in traditional specifications for roadbase and sub-base materials are based on universal standards applied to all traffic levels. Where the materials fail to meet these criteria they are termed “marginal” or “sub-standard".