Many rural roads are normally passable for maybe 95% of their length, but may then turn into an impassable quagmire for the remaining 5% where they are crossed by watercourses or at low points in the alignment. Drainage and water crossing structures form a major part of the construction cost of a road, typically accounting for up to 40% of the total cost. Once a road has been constructed the passability and maintenance cost are closely linked to the quality of the cross drainage provision for the road.
It is clear that road structures are an important aspect of road design and construction. Unfortunately it is an aspect that is often given little or insufficient attention which is shown by the fact that when roads become impassable it is usually where they cross a watercourse. Although the length of road structures forms only a very small fraction of the total road length the time spent on their design must be a much greater portion of the total planning process.
Engineers and managers are also usually hampered by the national standards and their range of solutions allowable to designers and construction teams. It seems that only unreinforced or reinforced concrete are permitted solutions (aping developed country practices). This unfortunately prevents the use of a whole range of low cost techniques that are PROVEN, and make the best use of local resources: labour, skills, materials and enterprises. These techniques are far more appropriate in an environment of low labour costs and high credit and capital costs.
Low Cost Structures are an essential and integral component (with Low Cost surfacing) of an affordable Basic Access approach to support social and economic development of rural areas and to facilitate poverty reduction.
gTKP has cooperated with a number of interneational organisations to develop a guideline on Small Structures for Rural Roads.
If you would like to make a contribution to this topic or help to 'sign-post' any key documents on the topic for gTKP partners and users, please contact Rob Petts: firstname.lastname@example.org
Updated May 2010