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Road construction and improvement projects (usually comprising widening, pavement reconstruction or resurfacing and improvements to horizontal geometry) are conventionally subdivided into the following stages:

  • feasibility study;

  • preliminary design;

  • detailed design;

  • construction; and

  • operation and maintenance.

Low-cost road projects located in flat or gently rolling terrain typically incur costs in the following proportions (though percentages can vary significantly from project to project):
  • 1% feasibility study;

  • 2% design; and

  • 97% construction.

For new roads in hilly and mountainous terrain several alignment options may exist, each with its own implications for length, ease of construction, stability and cost. Decisions made over alignment selection and the choice of cross-section can have profound effects on the cost of construction and the performance of the works during operation and maintenance. Investments in desk studies and engineering geological field investigations during the feasibility study and design stages can assist this decision-making and help avoid otherwise unforeseen ground conditions and stability problems during later stages. It is recommended that the opportunity be taken during these early stages to carry out these studies, especially in difficult and complex terrain. A cost distribution between the three main project stages might then be of the order of 5%, 5% and 90% respectively. For example, in the case of the Arun III hydropower access road in Nepal, where comprehensive preparatory studies were undertaken, the combined cost of the feasibility study and design amounted to

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