About the filter

When do roads’ benefits outweigh their costs? Economic feasibility studies can provide the answer, but time and financial limitations mean that many of these studies fail to accurately represent roads’ full costs. Further, studies are seldom done comparatively, so governments can’t effectively prioritize. In order to determine which road development projects warrant closer, more detailed examination, CSF has developed the Roads Filter Tool. Rather than examining roads one at a time, the Roads Filter compares an array of potential road investments, identifying the projects that merit closer scrutiny due to their associated risks.

We have applied the Roads Filter to 36 road construction and improvement projects across five countries in the Amazon region. The original list was compiled through interviews with conservation experts in each country and contains projects perceived as posing some degree of threat to natural ecosystems. The Roads Filter ranks selected projects depending on their level of economic, environmental, socio-political, and cultural risk (or inversely, the potential for conservation by avoiding construction). The overall risk of each project is assessed through an index built from 17 variables grouped into four categories and weighted according to their relative importance.

In order to combine quantitative and qualitative variables in index form, variables are represented as a numerical value between 1-5, with 1 being the best (least risky) in terms of economic feasibility and low environmental, social and cultural impacts. The roads with the highest risks present the greatest opportunities for conservation, in the sense that changing them or redirecting investment will have greater environmental benefits and minimal – if any – economic cost.

As with any index, the output of the Roads Filter gives a comparative measure, valid only for the 36 roads examined, but takes an effective step towards highlighting those road projects of greatest concern and in need of more thorough analysis. Output from the Roads Filter makes it possible to direct conservation attention to those projects that present the highest risk levels, overall or for categories of interest. Effort should be geared towards achieving more accurate and conclusive in-depth assessments of these projects’ economic, environmental, socio-political, and cultural implications.

Application of the tool and follow-up assessments can improve decision-making to aid both conservation and the development of cost-effective transportation infrastructure.

For a complete description of the methodology, please download the Technical Report.

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