A global implementation of the rural access index

The Rural Access Index (RAI) is one of the most important global development indicators in the transport sector. It is currently the only indicator for the SDGs that directly measures rural accessibility, and it does so by assessing rural populations' access to allseason roads. The RAI was developed by the World Bank in 2006, originally as a measure of poverty. The original 2006 methodology based itself on pre-existing household surveys, which had several disadvantages including inconsistency across countries, lack of regular updates and cost constraints, which limited the index's sustainability and accuracy. Following its adoption as Sustainable Development Goal (SDG) indicator 9.1.1 in 2015, the indicator received a new methodology taking advantage of geospatial techniques, published under the "Measuring rural access using new technologies" report in 2016. The World Bank has since endorsed an additional Research for Community Access Partnership (ReCAP) funded project led by the Transport Research Laboratory (TRL)—the RAI Supplemental Guidelines—which provided detailed guidance for calculating the RAI, notably with an alternative approach to the all-season aspect of RAI, focusing on the changing accessibility profile of road networks rather than relying on road surface quality alone or scarce physical measurements for road conditions. Nevertheless, neither the 2016 nor the 2019 methodologies were implemented globally, with official implementations published by the World Bank being restricted to more in-depth studies for selected countries mostly in Africa and the Middle East due to data source restrictions. Here we seek to fill in this gap by implementing the most up-to-date methodology endorsed by the World Bank's methodology supplemented by TRL's 2019 guidelines) at global scale with free remotely sensed datasets with global coverage. This dataset was produced by UN SDSN's SDG Transformation Center and is, to date, the only publicly available application of this particular method at a global scale.