  The Rural Access Index (RAI), one of the UN Sustainable Development Goal
indicators (SDG 9.1.1), represents the proportion of the rural population
residing within 2 km of all-season roads. It reflects the accessibility of
rural residents to transportation services and could provide guidance for the
improvement of road infrastructure. The primary deficiencies in assessing the
RAI include the limited studying area, its incomplete meaning and the absence
of correlation analysis with other influencing factors. To address these
issues, this study proposes the "Not-served Rural Population (NSRP)" as a
complementary indicator to RAI. Utilizing multi-source open data, we analysed
the spatial patterns of RAI and NSRP indicators for 203 countries and then
explored the correlation between these 2 indicators and other 10 relevant
factors. The main findings are as follows: 1) North America, Europe, and
Oceania exhibit relatively high RAI values (>80%) and low NSRP values (<1
million). In contrast, African regions have relatively low RAI values (<40%)
and high NSRP values (>5 million). There is a negative correlation between RAI
and NSRP. 2) There is spatial autocorrelation and significant imbalances in the
distribution of these two indicators. 3) The RAI exhibit a positive correlation
with the factors showing levels of the development of countries such as GDP,
education, indicating that improving the road infrastructure could reduce the
poverty rates and enhance access to education. And in contrast with RAI, NSRP
exhibit the completely negative correlations with these factors.
