# **1. Introduction**

Worldwide, billions of people are unable to access work and educational opportunities because transport services remain either unavailable or unaffordable. The Sustainable Development Goals (SDGs) include a goal to increase rural accessibility, but they do not set a target. Specifically, SDG indicator 9.1.1 refers to the proportion of the rural population who live within 2 kilometers of an all-season road. An " _all season road"_ refers to _"a road that is motorable all year round by the prevailing means of rural transport_ ." In countries with a significant monsoon season, this implies paved roads; but in drier countries, all-season roads can also include gravel roads.

Access to an all-season road is believed to significantly increase households’ welfare if it can help rural populations access new job markets and social services. For example, in Bangladesh, a road paving project implemented from 1997–2001 increased household expenditure by 9-10 percent on average (Khandker and Koolwal, 2011). Similarly, in Ethiopia, access to an all-season road reduced poverty by 7 percent, and increased household consumption by 16 percent (Dercon et al., 2008). However, a road may bring little economic benefit in areas with no market to sustain non-agricultural jobs.

One measure of rural accessibility is the Rural Access Index (RAI), defined by (Roberts et al., 2006) as "the number of rural people who live within two kilometers (typically equivalent to a walk of 20-25 minutes) of an all-season road as a proportion of the total rural population". (Roberts et al., 2006) assessed the RAI in a small number of countries using household survey data. However, this approach was costly, the surveys lacked spatial representativeness, and the resulting RAIs were not necessarily comparable between countries. Ten years later, (Iimi et al., 2016) proposed a new method based on GIS data and applied it in eight countries. They assessed the RAI using WorldPop data for rural population distribution and digitized road network data, including road condition, provided by national road agencies.

However, to be able to inform global policy for improving road access in rural areas, global-wide estimates are required. This is the first global study that attempts to provide such estimates. We go on to explore how rural access might be optimally increased via a sequential road upgrading strategy.

In this paper, we build on the approach developed by (Iimi et al., 2016) and use road networks extracted from OpenStreetMap (OSM) for 166 countries, to assess road access globally. Population data for these countries is, similar to Limi et al. (2016), taken from WorldPop.<sup>1</sup> We find that while most European countries have an RAI close to 100 percent, most developing countries are below 60 percent, all SubSaharan countries are below 51 percent, and 24 countries are below 20 percent.

We then explore the cost of increasing rural access in 19 countries with good quality data, using an algorithm that prioritizes investment in individual rural road segments based on their impact on rural access and connectivity. The results show that costs quickly balloon as the RAI increases, but also that they depend on geography, road network connectivity, population distribution, and road unit costs.

Finally, as a thought experiment, we assess the cost of providing regular food and medicine supply by drones to remote areas in Sierra Leone and compare the cost of doing so with the cost of paving roads. We find that even though drones cannot generate the same socio-economic benefits as roads, they can be a good short-term solution to increase rural integration until roads become affordable.

> 1 <mark>www.worldpop.org</mark>

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