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Global Map of Travel Time to Cities (2015)

Market accessibility is one of the most important and frequently used indicators in agricultural research and rural development. In Africa, the practice of trading agricultural products is still highly constrained by agricultural policies and poor transportation networks. Challenging road conditions, long distances, and inadequate road infrastructure add to travel times and transportation costs and therefore limit opportunities for farmers to sell their goods. Poor market access can also negatively impact farm production because the accessibility of critical agricultural inputs such as fertilizer, pesticides, and seed is also limited. Compared to urban households and those with easy access to markets, rural farm households without market access typically rely on their own production for most of their calorie intake. Inadequate market access, therefore, puts these households at greater risk of food insecurity. The more accessible markets are, the greater the population’s ability to remain economically self-sufficient and maintain food security.

A comparison of the market accessibility maps, which express travel time to different-sized cities (market centers), can help stakeholders better understand factors that determine farm performance. Following the seminal work of JRC in 2008, Travel time to major cities: A global map of Accessibility (led by Andy Nelson, a CSI Member at University of Twente/ITC), there have been country- or region-specific updates on the evolving accessibility (e.g., HarvestChoice’s update in Africa South of the Sahara). And finally, a new globally updated map of 2015 has been recently published by a consortium of accessibility mappers led by the Malaria Atlas Project at the University of Oxford.

Weiss, D. J., et al. “A global map of travel time to cities to assess inequalities in accessibility in 2015.” Nature (2018).

By incorporating open global road datasets from Open Street Map and Google, the team was able to increase the number of mapped road area by nearly five times compared to the earlier work. This new study presents “… where gaps in accessibility remain in 2015 and where the world can collectively address the most fundamental inequalities still experienced today.

All the underlying data of the study, including the data layers of market (city) accessibility and friction surface at 30 arc-second resolution, as well as example codes in Javascript and R languages are publicly available at https://map.ox.ac.uk/research-project/accessibility_to_cities.

Note that, while this new exciting update will help increase the relevancy of our spatial analyses especially in agricultural development domain for sure, the usual limitations of global accessibility analysis still apply (e.g., locally-adapted modes of transportation and their switches, abrupt slope changes, geopolitical conflicts, seasonal roads). As the authors write in the paper, there are still much to be done!

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