Ethiopia - Travel Time to Regional Centres (Overview Map Series) Scales: 1:1,000,000/1:1,500,000

Abstract

The accessibility indicated as "travel time" is calculated using the cost-distance function of ArcGIS by defining source features (e.g. regional centres from where the travel time is calculated) and a cost raster (each pixel indicates the amount of time needed to cross it). To calculate the cost raster, the model includes land cover (W LRC) to define the travel speed off-road, roads infrastructure, terrain that reduces the travel speed with increasing slope, rivers, and water-bodies. We essentially include all the available spatial data of a given extent that can in some way impact peoples travel speed. This includes things that can make us travel faster (e.g. roads), but also things that serve as brakes (e.g. slopes, water bodies) or even barriers (e.g. borders). When preparing the cost raster one must also consider what means of transportation are available to the people represent in the accessibility map. It is generally assumed that people use the fastest means of transportation available. This means travelling by car or bus on roads, or by foot when travelling off-road.