Access to markets and social services is a major determinant of economic status and welfare. Measurement of access is therefore of great importance for policy analysis and planning of interventions. The objective of this article is to expose readers to a new way of measuring and visualising accessibility—a potential accessibility index—and its applications. This index gauges connectivity of a specific location to large cities while taking into account the population of the cities or other destinations of interest and the transportation facilities to reach them. The potential accessibility index is used in the empirical literature to test the hypotheses from the ‘New Economic Geography’ regarding the impact of market access on regional economic growth. Along with recent developments in poverty mapping, this index has also been used to investigate the spatial relationship between poverty and market access. Accessibility indexes are gradually gaining acknowledgement of policy makers and development practitioners as important monitoring instruments of development. For example, a rural access indicator is part of the results measurement system for the World Bank's International Development Association (IDA) programmes