Spatial data is at the core of transportation analysis. Land use patterns, including the density of jobs and homes, and the locations of transportation infrastructure, such as stops, stations, and intersections, are frequently used to answer transportation planning questions. It is often useful to generate metrics at for a geographic zone. Not only does this allow for mapping and visualization, it often reflects the way that people use a transportation system – while a bus stop or rail station is located at a single point, passengers access it from the surrounding zone. In multi-modal analysis, considering zone-to-zone rather than point-to-point travel allows performance and accessibility assessments to compare or combine different modal options that serve the same areas.