Differences in how accessibility is measured or conceived of comes in different flavors and sizes. Differences often have to do with perspective. At its core, however, access is a concept that helps understand and conceptualize the complex relation between transport and land use in a city and their impacts on city organization, development, and planning to achieve more sustainable outcomes. Transport facilities increase the accessibility to customers by moving them to or through the right place, while locating firms increase accessibility by intensifying land development when they provide more stores. Measures of access begin with an account of the activity component. Access is the fundamental force for understanding cities. The task of measuring accessibility is similar to that of measuring network size, but requires a slightly more sophisticated approach. Accessibility differs from Network Size in that one multiplies each interaction by a function of the travel cost, such that distant interactions have less weight than nearby interactions.