The concept of TOD may provide a formula or pattern on various scales and certain levels of urban transportation infrastructure for the typical structure and configuration of sets of urban uses and spaces with established boundaries. A certain scale of primary use in TOD usually corresponds to certain scales of secondary use, and the employment opportunities correspond to the matching population of labor. Similar to the concept of neighborhood planning and design, there should be boundaries for defining a TOD with a certain mix of uses for the spatial structure and configuration.