Population density in inner city areas remains higher than in the suburbs. However, the population growth rate in the suburbs is also quite high. Areas of urban development in Bangkok can be divided into three zones: a commercial and historical zone, intermediate areas engulfed in urban sprawl, and the outer zone, which is currently used for residential and commercial purposes [31]. The built-up and residential areas consist of three categories. They are (1) an inner core area for conservation and tourism (high density), (2) an intermediate zone for the new Central Business District (CBD) and transportation hubs (medium density), and (3) newer residential districts (low density).