The concept of an optimum, or ideal, size of population concerns both theory and policy. Urban areas are very developed, meaning there is a density of human structures such as houses, commercial buildings, roads, bridges, and railways. Ideal Density for US Metro Areas. Urban density is a term used in urban planning and urban design to refer to the number of people inhabiting a given urbanized area. In a democratic system, planners need to be mindful of community character. Urban centre: must have a minimum of 50,000 inhabitants plus a population density of at least 1500 people per square kilometre (km 2) or density of build-up area greater than 50 percent. An urban area includes the city itself, as well as the surrounding areas. To an extent, this is what the new urbanist transect is about. Urban cluster : must have a minimum of 5,000 inhabitants plus a population density of at least 300 people per square kilometre (km 2 ). As we know there are people who love dense urban activity, those who prefer quiet, pastoral living, and plenty in between. Most people are unwilling to walk much more than half a mile on a regular basis, which means that destinations—jobs, stores, transit stops, and so on—are only within “walking distance” of people within a half mile of them. The ideal population size and density is on one hand, a matter of taste. Urban density is considered an important factor in understanding how cities function. Most inhabitants of urban areas have nonagricultural jobs. Researchers nailed down the optimum density from a health perspective: more than 32 homes per hectare. The study, from Oxford University and the University of Honk Kong, looked at the impact of density on more than 400,000 residents in 22 British cities, including London, Glasgow and Cardiff. An urban area is the region surrounding a city. As such it is to be distinguished from other measures of population density. "Urban area" can refer to towns, cities, and suburbs. Density is also very important for transportation. Low density urban sprawl is nasty in my view, take Sydney for example, the city centre is surrounded by suburbia 50km-80km deep on all sides, terribly inefficient as driving to and from work every day introduces so many more vehicles on the road, polluting the air and lowering overall life quality. 10 Principles for Making High-Density Cities Better Author Kaid Benfield ... Finding the right density and accompanying urban features for the right place is critical. Maps of Walkable Density vs. Many urban areas are called …