Sustainable cities = resource decisions today do not effect quality of life in the future. Cities need:
Effective transportation system
A mix of land uses
A variety of affordable housing
An effective infrastructure
Other civic amenities such as parks and green spaces
A maximum use of alternative energies
4 major problems cities face:
Transportation - lack of or overcrowded streets
Food - having enough local food to feed the city
Waste - Where to put it and how to treat it
Density - infilling (rezoning and rebuilding in populated areas) can lead to high density
Summary
In order to be sustainable there are certain things a city must have in order to support the population there. Necessities in cities are: an effective transportation system, diverse affordable housing, efficient infrastructure, various uses of land, parks or green spaces, plenty of diverse alternative energy, and other civic amenities. The four main problems that cities tend to face however, are lack of transportation or the roads being overcrowded, not having enough local food, build up of waste and where to put it or treat it, and the repeated rezoning and rebuilding in population areas can lead to a high population density.