Reconstruction and renewal 重建与复兴
Areas devastated by war or invasion challenge urban planners. Resources are scarce. The existing population has needs.
Buildings, roads, services and basic infrastructure like power, water and sewerage are often damaged, but with salvageable parts.
Historic, religious or social centers also need to be preserved and re-integrated into the new city plan.
A prime example of this is the capital city of Kabul, Afghanistan, which, after decades of civil war and occupation, has regions of rubble and desolation.
Despite this, the indigenous population continues to live in the area, constructing makeshift homes and shops out of salvaged materials.
Any reconstruction plan, such as Hisham Ashkouri's City of Light Development, needs to be sensitive to the needs of this community and its existing culture and businesses.
Urban Reconstruction Development plans must also work with government agencies as well as private interests to develop workable designs.
Transport within urbanized areas presents unique problems.
The density of an urban environment increases traffic, which can harm businesses and increase pollution unless properly managed.
Parking space for private vehicles requires the construction of large parking garages in high density areas.
This space could often be more valuable for other development.
Good planning uses transit oriented development, which attempts to place higher densities of jobs or residents near high-volume transportation.
For example, some cities permit commerce and multi-story apartment buildings only within one block of train stations and multilane boulevards, and accept single-family dwellings and parks farther away.
Floor area ratio is often used to measure density. 容积率经常被用来测算密度。
This is the floor area of buildings divided by the land area.
Ratios below 1.5 are low density. Ratios above five very high density.
Most exurbs are below two, while most city centres are well above five.
Walk-up apartments with basement garages can easily achieve a density of three. Skyscrapers easily achieve densities of thirty or more.
City authorities may try to encourage higher densities to reduce per-capita infrastructure costs. 城市当局鼓励更高的容积率来减少人均基础建设的花销。
In the UK, recent years have seen a concerted effort to increase the density of residential development in order to better achieve sustainable development.
Increasing development density has the advantage of making mass transport systems, district heating and other community facilities (schools, health centres, etc) more viable.
However critics of this approach dub the densification of development as 'town cramming' and claim that it lowers quality of life and restricts market-led choice.
Problems can often occur at residential densities between about two and five.
These densities can cause traffic jams for automobiles, yet are too low to be commercially served by trains or light rail systems.
The conventional solution is to use buses, but these and light rail systems may fail where automobiles and excess road network capacity are both available, achieving less than 2% ridership.
The Lewis-Mogridge Position claims that increasing road space is not an effective way of relieving traffic jams as latent or induced demand invariably emerges to restore a socially-tolerable level of congestion.
The Lewis-Mogridge Position认为增加道路空间不是一个缓解交通拥堵的一个有效方法，而应重建一个人们对拥塞的社会容忍度。