Source: adapted from Camagni, R., M.C. Gibelli and P. Rigamonti (2002) “Urban Mobility and Urban Form: the Social and Environmental Costs of Different Patterns of Urban Expansion”, Ecological Economics, Vol. 40, pp. 199–216.
The urban expansion of land uses can take place in five general forms:
- Infilling. New developments are set in areas that were previously unused or being redeveloped to new uses. Brownfield redevelopments are a good example of urban expansion opportunities on sites that have lost their economic significance, such as old industrial sites or abandoned terminals (waterfronts or rail yards).
- Extension. A standard form of expansion where land use is a development directly adjacent to existing land uses. New infrastructures such as streets and utilities are expanded from the existing network.
- Linear development. Similar to extension, but in this case, the expansion is shaped by an existing corridor of circulation such as a highway or a transit line (subway, light rail). It directly takes advantage of the accessibility offered by the transport infrastructure. In some cases, the development is the rationale to expand an existing corridor.
- Sprawl. A standard form of suburban development taking advantage of scattered lots. Each developer is taking advantage of an existing plot of land without much consideration of the existing urban pattern.
- Large-scale projects. The setting of a large infrastructure project such as a new port, airport, industrial zone, logistics zone, or intermodal rail terminal consumes a large amount of land. Its operational rationale is often very different from the existing landscape so the level of integration to existing land uses is problematic.