Diversity - Transit Oriented Development (TOD)
The diversity resulting from TOD comes from allowing it! The outcome is that traffic is not tidal. It may be easier to explain what this kind of diversity is not. It is not a dormitory suburb that is empty during the day or a business centre that is empty during the night. The diverse city resulting from TOD would be expected to at least be moderately urbanised (1,000-1,500 dwellings per km2 or 100-150 dwellings per hectare - Link), have at least double digit numbers of employees per hectare, include a spread of different types of shops/retail, and residents living within 400 to 800 m of transit stops, which provide services at 15-20 frequency per hour into the evening.
Using height near the station to get density risks robbing the pedestrian area of daylight by casting uncomfortable shadows and increasing wind speeds at ground level. We do want density but it needs to be balanced. The data for the top ten locations on the list below come from the Melbourne Southbank Structure Plan Nov09 Background Report. Note that ‘Four of the five highest dwelling density examples did not exceed 9 storeys. Higher buildings were associated with higher employment densities’ (p111).
The above list of neighbourhoods is not necessarily an example of Transit Oriented Development, but it gives examples of some neighbourhoods that have a mix of dwellings and employment, and some employment-only areas.
Coin St in London is an interesting example, having both high employment and high dwelling density with a Low- to Mid-rise built typology. Employment and dwelling densities can be equal in a low-rise built typology, but a high employment bias location is likely to be higher rise.
The Southbank study notes that ‘There was no discernible relationship between active edge and densities. There is a direct relationship between the building height within the study areas and the degree of activity at the street interface’ (p114).This means that as building height goes up, the buildings’ interface with the street becomes more negative.