Environmental sustainability is another dimension of the City Prosperity Index. Prosperous streets help to safeguard environmental sustainability while contributing to the prosperity of cities. The creation and (re)distribution of the benefits of prosperity should not destroy or degrade the environment. The natural assets of cities should be preserved for the sake of future generations and to promote sustainable development.
By promoting walkability and cycling, prosperous streets contribute to the reduction of air and water pollution and to the preservation of biodiversity.25 Along with public parks, waterfronts and “green” areas for recreational and productive purposes, prosperous streets help to reduce fragmentation of natural systems and reduce the spatial footprint through the careful design of infrastructure networks and settlements. The impact of pollutants on the ecological state of the city makes it imperative that streets as a “zone of maximum exposure” take centre stage when the study of environmental sustainability towards the achievement of prosperity is examined. Pollution emissions released on the street contribute to the most harmful effects on climate change, ozone depletion, ecological damage, street aesthetics, and human health.
The idea that streets are a “green” public good and are public spaces is one that needs to be examined. Non-motorized forms of transport, pedestrianization, cleaner fuels and reduced traffic congestion are just some of the measures that can limit the damaging effects of motorized transport and traffic congestion. These should be considered when planning streets of the future.
35 CHAPTER 2: PROSPEROUS STREETS:
CONCEPTS, METHODS AND MEASUREMENTS
BOX. 2.3: THE STREET-LED CITY-WIDE SLUM UPGRADING APPROACH ADVOCATED BY UN-HABITAT
In a recent publication and study drawn from more than a dozen slum upgrading programmes and projects throughout the world, UN-HABITAT presents an approach called street-led city-wide slum upgrading. There is nothing new about this approach except that it addresses the problems of slums in the world in a simple and straightforward manner that takes the street as the pillar for urban transformation of slums and uses the street and the area-based plan to trigger the physical, juridical, economic and social integration of slums into the city’s urban fabric and its urban planning and management regime.
Defining the streets and the street pattern is fundamental for this approach as it helps to rationalize the layout of slum settlements subject to upgrading and consolidation. It generates the spatial structure and urban patterns that are essential to transform slums into neighbourhoods and connect their economies and social processes to the city. It is an incremental development strategy that builds on streets that are prioritized based on their attributes to generate the highest impact in terms of connectivity to the city networks, public space, infrastructure provision, land regularization and security of tenure, and the economic opportunities for businesses and small-scale enterprises. Streets are treated as the primary conduits for social and economic transformation that benefit the city as a whole.
UN-Habitat’s strategy to improve the lives of slum dwellers – in response to the MDGs – is ingrained in the opening of streets as the forefront of urban regeneration and as primary pillars for a deep set of informal settlement regularisation strategies and area-based planning processes that are all part and parcel of a city development strategy. Streets are proposed as the starting point of settlement upgrading and the link for integration with the city and its development plan. The strategy can work at scale across all cities, being based on the common denominator of streets. It learns from the evolution of approaches applied so far and goes forward towards defining a strategic approach for urban transformation that takes advantage of streets.
The UN-Habitat approach promotes better planning and urban restructuring of slums and informal
settlements in order to improve mobility, accessibility and provision of basic services. The existing settlement morphology, particularly the street pattern and availability of open spaces, determine the extent to which improvements are possible.
UN-Habitat’s approach does not advocate ad-hoc infrastructure improvements that take the existing spatial and urban layout configuration of settlements for granted and leaves them intact.
The configuration of slums and informal settlements usually reflects a haphazard land occupation. Simply providing basic infrastructure and laying down pipes for water supply, drainage and sewerage networks as well as public lighting without rationalizing the urban spatial structure of these settlements has proven to be costly and counterproductive.
The street-led citywide slum upgrading strategy also suggests the need to shift from piecemeal project-based interventions to a citywide programmatic approach that comprises multiple interventions in multiple slums that will be reconnected to the city’s urban fabric and its infrastructure networks. It also advocates a shift from implementing a full fledge upgrading plan towards an incremental and phased approach that takes prioritized streets as part of an area-based plan linked to the citywide urban plan and closely bound to availability of finance.
It is argued that this phased and incremental approach suits cities and local governments plagued by financial difficulties.
The shift towards street-led slum upgrading reinforces community and residents participation in enumeration, mapping, and data collection for plan making as well as in deciding on the street pattern and which streets to prioritize.
It goes without saying that the proposed approach inevitably implies demolitions and relocation of residents living in properties that have to go for making room for streets and infrastructure provision. Therefore, the street-led strategy makes the case for securing land within the settlements – as part of the area-based plan – or in the vicinity of the settlement in order to enable relocation and resettlement that does not jeopardize the social and economic capital of affected residents.
Source: UN-Habitat, 2012, Street-led city wide slum upgrading
STREETS AS PUBLIC SPACES AND DRIVERS OF URBAN PROSPERITY 36
BOX 2.4: STREET CONNECTIVITY AND EMISSION OF POLLUTANTS
Street corridors naturally harbour more toxins as they are the sites of motorized mobility. This increases the complexity of the implementation of technical solutions. Review of literature shows that air toxins are up to 4 times more concentrated at street intersections than along the street. In order to lower street pollution, efforts needs to be made to reduce traffic congestion, to allow for more uniformity in vehicle travel speeds and to thoroughly examine optimal intersection density so as to identify the contribution of street design to this problem. .
A street network pattern can affect the production of pollutants by the amount of car travel that it necessitates and the speed at which cars can travel. The grid plan, with its frequent intersections, may reduce the proportion of trips made by car as they encourage walking and cycling due to the directness of routes that it offers to pedestrians. But it also makes the same routes more direct for cars, which could be an enticement for driving. The potential car trip displacement would result in a reduction of pollutant emissions.
Traffic jam in Beijing’s Central Business District, China. © Hung Chung Chih/ Shutterstock Adapted from State of New South Wales through the Office of Environment and Heritage’
Source: Kovalenko, Gredasova and Podrezenko, 2013
CONCENTRATION OF DIESEL EXHAUST
ZONE OF EXPOSURE
37 CHAPTER 2: PROSPEROUS STREETS:
CONCEPTS, METHODS AND MEASUREMENTS