The pattern of new urban and residential roads represents an essentially permanent backbone that shapes new urban form and land use in the world’s cities.
Thus, today’s choices on the connectivity of streets may restrict future resilience and lock in pathways of energy use and CO2 emissions for a century or more.
A rapid policy response, including regulation and pricing tools, is needed to avoid further costly lock-in during this current, final phase of the urbanization process.
As economic growth leads to an increasingly motorized world, energy use and greenhouse gas emissions from transportation are predicted to increase dramatically. The sector’s energy use is expected to rise by ∼44% between 2015 and 2040 under current policies, with CO2 emissions from transport oil combustion rising by almost as much.
Global energy and integrated assessment models indicate that even under aggressive efficiency and electrification scenarios, transportation energy and emissions will see more limited reductions compared to other sectors.
Most global analyses, however, model transportation energy demand as a function of income, energy prices, and technology and take little to no account of how the physical structure of urban centers shapes household decisions on vehicle ownership and travel or of community decisions on transport infrastructure and services.
While a large body of research shows that cities with high population density, connected street networks, and fast and frequent public transportation systems tend to have less vehicle travel at a given income level, such insights are hard to capture in global analyses.
One reason is that there are limited data on urban spatial structure at the metropolitan level and even fewer sources at the higher-resolution neighborhood level where household travel decisions are shaped.
If you want to know a culture, how it thinks and its education and level of awareness, look at its urban landscape design and street sprawl, it will tell you everything
Thus, policymakers have little insight into underlying trends and the characteristics of new development, let alone about how these trends may affect future energy use and emissions.
Type E often represents gated communities, as well as places with topographic barriers.
Demand for gated communities is often driven by a fear of crime or a search for social prestige, but many analysts have raised concerns about their consequences for social segregation and for allowing a high-income elite to opt-out of municipal service provision, as well as for their car dependence.
Worsening Sprawl and Its Consequences.
1.large parts of the world, recent urban growth has increasingly resulted in inflexible and disconnected street networks.
2.However, in the long run, sidewalk and transit provision, densities, land uses, and both formal and informal rule enforcement are malleable to social, economic, and policy influences
3.Given that many cities will continue to grow for decades, density may change and outlying regions may be subsumed into more contiguous development, but disconnected street routes will remain as a fundamental constraint.
4.In the long term, low-connectivity street networks lack resilience to adapt to changing pressures and resources and ultimately to densify toward a mixed-use, transit-integrated, energy-efficient urban form.
5.In this sense, they are effectively “density proof,” i.e., resistant to changing the mix of uses, modes of transportation, and density In addition, in a practical policy context, the regulation of development style and infrastructure is somewhat separable from decisions about the conversion of agricultural and natural lands into urban use.
6.Based largely on this logic, we expect street-network measure to be a key predictor of future climate, energy, health, and social outcomes related to urban form.
7.The impact of today’s street connectivity decisions on climate and other outcomes is amplified by the tendency of new development to mimic existing urban form.
8.A neighborhood with highly permeable streets is more likely to allow transit to access an adjacent future development, more likely to contain local services and jobs accessible to pedestrians living nearby, and so on.
9.Building high-connectivity, pedestrian-navigable streets in the adjacent development therefore has economic complementarities with the connectivity of the existing street network. In other words, one interpretation of our findings of persistence is a long-run path dependence in urban evolution, rendering any initial design decision all the more pivotal for future human and environmental outcomes.
10.street-network type is associated with low walkability, car orientation, and land-use segregation, gated communities have obvious significance for other global challenges related to economic disparities and social segregation.