Editing IPCC:AR6/SR15/Chapter-4 (section)

==== 4.3.3.3 Urban transport and urban planning ====

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Urban form impacts demand for energy (Sims et al., 2014) <sup>[[#fn:r320|320]]</sup> and other welfare related factors: a meta-analysis of 300 papers reported energy savings of 26 USD per person per year attributable to a 10% increase in urban population density (Ahlfeldt and Pietrostefani, 2017) <sup>[[#fn:r321|321]]</sup> . Significant reductions in car use are associated with dense, pedestrianized cities and towns and medium-density transit corridors (Newman and Kenworthy, 2015; Newman et al., 2017) <sup>[[#fn:r322|322]]</sup> relative to low-density cities in which car dependency is high (Schiller and Kenworthy, 2018) <sup>[[#fn:r323|323]]</sup> . Combined dense urban forms and new mass transit systems in Shanghai and Beijing have yielded less car use (Gao and Newman, 2018) <sup>[[#fn:r324|324]]</sup> (see Box 4.9). Compact cities also create the passenger density required to make public transport more financially viable (Rode et al., 2014; Ahlfeldt and Pietrostefani, 2017) <sup>[[#fn:r325|325]]</sup> and enable combinations of cleaner fuel feedstocks and urban smart grids, in which vehicles form part of the storage capacity (Oldenbroek et al., 2017) <sup>[[#fn:r326|326]]</sup> . Similarly, the spatial organization of urban energy influenced the trajectories of urban development in cities as diverse as Hong Kong, Bengaluru and Maputo (Broto, 2017) <sup>[[#fn:r327|327]]</sup> .

The informal settlements of middle- and low-income cities, where urban density is more typically associated with a range of water- and vector-borne health risks, may provide a notable exception to the adaptive advantages of urban density (Mitlin and Satterthwaite, 2013; Lilford et al., 2017) <sup>[[#fn:r328|328]]</sup> unless new approaches and technologies are harnessed to accelerate slum upgrading (Teferi and Newman, 2017) <sup>[[#fn:r329|329]]</sup> .

Scenarios consistent with 1.5°C depend on a roughly 15% reduction in final energy use by the transport sector by 2050 relative to 2015 (Chapter 2, Figure 2.12). In one analysis the phasing out of fossil fuel passenger vehicle sales by 2035–2050 was identified as a benchmark for aligning with 1.5°C-consistent pathways (Kuramochi et al., 2018) <sup>[[#fn:r330|330]]</sup> . Reducing emissions from transport has lagged the power sector (Sims et al., 2014; Creutzig et al., 2015a) <sup>[[#fn:r331|331]]</sup> , but evidence since AR5 suggests that cities are urbanizing and re-urbanizing in ways that coordinate transport sector adaptation and mitigation (Colenbrander et al., 2017; Newman et al., 2017; Salvo et al., 2017; Gota et al., 2018) <sup>[[#fn:r332|332]]</sup> . The global transport sector could reduce 4.7 GtCO2e yr <sup>−1</sup> (4.1–5.3) by 2030. This is significantly more than is predicted by integrated assessment models (UNEP, 2017b) <sup>[[#fn:r333|333]]</sup> . Such a transition depends on cities that enable modal shifts and avoided journeys and that provide incentives for uptake of improved fuel efficiency and changes in urban design that encourage walkable cities, non-motorized transport and shorter commuter distances (IEA, 2016a; Mittal et al., 2016; Zhang et al., 2016; Li and Loo, 2017) <sup>[[#fn:r334|334]]</sup> . In at least 4 African cities, 43 Asian cities and 54 Latin American cities, transit-oriented development (TOD), has emerged as an organizing principle for urban growth and spatial planning (Colenbrander et al., 2017; Lwasa, 2017; BRTData, 2018) <sup>[[#fn:r335|335]]</sup> . This trend is important to counter the rising demand for private cars in developing-country cities (AfDB/OECD/UNDP, 2016) <sup>[[#fn:r336|336]]</sup> . In India, TOD has been combined with localized solar PV installations and new ways of financing rail expansion (Sharma, 2018) <sup>[[#fn:r337|337]]</sup> .

Cities pursuing sustainable transport benefit from reduced air pollution, congestion and road fatalities and are able to harness the relationship between transport systems, urban form, urban energy intensity and social cohesion (Goodwin and Van Dender, 2013; Newman and Kenworthy, 2015; Wee, 2015) <sup>[[#fn:r338|338]]</sup> .

Technology and electrification trends since AR5 make carbon-efficient urban transport easier (Newman et al., 2016) <sup>[[#fn:r339|339]]</sup> , but realizing urban transport’s contribution to a 1.5°C-consistent pathways will require the type of governance that can overcome the financial, institutional, behavioural and legal barriers to change (Geels, 2014; Bakker et al., 2017) <sup>[[#fn:r340|340]]</sup> .

Adaptation to a 1.5°C world is enabled by urban design and spatial planning policies that consider extreme weather conditions and reduce displacement by climate related disasters (UNISDR, 2009; UN-Habitat, 2011; Mitlin and Satterthwaite, 2013) <sup>[[#fn:r341|341]]</sup> .

Building codes and technology standards for public lighting, including traffic lights (Beccali et al., 2015) <sup>[[#fn:r342|342]]</sup> , play a critical role in reducing carbon emissions, enhancing urban climate resilience and managing climate risk (Steenhof and Sparling, 2011; Parnell, 2015; Shapiro, 2016; Evans et al., 2017) <sup>[[#fn:r343|343]]</sup> . Building codes can support the convergence to zero emissions from buildings (Wells et al., 2018) <sup>[[#fn:r344|344]]</sup> and can be used retrofit the existing building stock for energy efficiency (Ruparathna et al., 2016) <sup>[[#fn:r345|345]]</sup> .

The application of building codes and standards for 1.5°C-consistent pathways will require improved enforcement, which can be a challenge in developing countries where inspection resources are often limited and codes are poorly tailored to local conditions (Ford et al., 2015c; Chandel et al., 2016; Eisenberg, 2016; Shapiro, 2016; Hess and Kelman, 2017; Mavhura et al., 2017) <sup>[[#fn:r346|346]]</sup> . In all countries, building codes can be undermined by industry interests and can be maladaptive if they prevent buildings or land use from evolving to reduce climate impacts (Eisenberg, 2016; Shapiro, 2016) <sup>[[#fn:r347|347]]</sup> .

The deficit in building codes and standards in middle-income and developing-country cities need not be a constraint to more energy-efficient and resilient buildings (Tait and Euston-Brown, 2017) <sup>[[#fn:r348|348]]</sup> . For example, the relatively high price that poor households pay for unreliable and at times dangerous household energy in African cities has driven the uptake of renewable energy and energy efficiency technologies in the absence of regulations or fiscal incentives (Eberhard et al., 2011, 2016; Cartwright, 2015; Watkins, 2015) <sup>[[#fn:r349|349]]</sup> . The Kuyasa Housing Project in Khayelitsha, one of Cape Town’s poorest suburbs, created significant mitigation and adaptation benefits by installing ceilings, solar water heaters and energy-efficient lightbulbs in houses independent of the formal housing or electrification programme (Winkler, 2017) <sup>[[#fn:r350|350]]</sup> .

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