Editing IPCC:AR6/WGII/Chapter-6 (section)

==== 6.3.5.5 Transport ====

<div id="h3-32-siblings" class="h3-siblings"></div>

A wide range of adaptation options are available for transport infrastructure and most provide a good benefit cost ratio (Doll, Klug and Enei, 2014; Forzieri et al., 2018). Options include upgrading infrastructure (which can often be achieved autonomously as part of standard repair and replacement schedules) and strengthening or relocating (critical) assets. Adaptation of road and rail networks in Australasia includes re-routing, coastal protection, improved drainage and upgrading of rails (Table 11.7.) In areas with substantial infrastructure deficits, such as much of Africa, investments in public transport and transit-oriented development are highlighted as desired mitigation-adaptation interventions within cities of South Africa, Ethiopia and Burkina Faso ( [[IPCC:Wg2:Chapter:Chapter-9#9.8.5.3|Section 9.8.5.3]] ). Adapting low carbon transport infrastructure will be crucial to ensure resilience to climate change impacts whilst simultaneously delivering mitigation goals (Shaheen, Martin and Hoffman-Stapleton, 2019; Costa et al., 2018).

[[#Wright--2012|Wright et al. (2012)]] calculated that strengthening bridges in the USA would cost USD 140–250 billion by 2090 (or several billion dollars a year), but costs are reduced by 30% if interventions are made proactively. [[#Koks--2019|Koks et al. (2019)]] calculate a benefit–cost ratio of greater than one for over 60% of the world’s roads exposed to flooding. The greatest benefits from adaptation of the global road network are in LMICs where reductions in flood risk are typically between 40% and 80%. [[#Pregnolato--2017|Pregnolato et al. (2017)]] showed that in the city of Newcastle upon Tyne (UK), two carefully targeted interventions at key locations to manage surface water flooding reduced the impacts of the 1-in-50 year event in 2050 by 32%. In permafrost regions, geo-reinforcement, foundation and piles can be strengthened (Trofimenko, Evgenev and Shashina, 2017), whilst passive cooling methods, including high-albedo surfacing, sun-sheds and heat drains can cool infrastructure (Doré, Niu and Brooks, 2016).

[[#Hanson--2020|Hanson and Nicholls (2020)]] calculate the total global investment costs for port adaptation to sea level rise and provision of new areas at USD 223–768 billion by 2050. However, adaptation of existing ports is only 6% of this. [[#Yesudian--2021|Yesudian and Dawson (2021)]] estimate the cost of maintaining present levels of flood risk in 2100 for the global air network will cost up to USD 57 billion (Monioudi et al., 2018; Esteban et al., 2020b).

New technologies and design innovations can improve the resilience of cars, trains, boats and other vehicles to cope with more extreme weather. Mobility transitions have the potential to improve mobility and accessibility, to influence urban form and to reduce vehicular use (and thereby infrastructure degradation), vehicle miles travelled and vehicle-based emissions (Sperling, Pike and Chase, 2018). For example, use of electric vehicles, hydrogen vehicles and greater uptake of public transport and other vehicles that reduce exhaust head emissions reduces the urban heat island ( [[#Kolbe--2019|Kolbe, 2019]] ). Carsharing can reduce carbon emissions by over 50% (Shaheen, Martin and Hoffman-Stapleton, 2019). Ride hailing, matching non-professional drivers of private vehicles with paying passengers, positively impacts low-income, low-car ownership households in Los Angeles ( [[#Brown--2018|Brown, 2018]] ), and fills market gaps in cities where public transit infrastructure is inadequate, unreliable or unsafe (Suatmadi, Creutzig and Otto, 2019; [[#Vanderschuren--2018|Vanderschuren and Baufeldt, 2018]] ), but can also create a precarious and insecure job market that impacts well-being ( [[#Fleming--2017|Fleming, 2017]] ). Whether the resulting impacts are positive or negative, largely depends on local, national and international policy and practices.

Safe and convenient walking and cycling (and public transport) infrastructure in cities reduces carbon emissions and urban heat island intensity, but also improve cardiovascular capacity which reduces heat stress (Schuster et al., 2017). In some regions, warmer weather may bring opportunities for increased uptake of cycling and walking, though precipitation or thermal discomfort caused by high temperature and humidity can reduce the use of active travel modes for commuting and recreation ( [[#Chapman--2015|Chapman, 2015]] ). Shaded pavements and lanes, and measures to mitigate the urban heat island can reduce risks to disruption of active travel thereby also enhancing mitigation (Wong et al., 2017).

Full system re-design may enable the greatest resilience but it does not usually have a good benefit–cost ratio (Doll, Klug and Enei, 2014). Moreover, Caparros-Midwood et al. (2019) show that transport infrastructure planners will not always be able to resolve trade-offs between managing climate risks and mitigating greenhouse gases without tackling other sectors. However, infrastructure planners should continually seek opportunities for positive infrastructure lock in where available (Ürge-Vorsatz et al., 2018).

<div id="6.3.5.6" class="h3-container"></div>

<span id="water-and-sanitation-1"></span>