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Adapting Urban Transport to Climate Change

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Overview

This article has been adapted from the GIZ Sourcebook on Adapting Urban Transport to Climate Change[1].


Transport is linked to all aspects of urban life: leisure, education, business and industry. Ensuring a resilient urban transport system is therefore necessary to avoid large and costly disruptions of urban life. As current weather impacts on transport will become more frequent and more extreme in the future, the number of days on which the transport system is confronted with extreme stressors will increase. If no adaptive measures are taken, more frequent disruptions and higher economic costs must be expected.

Adaptation in transport cannot be viewed in isolation nor be reduced to technical infrastructure fixes.

In order to deal with climate change, transport systems must be:

  • designed to cater for the mobility demands of all urban populations, including the poor, under changing climatic conditions, but also
  • try to minimise transport-related greenhouse gas emissions. This includes considering the consequences of adaptation strategies for mitigation.


Cities and Climate Change

Urbanisation rates average 2% globally, but are higher in many developing countries. Being home to more than three billion people, cities are major sources of greenhouse gas emissions.

At the same time, with high population and infrastructure densities as well as concentrated economic activities, cities are particularly vulnerable to the impacts of climate change and need to adapt.

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Vulnerability in Cities

It must also be noticed that not all people are equally vulnerable. Their vulnerability basically depends on two factors: the exposure to climate hazards and their ability to adapt to or avoid those impacts. In general, the urban population most vulnerable include children, ill and disabled people or the elderly, who are less able to cope with heat stress or to flee quickly in the case of a disaster. But also the urban poor – especially those most exposed, e.g. by living on floodplains or in poor quality housing –, who are not able to move or change jobs if their livelihood is threatened. These are also often the people least able to recover from a disaster, loss of home or income. Wealthy people on the other hand, are better positioned to take protective measures or escape when disaster occurs. For instance, a response to tropical storm warnings is to evacuate high-risk areas. However, due to limited access to (private) mobility this is not easily possible for the urban poor, when evacuation plans do not include sufficient (and free) provision of public transport to evacuate.

City governments can improve the resilience of their poor and vulnerable populations by catering to their specific needs. This includes the provision of an affordable, safe and inclusive urban transport system – especially in times of crisis. Poor neighbourhoods will have to be actively integrated into city, land-use and transport planning – not segregated – in order to increase the resilience of the urban majority and urban systems as a whole.

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Likely Impacts on Urban Transport Systems and Potential Adaptation Measures


Transport Infrastructure


Road Infrastructure, Bike Lanes, Walkways

Road infrastructure, including infrastructure for non-motorized transport (bicycle lanes and walkways), provides the foundation for most public, private and commercial mobility in developing cities. The table below gives a detailed overview of the relevant climate impacts on road infrastructure and possible adaptation measures.


Relevant climate impacts

Impact on road infrastructure

Possible adaptation measures

Increased temperature and more heat waves

  • Deformations of roads, slowing down or disrupting transport; melting of asphalt/dark surfaces
  • Increased asphalt rutting due to material constraints under severe exposure to heat
  • Planting roadside vegetation to decrease the exposure of roads to heat
  • Reduce overall exposure and provide cooling through green and blue infrastructure, such as parks and lakes, but also road-side trees or other shading
  • Proper design/construction, overlay with more rut-resistant asphalt or more use of concrete
  • more maintenance, milling out ruts


  • Thermal expansion on bridge expansion joints and paved surfaces
  • Bridge structural material degradation
  • New design standards may be needed to withstand higher temperatures
  • Increased maintenance

More frequent droughts (and less soil moisture)

  • Dry soils in combination with more intense rains will lead to more landslides and subsidence
  • Road foundation degradation due to increased variation in wet/dry spells and a decrease in available moisture
  • Dust and sand on roadways can be a safety hazard from several perspectives including reduced friction in braking, as well as less sighting of roadway markings
  • Assess the likeliness of impacts on road infrastructure (risk mapping)
  • Avoid new developments in high-risk areas
  • Monitoring of soil conditions of existing roads
  • Increased cleaning and maintenance of roadways

Sea level rise and coastal erosion

  • Risk of inundation of road infrastructure and flooding of underground tunnels in coastal cities
  • Degradation of the roadway surface and base layers from salt penetration



  • Create vulnerability maps to identify areas most at risk
  • Restrict developments in high-risk areas, e.g. along the shoreline; zoning
  • Integrate transport planning with coastal zone management
  • Enhance protective measures, such as sea walls, protection of coastal wetlands (as buffers)
  • Managed retreat, possibly including abandoning of certain transport infrastructure in the mid to long term
  • Build more redundancy into system
  • Design and material changes towards more corrosion-resilient materials
  • Improved drainage, pumping of underpasses and elevating roads

More extreme rainfall events and flooding

  • Flooding can affect all transport modes. The risks are greater in flood plains, low-lying coastal areas and where urban drains are overloaded or non-existent
  • Flooding of roadways and subterranean tunnels, especially where drainage is inadequate
  • Road damages and decrease of structural integrity due to erosion, landslides and increasing soil moistures levels.


  • Improve drainage infrastructure to be able to deal with more intense rainfall events, increasing capacity of drainage infrastructure to deal with increased run-off; include tunnels under large roads to facilitate speedy drainage
  • Audit drains regularly
  • Enhanced pumping
  • Create flood maps to identify most vulnerable areas, where infrastructure needs to be protected/improved/avoided in the future and assess alternative routes (this is vital for evacuation plans)
  • Make flood-risk assessments a requirement for all new developments
  • Restrict developments in high-risk areas
  • Improve flood plain management/coastal management and protective infrastructure
  • Early warning systems and evacuation planning for intense rainfall events and floods
  • Install signs high-above the ground that can alert pedestrians and motorists of unsafe zones, such as low-lying areas


  • Higher rivers or canals can lead to undermining and washing off of bridges
  • Ensure that bridges and related infrastructure is resilient to expected levels of flooding
  • Rainfall monitoring


  • Dirt roads and other roads with limited foundations and poor or no drainage are at risk of being washed away or scoured
  • Enhance foundations
  • Build all-weather roads
  • Improve green spaces and flood protection


  • Subgrade material underneath roads or pavements may be degraded more rapidly, loosing strength and bearing capacity
  • Enhance condition monitoring of subgrade material especially after heavy rains, flooding
  • Regular maintenance


  • Increased weathering of infrastructures
  • Use more durable material, such as more corrosion resistant material

More intensive and frequent storms

  • Damage to infrastructure fabric, bridges, flyovers, street lighting, signs and service stations
  • Risk of inundation by the sea during high winds, especially in combination with high tides and sea level rise
  • Assess if currently used design standards can withstand more frequent and intense storms
  • Adapt design standards for new bridges, flyovers, buildings etc to expected increases of wind speeds and heavy rains


  • Obstruction of roads due to fallen trees, buildings or vehicles because of strong winds
  • Disruptions and consequent safety and socio-economic impacts
  • Improve weather forecasting for better predictability of storms, leading to better preparation and potentially less damages (early warning systems, disaster risk management)
  • Emergency planning and evacuation routes omitting high-risk areas


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Rail-based Public Transport

The climate impacts on rail infrastructure are in large part similar to those on road infrastructure.

A few features of rail infrastructure are decisively different to road networks and deserve special attention when it comes to adaptation:

  • Infrastructure materials (e.g. iron)
  • Signalling equipment and electricity circuits
  • Underground infrastructure (tunnels)

To ensure that rail is resilient to partial system failure, e.g. when one or several lines are flooded, the electricity network for rail should be designed in a way that allows operating different lines or groups of lines independently. Otherwise flooding or other damage to one line may result in complete system shutdown and related cascading disruptions of mobility and economic costs.

A summary of expected impacts on rail-based transport and related adaptation measures are presented in the table below.

Relevant climate impacts

Impact on rail

Possible adaptation measures

Increased temperature and more heat waves


  • Buckling of rails and rail track movement because of thermal expansion leads to slowing down or disruption of transport
  • Adapted maintenance procedures, such as rail stressing[1] in the US [2]
  • New design standards may be needed for rails to withstand higher temperatures (this will have to be communicated to/undertaken by the national level)
  • Management procedures to impose differentiated speed limits
  • Improve systems to warn and update dispatch centres, crews, and stations. Inspect and repair tracks, track sensors, and signals.
  • Distribute advisories, warnings, and updates regarding the weather situation and track conditions.


  • Increased temperatures in underground networks (and trains)
  • Better (and flexible) cooling systems or air conditioning for underground networks, vehicles (trains) and metro stations
  • Temperature monitoring for underground infrastructures
  • Hot weather contingency plans
  • Design standard for power supply to meet anticipated demand within the life of the system (especially higher demands due to increased air conditioning needs in trains)


  • In cold regions higher temperatures may lead to less disruptions due to snow or ice, frozen rails, frozen signalling equipment etc


More frequent droughts (and less soil moisture)

  • Dry soils in combination with more intense rains will lead to more landslides and subsidence
  • Assess the likeliness of impacts on rail infrastructure (risk mapping)
  • Monitoring of high risk tracks and regular maintenance
  • Avoid new rail lines in high-risk areas

Sea level rise and coastal erosion

  • Risk of inundation of rail infrastructure and flooding of underground tunnels in coastal cities




  • Create vulnerability maps to identify areas most at risk
  • Restrict developments in high-risk areas
  • Integrate transport planning with coastal zone management
  • Enhance protective measures, such as sea walls, protection of coastal wetlands (as buffers), pumping of underground systems
  • Managed retreat, possibly including abandoning of certain transport infrastructure in the mid to long term

More extreme rainfall events and flooding

  • Flooding can affect all modes of transport. The risks are greater in flood plains, low-lying coastal areas and where urban drains are overloaded.
  • Increases in flooding of rail lines and underground tunnels
  • Railbed damages and decrease of structural integrity due to erosion, landslides and increasing soil moistures levels
  • Improve or build drainage infrastructure to be able to deal with more intense rainfall events, increasing capacity of drainage infrastructure to deal with increased run-off
  • Audit drains regularly
  • Create flood maps to identify most vulnerable areas, where infrastructure needs to be protected / improved / avoided in the future and assess alternative routes - for rail systems bypassing flooded areas will be more difficult than for roads and disturb operation
  • Make flood-risk assessments a requirement for all new developments
  • Restrict developments in high-risk areas
  • Improve flood plain management/coastal management and protective infrastructure


  • Underground systems/tunnels may be flooded, especially where drainage is inadequate
  • Passenger evacuation plans for underground systems
  • Enhanced pumping
  • Create vulnerability maps to identify areas of high flood risk
  • Restrict developments in high-risk areas


  • Stability of earthworks can be affected by intense precipitation due to build up of pore water pressures in the soil, especially after periods of hot and dry weather
  • Subgrade material underneath rails may be degraded more rapidly, loosing strength and bearing capacity
  • Enhance condition monitoring of earthworks, bridges etc especially after heavy rains, flooding (or storms)
  • Improved maintenance



  • Failure of track circuits with subsequent disruptions due to inability to detect the presence or absence of trains on rails and inability to send related signals



  • Increased weathering of infrastructures
  • Use more durable material, such as more corrosion resistant material

More intensive and frequent storms

  • Damage to stations/infrastructure fabric, bridges, flyovers, electrified tracks with overhead cables, train platforms, street lighting and signs


  • Assess if currently used design standards can withstand more frequent and intense storms
  • Adapt design standards for bridges, flyovers, stations etc to expected increases of wind speeds and heavy rains


  • Risk of inundation by the sea during high winds, especially in combination with high tides and sea level rise
  • Improve weather forecasting for better predictability of storms, leading to better preparation and potentially less damages (early warning systems, disaster risk management)


  • Obstruction of roads or rails due to fallen trees, buildings or vehicles due to strong winds
  • Leaf fall may be concentrated, decreasing rail security/adhesion
  • Increased occurrence of lightning strikes to rail signalling or electronic systems
  • Lightning strikes disrupting electronic signalling systems e.g. axle counters electromagnetic compatibility of railways
  • Wind fences for open rail infrastructure
  • For overhead lines: circuit breaker protection
  • Adapt design standard for signalling equipment
  • Emergency planning


[1] Rail stressing means that continuous welded rail is stressed (either through compression or through extension) into a state where fracturing (due to rail shrinking in cold) or buckling (due to rail extension in heat) of rails due to extreme temperatures can be avoided.

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Waterways

Urban waterways provide important transport infrastructure for freight transport, but also for public and private transport in some cities. The potential impacts and adaptation measures are summarised in table below. Where impacts are severe, certain waterways may have to be abandoned entirely or the construction of new waterways may become necessary.


Relevant climate impacts

Impact on waterways

Possible adaptation measures

Increased temperature and more heat waves

  • Increased aquatic vegetation growth could lead to clogging
  • Intensify maintenance of relevant waterways

More frequent droughts (and less soil moisture)


  • Decreased water availability in waterways could restrict their use and lead to more use of road networks


  • Assess the likeliness of constraints on urban waterway usage and plan for alternatives
  • Changes to navigation
  • Assess the viability of flow augmentation

Sea level rise and coastal erosion

  • Port facilities and coastal waterways could become unusable


  • Enhance flood defences such as sea walls, protection of coastal wetlands (as buffers)
  • Managed retreat, possibly including abandoning of certain infrastructure in the mid to long term; integration with coastal zone management

More extreme rainfall events and flooding

  • Reduced clearance under waterway bridges
  • Reduced navigability of rivers and channels
  • Plan for usage of alternative transport modes
  • Incorporate higher levels of flooding into future bridge design


  • Increase in silt deposits
  • Increased dredging of silt

More intensive and frequent storms

  • Storm damage on waterways
  • Increase structural monitoring and maintenance


  • Obstruction of rivers and channels due to floating debris
  • Contingency planning


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Public Transport

Public transport encompasses different means of transport: busses, mini-buses, vans, metro and trams, taxis, as well as rickshaws or three wheelers. In most developing cities, much of the public transport is concentrated on (mini) busses, as well as multiple forms of paratransit, using road infrastructure.

Importantly, planning for public transport must also be closely integrated with planning for road infrastructure (adaptation) to design an efficient and resilient system.

Public transport and informal paratransit needs to be resilient, because

  1. it is the only motorized mobility option for large parts of developing city populations, and
  2. to remain attractive also for those who could afford private motorized mobility to avoid modal shift towards more emission-intensive transport, which would further exacerbate climate change.

Vehicles will essentially have to be designed to withstand higher temperatures: On the one hand, rising temperatures will increase heat stress for passengers and drivers of busses and trains without cooling or air-condition, on the other hand the functionality of engines and the equipment of railway vehicles may suffer from extreme temperatures.

Furthermore, the impact of high temperatures on public transport without cooling could further reduce the quality and attractiveness of public transport systems and hence, in the long run, might support a modal shift towards air-conditioned private cars for those who can afford them. In this case, adaptation to increasing temperature goes hand in hand with building sustainable transport systems suitable for developing cities and providing an alternative to further motorization

The table below gives an overview of relevant climate impacts on public transport vehicles and operations.


Relevant climate impacts

Impact on vehicles or driving conditions

Possible adaptation measures

Increased temperature and more heat waves

  • Increased temperatures in busses and trains possibly leading to passenger and driver discomfort and heat exhaustion
  • Driver discomfort and exhaustion can lead to heightened accident levels
  • May lead to shifts from public to air-conditioned private transport if resources allow or to air-conditioned taxis
  • Use of more costly and more energy-intensive air conditioning systems
  • Sufficiently large opening windows
  • Tinted windows to shade off the sun
  • White painted roofs
  • Improved thermal insulation and cooling systems
  • Air conditioning, using systems without F-gases for not further increasing climate change effects
  • Driver training
  • For overhead buses: design standard for power supply to meet anticipated demand within the life of the system (especially higher demands due to increased air conditioning) and withstand higher wind speeds
  • For underground rail: develop hot weather contingency plans
  • Include new design standards in public procurement requirements of the public transport fleet


  • Wearing off or melting of tires
  • Overheating of equipment, such as diesel engines
  • New design standards may be needed to withstand higher temperatures (this will have to be communicated to/undertaken by the national level)

More extreme rainfall events and flooding

  • More events of difficult driving conditions with implications for safety, performance and operation, e.g. speed restrictions causing delays
  • Flooding of the public transport fleet, causing economic damages
  • Manage speed limits in bad weather conditions, e.g. reduce the running speed of trains
  • Drivers of public transport vehicles should be appropriately trained for extreme weather conditions, such as heavy rains, hail and wind
  • Planning for emergency routes
  • Early warning systems to evacuate high-risk areas
  • Flood insurance

More intensive and frequent storms

  • More events of difficult driving conditions or impossibility to drive, as well as derailments or collisions leading to disruptions and consequent safety and socio-economic impacts
  • Overturning of vehicles or trains


  • Driver training
  • Speed restrictions
  • Improve weather forecasting for better predictability of storms, leading to better preparation and potentially less damages (early warning systems, disaster risk management)
  • Emergency planning and identification of evacuation routes omitting high-risk areas

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Private Transport


Non-motorized Transport

Increasing events of adverse weather conditions like heavy rains, strong winds and extreme temperatures may lead to less walking and cycling trips, at least beyond a certain trip length. For short trips on the other hand, the impacts of extreme weather can be expected to be rather low. This underlines the importance of sustainable and dense urban design for resilient mobility. Dense urban design, at the same time, benefits the development of sustainable transport, reducing travel demand and related transport emissions, in turn reducing the climate impact and improving air quality.

Changes in temperature are already forcing cities to provide infrastructure for shading. The following image from Hangzhou (China) is typical of the shaded cycle way shadings that have been installed at intersections in China.


Cycle way shading in Hangzhou, China.jpg
Cycle way shading in Hangzhou, China


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Motorised Private Transport

Similarly to non-motorized transport, behavioural responses can be expected during adverse weather conditions. Empirical studies point to slower traffic speeds during rainfall events, leading to delays and disruptions. Accidents also become more likely under adverse weather conditions, although accident severity appears to decrease during precipitation, likely due to lower traffic speed. Consequently, precipitation leads to an increase in travel time with the most severe impacts on already congested routes and during peak hours. This is particularly relevant for many large cities already suffering from traffic congestion.

As for non-motorized transport, land-use planning favouring short-distances can reduce travel demand and hence the exposure to adverse climate conditions.

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Taking Action on Adaptation

First of all, information and awareness raising about the need to start adaptation today are important components to improve the capacity and the acceptance of both decision-makers and society to adapt. As adaptation of urban passenger transport cannot be limited to simple technical fixes, but also requires behavioural changes of transport users and a shift in thinking in planning approaches, adaptation must be understood as a social learning process. Convincing municipal government officials across departments of the local relevance of adaptation is a prerequisite for a successful adaptation strategy. In many cases this will require training key personnel and identifying so-called “adaptation champions” who will push the adaptation agenda within their departments.

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Basic Approaches to Adaptation

Three basic approaches to adaptation can be identified:

  • Retreat (or avoid)
  • Protect
  • Accommodate

These three approaches have been developed in the context of adaptation to sea level, but in general they are applicable to all climate risks.

Whereas retreating from areas at high risk of a climate hazard (be it sea-level rise, flooding, landslides or any other risk) may be a measure of last resort, in a planning context retreat translates into avoiding developments in high-risk areas in the first place and may be the cheapest option.

Protection can include both hard (e.g. sea walls) and soft measures (e.g. protection of mangroves to buffer storm surges). Protective measures are also not limited to sea level rise, or riverine flooding, but include any other means that help protect transport infrastructure or even mobility in the wider sense, such as green spaces or trees that provide shading, wind fences or additional drainage.

Whereas protection can be seen as “external” measures, accommodation means adapting the transport system or infrastructure itself. Accommodation also includes both hard (mostly infrastructure and vehicles) and soft measures (concerning the transport systems as a whole). Hard measures could be changing design standards and construction materials to withstand higher levels of flooding or temperature or including air conditioning in vehicles, whereas soft measures could encompass planning for emergency bus routes or even strengthening public transport networks to increase overall system resilience.

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The Framework for Effective Adaptation

Monitoring and gathering data on intense weather events and their consequences for the transport system (both now and in the past) can improve our understanding of the implications of climate change for transport, including their direct and indirect costs. This knowledge can then strengthen the basis for taking decisions on adaptation. Data should be systematically assessed, entered into a database and ideally be exchanged between cities to enhance mutual learning.

For adapting transport infrastructure an overarching strategy is needed, which basically consists of four elements:

  1. Careful spatial planning that avoids high-risk areas, includes green and blue spaces to counter heat island effects and creates relatively dense urban areas to avoid unnecessary transport demand. Nevertheless providing redundancy to cope with unexpected stressors, while integrating and connecting poor neighbourhoods. Spatial planning should be combined with risk mapping, as well as with regulatory policies, such as zoning, and safety requirements for road-side billboards and trees to avoid the risks of uprooted trees or billboards on the roads during floods or storms.
  2. Improving design standards of transport infrastructure to be resilient under changing climatic conditions, including the improvement of urban drainage and building codes. This will require an assessment of the suitability of current design standards under different climate change scenarios. Here, external expertise may be required. Design standards should be regularly audited and revised as required. Updated design standards can be integrated into procurement processes for infrastructure developments, giving conditional clearance to projects to ensure that climate resilient features have been incorporated.
  3. Insurance for transport infrastructure to divert (at least part of) the risk of climate impacts from city governments. Insurance premiums may be subject to regular maintenance of existing infrastructure and could thus function as incentive to ensure proper maintenance.
  4. Adaptation auditing of the urban transport network to first of all identify vulnerabilities and later on monitor progress and suitability of adaptation measures, as well as identifying new adaptation needs. Cities should also carry out regular road safety audits for all hierarchies of roads, as well as safety audits of other transport related infrastructure, such as bridges and drainage systems.

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Concluding Remarks

In many developing cities, the impacts of extreme weather events on urban transport systems can already be severe as experienced in the recent flooding of Manila in September 2009. This illustrates the importance of developing more resilient sustainable urban transport systems, especially as impacts are expected to get worse. To be truly sustainable, the transport system must work for all, also including the urban poor and the disabled. This will require addressing current deficiencies.

Adaptation of urban transport in developing cities must hence be seen in the larger context of addressing transport needs as a whole, if vulnerabilities of the urban system are to be minimised. Further work is needed on clearly defining realistic steps towards achieving a climate-proof, pro-poor and affordable urban transportation system in developing cities. For instance, more specific design standards that are suitable for developing countries are needed.

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Further Information

  • Further and more detailed information can be found on the homepage of the Sustainable Urban Transport Project. The Sustainable Urban Transport Project aims to help developing world cities achieve their sustainable transport goals, through the dissemination of information about international experience, policy advice, training and capacity building.
  • Access to Transport
  • Climate Change and Transport

References

  1. U. Eichhorst 2009, Adapting Urban Transport to Climate Change, Eschborn, Germany
  2. Rail stressing means that continuous welded rail is stressed (either through compression or through extension) into a state where fracturing (due to rail shrinking in cold) or buckling (due to rail extension in heat) of rails due to extreme temperatures can b avoided.