Authors and contributors
Pharoah Le Feuvre
IEA (2019), "Tracking Transport", IEA, Paris https://www.iea.org/reports/tracking-transport-2019
Global transport emissions increased by only 0.6% in 2018 (compared with 1.6% annually in the past decade) owing to efficiency improvements, electrification and greater use of biofuels. Transportation is responsible for 24% of direct CO2 emissions from fuel combustion. Road vehicles – cars, trucks, buses and two- and three-wheelers – account for nearly three-quarters of transport CO2 emissions. Emissions from aviation and shipping continue to rise, indicating that these hard-to-abate subsectors need more international action.
The transport sector is in a critical transition, in which existing measures to increase efficiency and reduce energy demand must be deepened and extended for compliance with the Sustainable Development Scenario (SDS).
This process should be set in motion over the next decade, as any delay would require that stricter measures be taken beyond 2030, which could noticeably raise the cost of reaching climate targets. Combined efforts across all transport modes, accompanied by power sector decarbonisation, will play a crucial role for achieving SDS goals.
Although energy demand and emissions from aviation and shipping have been increasing steadily, they have also continued to rise in all modes of road transport (cars, trucks, buses and two- and three-wheelers). As a result, the road share of total transport emissions has remained relatively stable since the turn of the century.
Road transport emissions have increased despite progress in electrification: the global share of electric car sales rose to more than 2.5% in 2018, and fleets of electric buses and trucks are being procured in more and more cities around the world. Therefore, continued growth in emissions is due largely to:
- Car buyers continuing to purchase larger, heavier vehicles, not only in the United States but increasingly in Europe and Asia. In Europe, the preference for larger cars, together with plummeting shares of more efficient diesel cars, is outweighing the impact of higher shares of electric car sales and caused the average new car CO2 emissions to rise in 2017 and 2018.
- Rising global GDP, together with the proliferation of online commerce and rapid (i.e. same-day and next-day) delivery, which continues to raise road freight demand.
Global transport sector energy intensity (total energy consumption per unit of GDP) dropped by 2.1% in 2018 after falling an average 1.5% per year between 2000 and 2017. However, to put transport efficiency on track with the SDS, energy intensity must drop by 3.4% on average annually from 2019 to 2030 – more than double the annual average rate of decrease since 2000.
For the transport sector to meet projected mobility and freight demand while reversing CO2 emissions growth, energy efficiency measures will need to be deployed to maximum effect.
Energy efficiency measures in transport can take many forms, including: managing travel demand to reduce frequency and distance, as well as dependence on high-energy-intensity modes (e.g. car and air); shifting travel to the most efficient modes; system-level and operational efficiency measures; and deploying energy-efficient technologies for vehicles and the fuels that drive them (e.g. electrification enables the use of motors that are far more efficient than internal combustion engines).
An integrated, coherent and co‑ordinated set of policies is required to put the transport sector on the SDS pathway. Measures at various levels of jurisdiction – within multi-country regional blocs, at national and subnational levels, and within cities – must spur progress in:
- Managing travel demand to reduce the frequency of trips, distances travelled, and dependence on cars, and to shift travel to the most efficient modes (i.e. the ‘avoid/shift’ approach).
- Improving the energy efficiency (i.e. fuel economy) of vehicles.
- Increasing the availability and use of sustainable, low-carbon fuels.
In addition to CO2 emissions, the SDS targets air quality improvements. Adopting cleaner fuels and enacting tighter emissions control standards for vehicles would improve outdoor air quality in the developed and developing world alike.
Many regulatory measures – including vehicle efficiency standards, zero-emission vehicle mandates and low-carbon fuel standards – can encourage adoption of more sustainable transport technologies.
For example, fuel economy standards have already proven their efficacy in reducing specific (per-kilometre) emissions of cars and trucks. For vehicle efficiency standards to remain effective, however, it will be critical that they evolve to:
- Reflect real-world operations. As the Dieselgate scandal so vividly demonstrated, it is possible for car manufacturers to comply with tests even as vehicles emit pollutants with serious health impacts. The same goes for CO2 emissions, but regulatory procedures can be improved, for instance through adoption of the WLTP, a testing system that incorporates real driving emissions, and in the case of local air pollutants, through efforts like the Real Urban Emissions (TRUE) initiative, which monitors in-use emissions.
- Broaden the regulatory scope beyond direct tailpipe emissions. Regulations should also cover the upstream emissions and sustainability impacts of fuel production and distribution. A 'well-to-wheels' approach should be adopted as new technologies such as electric and hydrogen vehicles, and alternative fuels such as biofuels, gain market shares. Policies should eventually extend beyond operations to vehicle production and disposal. While there are many practical challenges to this 'life-cycle' vehicle regulation approach (including overlap with policies covering other sectors), it is necessary to begin by gathering and analysing data to monitor the life-cycle impacts of current regulatory frameworks.
- Align standards with climate pledges. The disparity between policy coverage and stringency and the actions needed to meet emissions reduction goals is a major obstacle in curbing transport emissions growth. To be realistic and actionable, Nationally Determined Contributions must be founded on credible projections of transport activity and include policies to promote sustainable transport.
- Guard against regulatory loopholes and expand to encompass new technologies and business models. For example, one regulatory loophole could be closed by including trailer efficiency mandates in heavy-duty-vehicle efficiency standards, or even mandating vehicle efficiency standards for 2-wheelers (only China has such standards). Examples of regulating new business models include new ways to promote Mobility-as-a-Service, and fleet regulations for taxis and ride-sourcing platforms.
Fiscal policies can spur progress in both reducing emissions and raising air quality. Taxes that reflect the societal and environmental damage costs incurred by burning fuel influence passenger and freight mobility choices. People may reduce discretionary car trips or car-pool, purchase more efficient vehicles and drive more efficiently, choose alternative transport modes or not take trips at all. Reducing or phasing out subsidies (implicit or explicit) on transport fuels also impels these shifts.
Taxing at the point of vehicle purchase and/or circulation can also affect transport decisions. Differentiated taxation schemes, also known as 'feebates', can incentivise vehicle makers to provide more efficient technologies and consumers to purchase cleaner, more fuel-efficient cars. Ideally, taxation schemes should directly target performance outcomes, including CO2 or local pollutant emissions reductions.
With rising efficiency and more electric vehicles in circulation, eventually fuel taxes will not provide enough revenue for road infrastructure maintenance. Although electric vehicles do not emit local air pollutants, their societal impacts include congestion and road wear. A well-timed phase-in of road pricing to supplement fuel taxation will be needed to manage the transition to cleaner and more sustainable road transport.
The number of electric light-duty vehicles on the road has exceeded 5 million. Along with rising market uptake of electric cars, lower cost and better battery performance are making electrification of trucks and buses attractive for certain operations, especially in cities.
Meanwhile, China leads the world in urban train and high-speed rail expansion, with a significant amount of track laid rapidly in the past decade to supply electric, low-carbon passenger services for decades to come.
Reducing transport CO2 and pollutant emissions will require sustained policy efforts to enhance efficiency and electrification. Priorities also include anticipating and managing demand by steering new mobility developments in cities and long-term technology and policy visions for the hard-to-abate aviation, shipping and road freight subsectors.