Authors and contributors
Pharoah Le Feuvre
IEA (2019), "Tracking Transport", IEA, Paris https://www.iea.org/reports/tracking-transport-2019
Average fuel economy improvements in advanced economies (measured in Lge/km) slowed to only 0.2% between 2016 and 2017, with the trend even reversing in almost 20 countries. In contrast, the rate of improvement in emerging economies has accelerated from 0.2% in the first five years of tracking (2005-10) to 2.3% in the past two years.
Average LDV fuel economy improved in all regions between 2005 and 2017, though absolute levels and trends diverge widely among countries and regions.
Several factors have contributed to the recent slowdown in average fuel economy improvements:
- Diesel car sales have fallen rapidly in several major vehicle markets, especially Europe, which relies most on this powertrain technology. Since diesel cars tend to be more efficient than the equivalent gasoline vehicles, the shift away from diesel has impeded fuel consumption reductions.
In the largest EU markets, the diesel market share has declined by 5 to 15 percentage points since 2014, to be replaced only partially by more efficient electrified powertrains (hybrids, plug-in hybrids, battery EVs and fuel cell vehicles [FCVs]). The market share of newly sold electrified vehicles grew by 1 to 3 percentage points.
- Despite ongoing efficiency improvements within each vehicle segment, consumer demand for larger vehicles has risen significantly. This trend is common to all vehicle markets and has led to slackening in – or in some cases even reversals of – average national fuel consumption improvement rate.
The market share of sport-utility vehicles (SUVs) and pick-up trucks increased 11 percentage points between 2014 and 2017, to make up nearly 40% of the global LDV market; North America and Australia had particularly high market shares (around 60%). Most growth has been in the small SUV/pick-up segment, which includes many cross-over versions of popular passenger cars. The average fuel consumption of a small SUV/pick-up is more than 15% higher than the average medium-sized car, for which market shares have fallen the most in recent years.
- Finally, car market shifts between and within advanced and emerging markets have affected the global rate of fuel economy improvements. Emerging markets gained 2 percentage points over advanced markets between 2015 and 2017, and because average fuel economy in emerging markets is still worse, this shift slightly impeded overall fuel consumption improvements.
However, the share of vehicles sold in advanced markets has continued to shift away from North America to Europe, Japan and Korea. Vehicles sold in North America tend to be larger and less efficient, so as the share of vehicles sold in Europe, Japan and Korea has grown, so has the share of smaller and more efficient vehicles.
At the same time, sales have expanded rapidly in China (where regulations require significant fuel economy improvements) and India, a market traditionally been characterised by large shares of small, fuel-efficient cars. This has helped raise overall fuel economy in emerging economies.
The standards’ fuel economy improvement rates are based on laboratory-tested fuel consumption. However, the gap between tested and real-world driving fuel consumption is growing, and in key vehicle markets was as high as 50% in 2017. In all major vehicle markets with test standards, the gap has at least doubled in the past decade, prompting several countries to improve testing procedures.
Rapid electrification of the transport sector is vital to improve average fuel economy (electric motors are 2‑5 times more efficient than conventional powertrains), comply with energy efficiency standards and diversify the fuel mix.
The average fuel consumption of new LDVs sold in Norway in 2018 was 3.9 Lge/100 km. This achievement, attained mainly thanks to a newly registered EV market share of 47%, already exceeds the global GFEI target for 2030 by more than 10%, highlighting the potential for EVs to contribute to vehicle efficiency goals.
Meeting the 2030 GFEI target at the global level will require widespread adoption of regulations that set requirements for fuel economy improvements over time and/or mandate shares of efficient powertrains, and offer financial incentives to stimulate consumer demand for the best-performing vehicle technologies.
- National or supranational governments are responsible for setting fuel economy standards and taxation on vehicle purchases.
- National and local governments can boost sales of efficient vehicles by providing subsidies or other support. Budget-neutral financial policies, such as bonuses for efficient cars and additional taxes for inefficient ones, have been implemented by France, Sweden and other countries.
Long-term commitments are important to ensure that the investments necessary to deploy electrification technologies, which are crucial to meeting the GFEI targets in a phase where consumers are losing confidence in diesel, can take place. A growing number of countries aim to ban polluting powertrains in the medium term, or to mandate car manufacturers to include a minimum share of low-emission powertrains in their vehicle fleets.
Tightening the rules governing fuel consumption measurement during tests, as well as standards to guarantee on-road driving compliance, are essential to ensure that all stakeholders take action to meet the policy goals.
As the Dieselgate scandal so vividly demonstrated, it is possible for car manufacturers to comply with tests even though the vehicles emit pollutants with serious health impacts in real-world driving conditions. The same goes for CO2 emissions, but there are ways to improve regulatory procedures to fix this, as demonstrated by efforts to adopt a more representative test procedure, the WLTP, to incorporate real-world driving emissions and, in the case of local air pollutants, to monitor in-use emissions, as shown by the Real Urban Emissions (TRUE) initiative. These systems must be implemented at the national level.
It remains crucial that enough infrastructure be deployed to allow the wide use of alternative powertrains. For instance, setting targets to deploy refuelling stations along specific road corridors is relevant for national-level policy makers. Depending on the fuel type, local governments can help determine optimal deployment of refuelling infrastructure in various urban settings.
The car industry is one of the highest spenders on research and development, representing nearly 25% of global R&D spending in 2018 (Auto Alliance, 2018).
Numerous technologies can lead to fuel economy improvements, including:
- energy efficient tires
- improved aerodynamics
- fuel efficient combustion technologies and engine downsizing
- powertrain electrification
Reducing vehicle weight is a key means to improve fuel efficiency. Lightweighting techniques such as using high-strength steel and aluminium in the chassis can reduce the mass of the vehicle while cutting both fuel consumption and total life-cycle CO2 emissions (Serrenho, 2017).
So far, however, most of the fuel economy benefits of lightweighting have been offset by the increased weight of upscale features, safety enhancements and increased vehicle size in many markets.
Despite the increasing market share of EVs, IEA scenarios show that a large share of the LDV fleet will be powered by internal combustion engines (ICEs) in conventional, hybrid and plug-in hybrid configurations until at least mid-century. Reducing ICE CO2 emissions is thus a key part of a balanced strategy for limiting atmospheric CO2 levels. Improving ICEs is also a cost-effective CO2 mitigation strategy.
ICEs operating on electrofuels generated when excess renewable electricity is available may even promote more rapid decarbonisation of the electricity supply while providing near-zero carbon emissions. Additional CO2 emissions reductions could also be gained through the use of bio-derived or other low-carbon fuels along with ICE design optimisation to take full advantage of their properties.
Reducing local pollutant emissions of particulate matter, unburned hydrocarbons and nitrogen oxides from ICEs remains an important challenge. The move to vehicle hybridisation with start-stop systems can also result in higher pollutant emissions if exhaust after-treatment devices are not operating effectively (SAE, 2018).
Although the average weight of new LDVs remained relatively stable globally during 2015‑17, in more than two-thirds of countries average LDV weight actually increased – with increases in three-quarters of countries in 2016‑17 alone. This is the result of three counterbalancing trends: first, growth in the market share of large LDVs (SUVs and pick-up trucks) raised vehicle weight.
At the same time, however, an increasing volume (and share) of vehicles were being sold in emerging economies. These vehicles tend to be smaller and lighter than new vehicles sold in advanced economies, which tempered the effect of higher large-LDV sales.
Finally, lightweight materials such as advanced high-strength steel, aluminium, thermoplastics and even carbon fibre composites are used more widely in new LDVs sold in all markets because they have the potential to improve safety, performance and fuel economy while making the vehicle lighter.
Many thanks to Paul Miles and his colleagues working with the Combustion Technology Collaboration Platform for contributing content for the innovation gap on "Advanced internal combustion engine technologies."
Paul Miles (Sandia National Labs), Zifei Yang (ICCT), Francois Cuenot (UNECE).