Rapid gains in energy efficiency limit increases in energy used in transportation despite rapid growth in the demand for transport services.
In the ET scenario, the demand for transport services almost doubles, but quickening gains in engine efficiency mean that energy consumed increases by only 20%.
The growth in energy used in transport is concentrated within developing Asia, which accounts for 80% of the net increase, as rising prosperity increases demand for both the quantity and quality of transport services.
The increase in energy consumed across different modes of transport is affected by the pace of efficiency improvements. The efficiency of the average internal-combustion-engine car improves by nearly 50% in the major global car markets; truck efficiency also records substantial gains. As a result, the rate of demand growth in the road sector decelerates significantly, leading the slow-down in overall transport demand growth.
In contrast, the scope for further efficiency gains within aviation and marine is more modest. These modes account for nearly half of the increase in energy used in transport in the final decade of the Outlook, even though their combined share of total transport demand today is only 20%.
The transport sector continues to be dominated by oil, despite increasing penetration of alternative fuels, particularly electricity and natural gas.
In the ET scenario, the share of oil within transport declines to around 85% by 2040, down from 94% currently. Natural gas, electricity and biofuels together account for more than half of the increase in energy used in transport, with each providing around 5% of transport demand by 2040.
Oil used in transport increases 4 Mb/d (220 Mtoe), with the majority of that demand stemming from increased use in aviation and marine, rather than road transportation.
Electricity and natural gas in transportation increase by broadly similar volumes (120 Mtoe), with the increased use of electricity concentrated in passenger cars and light trucks; and the rising demand for natural gas largely within long-distance road haulage and marine.
The use of biofuels increases by just under 2 Mb/d (60 Mtoe), predominantly in road transport, with some increase in aviation.
An alternative ‘Lower carbon transport’ scenario considers the scope for greater fuel switching, as well as faster efficiency gains.
Electric vehicles continue to grow rapidly, concentrated within passenger cars, light-duty trucks (LDTs) and public buses.
In the ET scenario, the number of electric vehicles reaches around 350 million by 2040, of which around 300 million are passenger cars. This is equivalent to around 15% of all cars and 12% of LDTs.
The use of electric passenger cars is amplified by the emergence of autonomous cars (AVs) from the early 2020s offering low-cost, shared-mobility services, predominantly in electric cars. As a result, around 25% of passenger vehicle km are powered by electricity in 2040, even though only 15% of cars are electrified.
The rise in global prosperity leads to a shift away from high-occupancy road transport (buses) to private vehicles, reducing the global load factor for road vehicles (i.e. the average number of passengers per vehicle). This trend is compounded in the second half of the Outlook by the falling cost of road travel associated with the growing availability of low-cost shared mobility services using autonomous vehicles.
The fall in the global load factor for road vehicles and associated increase in road congestion is a key challenge facing the global transport system over the Outlook.
Despite significant increases in vehicle efficiency and electrification, carbon emissions in the transport sector in the ET scenario continue to increase.
The alternative ‘Lower-carbon transport’ (LCT) scenario includes a large number of measures designed to reduce carbon emissions in the transport sector, including:
As a result of these measures, CO2 emissions from transport in the LCT scenario fall by 2% (0.2 Gt) from 2017 levels, compared with an increase of 13% (1.1 Gt) in the ET scenario.
Compared with the ET scenario, the majority of the reduction in emissions stems from road transport, particularly via fuel switching. This reflects the importance of road transportation relative to marine and aviation; and the greater scope to electrify different aspects of road use. Increased electrification accounts for around a half of the reduction in emissions relative to the ET scenario by 2040.
Compared to the current levels of emissions, improving levels of efficiency within transport mean that the rapid growth in the demand for transport services over the Outlook can be met with almost no increase in energy consumption. The most important driver of these efficiency gains is the significant tightening in vehicle emissions standards, much of which is already reflected in the ET Scenario. The use of car scrappage schemes also helps to improve average car efficiency.
The contribution of fuel switching in reducing emissions from current levels is less significant. Increasing electrification accounts for around half of the gains from fuel switching, with the majority of the remainder reflecting greater use of biofuels, which increase by around 4 Mb/d to 6 Mb/d by 2040.