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The role of energy demand reduction in achieving net-zero in the UK: Transport and mobility

18 October, 2021

The role of energy demand reduction in achieving net-zero in the UK: Transport and mobility

Christian Brand

Jillian Anable

Greg Marsden

Report   Transport & Mobility

Christian Brand, Jillian Anable and Greg Marsden


The black sheep of energy

The transport sector continues to have a significant dependence on oil, with a share of 95% of all global transport energy use in 2015, and this has not changed since the 1970s (IEA, 2018). In the UK, road transport accounted for just under three quarters of transport energy consumption in the UK in 2017, with the remainder almost entirely from air travel (23%). Of the road component, energy use from cars accounts for more than half (60%), with most of the remainder coming from ‘light duty vehicles’ (vans) (16%), heavy goods vehicles (HGVs) (17%) and buses (3%) (BEIS, 2019). Energy use from transport has increased by 16% since 1990 (6% since 2013) against a UK economy-wide decrease of 4% (CCC, 2018; BEIS, 2018) and remains 98% dependent on fossil fuels. It has grown as a share of overall carbon emissions with no net reduction between 1990-2017 (vis-à-vis –43% for all sectors combined).

The response so far

The primary focus of UK policy has been to change the vehicle fleet from petrol and diesel, first to ultra low emission vehicles (ULEVs), and then to zero-emission vehicles (ZEVs) (ULEVs produce < 75 g/km CO2 under the existing test cycle and includes pure Battery electric vehicles (BEVs), Plug-in hybrid electric vehicles (PHEVs). Zero emission vehicles emit no carbon or pollution from the tailpipe and include BEVs and Fuel cell vehicles. Strictly these are only zero emission when powered by renewable or zero emission electricity (DfT (2018a)), primarily through electrification. A lack of progress with heavy goods vehicles and aviation persists, but the unexpected change is the increase in new car energy consumption and CO2 (SMMT, 2018). Switching from diesel accounts for a small proportion of this increase; the main culprit is a continued swing towards larger passenger cars, particularly Sports Utility Vehicles (SUV), which use about 15% more energy than their hatchback or sedan equivalents. Electric vehicles accounted for 8.8% of sales in 2020 (up from 2.5% in 2019) (SMMT, 2020), with two out of five sold being plug-in hybrid electric vehicles (PHEVs). PHEVs have shown to perform little better in terms of energy use and carbon emissions than the most efficient conventional ICE vehicles in real world conditions, as they have been shown to operate in electric mode for only a third of the miles travelled (Plötz et al, 2018a; Plötz et al, 2018b; Plötz et al, 2020). This gap between declared vehicle performance and real-world results prevails across all vehicle types and technologies.

For new cars, fleet average test cycle data suggest a 30% reduction in tailpipe CO2 since 2000. In practice, there has only been an estimated 9% reduction in tailpipe emissions in real-world conditions, and only 4% since 2010. The ‘performance gap’ between official and real-world values grew over time, peaking at 40% in 2016 (NEDC test cycle). This gap has effectively negated any reported savings from efficiency improvements over the past decade.

What about transport after Covid-19?

Car traffic levels returned to around 85% of pre-Covid levels in September, whilst bus use was at 60% and rail 30% of pre-Covid levels. Light and heavy goods vehicles were above pre-Covid levels giving an overall reduction in traffic levels of 10%. This is dropping a little further as areas enter further levels of restriction. Cycling levels more than doubled during the peak lockdown restrictions but most of this appears to have been leisure related travel and is falling back as the autumn draws on.
The recovery from Covid-19 has a number of uncertainties for transport. Economic recovery means doing more stuff, which may mean more mobility. There are parts of the economy which have not fully re-opened yet. On the road to recovery, fewer local jobs means travelling further to find work. Less flying abroad means more staycationing and domestic travel demand – an effect of the pandemic that features prominently in the LED scenarios. Having a ‘civic duty’ to not use public transport, a mode already in decline Before Covid-19 (‘BC’), means more use of other modes instead. Work has suggested that a plausible best case for bus use might be reaching 85% of pre-pandemic levels (UTG, 2020). For some people, this could mean resorting to buying a (more polluting second hand) car. Others may not see the need to hold on to so many vehicles if they travel less often.

Homeworking rarely leads to lower net energy demand (Hook et al, 2020). More energy is used at home (rarely countered by equivalent reductions in office space and energy use) and people move to live further from where they work because now they can. And the businesses themselves expand their source of workers and their geographical sphere of activity as ICT becomes integrated and synonymous with evolving business practices (Faulconbridge et al, 2020). However, the scale of the shift in ICT reconfiguration associated with Covid-19 may produce different outcomes if travelling into work on many fewer days a week sticks.

The recession may well lead to an extended dip in car use as we have seen historically during such times. However, previous recessions have not been accompanied by a crisis in public transport use. It is also plausible that we will see more cycling AND more car use. It is therefore also possible that the transport sector could return to being the only UK sector other than agriculture and land-use change to have higher emissions now than in 1990. Overall, the pandemic seems to have changed little with respect to the priorities that existed beforehand. Capitalising on the positive aspects of demand reduction which have been seen is at best mixed. National government has been keen to “get people moving” although businesses have been more circumspect. Whilst a positive new cycling strategy has been published it does not come with new money and the Road Investment Strategy 2’s (RIS2) roads programme remains a commitment (DfT, 2020). It appears that the primary push will continue to be to accelerate electrification despite an understanding that this will not be sufficient to be Paris compliant.

What else can be done?

This almost universal focus on improving energy consumption per passenger-km or tonne-km travelled ignores the other two core elements of the Avoid-Shift-Improve hierarchy of avoiding travel in the first place (trip reduction due to change in activity) and shifting travel to more sustainable modes (reduction in energy use per passenger-km or tonne-km travelled) (Schipper and Marie-Liliu, 1999; EEA, 2011; Gota et al, 2019). This hierarchy has been used to emphasise the priority ordering and layering of our scenarios that stand apart from the dominant supply and vehicle technology-oriented approach to energy reduction and decarbonisation in the sector. Our scenarios thus reinforce the growing consensus that relying on technical solutions alone is insufficiently rapid and risky, and that policies influencing the demand for travel and mode switching should have a more prominent role (CCC, 2018; CCC, 2019). Here the demand for the mobility itself (i.e. the distances travelled and the travel modes used) will be at least as crucial to future energy demands as the fuel types and efficiencies of the vehicles.

The drivers and prospects for travel demand change

Since the early 1990s (but only now being retrospectively understood), actual road traffic growth has been systematically less than forecast so that the hitherto uninterrupted growth in car use is no longer the dominant trend. Periodic discussion of ‘peak car’ has led into investigations of the evidence (Marsden et al, 2018; Melia et al, 2018), which reveal that structural changes in travel demand due to shifts in the pattern and location of activities, social changes including delayed family formation, economic changes in the nature of retail and employment (especially youth employment), and possible impacts of mobile internet access, all correlate with a downward trend in overall trip rates and distances travelled.
These trends are manifesting differently among different groups and in different locations; only an aging cohort of people, now over 60, has contributed to traffic growth, while successive cohorts of younger people have shown a reduction in driving license holding, car ownership, and car use (DfT, 2018a). The largest reductions in per capita distances travelled by car have been in the two highest income quintiles (CCC, 2018).

Such findings sit alongside a very substantial body of experience and evidence about the effects of policy interventions intended to address a much wider range of policy objectives than energy use alone, including health, quality of life, commercial vitality, safety, and equity. These various objectives have all tended to converge on policy packages aimed at reducing the need to travel by better land-use planning, restrictions on car use in central, residential, and environmentally sensitive locations, and facilitating transfer of car trips to public transport, walking and cycling by reallocation of expenditures, street design, pricing and regulation. This allows for a policy perspective where reduced energy use does not run counter to quality of life but arises from measures designed to enhance it. Conversely, relying mainly on electrification of vehicles to reach carbon targets can have the consequence of increasing traffic congestion because of the lower cost and lower taxation of electric fuel (as much as an additional 44bn vehicle miles per year by 2050) (DfT, 2018b).

Thus, the pattern of co-benefits, empirical evidence on trend shifts and policy implantation, and better understanding of influences on demand, give scope for considerably more ambitious reductions in passenger transport energy and carbon use than have been assumed in much of the UK policy response to date (DfT Road to Zero, Clean Growth Strategy, CCC). Moreover, evidence suggests a lower rate of demand for passenger mobility is a necessary and a credible future, but that this would require a different policy package to ‘scale up’ and ‘lock in’ the new demand patterns, alongside new vehicle technology.

Publication details

Brand, C., Anable, J. and Marsden, G. 2021. The role of energy demand reduction in achieving net-zero in the UK: Transport and mobilityOpens in a new tab. Centre for Research into Energy Demand Solutions. Oxford, UK. 

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