Shifting the focus: 4 Transport & mobility

Jillian Anable and Phil Goodwin

Introduction

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, 2018a – figures derived from Tables 2.01 and 2.02). Energy use from transport has increased by 16% since 1990 (6% since 2013) against a UK economy- wide decrease of 4% (CCC, 2018a) 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) (CCC, 2018a).

The treatment of transport in the Clean Growth Strategy (CGS), as well as subsequent pronouncements in the Road to Zero (R2Z) (DfT, 2018a) and the Future of Aviation (DfT, 2018e) strategies, assumes that the demand for travel will continue to grow, and seeks to reduce the use of fossil fuels by:

• accelerated deployment of more efficient end-use technologies (road vehicles, trains, aircraft and ships); and
• changes in the dominant fuel source, predominantly from electrification and biofuels.

The primary focus is changing the vehicle fleet from petrol and diesel, first to ultra low emission vehicles (ULEVs), and then to zero-emission vehicles (ZEVs) (ULEVs produce < 75 gCO2/km 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. This focus is reflected in 44 actions out of the 46 listed in the R2Z Strategy (DfT, 2018a).

This chapter reinforces the growing consensus that the ambition in relation to fuel switching and vehicle efficiency could and should be strengthened. We nevertheless question the almost exclusive reliance upon technical improvements for two main reasons.

• The Department for Transport’s (DfT) own scenario forecasts (DfT, 2018b) show that the uptake of ULEVs is likely to put upward pressure on traffic growth by lowering the costs of motoring. “Clean” growth involves more than attending to the carbon implications; it means considering the combined effects of continued car dependency leading to more urban sprawl, inactive lifestyles and congestion together with the lifecycle impacts of vehicles and batteries, charging infrastructure, and road and car parking capacity.
• The almost exclusive reliance on technical solutions will only be able to produce the necessary reductions if the DfT’s lower traffic growth futures are assumed. Evidence suggests a lower rate of demand for passenger mobility is credible, but this would require a different policy package to achieve and “lock in” the new demand patterns. Thus, whether we assume underlying high growth trends whereby technological developments cannot hope to mitigate the externalities from traffic demand, or we assume that lower or even negative rates of growth could instead be enabled, a different suite of policies focused on shaping the demand for travel is required.

In its rather critical response to the DfT’s R2Z strategy, the Committee on Climate Change (CCC) also pointed to the dangers of relying on technical solutions, suggesting that policies influencing the demand for travel should have a more significant role. They recommended that the DfT should “set out a vision for future travel demand” (CCC, 2018b) and this chapter contributes to that vision (The early work in CREDS will focus on passenger demand, including some limited focus on aviation. Additional funding may be directed to heavy goods vehicles and freight. Whilst the core arguments expressed here will apply also to freight, aviation and shipping, the balance of the issues will differ). The remainder of this Chapter focuses largely on road passenger transport. Issues related to low carbon fuels for heavy vehicles are addressed in Chapter 6.

Uncertainties in forecasts of the volume of traffic

The context of forecasting traffic has changed fundamentally in recent years, and this is reflected in future scenarios which span from continual high growth (as happened up to the late 1980s), to low growth or even decline, as has happened since the 1990s). In either case, 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.

For many years, DfT forecasts of traffic volume, used as the basis for calculating projected energy use, comprised a long-term uninterrupted continuation of high rates of growth, with rather narrow sensitivity tests intended to allow for uncertainty in economic performance, population, and fuel costs.

However, it became apparent that the forecasts systematically overestimated traffic growth (for reasons which are not entirely agreed) and since 2015 the official traffic forecasts have used a scenario approach with a much wider range of possible futures, none of which are given precedence as a “most likely” official view of the future. The 2018 scenarios, and the DfT’s estimates of their CO2 implications, are shown in Figures 8 and 9.

Scenarios 1 to 5 are forecasts with different assumptions about economic growth, population and fuel price, with Scenario 1 as a “reference case” using long-standing assumed demand relationships. It predicts an increase in traffic volume of 35% and a calculated reduction in CO2 of 22%, with the share of electric cars and light goods vehicles (vans) growing to 25% of miles travelled by 2050.

Clearly a penetration of 25% electric vehicles by 2050 is not compatible with meeting carbon reduction commitments. Scenario 6 is an alternative reference case forecast based on the trend for decline in trip rates recently observed, which gives substantially lower demand growth, and proportionately less CO2 emissions. This is discussed further below. Scenario 7 is not a forecast as such, but a trajectory of what would happen if electric vehicles are assumed to meet nearly 100% penetration of cars and vans by 2050. In this case, CO2 would fall by about 80%, with most of the deficit accounted for by non-car and van road traffic. Upstream and embodied emissions are not accounted for.

This base then allows us to consider the feasibility of relying only on technical change, and a starting point for considering the scope for changes in the volume and structure of traffic.

Feasibility of relying on energy efficiency improvements and electrification

The CGS and R2Z’s aims for a reduction in CO2 emission from transport emissions by technology, without changing demand, do not appear to be based on a realistic assessment of what is practically possible. We outline two further points of potential failure: an inadequate treatment of targets for ULEVs, and the gap between declared vehicle performance and real-world results.

Weak targets for uptake of ultra-low emission vehicles (ULEVs)

Only targets defined in terms of the penetration of ULEVs, rather than the energy service they provide, are used to frame UK transport policy and its carbon and energy implications. Moreover, these targets are themselves weak and muddled, with relevant Government departmental and CCC publications recommending, or working with, different targets (Table 1). The differences relate to the target years (mostly either 2030 or 2050), the inclusion of cars and vans or just cars, the expression of the target in relation to new vehicle sales or the proportion of vehicles on the road. Only the DfT traffic forecasts supply a figure in terms of the proportion of vehicle miles travelled. Targets are further weakened by the continued confusion about which technologies are expected to be included in the definition of a ULEV. These differences make it challenging to compare ambition across reports, Government departments and over time.

Table 1 demonstrates how policy has evolved very slowly, even on road vehicle technology: by allowing hybrid vehicles to be included, the 2040 target in the R2Z strategy is possibly even less stringent than was proposed six years earlier in the 2011 Carbon Plan. Moreover, the official 2040 target is weak by international standards: Norway aims for all new car sales to be ULEVs by 2025; Scotland by 2032, and the Netherlands, Denmark, Ireland, Austria, Slovenia, Israel, India and China aim for this by 2030 (Committee on Climate Change, 2018a for a review of these targets).

Table 1: Targets and recommendations for uptake of ULEVs in England and Wales

	2030 (/35)	2040	2050
HM Government, December 2011		All new cars and vans to be “near zero emission at the tailpipe”
Committee on Climate Change, November 2015	60% of new cars/vans ULEV by 2030
Defra & DfT, July 2017		End the sale of all new conventional petrol and diesel cars and vans by 2040
HM Government/CGS, October 2017	30% of new car sales will be ULEVs and possibly as much as 70%	End the sale of new conventional petrol and diesel cars and vans by 2040	Every car and van on the road should be zero emission in 2050
DfT RTF, July 2018	Approx. 35% of the car and van on road fleet (deduced from figure 19, page 42 of DfT, 2018)	Approx 80% of on road fleet and 100% of sales of cars and vans are zero emission by 2040	25% (S1) – 100% (S7) of miles travelled by cars and vans in the fleet.
DfT / R2Z (July 2018)a	At least 50% (and up to 70%) of new cars (and up to 40% of new vans) will be ULEVs	All new cars and vans will have “significant zero emission capability” and the majority will be 100% “zero emission”	“By 2050 we want almost every car and van to be zero emission” (not specified if this is sales or on road)
Committee on Climate Change, October 2018b	100% of new cars/vans ULEV by 2035
BEIS Committee, Oct 2018	100% of new cars/vans ULEV by 2032
a The proportion of zero emission mileage is modelled as if these were electric vehicles (p30). b The CCC net-zero advice published in May 2019 kept this target but added “If possible, an earlier switchover (e.g. 2030) would be desirable”

In any case, a stated target is not seen to be a strong enough signal for all actors concerned (Including by the CCC, the National Infrastructure Commission, the UK Energy Research Centre and others). Instead it needs to be a ban to be supported by (potentially UK-independent) legislation. In addition to ‘fuzzy” targets, the R2Z contains only unspecified delivery mechanisms. This is especially surprising given the slower than expected uptake of electric vehicles thus far, especially pure battery variants which only comprised around 0.5% of car sales at end 2018, compared to 1.5-2% for plug-in hybrids (PHEVs).

Preliminary analysis by researchers involved in CREDS shows the inclusion of hybrid technologies could lock significant amounts of fossil fuel into the sector well beyond any target date (Based on new approach in Brand et al, 2017). Figure 10 shows the Internal Combustion Engine ‘ICE ban 2040”scenario representing the loosest definition of ULEVs which allows both conventional hybrids (HEVs) and PHEV cars and vans. When compared to 1990 levels, this scenario shows reductions in tailpipe CO2 emissions of only 61% by 2050. When also banning new HEVs from 2040, the results show a 88% drop, or 93% if from 2030. This suggests that the trajectory for urgent CO2 savings requires phasing out all forms of conventionally fuelled ICE and HEV cars and vans by 2030 and that net-zero (for tailpipe emissions) may only be achieved by also phasing out PHEVs by this date.

This analysis is heavily dependent on the assumption that new car and van CO2 emissions for all propulsion systems will undergo continuous improvement (Brand et al, 2017) and that a generous proportion of miles undertaken in PHEVs will use the electric battery (largely for urban driving, i.e. approx. 40% of the total mileage with motorway and rural driving assumed to mostly use the ICE). This compares to 73% of PHEV driving done in electric mode assumed in the R2Z analysis (DfT, 2018c pp. 130) (Note that in the linked report on the modelling methodology, this figure is reduced to 62%). This is important because, so far, 3 out of every 4 plug-in vehicles sold in the UK has been a PHEV. In the summer of 2018, analysis of real-world fuel consumption data on 1,500 company owned PHEVs (comprising seven models) (Middleton, 2017; Hollick, 2018) found the vehicles only achieved an average of 45mpg or 168 gCO2/km compared to their advertised average consumption of 130mpg or 55 gCO2/km.

The report concludes: “On the evidence of our sample, one has to question whether some PHEVs ever see a charging cable” and suggests PHEVs would attract the highest rate of company car tax if they were to be assessed on their real instead of on laboratory test results.

Real-world performance

Until recently, the EU mandatory regulations for new cars would appear to be a resounding success for CO2 standards. The rate of reduction in official average tailpipe CO2 values of new passenger cars in the EU increased from roughly 1% per year to more than 3% per year after their introduction in 2009. However, two factors mean this success is not all that it appears.

Firstly, there has been no improvement in tailpipe emissions in the UK since 2015 and average level of CO2 emissions of new cars sold in September 2018 was 128.3 gCO2/ km, the highest recorded since July 2013. A switch away from diesel only accounts for a small proportion of this increase, the main culprit being the swing over the past decade towards larger passenger cars, particularly SUVs (dual purpose vehicles) while the rest of the market declines (SMMT, 2018). SUVs now account for around a quarter of car sales in the UK with no sign of slowing down. Somewhat shockingly, this proportion holds true for electric vehicles (BEVs + PHEVs) – 25% of all the 32,048 plug-in cars registered by the end of 2017 comprised one make and model only (Mitsubishi Outlander) – an SUV in the form of a PHEV and one of the most polluting cars on the road when not driven on the electric battery.

Secondly, although the above figures suggest a 30% reduction in tailpipe CO2 emissions since 2000, these are based on test cycle measurements. 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 has grown over time, standing at 42% in 2016 (Teitge et al, 2017), although this gap has now stabilised. This gap has effectively negated any reported savings from efficiency improvements over the past decade.

The regulatory failure of the test cycle versus real-world emissions was not mentioned in the CGS but was addressed in the narrative of the subsequent R2Z which frequently noted it would be considering “real-world” emissions. A new test procedure, the Worldwide Harmonized Light Vehicles Test Procedure (WLTP), is being currently being phased in. Whilst a step in the right direction, the WLTP is not a silver bullet and will not close the performance gap on its own. The discrepancy matters to how meaningful the regulatory or stretched targets are and thus how quickly forward projections will be met. Whilst it could be argued that if electricity is zero carbon this should not matter, the energy efficiency of the transport system is an important issue in its own right and will become more important as vehicles play a key part of the electricity storage solution to balance electricity demands on the grid.

Prospects for travel demand change

Collapse of “business as usual” trajectories of travel demand

The CGS generally adopts an approach of identifying a firmly established baseline forecast of demand, given by reasonably clear economic trends, and treating this as either inevitable or as a target for policy intervention only after other largely technical solutions have been exhausted. Yet, in the context of travel, there is now a strong evidence base that the trends have changed, and continue to do so. 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; Chatterjee 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. These trends are manifesting differently among different groups and in different types of built- up area (BUA) (Figure 11).

This shows a reduction of 20% and 10% respectively among the two younger groups, an increase of 12% among 60+ year olds with differences in the magnitude (but not direction) of these changes in different places. The outcome is that since the early 1990s, aside from general population growth, it is only an aging cohort of people, now over 60, that has contributed to traffic growth, whereas successive cohorts of younger people have shown a reduction in driving licence-holding, car ownership, and car use.

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. This is seen in the DfT Scenario7 above, where 100% electrification has the highest level of traffic growth.

Thus, it is no longer adequate to adopt what used to be the central or most likely traffic forecasts produced by the DfT as the official view of future trends in demand and, from these, calculate the scale of technological deployment needed to mitigate the carbon consequences of this growth. There is a need for new approaches to demand analysis on how to treat the scope for such policies. Underpinning the observed changes, there are new theoretical understandings of the dynamic processes of travel demand, where changes can happen through demographics, migration, churn, habit formation and breaking, and interactions with land use outcomes, disruptions and social norms. In other words, “societal needs and demands are not given: they are negotiable, dynamic, and in part constituted by technologies and policies, including those of efficiency” (Shove, 2017).
Thus, the pattern of co-benefits, empirical evidence on trend shifts and policy implementation, and better understanding of influences on demand, give scope for considerably more ambitious reductions in passenger transport energy and carbon use than has been assumed in the CGS, DfT and CCC publications. 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 achieve and lock-in the new demand patterns, alongside new vehicle technology.

Recommendations for policy

Travel behaviour is already changing in ways that provide opportunities to enable a lower growth trajectory to be deliberately locked-in. National and international examples of sustained lower car-dependent lifestyles indicate that this can be achieved at least in some localities. Such a prospect puts much greater emphasis on policies which influence and provide for more energy-conserving lifestyles, including: emerging models of car “usership“, changing social norms around mobility, new spatial patterns of population growth, the changing nature and location of work, education, housing, healthcare and leisure, reconfiguration of travel by digital technology, and new ways of paying for road use or energy (electricity).

The Avoid-Shift-Improve (Schipper & Liliu, 1999) hierarchy has been used to emphasise the priority ordering and layering of our recommendations that stand apart from the dominant supply and vehicle technology-oriented approach to energy reduction and decarbonisation in the sector. The recommendations focus on surface passenger travel and are targeted at national and local policy makers.

Avoid travel demand and car ownership

Lock-in recently evidenced demand changes

Where specific groups have already shown flexibility in demand, there should be targeting to lock-in those changes, and to extend the behaviour to wider numbers. This can be done through policies such as car clubs, smart ticketing, investment in rail and in digital technology. Access to subsidised or free public transport is at present largely determined by age, and it is clear that behaviour patterns also show strong age effects, but making best use of this may justify an overall review of age boundaries both for the young and old. Improving the experience for these sub-groups of living without a car should not only improve the chances of them opting to live without one (or with fewer per household than they might have done) for longer, but will simultaneously improve non-car travel for a wider set of people and places.

Design regulatory frameworks to steer emergent innovations (e.g. On-Demand mobility, autonomous vehicles) to deliver societal benefit and avoid high travel lock-in in the future

Ignoring the dynamic interactions between society and technology led to the performance gap in real-world energy consumption of vehicles. We are in danger of repeating this mistake with respect to new forms of “on-demand”mobility services, relinquishing of ownership in favour of shared assets, autonomous vehicles and the two- way integration of vehicles and the electricity grid (see for example Wadud et al, 2016). To ensure these developments reduce vehicle miles travelled, a “preventative” regulatory framework designed to enable these innovations to result in a net increase in co-benefits such as social inclusion and transport and energy system flexibility is needed. Specific interventions such as mandating the use of autonomous vehicles in shared contexts, public investment in car-clubs or on-demand services in rural areas and designing car scrappage schemes to accelerate the uptake of mobility packages as opposed to new vehicles, will be necessary (Transport for West Midlands is trialling a Mobility Credits Scrappage Scheme from March 2019).

Develop a cascading framework of national and local support for car clubs

Having access to a shared vehicle has been shown to lead to reductions in personal car ownership and miles driven, as well as increased use of other modes of transport (Marsden et al, 2018). This reduction includes households giving up a car completely, but equally important is reducing from, say, two cars to one car. More creative support options can be explored at the national and local levels to ensure that more people can opt out of owning a car in favour of accessing shared car club services.

These support options can take the form of both carrots (e.g. supporting interoperable underpinning ICT infrastructure, “smart”design of car scrappage, integrating shared travel into multi-modal journey-planning apps, providing dedicated car parking, charging and signage to car club vehicles) and sticks (e.g. parking charges and restrictions in residential areas and workplaces for privately owned vehicles). The benefit of a nested approach to national and local support for car clubs is evident from Scotland, where there was membership growth of 29% between 2016 and 2017 (Steers Davies Gleave, 2018). The overall aim would be to reduce the size of the passenger car fleet as well as accelerate its decarbonisation as vehicles are utilised more intensively and renewed more frequently.

Incentivise the coordination of transport and planning objectives to reduce the need to travel

Enabling travel avoidance is chiefly a matter of coordination of planning and transport objectives in the housing type and location, density of development and location as well as timing of services (including workplaces, schools and healthcare). Local authorities receive bonuses for achieving housing targets with none of this bonus tied to the travel and energy efficiency of the developments. Businesses also need to be engaged through incentivisation of the reduction of their travel footprint, including commuting, perhaps linked to an expanded system of Display Energy Certificates. Similarly, there should be greater integration between the planning and prioritisation of investment in digital infrastructure and transport to support many of the above initiatives but also to deliberately substitute some travel by virtual access in ways that avoids further spatial fragmentation and net increases in demand.

Develop a zero-growth indicator

By adopting a scenario approach for car travel, the DfT analysis suggests de facto acceptance of a varied range of potential growth scenarios for alternative modes. Under this multiple scenario approach, policies need to be appraised themselves not under a single scenario, but under the assumptions of at least the high growth and low growth possibilities. This itself means that flexibility and adaptability – if (when) forecasts turn out to be wrong – becomes an advantage. This flexi-appraisal would be extended to non-transport transport policies – i.e. traffic-generating land use developments, service reductions in rural areas and policies leading to the centralisation of core services such as health and education.

From this, it is possible to imagine the development of a zero traffic or transport energy growth objective, or indicators based on capacity constraints on the electricity grid. For instance, Norway has adopted a zero-growth objective for car traffic in urban areas embedded in a national transport plan which introduced “urban environmental agreements” (Norwegian National Rail Administration, 2016). This will involve environmental and time differentiated road tolls linked to “stronger investment in urban areas”.

Incentivise local authorities to achieve a zero-growth indicator

The CGS does not address the issue of scale and location. Nevertheless, place-based industrial strategy is gaining traction as a key principal of innovation programmes at the European and UK levels. Just as we have highlighted that recent changes in travel demand have been unevenly distributed, the uptake of technology, including energy generation, will also differ. Methods of analysis, policy design and appraisal need to work with this geographical diversity. In particular, local authorities need to be incentivised to reach the zero-growth target indicator outlined above.

Shifting travel to the most sustainable modes

Systematic support for the very lowest energy modes of transport

Enabling and encouraging a shift from private motorised travel to more energy efficient modes requires systematic support for the very lowest energy methods of transport – walking, cycling (including e-bikes and e-scooters) and public transport, through investment programmes on both capital and revenue spending, priority use of road space, and an expansion of “soft”or “smarter”methods of encouraging behavioural change. The goal would be to design “a mobility system where it is more normal to take part in activities using the most sustainable modes more of the time” (Marsden et al 2016).

Institute a new approach to prices and taxes to reflect a fuller range of costs and benefits

A new approach to transport pricing would ensure that the relative prices of different transport options reflect the full range of costs and benefits to the consumer, including health, energy, embedded emissions, congestion and other environmental impacts.

Restructuring prices could include direct subsidy to lock-in sustainable travel choices by charging for use of scarce resources at a rising unit rate where more is used. Such pricing mechanisms would therefore expand the traditional notion of road user charging to reflect wider transport and energy system usage and will incorporate thinking on how to avoid increases in demand that may be stimulated by lower motoring costs of ULEVs.

Improving efficiency of individual modes

Improve the efficiency of vehicles in use, particularly through increased occupancy

A focus on efficiency of vehicles in use is much more than eco-driving. It considers maximising assets in ways that substantially reduce single car occupancy and individual ownership. There is no detectable policy weight placed on the efficiency of vehicles in use, even though increasing vehicle occupancy, potentially through mobility sharing platforms, would ratchet down energy intensity of travel considerably. There are a number of potential types of initiative targeting both businesses and individuals, again falling into carrot (mileage fee reimbursement rates and salary sacrifice incentives) and stick (regulation of the “grey fleet” (use of own cars on business travel), parking restrictions and fees) as well as a review of company carbon accounting to incorporate commuting travel.

Restructure ULEV targets to include phasing out hybrid cars

As our own empirical work has highlighted, the trajectory for urgent CO2 savings requires phasing out all forms of conventionally fuelled ICE and HEV cars and vans by 2030 and that net-zero (for tailpipe emissions) may only be achieved by also phasing out PHEVs by this date. The current wording of targets is at best muddled, but at worst leaves the door open for hybrid vehicles, and subsequent locking-in of a substantial amount of fossil-fuelled mileage during and beyond the target dates.

Regulate to reduce the availability and sales of large cars

The stagnation in average CO2 emission values of new passenger cars in the UK in recent years has much to do with an upsurge in purchase of larger cars. Some of this trend is likely to be due to people choosing to apply the savings from greater energy efficiency to buy more comfortable, more reliable, or more prestigious vehicles which, being larger and heavier, use more energy than necessary for like-for-like journeys. The implication is that measures of energy efficiency which reduce costs can only be fully effective if they are combined with other measures to prevent or offset such countervailing processes. In this case, regulation of sales-weighted average new car carbon emissions is failing and needs to be redesigned to, once again, lock-in the net benefits of this policy. This could potentially involve regulating to phase out the largest vehicles or restrict their use to genuinely appropriate circumstances.

References

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