Decarbonising road transport by 2030: what ‘net’ must really mean now

Current progress towards the West of England's net zero ambition for road transport is behind where it needs to be. Three key factors are limiting progress: car dependence, the pace of the gradual transition to electric vehicles (EV) and limited political support for behaviour change measures.  

Achieving a low-carbon transport system will require better coordinated leadership, public engagement and a focus on creating everyday mobility choices that genuinely rival the private car. 

The West of England's transport emissions picture [1]

Total estimated greenhouse gas (GHG) emissions for the West of England were 5,084 kilotonnes of carbon dioxide equivalent (KtCO₂e)[2] in 2022 (DESNZ 2025). Of these total emissions, 42% were estimated to come from road transport (see Table 1).

Table 1: 2022 GHG emission profile for the West of England in KtCO₂e and transport as a percentage of total emissions

Source: DESNZ 2025

The vast majority (97%) of the region's ground-based transport emissions are related to road transport, with a third of these coming from motorway emissions – which local authorities have little or no influence over (see Table 2).

Table 2: 2022 GHG emission profile for transport emissions in the West of England in KtCO₂e and as a percentage of total transport emissions

Motorway emissions are a particular challenge in South Gloucestershire and North Somerset, whereas A-roads and minor roads are the dominant contributors in the City of Bristol and in Bath and North East Somerset, as shown in Table 3.

Table 3: 2022 transport GHG emission profile for the West of England by local authority in KtCO₂e

Source: DESNZ 2025

‘Net zero’ means ‘zero’ for transport

The West of England is not unusual in having a high proportion of GHG emissions associated with road transport. Indeed, across the UK as other sectors improve their performance, transport has come to represent a growing share of the country's total emissions.

The West of England local authorities’ transport emissions targets derive from the broader net-zero emissions targets that each has endorsed for 2030. However, it is not clear precisely what ‘net’ means in the transport sector – one that offers few prospects for removal of ambient carbon. For transport, it therefore seems that ‘net zero’ means ‘zero’, in other words the complete elimination of emissions by 2030.

The scale of the challenge

The West of England local authorities have calculated the steps needed to meet the 2030 target.

• In Bristol, 90% of cars need to be electric by 2030 and the total volume of car journeys in the city reduced by 40%.

• Reflecting the more rural context, one of Bath and North East Somerset’s scenarios combine a 7% decrease in the number of car journeys and a 25% reduction in the distance travelled by car. Further, 90% of cars need to be substituted with EVs – 15% of which can be hybrid.

• North Somerset also aims to reduce road traffic by 25%. It combines this with support for the national Zero Emission Vehicle Mandate (ZEVM) targets for transitioning to EVs.

• South Gloucestershire places greater emphasis on its own leadership and qualitative assessment rather than specific quantitative targets.

What is clear is that all the local authorities see a distinction between interventions that they can directly influence and those that they can only facilitate. Broadly, the local authorities have reduced their own transport emissions to a greater degree than the 9% headline figure for the region's total transport emission reduction (WECA, 2025).

The ‘avoid-shift-improve’ strategy

The region's local authorities' transport strategies include elements of the ‘avoid-shift-improve’ hierarchy that is widely used by organisations such as the United Nations Environment Programme and the Intergovernmental Panel on Climate Change (IPCC).

‘Avoid’ measures reduce or eliminate the need for carbon-intensive activities. In the transport sector, this relies on integrating transport and spatial planning. Evolving the existing built environment to meet the ‘15-minute city’ principles would mean that daily goods and services can be reached from homes and offices within 15 minutes’ travel on foot, by bike (or similar) or public transport. New developments then need to be in places where it is realistic that they can be public transport-oriented and designed in a way that is not car-centric.

Such an approach is not easy to deliver. The location choices of businesses providing everyday goods and services is a market-led activity. What's more, aside from a minority of low-car developments in the heart of major cities, developers continue to provide housing solutions that are reliant on car access and use.

A 'shifting' strategy moves activities to lower-carbon alternatives. In transportation, the recipe for this is well understood. People and goods need to transfer from low energy efficiency, high emissions modes of transport, like internal combustion engine cars, to high energy efficiency, low or zero emissions modes.

Some cities around the world have already made significant progress in making this transition. If Copenhagen achieves its net-zero goal by 2030, which remains possible, it will be based on 70% of trips – both to and within the city – being by bike, on foot or public transport, and 30% by car (Copenhagen City Council, 2022).

The role of bikes and buses

In the West of England, bicycles and buses remain at the centre of plans for an integrated transport system. They also offer the most viable means of achieving modal shift by 2030 – it is relatively easy to increase their capacity and broaden their accessibility. Other options that can contribute in the short-term include e-scooters, often used for first/last mile access, and employee carpooling. Light rail or another form of mass transit may contribute in the medium to long term.

Buses will not attract car owners unless they receive clear, effective on-street priority that enables them to deliver competitive journey times – bus-only streets, for instance. Crucially, bus services must also be seen as reliable and well-integrated.

Metrobus has improved service quality in the West of England, but congestion still undermines reliability. WECA reports that high ‑priority Metrobus routes offer reduced journey times, with 30% growth in users between 2019 and 2024 (WECA, 2024).

Yet networkwide punctuality and reliability remain inadequate. Both are therefore targets for improvement in the Bus Service Improvement Plan (ibid). Indeed, even small interventions, such as updated revenue protection policies and new validation technologies, could help to remove current delays around ticket checks.

Further, buses must be seen as a cost competitive option. Bus fares have increased relative to motoring costs over the last decade, (RAC Foundation, 2026) while car electrification has raised fixed costs but lowered operating costs for many owners. Local authority measures (such as parking charges, permits, workplace parking levies, clean air zones) and national measures (including fuel duty, forthcoming EV road user charges) need to be managed to make public transport more competitive. This is politically difficult where services do not cover all citizens.

Raising cycling levels requires measures to address a range of individual and systemic barriers. Key barriers to cycling include road safety, weather, hilly terrains and rider capability. E-bikes reduce some of these barriers, but safety remains a dominant challenge. Safe infrastructure and traffic management are essential. Some people will only cycle with effective traffic calming, while others require full segregation (kerb protected lanes or offroad routes). Offroad routes must consider personal security, with lighting installations appropriate in some locations.

Improved infrastructure can incentivise more people to cycle. In turn, increased visibility can become a reinforcing social norm. It is believed that as cycling becomes more common-place, motorists become more accommodating, too, although this is helped by effective traffic management measures.

But what about rural travel?

Suburban and rural areas remain more challenging territories for public transport and cycling. It is the daily car journeys of 2-25 miles – which often take place at least partially outside of cities – that have been shown to contribute the most carbon emissions (Department for Transport, 2009).

Suburbs and rural areas are therefore critical to decarbonisation policy. Improving bus services outside cities will play an important role here, as will transport interchanges or ‘mobility hubs’ that enable people to transfer from car to limited-stop buses or, where they exist, trains (Parkhurst and Meek, 2014).

To the extent we need motor vehicles, let them be electric

Turning to ‘improvement’ measures (those that make the remaining activity cleaner or more efficient in the 'avoid-shift-improve' hierarchy), the IPCC (2022) leaves no doubt that the electrification of a vehicle fleet powered by low-GHG electricity is the single most important transport decarbonisation step. This is key given that road transport is integral to today's economy – in other words, to the extent that we need motor vehicles, let them be electric.

The West of England authorities have set 2030 targets of up to 90% for fleet electrification – a target which is now not achievable. The average car is now used for nine years and 10 months (RAC Foundation, 2025), with fleet proliferation reflecting gradual replacement as cars come to the end of their use. As such achieving the 90% target will require roughly a decade of extensive electric sales. The Zero Emission Vehicle Mandate (ZEVM) now requires only 80% of new cars sold in 2030 to be zero emission, suggesting a 90% fleet proliferation closer to 2040 than 2030 under current policies.

Still, we cannot rely solely on electrification as a technical fix that requires no behavioural changes (Parkhurst, 2025). Current EVs are far from being net zero. Given vehicle production practices and the degree of decarbonisation of the energy grid that recharges them, EVs to date have approximately halved emissions compared with an equivalent internal combustion engine vehicle. Although, this advantage is expected to grow sharply as energy and automotive production sectors decarbonise.

The electrification transition is itself an uncertain target that is subject to political and technical constraints. The ZEVM targets may yet prove politically untenable. Around one-third of UK households have no home charging possibility (ChargeUK, 2024), but energy sector practices and taxation policy have resulted in a situation where public charging costs can be up to 13 times higher than the most attractive domestic tariffs. This has created clear winners and losers from the transition.

In November 2025, Government announced the intention to introduce, from 2028, an additional road user charge only for cars that can be plugged in. If the cost difference between public and home-based charging is not significantly reduced, then the new road user charge may prove to be the ‘final straw’ breaking the back of public support.

The 2030 targets set by West of England authorities had correct intentions

The 2030 net-zero targets for transportation set by the West of England authorities were accurate if national transport decarbonisation targets are to be achieved. But the region remains a long way from meeting them on schedule.

This reality underscores the need for increased action and better leadership in the region and nationally. Indeed, the limited progress around transport decarbonisation is not unique to the West of England.

Some argue that it has resulted from emphasis being placed on the wrong end of the ‘avoid-shift-improve’ hierarchy (SLOCAT Partnership, n.d.). The intended logic of the approach is to start with avoiding carbon-emitting travel, then shifting to more sustainable modes for travel that cannot be avoided and then improving the travel that cannot be shifted.

In practice, the behaviour change required to implement this approach has not received sufficient political support. This reflects the so called ‘structural’ constraints that have resulted in society being dependent on the car. Thus, the focus so far has been on ‘improving’ – i.e. the electrification of the vehicle fleet. Yet, it is only since the beginning of the 2020s that vehicle electrification has entered the mass market; too late to have sufficient impact on the 2030 targets.

In the West of England, it is now important to emphasise that the GHG problem is one of cumulative emissions, so the timeliness of progress is of increasing importance as time passes. With the EV transition behind schedule and uncertain, it is important that policy interventions emphasise cars as one part of a broader transport system, whereby cost competitive, convenient and reliable options enable people to make most of their journeys by other means.

Conclusion

The data show that while the West of England’s 2030 transport decarbonisation targets were appropriately ambitious, current progress is falling short. Although the region's local authorities recognise the scale of the challenge, delivery remains constrained by car dependence, limited political support for behaviour change measures and the pace of the EV transition.

Progress will depend on rebalancing strategies toward the ‘avoid–shift–improve’ hierarchy, including prioritising reduced travel demand and largescale modal shift from private cars to public transport or cycling. This must be supported by integrated planning, high quality bus and cycling networks, and consistent national policy.

As the region resets its trajectory toward 2050, the urgency of cumulative emissions highlights the need for sooner, deeper action. Achieving a resilient, low-carbon transport system will require coordinated leadership, public engagement and a renewed focus on creating everyday mobility choices that genuinely rival the private car.

Footnotes

[1] This policy insight uses DESNZ regional emissions data, which exclude aviation emissions. Percentage totals differ from other insights which include air transport services, but the emission figures for road transport are identical.

[2] Different greenhouse gases have different warming effects and remain in the atmosphere for different durations. To provide a unified account of the total warming effect, their impact is converted into a comparable amount of CO₂. For instance, methane has a higher warming effect but a shorter lifespan than CO₂. This is expressed in equivalent terms as a CO₂e of ~80, meaning that every unit of methane has the same warming effect as 80 units of CO₂.

Different greenhouse gases have different warming effects and remain in the atmosphere for different durations. To provide a unified account of the total warming effect, their impact is converted into a comparable amount of CO₂. For instance, methane has a higher warming effect but a shorter lifespan than CO₂e. This is expressed in equivalent terms as a CO₂e of ~80, meaning that every unit of methane has the same warming effect as 80 units of CO₂.

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