Highlights
Deliberative engagement in transport policy is a feasible and constructive approach and adds to its democratic legitimacy.
Fairness in transport is a complex concept and requires considerable translation efforts for effective policy practice.
Sentiments are broadly aligned for a fair treatment of different social groups and priorities of fairness principles.
Fair car use budgeting aids deliberation and policy design but needs more research to refine its roles and utility.
Car use budgets are grasped by the public and useful for discussing limits and a fair distribution of the benefits of driving.
Abstract
This paper investigates notions of fairness and the role of deliberative exercises as part of urban transport policy design. Its point of departure is the sufficiency principle informed by conditions of scarcity for private car use in cities. It focuses on questions of fairness in assigning hypothetical car use budgets for the case of London. Two different budgets are considered, one associated with carbon emission ceilings and another for space constraints. The study that underpins this paper is based on a mixed method approach including a dedicated representative survey for London, a deliberation simulation based on a citizens’ jury with nine participants and a pilot behavioural experiment alongside interviews with a total of 19 London car drivers. Three key findings are established: First, deliberative engagement can be a constructive and feasible approach adding to the general democratic legitimacy of decision making in transport policy. Second, while fairness deliberations, perceptions and sentiments are complex, coherent understandings do emerge for both differential treatments of social groups and priorities of fairness principles. Third, car use budgets may be a helpful tool that can be indirectly utilised for policy design and deliberative formats. While they are generally understood by participants as useful tool to consider implications of limits and distributional questions of driving, they require additional research and testing to refine their role and utility. Alongside, the pilot experiment revealed the utility and feasibility of several methodological approaches, some ready for scaling other requiring further refinement. The use of mobility tracking and the deliberative approach to car use budgeting were confirmed as scalable.
1. Introduction
As the sustainable urban transport paradigm of “avoid, shift, improve” (Estermann, 1991; Heinze, 1993; Bakker et al., 2014) has entered mainstream transport policy in European cities (TUMI, 2019), transport debates have become noticeably politicised and polarised (Dudley et al., 2022; Rode, 2023; Karjalainen, 2024). As measures such as low-traffic neighbourhoods, generous bicycle infrastructure, low-emission zones, superblocks, higher parking fees, road pricing, speed restrictions and walkability improvements have been scaled up, some have challenged the fundamentals of urban transport transitions (Wågsæther et al., 2022; Marquet et al., 2024). A central theme underpinning the backlash are fuzzy notions of fairness and allegations of overreach by city governments pushing through “unpopular” solutions.
This paper examines how perceptions of fairness can put transport transitions at risk, aiming to better understand how people can be involved in developing fair urban transport policy. In particular, it looks at deliberative approaches (Dryzek, 2000; Floridia, 2018) such as citizens’ assemblies and juries (Guerrero, 2014; Curato et al., 2021) as an alternative to more conventional participatory methods. Related democratic innovations have shown a considerable potential to overcome polarisation, confrontation and even conflict (Garry et al., 2021).
At the core of this is the concept of sufficiency – what is “enough” in urban transport? – and notions of fairness with regard to how (and whose) mobility is constrained. While efficiency and sustainability are discussed explicitly, notions of sufficiency are more often only implied usually around the ‘avoid’ dimension of the above-mentioned sustainable transport paradigm. They underpin measures such as 15-min cities, urban compaction, accessibility planning, walkability and micro-mobility. Rather than focussing only on movement functions, they consider which level of mobility may be enough or could be replaced by otherwise improving access to opportunities.
More recently, an explicit sufficiency tool in transport has been introduced: mobility budgeting (Millonig et al., 2022) with a fixed budget for mobility (irrespective of transport modes) – for example, in the form of mobility cards. Mobility budgets have also been conceptualised as actual consumption ceilings, recognising individuals’ responsibility to attenuate the negative impacts of their travel. The latter approach informs the concept of car use budgets (Rode, 2024), which is applied in this paper.
The study focuses on London, where progressive transport policies have been introduced by still relatively young institutions such as the Mayor of London, the Greater London Authority and Transport for London (TfL) alongside many of the city's 33 boroughs. London is Europe's most congested city (INRIX, 2024), and the mayoral elections of May 2024 confirmed a strong and stable mandate for further reductions in car use and its negative impacts, including an ultra-low emission zone and low-traffic neighbourhoods. At the same time, the political debate in the run-up to the elections revealed considerable discontent and polarisation associated with the sustainable transport agenda and related policy instruments (YouGov, 2024). Put simply, the wide ranging, decade-long consensus of no longer building new roads for London is not matched by agreement on how to distribute existing road space.
Earlier TfL analysis had found that six out of nine groups in its customer segmentation research showed a considerable willingness to shift their travel towards more sustainable modes (TfL, 2017). Yet a notable number of residents, particularly in Outer London, strongly oppose recent green transport measures, such as the expansion of London's ultra-low emission zone (YouGov, 2024). Such attitudes stem partially from concerns about a lack of alternatives to driving. They also increasingly overlap with lower-income people's frustration at being priced out of the city and having to relocate to areas underserved by public transport (Smith and Barros, 2021).
Progressive policy-makers in London widely agree on a strategy of “showing what change looks like” (Davis and Altshuler, 2018) as a way to build support. Based on this theory of change, instead of involving people from the outset, some have argued for delivering proof of concept first and then proceeding with consultations about the permanent implementation of transport measures. With that as the point of departure, this paper investigates (1) fairness framings by the general public for managing car use in London, (2) the role of mini-publics in putting forward more consensual interventions, and (3) how deliberative efforts affect the attitudes and behaviour of both participants and non-participants. The overarching research question is:
What can we learn from a deliberative approach when addressing sufficiency and a fair distribution of car use budgets as part of transport policy
In particular, we sought to learn whether deliberating jointly on fairness in transport and reaching a shared understanding could increase acceptance of travel behaviour change and related policies. To address this research question, we applied a novel mixed-method approach involving a representative survey and a pilot experiment with a citizens’ jury coupled to a behavioural study and in-depth interviews with London car drivers.
The paper is organised as follows: Section 2 reviews the literature on sufficiency in transport, mobility budgeting, transport equity/fairness, and the relationship between deliberation and transport policy acceptability. Section 3 presents our research framework, mixed-method approach and key research phases. Section 4 discusses our main findings linked to perceptions of fairness, including the differentiation of social groups, the fairness approach and the role and legitimacy of a citizens’ jury. Section 5 proceeds with how the deliberative approach operationalised car use budgets and presents the behavioural and attitudinal findings. A final, substantive Section 6 covers the key insights gained from the experiment and its implications for policy and practice.
2. Sufficiency and equity in urban transport
This project applied two fundamental concepts from the literature to the transport domain: sufficiency and equity. While necessarily brief and concise, this literature overview takes a slightly broader scope than usual, reflecting the central roles these texts play in shaping our study's conceptual framing. The concept of sufficiency underpins the idea of mobility budgets and its interpretation as car use budgets. Our focus on fairness concerns procedural fairness in particular and briefly covers contemporary discourse on citizen deliberation and mini-publics.
2.1. From sufficiency to mobility budgeting
At the most basic level, the concept of sufficiency refers to “an amount of something that is enough” (Cambridge Dictionary, 2024), though more recently, it has been equated to a much wider recognition of ‘enoughness’ (Jungell-Michelsson and Heikkurinen, 2022). In the context of sustainable development, sufficiency is sometimes referred to as a third core principle, along with efficiency and consistency (Princen, 2005, Schäpke and Rauschmayer, 2014), and generally means adjusting consumption to be in line with available resources. The term has been used in ecological economics, political ecology and ecological philosophy (Jungell-Michelsson and Heikkurinen, 2022). Applying it to public policy, Spangenberg and Lorek (2019) stress that “sufficiency requires radical change redefining the rules of the game, incremental steps will not be enough” (p1077). Important related knowledge gaps concern a better understanding of quantifiable, domain-specific sufficiency levels and their operationalisation (Jungell-Michelsson and Heikkurinen, 2022).
Arguably, one of the biggest political tests for the sufficiency principle is to apply it to transport and mobility. Here it may clash with desires of unrestricted mobility that are often equated to freedom (Sager, 2006). Notable work on sufficiency in transport includes a general introduction by Waygood et al. (2019) and its application to bicycle subscription business models (Niessen et al., 2023).
So far, however, the sufficiency principle has found little direct recognition in transport policy (Rode, 2023). In the words of Ternes et al. (2024), “discussions of ‘not enough’ are not mirrored by discussions of ‘too much’” (p9). There is only a niche interest in excess travel (Wadud et al., 2022; Cass et al., 2023), even though some consider sufficiency fundamental for achieving urgent sustainability outcomes in the sector (Millonig et al., 2022). Rode (2023) suggests that many sustainable transport interventions implicitly apply the principle, particularly those based on the “avoid, shift, improve” paradigm (Bakker et al., 2014).
Mobility budgets are a rare explicit operationalisation of sufficiency in transport. They can take many forms. Corporate or employee mobility budgets replace company cars with a predefined budget for travel expenses (Schlegel and Stopka, 2022; Zijlstra and Vanoutrive, 2018). Individual mobility budgets propose an allocation of budgets for personal travel, typically derived from carbon budgets (Millonig et al., 2022; Arhipova et al., 2023) and informed by transport-related carbon permits (Harwatt, 2008; Wadud, 2011). Taking a needs-based perspective, such budgets have also been proposed as “floors” – for example, with a yearly travel budget of 3500–4500 km as sufficient mobility in Europe (Holden, 2016). Mobility budgets for public policy could also build on personal carbon trading (Fawcett, 2010; Raux et al., 2015), use “mobility coins”, a multi-modal tradeable credit scheme (Hamm et al., 2023), or underpin a fairer design of established policy instruments such as road pricing (Rode, 2024).Across these applications, the concept of mobility budgeting remains vague and can range from allowances to rationing. Referencing Hajer (1995), Zijlstra and Vanoutrive (2018) suggest that ambiguity is typical for successful policy concepts and may contribute to the appeal of mobility budgets. Conversely, transport sufficiency and associated interventions face the general risk of growing opposition and polarisation as the level of specificity or proposed interventions increases (Mau et al., 2023).
The interpretation of mobility budgets that underpins this study is more concrete, the mode-specific approach of car use budgeting (Rode, 2024). Here, the budgets assigned to individual car users are based on the scarcity of urban street space, but they could also be based on carbon emission ceilings. The suggested core unit for car use budgets is the number of kilometres driven within a given urban cordon and time period. At various levels of granularity and complexity, these budgets are arrived at by analysing the total space available for circulating traffic within a given urban area or subdivision, the number of cars usually operating within that area, and assumptions for the temporal distribution of trips. The resulting average number of kilometres that can be travelled per day, for example, reflects a threshold use of road space by vehicles not exceeding acceptable levels of congestion.
Transport sufficiency and mobility budgeting have considerable social equity implications. We can directly detect the obvious distributional question of how limited transport resources are shared among different residents and societal groups. But equally, the distribution of negative externalities from travel needs to be considered alongside other fundamental aspects of absolute and procedural fairness