The close relation between traffic avoidance, a modal shift to environmentally friendly modes of transport and the spatial structures in which mobility takes place is the subject of several studies. For instance, van Wee (2002: 269), Handy (2005: 1) and Ewing and Cervero (2001: 87) are all firmly convinced of the academic evidence demonstrating the impact of land use policy on travel behaviour. Still, there is insufficient knowledge and too few studies on how and in which exact way specific characteristics of the built environment or land-use changes influence physical activity and travel decisions (Van Wee 2002: 270; Handy 2005: 3; also Holz-Rau/Scheiner 2020: 398 ff.). A recent study analysed the specific links between certain land-use factors (e.g. regional accessibility, density, functional mix, roadway design) and planning objectives such as emission reductions and concluded that these factors can contribute considerably to reduced vehicle ownership and travel, per capita vehicle mileage and an increased use of alternative modes (Litman 2020: 3 f.). According to Ewing and Cervero (2001: 106), the variable of mode choice has received most academic interest in studies about the connection between land use and travel. Besides the built environment, however, they argue that this variable is also strongly influenced by socioeconomic factors (Ewing/Cervero 2001: 87).

Even though it remains indisputable that manifold different factors such as socioeconomic development or the size and density of a city or region have a strong impact on mobility behaviour, it seems obvious that the integration of land-use and transport planning is of central interest within the aim of sustainable mobility transitions. Their integration is undisputedly one of the key leverage points for sustainable mobility. Already in 1958, Colin Clark referred to transport as the “maker and breaker of cities” (Clark 1958). In addition to improving traffic routes and traffic safety, traffic planning’s main tasks include the improvement of public transport, increasing the share of pedestrian and bicycle traffic as well as public transport, the reduction of noise, air pollutants and climate gases, and the realisation of a city or region of short distances.

https://www.umweltbundesamt.de/themen/verkehr-laerm/verkehrsplanung/kommunale-verkehrsplanung#integrierte-verkehrsentwicklungsplanung-kommunen-stellen-weichen (09.03.2021).

Against this background, guiding principles for an integration of land-use and transport planning were developed decades ago, and postulated spatial development that saves transport and is oriented towards sustainable types of mobility (Beckmann 2020: 285). In discussions about sustainable urban development in the 1990s, the concept of a city of short distances emerged, describing an urban environment in which places of everyday life – such as workplaces, educational and supply facilities or recreational areas – can be reached within a short time and without being dependent on a (private) car (Beckmann/Gies/Thiemann-Linden et al. 2011: 21 f.). The planning principles behind this vision are accessibility, a functional mix of uses, density, good walking and cycling environments and generally a high-quality urban environment (Beckmann/Gies/Thiemann-Linden et al. 2011: 22; Gertz/Flämig/Gaffron et al. 2018: 305 f.). The scopes of action lie in densifying the urban structure by strictly prioritising inner rather than outer development and hence brownfield rather than greenfield development, enforcing changes in the use of areas and redistributing the road space in favour of public transport, walking and cycling (Curtis 2008: 109; Gertz/Flämig/Gaffron et al. 2018: 307 f.; Gil Solá/Vilhelmson/Larsson 2018: 5 f.). Looking beyond such measures of densification and spatial redistribution in urban structures, the strategic principle of public-transport-oriented development is relevant. The intention here is to locate urban growth in close proximity to public transport stations, whether in the form of housing settlements or other uses (Gertz/Flämig/Gaffron et al. 2018: 306). Today this approach is also discussed in similar concepts like the 15-min-city, an access-focused urban perspective to reorganising urban life (e.g. Pozoukidou /Chatziyiannaki 2021).

In the past, it has often proved difficult to raise the potential of an integrated approach of land use and traffic, as both planning perspectives are characterised by a large number of different political levels of responsibility and departments (Beckmann 2020: 278, 285), with sometimes contradictory interests and goals.

The implementation of traffic-avoiding spatial structures places high demands on local decision-makers and planning officials. Besides “a shift away from a traditional transport policy paradigm”, the implementation of such structures is influenced by “intra-organisational working relationships, professional cultures and institutionalised working practices” (Hrelja 2015: 2). Above all, the sectoral division of responsibilities between transport and land-use planning authorities is considered a crucial barrier to sustainable mobility development as it leads to competing agendas and hampers strategic thinking, creativity and innovation (Kennedy/Miller/Shalaby et al. 2005: 395; Hull 2008: 102; Stead 2008: 144). Consequently, there is growing demand for a holistic and integrated approach to land-use and transport planning on a political level as well (Hrelja 2015: 1; Kennedy/Miller/Shalaby et al. 2005: 395; Gil Solá/Vilhelmson/Larsson 2018: 5). Precisely, policy integration is defined as “the management of cross-cutting issues in policy-making that transcend the boundaries of established policy fields, and which often do not correspond to the institutional responsibilities of individual departments” (Stead/Geerlings 2005: 446).

Frequently mentioned barriers to integrated planning approaches include diverging professional practices, goals and jurisdictional borders between the involved sectors as well as mismatching time horizons of associated sectoral programmes (Hooghe/Marks 2003: 239; Stead 2008: 142; Stead/Geerlings 2005: 447; Te Brömmelstroet/Bertolini 2010: 86). Further, short political cycles lead to politicians being inclined to prioritise issues with short-term effects that tend to generate public support more easily. Although there is often much political support expressed for integrated policy-making and cross-cutting issues like sustainable development, support for the subsequent implementation tends to be rather weak (Stead/Geerlings 2005: 450). A precondition for integration is hence the political courage to take unpopular decisions and redistribute funding towards sustainable land-use and mobility developments (UBA 2017: 9).

The close link between regional and transport planning is obvious. Taking a closer look at the planning reality in two German cities, this paper deals with the following research questions: What can sustainable transport development through integrated (regional) planning look like? How integrated are the two cities’ planning approaches not only in terms of goals and targets, but also in procedural and culture-led aspects like informal networks and joint decision-making? We start from developing a conceptual framework inquiring into the political in the integration of land-use and transport planning according to the three well-established governance dimensions of polity, politics and policy (Section 2). Then, in the next step, we analyse the two German case studies, Dortmund and Hannover, and accordingly evaluate the level of integration (Sections 3 and 4). In the final section, we reflect on the results presented and draw a bigger picture of the role of integration in a transition towards sustainable mobility.

The aim of a more sustainable mobility system has attracted renewed attention in the context of climate change, CO₂ emission reduction and the contribution the transport system is able to make here. One key issue discussed is a (re)organisation of our cities and regions to produce increasingly less traffic for everyday needs. The following conceptual framework builds upon this approach, emphasising the integration of land-use planning and transport planning for more sustainable outcomes in the built environment, especially neighbourhoods with mixed land uses, short distances and good accessibilities for everyday needs. The focal point of our analysis is therefore the political dimension and the negotiation processes relevant to the integration of land-use planning and traffic planning, focusing on outcomes in terms of policy papers or joint strategies rather than the direct outcomes in the built environment.

In general, integrating land-use and transport planning is a matter of intensified interaction between different sectors. Nevertheless, there are different levels of integration, not all of them follow the same logics, procedural ways forward and joint decision-making. Stead (2008: 140) considers that integration represents a higher level of joint decision-making than mere cooperation and coordination. Whereas cooperation refers to dialogue and information sharing between otherwise independent departments with the aim of improving the output for individual goals, coordination intends to adjust sectoral policies to make them more coherent and avoid conflict, contradictions and redundant duplicated work (Schermerhorn 1975: 847; Peters 1998; Stead/Geerlings 2005: 445; Stead/Meijers 2009: 322). By including both cooperation and coordination (see Figure 1), an integrated approach applies the same goals for all the involved sectors in order to create synergies between them; the intended outcome is one joint policy (Stead/Geerlings 2005: 451; Stead/De Jong 2006: 4; Stead/Meijers 2009: 322 f.). Generally, a government’s overall, cross-cutting goal (e.g. sustainable development, quality of life) leads to results that may strongly differ from the outcomes preferred by specific sectors (Stead/De Jong 2006: 4; Stead/Meijers 2009: 323 f.). However, the intense cross-sectoral interaction requires more resources in terms of formal and informal arrangements and dialogue formats. Therefore, the involved actors are less autonomous and more interdependent, with less clearly defined responsibilities and the setting of joint decision-making (Stead/Meijers 2009: 321 ff.).

An integrated planning approach expands the network of actors from within the local authority to include private stakeholders as well as the public (UBA 2017: 5). As public transport services are mostly delivered (semi-)privately in Germany, strong market regulation is necessary to guarantee sustainable development (Kennedy/Miller/Shalaby et al. 2005: 401; Dziekan/Zistel 2018: 350). With new forms of mobility like shared mobility or mobility as a service entering the market on a more business-oriented footing, the network of actors such as private stakeholders is even growing. An integration of these services with public transport in the form of mobility hubs has recently been discussed in academia and practice, as has its contribution to more sustainable multi-optional mobility behaviour (e.g. Utriainen/Pöllänen 2018: 19). Besides involving the private operating companies, “it is only when there is sufficient public support for change, that action will take place” (Banister 2008: 76) since public support increases political will (Kennedy/Miller/Shalaby et al. 2005: 400; GPSM 2015: 10 f.; Thomas/Pojani/Lenferink et al. 2018: 1205).

In sum, Hrelja (2015: 11) is just one of those who argues that existing organisational structures and coordination mechanisms are often not beneficial for integration. Other scholars have focused on the investigation of integration as well, each with a different perspective and focus: Busscher, Tillema and Arts (2013: 492) focused on similar management approaches in transport and planning, Tennøy and Øksenholt (2018: 93) analysed changing structural conditions, and Lowe, Whitzman and Giles-Corti (2018: 180) concentrated on integrated policy-making.

Accordingly, the idea of a comprehensive understanding of the level of integration involves analysing precisely these barriers of integration, institutionalised in well-established governance forms and planning cultures in both sectors, land-use planning in general as well as transport planning. Therefore, the three dimensions of the political seem highly suitable: polity, politics and policy. In applying these terms directly to transport policy, Sager (2007: 270) similarly argues that “the trichotomy of polity, policy and politics is a useful, because parsimonious order for categorising the various factors influencing policy making that policy research identifies”. While the polity dimension denotes the institutional organisation and structures as well as compositions of such structures, politics refer to the active process of implementation characterised by actor behaviour, actor interests and constellations of negotiations, and policy specifies the material elements or instruments emerging from and used in political processes, i.e. single measures, projects or political programmes (Sager 2007: 274 ff.). For the purposes of this research, we used an understanding of these terms that was specifically adapted to the integrated planning field of interest by scholars in land-use and transportation planning (Hrelja 2015: 2; Schwedes 2018: 8 ff.; Rode 2019: 42 f.) (see Table 1).

Polity (form) aspects of integration refer to organisational structures and formal frameworks within which planning takes place, including factors such as institutionalised working practices and the distribution of responsibility and power across and within tiers of government (Hrelja 2015: 2; Schwedes 2018: 8; Rode 2019: 42). The intention in the polity dimension is to remove sectoral boundaries and establish joint responsibilities integrating transport concerns into formal land-use planning. Rode (2019: 48) and Stead (2008: 143 f.) identify a central coordinating committee and hence some top-down hierarchical organisation that bundles all land-use and transport functions as crucial for an integrated planning approach. Within the framework of such an overarching steering unit, common visions and targets can be articulated and adhered to more easily (Mu/De Jong 2016: 62). Several scholars even make a case for establishing such a formal coordinating body on a regional level to promote cooperation between adjacent local governments (Kennedy/Miller/Shalaby et al. 2005: 398; Marsden/May 2006: 782; Pucher/Buehler 2008: 522; Gertz/Flämig/Gaffron et al. 2018: 314; Thomas/Pojani/Lenferink et al. 2018: 1204). In order to soften or even remove jurisdictional boundaries and make actors more interdependent, institutionalised and constant, cross-sectoral teams should further be developed (Stead 2008: 144 f.; Mu/De Jong 2016: 56).

Politics (processes) describe informal factors like daily working practices and negotiation processes which influence planning outcomes (Hrelja 2015: 2; Schwedes 2018: 9; Rode 2019: 43). The dynamic and temporal nature of the politics dimension (Rode 2019: 43) mostly distinguishes it from the institutionalised structures in the polity dimension, which are considered steady and non-temporary. Nevertheless, the institutionalised structures of the polity dimension alone do not guarantee integration (Stead/Geerlings 2005: 452). Rather, the networks within those structures, i.e. informal communication and negotiation processes, are crucial to facilitating integration (Kennedy/Miller/Shalaby et al. 2005: 398 f.; Stead/Geerlings 2005: 449; Rode 2019: 54 f.). In planning research, these local specific characteristics are often declared as planning culture within these institutionalised structures which enable or hinder integration (Levin-Keitel/Othengrafen 2016: 84 f.). This is associated with governments becoming part of a larger governance framework in which informal, soft instruments are applied and a multitude of stakeholders is involved (Marshall/Banister 2007: 1; Gawron 2010: 15; Knieling/Klindworth 2016: 6). Scholars assume that a working culture characterised by trust and collective responsibility facilitates integration, as it is a precondition for achieving consensus and shared objectives between all actors (Banister 2008: 79; Stead/Meijers 2009: 327). This can be strengthened through regular cross-sectoral meetings and systematic dialogue formats (e.g. common workshops or field trips) which raise mutual understanding as well as cross-sectoral capacity and build a common knowledge base (Stead 2008: 144; Hrelja 2015: 6; Koglin 2015: 59 f.; Mu/De Jong 2016: 57). Further, multi-disciplinary working groups and committees are beneficial (Stead/Geerlings 2005: 446; Stead 2008: 144). In this way, collective responsibility for cross-cutting issues is accepted more easily and such topics can be dealt with more effectively.

The third dimension of policy (content) denotes the specific content formulated in strategic programmes or visions through goals, values, guiding concepts and intended strategies (Schwedes 2018: 9). Whereas polity and politics collectively form the body of governance, the policy dimension describes the content-related outcome of the formal and informal actions in the other two dimensions. In the policy dimension, strategic documents such as political programmes, visions or (cross-)sectoral plans are a relevant instrument for integration and even sustainable development, among other things, since they can steer political decisions in the long-term (UBA 2017: 12; Gertz/Flämig/Gaffron et al. 2018: 315; Rode 2019: 43). Fully integrated policies are of cross-sectoral nature and entail shared goals and principles that are not bound to the land-use or transport sector but break down these “traditional silos” (Curtis 2008: 108).

All the aforementioned factors and dimensions considerably promote integration in policy-making and planning. Yet, it is only through their parallel application that they take effect; no factor alone is sufficient to promote integration (Stead/Meijers 2009: 328). In order to demarcate integrated planning from cooperation or coordination, scholars emphasise the importance of increased formality; it is the institutional design which needs to be adapted in order to establish structures in which efficient and lasting levels of trust can be produced and reproduced between the actors (Stead 2008: 146 f.; Mu/De Jong 2016: 57). Stead (2008: 146) even identifies cross-sectoral budgeting arrangements as crucial to distinguish the highest level of integration from coordination and cooperation.

Desktop research helped us to portray the current state of knowledge on the topic in question and build a conceptual framework. In the context of the case studies, we conducted seven semi-structured interviews with policy-makers and key stakeholders with respect to transport and land-use planning (three interviews for Dortmund; four interviews for Hannover). All seven interviewees were chosen and contacted due to their involvement in and contribution to the focus topics in the two case studies. In order to keep the discussions focused on the research questions, we developed an interview guide in advance, which was the same for each of the conducted interviews. The guide was composed mostly of open-ended questions, some of which were additionally accompanied by follow-up questions in order to enhance the precision of answers. We developed the interview guide based on the relevant factors that were identified in the conceptual framework. We analysed the accrued data using Mayring’s (2000: 3) method of qualitative content analysis. The results from the interviews are anonymised. We selected the two cities Dortmund and Hannover as case studies due to certain similarities, which proved to be a good basis for comparison. These similarities include, for instance, that both cities have comparable population figures (size and density), are classified as higher-order centres and located in a larger region, and are designed as car-friendly cities with public transport systems characterised by a similar number of annual passengers. Further, we identified a need for action with regard to sustainable mobility development in both cities, e.g. in terms of exceeding air pollution limits. In the following, we briefly introduce the two cities in connection with their current situation of sustainable mobility.

The following comparison depicts similarities as well as differences between the two approaches in the three governance dimensions of polity, politics and policy. Especially the aforementioned substantive differences with regard to governmental levels of authority of public transport need be borne in mind here.

The conducted research has shown that traditional governance approaches with clearly separated policy sectors and little intersectoral interaction are not appropriate for addressing the issue of sustainable mobility development. We referred to a strand of the literature that suggests that integrated cross-sectoral problem-solving strategies are necessary to facilitate long-term strategic development towards sustainable urban mobility. Integrated land-use and transport planning requires effective governance bodies with modified organisational structures and network formats. With the aim of ‘looking behind the curtain’ and analysing integrative approaches, we identified facilitating factors in the three governance dimensions polity, politics and policy. The policy dimension requires a paradigm shift, resulting in an increased focus on cross-cutting goals such as sustainable development instead of sectoral targets, and giving more weight to qualitative (i.e. social and environmental) aspects of the transport system. In order to implement these policies, the increased removal of institutional barriers (polity) as well as extensive and flexible network structures (politics) between the land-use and transport sectors are crucial.

With regard to the two case studies’ approaches, it first needs to be taken into account that public transport planning takes place on different governmental levels in the two different contexts, namely on the regional level for Hannover and the local level for Dortmund. In their current approach, both case studies aim to reduce climate-damaging emissions, primarily by promoting sustainable transport modes. However, we found that Dortmund and Hannover are at different stages in the integration process. We argue that (a) the generally polycentric character of the Ruhr region and (b) the lack of a strategic steering authority on the regional level kept the city of Dortmund from changing its transport planning paradigm for quite some time. Consequently, the climate-friendly focus has only been recently developed in Dortmund. In turn, the general regional management combined with the monocentric nature of the Hannover Region initiated and facilitated the consideration of integrated planning at an early stage. Not only did the former make it easier to formulate cross-sectoral strategic climate targets for the whole region, but the strong power of the Hannover Region also enabled the alignment of all concerns with the strategic goals and the efficient coordination of local interests. Apart from the differences in formal regional coordination, both case studies still show a fairly high degree of sectoralisation in their administrations’ institutional design (polity). In conclusion, the mono- or polycentric nature of the two case studies does not automatically lead to better or worse integration in terms of politics – this simplistic understanding does not do justice to the complex structural conditions. However, the two relevant divisions in the Hannover Region are closely linked by an employee working for both sectors who thus integrates regional planning and transport planning in person. The politics dimension revealed the biggest difference between the two case studies: networks of cross-sectoral working relationships are much more extensive in Dortmund than in Hannover, where informal interaction mostly takes place in a topic-related way (see Figure 2).

We conclude that soft governance instruments in informal and flexible network structures (politics) are a necessary precondition and assumedly a first step towards integration, whereas political will, shared strategies (policy) and finally institutional design (polity) are necessary to ensure the real integration of planning approaches at some point. We identify true political will to be essential for realising a sustainable mobility future. This simultaneously represents a potential obstacle due to the assumed structural problem of democratic systems to implement long-term goals that do not generate short-term election votes. Leite, Leiren, Zibell et al. (2008: iv) argue that “the selfcontained political and administrative will to pursue a regional planning concept” was one of the main success factors in the Hannover Region. Without political will, a paradigm shift in transport planning simply cannot be realised since the administration cannot act in an integrated way without being supported by high level politicians (Interview H6). The interviews revealed that politicians in Dortmund prioritised the car for a long time, which kept the city from changing its transport planning paradigm and thus the focus of its policy dimension. We further assume that no institutional condition of the polity dimension will help if political consensus on sustainable mobility development is not existent.

We detected that both case studies are aware of the fact that traditional planning approaches with clear sectoral boundaries no longer work when targeting sustainable mobility development and that a more coordinated, integrated approach is required. Despite the case studies’ different starting situations, they can still learn from each other in some way. For Dortmund, the main field of action lies in the policy dimension, where overarching strategic targets for sustainable development at city-wide level – similar to the climate-related targets in the Hannover Region – would provide guidelines for further actions in all policy sectors. In this way, transport concerns could be embedded in a cross-sectoral context and additionally integrated into formal spatial plans. Further, more institutionalised intersectoral structures should be implemented in Dortmund. Especially the example of the employee working in two relevant divisions in Hannover can serve as a positive role model for Dortmund here. Similar structures could increase the intersectoral capacity and provide more possibilities for activity coordination.

Hannover, in turn, can learn considerably from Dortmund’s politics dimension. It seems that the Hannover Region is to some extent resting on its past success in developing high trust levels, collective responsibility and a common knowledge base between the relevant sectors. However, such collective behaviour needs to be reproduced over and over again in order to maintain efficient network structures. In this regard, Hannover can learn from Dortmund’s approach with regular cross-sectoral meetings and ongoing dialogue formats. In conclusion, the monocentric spatial embeddedness of Hannover shows some advantages in the institutional arrangements at a first glance, although Dortmund and its more informal cross-sectional approach provide insights into a less formalised integrated approach which is in no way inferior to the former.

Stead (2008: 146) argues that perfect integration is not possible and that a certain degree of incoherence is unavoidable in a political system involving a multitude of actors with different priorities, interests and instruments. Although there is wide consensus on integrated planning being favourable, Stead and Meijers (2009: 329) also identified generally poor understanding of the concept itself and of how it can be achieved. As a matter of fact, they referred to it as “fuzzy, rather like the concept of sustainable development” (Stead/Meijers 2009: 329). So, with our analysis of the integrated planning approaches in Dortmund and Hannover we aim to shed some light on these often-unseen practices behind closed doors, to make the concept of integration less fuzzy and easier to grasp.

A limitation to the comparability of the two case study cities can be identified with regard to the different governmental levels (regional and local) with authority over public transport planning; this leads to differences between the possibilities and capacities available to the cities for the implementation of integrated planning. In this regard, a stronger consideration of the vertical component of integrated planning, i.e. the study of structures and practices between governmental tiers, holds great potential for future research. Moreover, we only superficially touched upon the involvement of actors from outside the administration, e.g. the public and the public transport operating companies. Subsequent research could reveal the specific interactions in all existing networks and deal, for instance, with the effects of public participation on integrated planning processes. Moreover, further research is required in terms of a detailed analysis of the relevant interdependencies between transport and other sectors, e.g. retail or housing development.