The paradoxical nature of greening transportation: an analysis of tensions in buyer–supplier dyads

Abstract

Purpose

Contradictory sustainability priorities and perspectives among supply chain actors in greening transportation can be challenging. Several of these contradictions can be described as paradoxes (i.e. interests that are logical in themselves, but become irrational when perceived together). The aim of this study is to increase the understanding of paradoxical tensions hampering the greening of transportation in transport buyer–supplier dyads.

Design/methodology/approach

A case study method targeting greening transportation in two transport buyer–supplier dyads was applied, followed by an analysis with a point-of-departure in paradox theory.

Findings

Tensions related to performing, belonging, learning and organizing paradoxes in greening transportation were identified. These tensions arise as a consequence of actions, perspectives and other tensions, within three identified loci in individual companies and in dyads.

Research limitations/implications

By identifying examples of tensions through the lens of paradoxes in a particular setting, this study provides an increased understanding of why the transition toward green transportation goes slow, despite the high ambitions of involved actors. The suggested framework provides a novel contribution to the literature that further increases the understanding of tensions, by providing additional insights into where tensions arise and how actions, perspectives and tensions in one place of a locus spectrum can disseminate along that spectrum.

Originality/value

This study is original because it applies paradox theory and the four categories of performing, belonging, learning and organizing within the field of greening transportation, and in particular as a lens to study interactions between different actors.

Citation

Björklund, M., Forslund, H. and Ülgen, V.S. (2024), "The paradoxical nature of greening transportation: an analysis of tensions in buyer–supplier dyads", International Journal of Physical Distribution & Logistics Management, Vol. 54 No. 6, pp. 532-557. https://doi.org/10.1108/IJPDLM-11-2023-0406

1. Introduction

If companies are to be part of the solution to one of today’s most complex problems—sustainability—they need to approach business and society as interrelated (Montabon et al., 2016; Slawinski and Bansal, 2015). Sustainability cannot be created by one company alone, companies also depend on the environmental performance of their suppliers (Awan, 2019; Gimenez and Sierra, 2013; Multaharju et al., 2017; Tachizawa and Wong, 2014; Villena and Gioia, 2018). Despite the early recognition of the importance to consider the environmental impact from both product and transport suppliers (see, e.g. Wu and Dunn, 1995), few studies on supply chain sustainability consider the transport sector (e.g. Ashraf et al., 2022; Centobelli et al., 2020). Furthermore, few studies focus on transport suppliers specifically, despite their presence in each supply chain interface (Multaharju et al., 2017; Piecyk and Björklund, 2015; Wu and Dunn, 1995). Sustainable transportation has for a long time been put forward as an important aspect of sustainability (Aronsson and Huge-Brodin, 2006; McKinnon and Woodburn, 1996; Multaharju et al., 2017) considering transportation’s share in global greenhouse gas emissions, and its emissions of hazardous particles and noise (e.g. McKinnon et al., 2015). Transport suppliers (i.e. those responsible for operating freight transport) are often held accountable for any negative environmental impact (Evangelista, 2014). In taking responsibility, however, transport suppliers are also dependent on their customer, the transport buyer (Forslund et al., 2022; Sallnäs, 2016). Transport buyer’s and supplier’s greening of transportation, therefore, deserves more research attention.

Attempting to improve sustainability in supply chains involves multiple paradoxical tensions (Hahn et al., 2018; Montabon et al., 2016). These tensions can surface between contradicting key performance indicators (KPIs) on cost and environment (Pålsson and Sandberg, 2022; Xiao et al., 2019) and between different stakeholders’ competing interests (Montabon et al., 2016; Schad et al., 2016; Ülgen, 2020). Sustainability involves the recognition of diverse and often conflicting interests from a wide set of stakeholders. For companies, this implies the need to simultaneously address multiple desirable but contradictory interests. Some of those contradictions may be paradoxes, interests that are logical in themselves but become irrational when perceived together. Paradoxes imply tensions that persist over time (Hahn et al., 2018; Schad et al., 2016; Smith and Lewis, 2011). In practice, on an aggregate level, tensions can manifest when supporting certain greening initiatives and not others while considering equity and fairness. Sustainability reports, from both transport buyers and suppliers, often discuss the tensions of balancing economic, environmental and social sustainability. An example is when the use of electric vehicles is not possible based on their cost. According to Van der Byl and Slawinski (2015), the paradox lens offers a way to recognize the interrelatedness of contradictory sustainability elements and the paradoxical tensions created between them. Understanding tensions provides an increased understanding of why the transition toward green transportation goes slow, even when involved actors have high environmental ambitions (Sallnäs and Huge–Brodin, 2018). Previous studies give some insights into why environmental practices are diminished or lost between transport buyers and suppliers, by providing examples of different tensions. However, the research can be described as scattered and lacking a holistic overview. Tensions deserve to be examined in more detail. In order to contribute to a better understanding of these tensions and the green transport context, which is in line with the suggestions for further transport-oriented research proposed by Ashraf et al. (2022), the aim of this study is:

To increase the understanding of paradoxical tensions hampering the greening of transportation in transport buyer–supplier dyads.

The paradoxical tensions can be understood in terms of the four categories performing, belonging, learning and organizing (Smith and Lewis, 2011). Such paradox categories have previously been applied for studying tensions in logistics and Supply Chain Management (SCM) (e.g. Sandberg, 2017; Maalouf and Gammelgaard, 2016). The understanding of paradoxical tensions can also include where they arise (Zehendner et al., 2021), i.e. their loci and why. It is acknowledged that tensions are intertwined with other tensions and contribute to new tensions (Maalouf and Gammelgaard, 2016; Jarzabkowski et al., 2013). Such details on why and where tensions arise can provide a deeper understanding of paradoxical tensions hampering the greening of transportation. This leads to the following research questions:

RQ1.

How can paradoxical tensions hampering the greening of transportation be characterized in terms of performing, belonging, learning and organizing?

RQ2.

Where—in what loci—and why do paradoxical tensions, hampering the greening of transportation arise?

This study takes its starting point in the literature on greening transportation from the perspectives of transport buyers and suppliers, their challenges and tensions and paradox theory. A dyadic case study brings empirical insights into the studied phenomena, thereby contributing to the limited research on sustainable SCM using empirical data from more than one supply-chain actor (Forslund et al., 2022; Zehendner et al., 2021). In Section 4, empirically identified paradoxical tensions are presented, and paradox theory is applied to bring detailed insights into the different tensions by characterizing them and suggesting propositions (i.e. answering RQ1). With a point of departure in the loci and reasons why tensions arise presented in the empirical findings, Section 5 further analyzes and discusses common reasons why tensions arise and how tensions may cause tensions in other loci. Propositions are suggested (i.e. answering RQ2). A framework is presented, providing a holistic overview of tensions hampering the greening of transportation. Furthermore, loci are identified and novel insights into why tensions arise are presented. Finally, conclusions, contributions and aspects to be addressed in future research are presented in Section 6.

2. Frame of reference

2.1 Greening transportation

In sustainable transport research, most research is either buyer- or supplier-focused and rarely has a dyadic empirical scope (Jazairy et al., 2021; Sallnäs, 2016), even if some studies claim that triads should be the minimum scope (e.g. Larson and Gammelgaard, 2001; Prataviera et al., 2023). Transport buyers and suppliers are often studied separately, which suggests their complex dyadic interactions are under-researched (Jazairy, 2020). Transport suppliers cannot drive change by themselves, they are dependent on the involvement of transport buyers (Wu and Dunn, 1995; Aronsson and Huge-Brodin, 2006), as greener transport services often are developed in the interface between the buyers and suppliers (Martinsen and Huge–Brodin, 2014). Huge–Brodin and Evangelista (2020) concluded that smaller transport suppliers adapt to their most demanding buyers, whereas buyers are known to design transport services based upon offers from transport suppliers, which illustrates those dependencies (Sallnäs and Björklund, 2020).

Suppliers might be ahead of buyers when it comes to transport-related sustainability initiatives (Forslund et al., 2022). Pressure from stakeholders such as governments and customers has created opportunities for transport suppliers to include environmental considerations in the business strategy and consider environmental issues as service offers (Sallnäs and Björklund, 2020), such as offering environmental reporting (e.g. Forslund et al., 2022). Transport suppliers have taken several managerial initiatives in greening transportation, e.g. increasing fill rates by changing schedules and reallocating transport capacities (Rogerson and Santén, 2017). Also, a transition toward greener transportation technologies through increased use of renewable fuels, the use of more efficient engines (Jazairy et al., 2021) and modal shifts from, e.g. road to sea (Rogerson et al., 2020) or rail (Monios and Bergqvist, 2016; Sallnäs et al., 2022) is present.

In line with traditional purchasing, transport purchasing can be described as a process with sequential phases and activities. The first part of the purchasing process—sourcing—includes defining buyer requirements, identifying and evaluating suppliers and contracting (see, e.g. Zimmer et al., 2016). Environmental requirements for transportation can be CO₂ emissions (Forslund et al., 2022) or fuel types and engines (Martinsen and Björklund, 2012). Gathering sustainability information on potential suppliers’ transportation includes such activities as surveys to potential suppliers, supplier visits and requests for proposals (RFPs) (Jazairy, 2020). The environmental aspect can be included in the contract agreement (see, e.g. Björklund and Forslund, 2013) or have little to no influence on the selection of suppliers or the content of the written contract (Wolf and Seuring, 2010). The second part of the process—supply—is associated with the operational execution of transportation (Jazairy, 2020): the development thereof and the ordering and monitoring of the service delivery (Zimmer et al., 2016). Monitoring sustainability performance includes activities to secure compliance with the requirements of the contract agreement through audits, for example (Zimmer et al., 2016), as well as continuous follow-up of transport suppliers’ fuel use or CO₂ emissions (Björklund and Forslund, 2013). Furthermore, buyers who include environmental performance in transport contracts do not necessarily consider how to measure performance and how to handle non-compliance (Björklund and Forslund, 2013). Jazairy (2020) also identified a lack of monitoring of environmental performance in purchasing greener transportation. Supplier monitoring can be an important basis for supplier switching, as well as a trigger for supplier development activities (Ülgen, 2020; Zimmer et al., 2016). Gimenez and Sierra (2013) put forward the importance of simultaneously applying monitoring and collaboration to achieve the highest environmental output. Villena and Gioia (2018) noted that buyers often employ more collaborative as well as monitoring-based approaches with their first-tier suppliers, whereas the cascading of requirements and monitoring is seldom utilized for lower-tier suppliers.

2.2 Tensions in greening transportation

Even if prior research mention tensions between transport buyers and suppliers in their strive toward green transportation, knowledge can be described as scattered and lacking a holistic overview. The slow green upkeep in practice can be a consequence of the buyer’s and supplier’s different prioritizations (Sallnäs, 2016; Sallnäs and Huge–Brodin, 2018). The transport actors’ different levels of green awareness may also cause tensions that hinder green upkeep (Wolf and Seuring, 2010). Buyers might engage in actions aimed at greening transportation with the primary purpose of accessing the environmental competence of the supplier (Sallnäs and Huge–Brodin, 2018). Martinsen and Björklund (2012) proposed that the transport suppliers perceive themselves to be ahead of buyer requirements. The buyer’s environmental requirements tend to be weaker and less specific, and at the same time more general and standardized, than the more concrete and detailed offerings from transport suppliers (Huge–Brodin and Evangelista, 2020). The type of requirements placed by the buyer can even lower environmental performance (Jazairy, 2020).

Environmental sustainability is a concept not easily operationalized or captured, the KPIs applied and views on what they constitute vary largely (Piecyk and Björklund, 2015). As do the different ways of assessing environmental impact (Sallnäs and Björklund, 2020). Arvidsson (2013) was early to recognize paradoxes related to improved efficiency in a study of green urban transportation, both within and between sustainability dimensions, such as that improved load factor can negatively impact both total cost and emissions. Moncef and Dupuy (2022) studied paradoxes between economic, environmental and social sustainability perceived by different kinds of transport suppliers and generated by the logistics management of transport buyers. One example is when economic concerns of logistics management clash with social and environmental promises in last-mile logistics. The understanding of sustainability may be a collection of individual views, rather than a homogenous company view (Busse et al., 2016), which complicates the goal setting and impedes sustainability performance improvements. Finally, when expanding this dyadic view to the transport supply chain or network, the mentioned challenges in coordinating various interests, practices and logics multiplies, based on the number of relations that the buyer (Tachizawa and Wong, 2014) and supplier (Ülgen, 2020) need to manage.

2.3 Paradox theory for the understanding of tensions

Smith and Lewis (2011) argued that companies face multiple paradoxical tensions that may be better addressed as interrelated contradictions, not merely as being interrelated or contradictory. “Tensions” refers to contradictory requirements, whereas “paradox” refers to the recognition that such tensions are interrelated and should therefore be simultaneously considered (Slawinski and Bansal, 2015). Smith and Lewis (2011, p. 382) defined paradox as “contradictory yet interrelated elements that exist simultaneously and persist over time.” This highlights two core characteristics of paradoxes: contradiction and interdependence (Schad et al., 2016). The paradox lens offers a way to understand organizational tensions by drawing attention to those oppositional elements and the challenges related thereto (Schad et al., 2016). In logistics and SCM research, the awareness of tensions among different goals and strategies is not new. Tensions in SCM research are, however, primarily regarding operational performance, whereas more strategic tensions have received relatively less attention (Sandberg, 2017).

The paradox lens is recommended for exploring the tensions inherent in sustainability (Van der Byl and Slawinski, 2015). “A paradox perspective on corporate sustainability accommodates interrelated yet conflicting economic, environmental, and social concerns with the objective of achieving superior business contributions to sustainable development” (Hahn et al., 2018, p. 237). According to Xiao et al. (2019), purchasing managers would typically pursue traditional purchasing targets such as delivery reliability, quality and cost, while sustainability managers—who are in charge of implementing and auditing sustainability practices at the suppliers—would give preference to other opposing aspects. Accepting tensions and exploring contradictory interests from the perspective of both/and possibilities, instead of either/or solutions as with trade-offs, fosters strategies that attend to different sustainability objectives simultaneously, even if they are conflicting. This allows for creative solutions to complex problems such as sustainability (Hahn et al., 2018; Smith and Lewis, 2011; Van der Byl and Slawinski, 2015) and the ability to address environmental issues, even in the absence of immediate business benefits or when the business benefits remain unclear (Hahn et al., 2018).

2.4 Four categories of paradoxes

Several researchers have studied paradoxes and tensions that apply to the performing, belonging, learning and organizing categories, building on the work of Smith and Lewis (2011). Performing paradoxes address goals in organizations and arise out of a multitude of internal and external stakeholders with potentially contradictory requirements directing organizations to try to follow competing strategies and attain conflicting goals and objectives (Schad et al., 2016; Smith and Lewis, 2011). Those contradictions can lead to tensions for individual actors as they may need to perform contradictory roles and activities while struggling to respond to either the conflicting requirements within their own roles or the conflicting requirements of others with whom they share tasks (Jarzabkowski et al., 2013). Sustainability and a simultaneous focus on economic, social and environmental objectives often result in sustainability performing tensions (Hahn et al., 2018). Xiao et al. (2019) illustrated those tensions, where sustainability goals are suppressed for the sake of cost reductions, both among purchasing managers and sustainability managers in line with how the conflicting objectives are typically prioritized (Montabon et al., 2016; Sallnäs and Huge–Brodin, 2018). According to Pålsson and Sandberg (2022), performing paradoxes are often manifested or enforced in contradictory KPIs. Sandberg (2017) noticed the performing paradox between “traditional” logistics performance KPIs of cost and service vs green KPIs (e.g. CO₂ emissions). Similar to other researchers, Moncef and Dupuy (2022) noted that they found performing paradoxes to be the dominating category.

Belonging paradoxes address identity and interpersonal relationships. They are tensions of identity, values and beliefs in organizations (Jarzabkowski et al., 2013; Smith and Lewis, 2011). Tensions may arise between individual action and group belonging and regards individual and collective affiliations and competing values and roles (Schad et al., 2016; Tóth et al., 2022). Tensions can surface among different hierarchical levels, from individuals to companies to supply chains (Pålsson and Sandberg, 2020) or horizontally between cross-functional teams and functions (Maalouf and Gammelgaard, 2016). This also shows that tensions can arise in different loci such as on a particular hierarchical level such as top management or more generally within one company (in line with Sandberg, 2017). In a sustainability context, tensions occur when organizational members hold competing values and identities regarding environmental matters (Hahn et al., 2018). In interactions, actors struggle to reconcile the values and beliefs of their immediate group with those of other groups and/or the overall organization (Jarzabkowski et al., 2013). Actors may be responsible for achieving different sides of the paradox, yet simultaneously be accountable for overall organizational performance (Smith and Lewis, 2011).

Learning paradoxes address knowledge and learning in organizations and arise when dynamic systems change, renew and innovate (Smith and Lewis, 2011). Change involves tensions between building on past knowledge, while at the same time, needing to destroy it to move forward and creating new future ways of working. New ideas challenge current and historical knowledge. Learning paradoxes thus regard tensions between current and new knowledge and understandings and between stability and change (Maalouf and Gammelgaard, 2016; Pålsson and Sandberg, 2020). Tóth et al. (2022) illustrated learning paradoxes with the information superabundance that arises when customers gain access to increasingly vast information. Detailed reports were described as both a blessing and a curse, as it gave transparency into every deviation, which could damage customer perceptions of quality, even when the deviations did not affect product performance.

Organizing paradoxes address processes in organizations. Organizations encompass multiple sub-systems that act independently and are still part of an interdependent overarching organizational system (Jarzabkowski et al., 2013). Competing organizational design logics can cause tensions between, for example, collaboration and competition, controlling or directing and empowering, alignment and flexibility, centralization and decentralization (Pålsson and Sandberg, 2020; Smith and Lewis, 2011). Organizing paradoxes may be generated by separating potentially contradictory areas into different divisions (Jarzabkowski et al., 2013). It can regard the question of whether sustainability should be fully integrated into the core structure of the organization (e.g. being at the mercy of the dominant commercial logic) or be completely separated and potentially marginalized in the outer reaches of the organization (Hahn et al., 2018). The organizing paradox can be illustrated by the degree of collaboration between a buyer and supplier. Fewer-but-closer supplier collaborations can create advantages in terms of continuous improvements and increased control of sustainability-related issues but also disadvantages in terms of increased dependency on suppliers, which can lead to decreased negotiation power and lock-in effects (Sandberg, 2017).

To sum up, the four categories of tensions (i.e. performing, belonging, learning and organizing) provide a basis for addressing RQ1 on how identified paradoxical tensions can be characterized. While the literature provided some scattered insight into loci – where tensions arise, such as on the organizational or supply chain levels or between different functions, little insights were gained related to RQ2 on why tensions arise and more holistically the different loci that are in play.

3. Methodology

3.1 Research design and sampling

To explore a seldom-examined phenomenon—in this case, paradoxical tensions in transport buyers’ and suppliers’ strive toward green transportation—it is important to interact with and gain in-depth empirical input and understanding of the unique aspects of the phenomenon and the situation, in line with Bryman and Bell (2022) and Merriam (2009). These demands can be met by a qualitative case study with interviews complemented with information from, e.g. Website and available public sustainability reports, in line with recommendations by, for example, Bryman and Bell (2022).

The supply-chain manager of one transport buyer identified as a sustainability leader in its industry was approached. Based on our description of experiences and the type of respondents needed, additional respondents were identified, applying a common non-probability, indirect sampling method known as snowball sampling (Bryman and Bell, 2022). By targeting two of the buyers’ most sustainability-oriented transport suppliers, two contractual buyer–supplier dyads were addressed. The chosen suppliers and their innovative greening–transportation projects are mentioned in the buyer’s sustainability report 2021. The anonymized companies, their characteristics (center left for their total operations, center right for the studied relationship) and respondents (with abbreviations) together with other information sources are presented in Table 1.

3.2 Data collection and analysis

A semi-structured interview guide (see Appendix) was constructed based on the literature and sent in advance to each respondent in preparation. Zoom interviews, each lasting 60–90 min, were conducted with the respective respondents. To ensure insights based on relevant responsibilities, respondents were first asked to describe their current position, title and professional background. Open questions were followed by probing to ensure concepts identified in the literature were covered. Notes were taken by each of the researchers and were consolidated (thus applying investigator triangulation), making up the raw empirical data.

The analysis followed Carney’s (1990) three-level ladder of analytical abstraction. All interview notes were first coded into the four categories of paradoxes. All involved researchers read the raw empirical data to reach a consensus regarding what types of statements and data were captured by the different paradox categories. This resulted in the identification of first-order empirical examples, presented in condensed form. The empirical examples in each category were then analyzed separately and aggregated, resulting in themes in the form of second-order tensions. The applied inclusion criterion is that the tension is present in both dyads. However, prominent tensions not identified in both dyads, are included when the lack of presence for the second dyad could be understood by one actor’s characteristics. The third level included the development of propositions taking a point of departure in common patterns identified among the tensions.

To secure trustworthiness, credibility was strengthened by letting respondents review their “case descriptions” to corroborate the empirical findings with the respondents’ perceptions (Halldórsson and Aastrup, 2003; Diefenbach, 2009). Credibility was also strengthened by involving several interviewees from different case-relevant functions in each organization and targeting them with the same issues and by data triangulation, adding the sustainability reports as a source of data in line with, e.g. Diefenbach (2009). Investigator triangulation involving three researchers in all stages of the research process and the use of citations to highlight links between data sources and the contributions thereof strengthens the study’s confirmability and credibility. Transferability has been sought by describing the context surrounding the study, for example, and by clearly outlining the study’s implications to literature and practice and stating the study’s limitations and future research area. Ensuring that all respondents addressed the pre-determined interview areas/topics supported the dependability of the study.

4. Empirical findings and analysis – tensions hampering the greening of transportation

This study reveals several paradoxical tensions hampering the greening of transportation, arising in the studied transport buyer–supplier dyads. Following Carney (1990), in this section, these tensions are described and structured according to the four categories performing, belonging, learning and organizing. Empirical examples for each tension are presented in Figure 1.

4.1 Performing-oriented tensions

The tension of hampering requirements stems from the buyer’s high environmental ambitions and results in complex bureaucratic sourcing processes that include a combination of actions such as RFPs, surveys and visits, instead of focusing on only one activity as described in Jazairy (2020), and a vast number of requirements to fulfil. “There is a lot the suppliers could be disqualified by. […] Resources are required just to be part of the tendering process […] [S]ome [small] suppliers are having a tough time” (TB:PM). One explanation for the use of combined activities is that it provides a more nuanced picture of the supplier’s green performance. It does call for more administrative resources which in turn creates tensions. As Huge–Brodin and Evangelista (2020) observed, a possible consequence of smaller transport suppliers adapting to their most demanding buyers would be that resource-weak suppliers need to adapt to very complex, resource-demanding processes and take resources from activities intended for greening transportation. For some, this will likely result in green suppliers, as a consequence of their small size, abandoning ambitious buyers. Also, the suppliers note hampering requirements, such as the resource-intensiveness of the buyer’s new control-based monitoring, stemming from actions such as placing strategic requirements for better visibility and control, which includes requests for receipts to verify the contracted environmental performance. This is exemplified by “The administrative cost for submitting the sub-contractors’ receipts for fuel is quite high” (TS2:SS). This tension is also acknowledged by TS1.

Contradictory sustainability KPIs are identified due to conflicting economic, delivery service and environmental goals. An example is when the use of electric vehicles is not possible based on their cost, thus hindering the achievement of the CO₂-reduction targets, as mentioned on TS2’s website. The goals are manifested and enforced in and by contradictory KPIs, as highlighted by Pålsson and Sandberg (2022), and the economic KPIs tend to supersede the environmental. A tension was also found between “traditional” logistics-performance KPIs and environmental-performance KPIs. According to TS2:KAM, “Another transport provider, with a 10% longer lead-time [than specified] and a 7% lower price [than ours] got the business [despite lead-time being a requirement in the tender].” Despite placing exact requirements for certain KPIs, such as lead times, buyer actions to adjust and balance the different KPIs, e.g. lead time vs. price, affecting the outcome of the sourcing decision, and “affecting their [the buyer’s] central KPI [CO₂ reductions] negatively.” This sends mixed messages to the supplier and tensions surface between buyer and supplier. Also, within the buyer, the tension of contradictory sustainability KPIs arises based on the need to manage the complex environmental sustainability area, not as economic sustainability, captured in only one parameter. “Unfortunately, the sustainability goals are not monetary. It is easier for purchasing—they have one single KPI [cost]” (TB:SPM). Purchasing also acknowledges this tension but sees it differently: “We make the best trade-off we can based on the CO₂ goal and the budget we have available to reach it” (TB:PM). Contradictions in relation to sustainability KPIs are acknowledged by TS1 related to what is included in the main environmental KPI, CO₂-reduction. “The buyer’s focus is on vehicle emissions (e.g. fuel or engine type), we focus more on other means” (TS1:SM), referring to, e.g. fill rates or eco driving. This example indicates tension within the environmental KPIs, manifested as narrower or broader KPIs. This impacts the buyer’s assessment of the supplier during sourcing decisions and the value attributed to the supplier throughout the contract duration. The findings of contradictory KPIs expand the findings of Sandberg (2017) from a global product-sourcing context, and Moncef and Dupuy (2022) from a last-mile logistics setting, to a European transport-sourcing context.

Parts–whole tensions arise as a consequence of independent subsystems being part of an interdependent overarching system, as discussed in Jarzabkowski et al. (2013). In this study, the empirical result revealed several such tensions categorized as performing tensions, related to different forms of system boundaries, such as national or operational boundaries. “There is different legislation in different countries. This can work against you” (TB:SD). Even if legislation is logical from a national perspective, it creates tensions for companies having operations, customers and suppliers in several countries. Another example considers the suppliers’ attempt to consolidate goods from different buyers with different sustainability requirements to reduce transport demand. “The different buyers want to control their own pallets; they want to believe there are more dedicated shipments than there are” (TS2:ES). Parts–whole tensions are also noted by TS1 in that the buyer does not always acknowledge the need to balance flows and avoid empty return transports. This can likely only be managed if the buyer acknowledges, accepts and acts as just one part of the supplier’s transport system. Otherwise, there is a risk that their requirements and sourcing decisions lead to supplier measures counteracting or even increasing total CO₂ emissions by focusing on implementing greener trucks on inefficient, unbalanced flows, as put forward in TS2’s 2021 sustainability report. The parts–whole tensions identified in this study hence relate to system boundaries outside the scope of a single organization.

4.2 Belonging-oriented tensions

The empirical evidence indicates that tensions of identity are visible on multiple levels, based on differences in perspectives (not manifested as actions) and values related to sustainability. This study’s supply-chain perspective allowed for interorganizational tensions to present themselves. The first belonging-oriented tension is sector identity, identified as an inter-organizational tension between the buyer and suppliers. As a heavy-vehicle manufacturer, the buyer’s focus on the sustainability of vehicles is observable from the buyer’s website and sustainability report. The sustainability focus and offer of TS1 are broader and range from the planting of trees and clean energy use to training programs for drivers and securing a high fill rate. “We are focusing on other things besides the truck” (TS1:SM). This broader view can be a result of different priorities (Sallnäs and Huge–Brodin, 2018). The supplier’s greening activities, in addition to the vehicle emission-related performance in the buyer’s flows, are not generally considered during sourcing, however, “A high fill rate can still benefit a carrier during supplier selection as a soft value” (TB:SPM). Both suppliers note a contradiction in the buyer’s roles as a vehicle manufacturer and transport buyer. The suppliers perceive the buyer’s lack of understanding of transportation procurement based on their reluctance for longer contracts. “It hinders the sub-contractors from investing in environmentally friendly vehicles. The ‘buyer’s vehicles’ are part of the sustainability solution” (TS2:ES).

The tension hierarchical identity is an intra-organizational tension identified within the buyer (between the buyer top management and different business functions) and within the buyer group (between the headquarters and the buyer). The first example manifests as a gap between the highly sustainability-ambitious top management of the buyer and the purchasing function. According to TS2:SS: “I’ve been at several external seminars, it’s interesting to hear […] high ambitions from the top, but the purchasing process is not really sustainability-focused. It is more focused on logistics, lead times, and price.” This, in turn, creates tensions in the form of unclarities between the buyer and TS2. Hierarchical identity tensions are also manifested in a gap between the top management and the sustainability and sourcing functions in view of the overall guiding KPI, where the functions wish for additional finer measures that would capture improvement efforts outside the CO₂ reductions related to engines and fuels. The second example of the tension, as mentioned by TB:SPM, exists between the less sustainability-focused headquarters and the buyer, which is exhibited in differing sustainability requirements from sister companies. “We are part of the same group, where sister companies have, in part, lower requirements when sourcing transportation. Some transport suppliers are suppliers to both.” Both these tensions enrich the findings of Tóth et al. (2022) and their “professional identity” and Schad et al. (2016) regarding competing collective roles. Our study did not identify any hierarchical identity tensions experienced by TS1, which can be related to their characteristics of being a smaller transport supplier. The larger supplier, TS2, is the one to bring the tensions forward, likely as an effect of them interacting more with the buyer on a strategic level.

The final tension within the belonging paradox is that of functional identity, an intra-organizational tension identified within the buyer. It is illustrated by the differences in values and perspectives regarding sustainability between functions “Purchasing can push that an okay supplier is good, but we [sourcing] do not want to look only at price” (TB:SPM). This further highlights a contradiction between priorities based on different perspectives of what constitutes a good enough supplier. The tension of functional identity is also recognized by TS2:KAM: “I was at a workshop with the sustainability function [of the buyer] with our global innovation team. Purchasing was not there. There is a gap between sustainability and purchasing.” One reason the purchasing function was not present could be that they value sustainability less than the sustainability function. According to TB:SD, the buyer is prepared to pay more for sustainable transportation. TS1:SM see the situation differently: “More sustainable trucks are more expensive, this should be supported by purchasing. There should be a consensus, a common interest within the buyer.” This indicates contradictory perspectives and words, resulting in different practices between buyer functions. Similar claims are made by TS2. With support from Busse et al. (2016), one explanation for the differing views could be that the understanding of sustainability is a collection of individual views rather than a company view, which in turn creates the identity of different functions.

4.3 Learning-oriented tensions

Inertia in purchasing process are learning tensions surrounding green work. This process is designed by purchasing with directives, based on the perspectives of the buyer group headquarters. The purchasing process is perceived as rigid by those directly involved in greening transportation. The rigidity is exemplified by initiatives, such as modality changes or fuel switches, which, as suggested by Rogerson and Santén (2017) and Jazairy et al. (2021), cannot be implemented during the contract period as they are part of the contracted delivery. “This is flabbergasting, really! If we want to work with development […] then we need to terminate the contract and go to tender. If we do this, no one wants to work with us” (TB:SPM). To allow for greening of transportation, the sustainability and sourcing functions of the buyer favors longer contract periods, whereas purchasing prefers and ensures shorter contract periods. TS1:SM notes short, as well as unpredictable contract periods “it might be prolonged 1–2 years, or they [the buyer] say ‘we are going to tender’.” According to TS2, subcontractors ask for five-year contracts, instead of one-to-three years. Short or unpredictable contract periods mean that larger leaps toward greener transportation such as electrification become too risky for the supplier, giving additional insights to Forslund et al. (2022), by highlighting contract duration as a key hampering factor. The contradiction between the static process and a longer contract period is clear. One part of the explanation of the buyers’ reluctance to work with longer contract periods can be found in its powerful position that enables them to not be involved in risk sharing, which otherwise longer contract periods can facilitate (Jazairy, 2020).

Inertia in green upkeep refers to tensions within the core of greening-transport knowledge. According to the buyer, suppliers “know” from earlier experience that a green tender means that most buyers want low costs, i.e. a tension between old knowledge and new. Suppliers then provide offers with less innovative, and therefore less expensive, solutions slowing down the transition toward green transportation, creating tensions between what is (such as the type of fuel used) and what could be. Or, as expressed by TB:SPM, “No-one wants to say that greening is more expensive.” This is expected to be particularly actualized during each recession, which can serve as an explanation of why this tension would resurface over time. The buyer’s slow knowledge-building regarding the green solution suggested by TS2—insetting—has delayed its implementation. Insetting, according to TS2’s webpage and sustainability report, provides the buyer with a fossil-free transport solution. “We are happy to see that after two years of discussions the buyer is onboard from next year” (TS2:ES). This delay can, in part, be attributed to buyer-internal resistance, due to a belief that a different follow-up methodology would be required to verify greening. The inertia in green upkeep can also be understood from TBs reactive financial support for the development and tests of new greener fuel solutions, exemplified by TS1:SD: “We [the supplier], have to speak about compensation with purchasing.” The inertia can be a result of different prioritizations among which greening practices to implement (Sallnäs, 2016) or that the understanding of sustainability differs between individuals in a company (Busse et al., 2016). Another explanation to the inertia in green upkeep can be the result of network effects (Tachizawa and Wong, 2014) as the buyer has several transport suppliers that offer different and potentially contradicting, greener solutions. This results in buyer difficulties adapting to different solutions.

4.4 Organizing-oriented tensions

One tension can be found in the strive toward the buyer-controlled flexibility of the supplier. This tension is between controlling or empowering the supplier to deliver the required service in the way they see fit (e.g. Smith and Lewis, 2011). The buyer’s desire to control the delivery of greener transportation makes them want the transparency of any sub-contractor involved in the service delivery, as noted by Jazairy (2020). Simultaneously they are aware of the type of difficulty this may mean to the supplier, thereby displaying an important understanding of the paradoxical tension they are facing. “When the tender is finalized, we also want a list of who will be driving, but this is not easy, their network is dynamic” (TB:SPM). The supplier’s need for flexibility in supply was also acknowledged by TS1:OM: “The sub-contractors are more commonly used if the volumes go up quickly,” and in the sustainability report of TS2 (2021), stating that they offer their customers flexible solutions to respond to different supply-chain needs. Another example of the buyer’s strive for control is to keep the supply chain short and just communicate with the contracted supplier, a situation recognized from another study of greening transport supply chains (Forslund et al., 2022). A short supply chain is in line with recommendations by Villena and Gioia (2018), who emphasized the risk of lower-tier suppliers. In their study, they focused on sub-suppliers in countries with a history of social and environmental problems, unlike the context in which TS2 operates, where subcontractors are often required to cater to fluctuating demand. TS2 highlighted the challenges of transferring requirements to their sub-contractors. The buyer’s unwillingness to acknowledge their presence, and the more complex reality the supplier faces, risks the creation of additional tensions toward the buyer.

The second tension, headquarters’ involvement, relates to the buyer and buyer group’s corporate and directives structures (intra-organizational). Some functions within the buyer have a clearer directive and reporting structure with headquarters, whereas others report to the buyer’s top management. This leads to functions having different attitudes toward headquarters, and tensions therefore build up between organizational levels and functions: “I want purchasing to challenge the headquarters themselves, they need to start working in a different way. Currently they [purchasing] are rubbing them [headquarters] the right way” (TB:SPM). This tension is related to delegation and control, as discussed in Lüscher and Lewis (2008) and Smith and Lewis (2011). Interestingly, supplier assessments and prequalification in our study are delegated to the buyer’s sourcing organization, yet they remain under headquarters’ control, as the directives given to purchasing stipulate the criteria and responsibility for supplier selection. This tension further affects belonging tensions between hierarchical levels as well as between functions. This buyer-internal organizing tension is not perceived by any of the suppliers. As it is understood to be the ‘source’ of the hierarchical identity tension between top management and purchasing and the functional identity tension between, e.g. sourcing and purchasing (both in the belonging category) it is included here despite not fulfilling our initial inclusion criterion.

4.5 Propositions related to the characterization of tensions

To take the final step of the three-level research model by Carney (1990), propositions related to the characterization of tensions are suggested. Greening transportation is a broad and complex matter, that can be hampered by several tensions in all four paradox categories. Tensions, have been found in the more general management studies of paradoxes (e.g. Schad et al., 2016), in the general SCM and logistics literature (Sandberg, 2017; Maalouf and Gammelgaard, 2016), as well as in the green SCM and logistics/transport literature (Sallnäs and Huge–Brodin, 2018). With tensions identified in all four paradox categories, some of our findings, are similar to those of for example Xiao et al. (2019), where sustainable performance goals are suppressed to lower costs; Sallnäs and Huge–Brodin (2018) who found different priorities in the greening of transportation among actors with different organizational belonging or Jazairy (2020) who observed shippers using their power in the greening of transportation to decrease their risks. For some categories, such as learning, the tensions are said to be difficult to observe as they are strongly intertwined with other tensions in other categories. Nevertheless, they contribute to the manifestation of those other tensions (Maalouf and Gammelgaard, 2016; Jarzabkowski et al., 2013). In our study, learning tensions were readily identifiable, however, the findings do suggest that these learning tensions are, to some extent, the result of actions and perspectives within other categories than learning. Our findings indicate that tensions are rater easily identifiable across all categories and a first proposition (P1) is therefore suggested: Tensions in all four paradox categories hamper the greening of transportation.

Tensions in one category can be closely related to tensions in another category, such as when the ’headquarters’ involvement’ (organizing category) is understood to cause tensions between, e.g. buyer functions (functional identity). Such interdependencies have been previously identified by, e.g. Lüscher and Lewis (2008) where systemic contradictions within organizational structures created performing and belonging tensions, as individuals were met with mixed messages about organizational values. Such mixed messages may become stable patterns affecting interactions over time. Such a connection, and plausible causation, has, in this study, only been identified from the organizing category to other categories, why a second proposition, based on our empirical data, (P2) is suggested: Tensions in the organizing category create tensions in other categories.

The literature on greening transportation sometimes differentiates between issues of managerial and technical character (e.g. Jazairy, 2020; Rogerson and Santén, 2017). In terms of vehicle technology, no examples of missing, incomplete or incompatible technologies that initiate tensions were expressed in the dyads. Issues of managerial character, such as differing views on, for example, the importance of fill rate (i.e. belonging category, sector identity tension) and the ambiguity of the buyer’s prioritization between delivery service and sustainability (i.e. performing, contradictory KPI tension) serves to illustrate that predominantly issues of managerial character initiate tensions, yet have the potential for greening transportation. The third suggested proposition (P3) is: Issues of managerial rather than technological character initiate tensions that hamper the greening of transportation.

5. Analysis and discussion – why and where tensions arise

Three common patterns have been identified in the empirical material regarding why tensions hampering the greening of transportation in transport buyer–supplier dyads arise. First, tensions can arise due to actions, such as defining requirements or decisions made. Second, tensions can arise due to perspectives of functions/companies, such as how they value sustainability in relation to other objectives or how different aspects of sustainability are valued. Finally, tensions can disseminate and generate other tensions. Because of this, dissemination can occur in several stages, such as an activity leading to a tension that results in the emergence of new tensions. Tensions can also be understood based on where they arise—their loci—e.g. on strategic or operational level (Sandberg, 2017) or at company or supply chain levels (Pålsson and Sandberg, 2020; Zehendner et al., 2021). It should be acknowledged that conceptualizing why (caused by actions, perspectives and/or other tensions) and/or where – in what of three identified loci spectra – paradoxical tensions arise, not was found in earlier literature in the area of greening transportation (such as Sallnäs and Huge-Brodin, 2018), the focus was rather on how to mitigate or relax tensions. Three, not mutually excluding loci of tensions were identified among the presented empirical findings, each of which is understood as a spectrum. (1) From company internal to supply chain, (2) From sourcing to supply (in the purchasing process) and (3) From strategic to operational levels.

Table 2 illustrates how actions, perspectives and tensions (noted in parentheses after each empirical example) in one part of the locus spectrum can become tensions in another part of that locus (only those tensions, that disseminate along a spectrum, are included in Table 2). The finding that tensions disseminate along a loci spectrum is also new in the greening transportation literature. Table 2 also shows how the different loci are not mutually excluded as internal actions, for example, during sourcing, can disseminate and create tensions, during supply, also for other actors in the supply chain, as exemplified by the Parts-whole tension in the performing category. Finally, the table also provides a link between the two different research questions addressed in this study.

Examples of how actions, perspectives and tensions “disseminate” from one part of the locus spectrum, creating tensions in another part within that locus, will be elaborated further. Locus 1 captures the dissemination from internal within a company, to dyads and sometimes to the supply chain, which extends the suggestions from studies of sustainable (product) supply chains of Van der Byl and Slawinski (2015) and Zehendner et al. (2021) into the transport context. The empirical findings clearly indicate that actions and perspectives within one actor tend to disseminate as tensions, to other actors in the supply chain. Such dissemination of paradoxical tensions from buyers to LSPs in a transport context, was found by Sallnäs and Huge-Brodin (2018) and Jazairy (2020). In our specific case, not only paradoxical tensions but also actions and perspectives, primarily stemming from within the buyer, have been seen to create tensions, within all four paradox categories, also for the suppliers. Such as when the large buyer has complex requirements or routines (actions) to which suppliers and sub-contractors have difficulties adhering (Table 2, performing category – hampering requirements). These findings provide an increased understanding of the network paradoxes that are found in transport buyer–supplier relations (see, e.g. Sallnäs and Huge–Brodin, 2018) and are understood to be a consequence of buyer power in supplier selection and evaluation, similar to what Forslund et al. (2022) identified in a transport supplier–retailer dyad. Expanding from dyads to supply chains implies that challenges in coordinating practices and logics multiply (e.g. Ülgen, 2020; Tachizawa and Wong, 2014). As shown in Table 2 both internal actions and perspectives cause tensions to arise in this locus. The fourth suggested proposition (P4) is: Company internal actions and perspectives cause tensions that hamper the greening of transportation to arise between actors in the supply chain.

Locus 2 is in relation to the purchasing process’ sourcing and supply phases (Zimmer et al., 2016). Sourcing (e.g. placing requirements) is more commonly focused than supply (e.g. monitoring) both in the green transportation literature (Forslund et al., 2022; Jazairy, 2020; Björklund and Forslund, 2013) and the green SCM literature (Zehendner et al., 2021). Even if not referred to as loci, the dissemination from sourcing to supply has to some extent been described in literature. The effects of sourcing decisions may therefore not be well enough understood, as suggested by Sandberg (2017). The empirical findings demonstrate that actions taken and tensions created during the sourcing phase disseminate and create tensions during the supply phase. One example is the buyer’s move from trust-based to control-based monitoring (action). Collecting receipts for purchased fuels, as stipulated during sourcing, will affect the supply phase (Table 2 performing – hampering requirements). During supply, this monitoring affects both buyer and supplier through increased administration and the need to develop new routines. The step in the direction toward knowing rather than believing, comes with a need to shift resources from actual greening to verifying greening. Another example is when sourcing requirements are static during contract periods (action), hampering greening-transportation initiatives, such as modality changes (e.g. Rogerson et al., 2020; Monios and Bergqvist, 2016; Sallnäs et al., 2022) or other green applications (Jazairy, 2020) during supply (learning category – inertia in purchasing process). Despite several identified belonging-related tensions related to sourcing, no dissemination of these to supply were identified. This finding does however not suggest that such dissemination cannot happen. As shown in Table 2 actions as well as tensions cause (other) tensions to arise in this locus. The fifth proposition suggested (P5) is: Actions and tensions in the sourcing phase of the purchasing process can cause tensions to arise in the supply phase and further hamper greening transportation.

Locus 3 is the strategic to operational levels, contributing to what Sandberg (2017) identified as being less researched in SCM: the strategic level. Actions, perspectives and tensions on the strategic level create tensions on operational levels such as the buyer’s strategic KPI for CO₂ reductions (perspective), that fits well for, e.g. external reporting, while the operational level realizes that this KPI does not fit all their improvement ambitions as it does not capture all improvements made (Table 2 belonging – hierarchical identity). Some of the strategic to operational level tensions appear related to the different perspectives regarding for example sustainability ambitions (Table 2 learning – inertia in purchasing process). Both these examples add detail to the misalignments found by Jazairy (2020) between strategic and operational levels in green transport buyer/supplier relationships. This is an added complexity of being part of a larger corporate group as it also creates tension on the operational level with suppliers, as they are requested different levels of sustainability when driving for different sister companies within the group, as noted by the sourcing function (belonging – hierarchical identity). As shown in Table 2 actions, perspectives and tensions cause tensions to arise in this locus. The sixth, and final, suggested proposition (P6) is: Actions, perspectives and tensions on the strategic level disseminates to the operational level and hamper greening transportation.

Based on the findings, Figure 2 suggests a framework that can be applied to increase the understanding of paradoxical tensions hampering the greening of transportation in transport buyer–supplier dyads. To increase the transferability of the framework, the context-dependent tension “sector identity” related to the vehicle manufacturing sector has been excluded.

6. Conclusions and further research

6.1 Conclusions

For companies to become part of the solutions for sustainability, a deeper understanding of the characteristics of paradoxical tensions is needed. Paradox theory is used in this study to identify paradoxical tensions that can help us better understand why the transition toward green transportation goes slow, even among ambitious, proactive actors. In response to RQ1, several tensions, outlined in Figure 1, were identified in both studied dyads (see exception in hierarchical identity). Furthermore, tensions fitting into all four paradox categories were identified, underscoring the complexity of greening transportation.

Three different loci were identified when answering RQ2, which provided an additional lens to the four categories commonly applied in paradox theory. The identified tensions and the different loci—including the finding that tensions arise due to actions, perspectives and/or other tensions and disseminate within a locus spectrum or between loci—and the associated six propositions, have a good potential to increase the understanding of and provide a holistic overview of what hampers the greening of transportation. We therefore suggest an expansion of the four categories of paradoxes by also including the loci where actions, such as requirements placed and routines applied, perspectives such as priorities of different functions or levels and tensions, such as contradictions and different interests between stakeholders, cause (new) tensions to arise. The framework presented in Figure 2 ties the RQs together, providing an overview that increases the understanding of paradoxical tensions in transport supplier-buyer dyads that hamper the greening of transportation. It does so by adding loci of these tensions and the reasons to why tensions arise, to the more commonly applied categorization framework.

Contributions to literature and research lie in the combination of paradox theory and greening transportation on a more detailed level. Our study in a transport context addresses a gap mentioned by, e.g. Ashraf et al. (2022) and Centobelli et al. (2020). Looking at the greening of transportation between transport buyers and suppliers through the paradox lens while applying the categories of performing, belonging, learning and organizing has led to the identification of multiple tensions, including but not limited to the tensions inherent in the sustainability concept. In addition to commonly highlighted tensions between costs and environmental KPIs (see, e.g. Sandberg, 2017; Arvidsson, 2013), our study provided additional holistic insights into tensions that arise between conflicting methods of capturing and valuing environmental performance KPIs. Identified tensions in the four categories are illustrated in Figure 1. Figure 2 presents a novel contribution to literature. It expands the findings of Zehendner et al. (2021) who, in a sustainable SCM setting, found that tensions arise at different levels in the supply chain. This study acknowledges additional loci of tensions and further explores how tensions disseminate within loci spectra, such as from internal to supply chain, from sourcing to supply and/or from strategic to operational level. The findings also extend the understanding of why tensions generally arise presented by Maalouf and Gammelgaard (2016) and Jarzabkowski et al. (2013), by providing examples of how not only tensions, but also actions and perspectives, contribute to new tensions. The study, therefore, (humbly) adds another dimension to tensions in the commonly applied paradox categories of Smith and Lewis (2011). Our findings also provide several novel examples and insights regarding paradoxes in the greening of transportation (to e.g. Sallnäs and Huge-Brodin, 2018; Moncef and Dupuy, 2022; Jazairy, 2020; Forslund et al., 2022). It contributes a more holistic view of paradoxes within the greening of transportation not identified in previous green transport and logistics literature. For instance, Moncef and Dupuy (2022) had a narrower focus on paradoxes between economic, environmental and social sustainability while Sandberg (2017), even if using the four paradox categories, had a focus on global sourcing. Other studies of greening transportation (sporadically) highlighted individual/isolated tensions such as three examples of network paradoxes (Sallnäs and Huge-Brodin (2018), without attempting to shed light on all the tensions present. It was found that belonging tensions are caused by perspectives only, while learning tensions are caused by actions, perspectives and other tensions which make them particularly complex. In terms of loci, it was found that the strategic to operational level locus was particularly challenging for the same reasons, they can be caused by actions, perspectives and other tensions.

The transferability of this contribution might also stretch from the research field of green transportation into sustainable transportation, logistics and SCM. Furthermore, as tensions and loci were identified in both studied dyads (see exception in hierarchical identity), this may indicate their presence in contexts involving LSPs of varying sizes and geographical scopes. Propositions suggesting patterns among tensions and plausible relations between tensions and loci are another contribution to the extant research. Furthermore, this research provides several arguments and an increased understanding of the often-presented need for increased transport buyer–supplier communication and collaboration to facilitate the greening of logistics and transportation (e.g. Forslund et al., 2022; Jazairy, 2020), by showing that the tensions, even those arising within one actor or function, often disseminate to other functions and actors. Prior research on paradoxes in logistics (e.g. Jarzabkowski et al., 2013; Maalouf and Gammelgaard, 2016) has indicated difficulties in identifying learning tensions. Our study’s focus on sustainability, an area where new methods and tools are needed to reach higher grounds, is suggested as to why learning tensions related to new knowledge and processes were more easily identified, therefore contributing to the knowledge on learning tensions.

Managerial contributions are opportunities to distinguish tensions in greening transportation and the acknowledgement that a simple trade-off (e.g. between environmental, social and economic sustainability as well as in relation to delivery service) cannot remove the tension on a long-term basis. The tension will resurface as long as the contradiction between the three areas remains. Paradoxes persist over time and must be managed, not eradicated. Understanding this is a necessary first step before identifying ways to manage contradictions in greening transportation. This study also provides insight into the many categories and loci in which tensions arise and how easily they propagate along loci spectra. Finally, it sheds light on why tensions arise, related to actions, perspectives and other tensions. This is particularly notable in the strategic to operational level locus in which managers have large responsibilities. Furthermore, several concrete ways to manage tensions can be suggested, such as the need for increased knowledge sharing between the actors in the future progress toward green transportation. To mitigate the tensions created by the buyer’s sustainability (and other) requirements, there is a need to enhance the buyer’s understanding of the actual greening effect experienced by transport suppliers. One example is the shift from trust-based to control-based monitoring which creates tensions necessitating the development of routines that satisfy both buyer and supplier and the establishment of clear role divisions between them. Our findings also clearly indicate that managers need to be aware that tensions on the strategic level are likely to disseminate to other levels in the organization. The transferability of the empirical findings and results is most likely to be found on an aggregated level, as buyer requirements, for example, largely vary depending on business ambitions and strategies.

6.2 Limitations and future research

This study has investigated two dyads with a single transport buyer, which can limit the transferability to other situations. Some of the findings made are likely to be context or case-specific, even if some actions have been taken to increase transferability, such as not including sector identity as a tension in the suggested framework. Other contexts could be interesting areas targeted by future research. Tensions like the headquarters’ involvement is expected to be identified in larger companies or corporations. Smaller companies are however not completely without risk of having differing directives and reporting structures affecting decision-making and identities, which is why, in relation to smaller companies, the transferability can be worthwhile investigating further. As the transport industry is largely comprised of smaller companies and TS2 is not representative of those, the model could also be tested for the influence of transport-supplier size. Our expectation is that smaller transport suppliers would not be less affected by the identified tensions. Smaller suppliers may instead be more affected by the resource intensiveness of verifying and reporting greening, leaving fewer resources for actual greening efforts. Some of the buyer’s most sustainability-oriented transport suppliers are studied, which can be a limitation and reduce the possibilities to transfer the findings to less sustainability-oriented transport suppliers. As the studied suppliers have come further on their greening journey, they have made the easiest greening initiatives and, at this stage, perceive many tensions. It is conceivable that also currently less green transport suppliers will embark on a similar greening journey and eventually encounter similar tensions.

The propositions suggesting patterns among tensions, and plausible relations between tensions and loci, can be further investigated for explanations of tensions hampering the greening of transportation. As paradoxes and tensions can arise in the interface between companies, a limitation can be that only dyads were addressed. It is expected that a larger scope, beyond the contractual relationship between transport buyer and supplier could lead to more tensions revealed. This could mean a triadic scope (including sub-contractors, senders or receivers of the goods) or larger interrelationships in supply chain networks. Moreover, the potential propagation of tensions and/or their effects could be better understood by this larger scope and should be considered for future research. One example highlighting this is the difficulties in monitoring green performance when subcontractors are included in the transport supply chain. Indications that the risk for tensions increases as the scope increases have been shared, for example, through the buyer limiting the number of actors and the number of tiers in the transport supply chain to keep them manageable.

The difference between paradoxical tensions and other tensions, in line with the discussion on paradoxes vs. dialectics or dilemmas (e.g. Smith and Lewis, 2011; Pålsson and Sandberg, 2022) could be elaborated further. To the best of our knowledge, the identified tensions are paradoxical tensions that are likely to persist over time, yet this could be better clarified in longitudinal studies. The sequence in which tensions occur is another interesting area for future research, as some of our empirical findings indicated that some tensions initiate other tensions. A plausible sequence is that the organizing paradox, with the buyer group headquarters and the buyer as separate entities with their related directives and reporting structures, influence primarily belonging and performing tensions. A thorough investigation of the sequence and relationship between tensions is a relevant way forward. Performing includes many tensions between buyer and supplier, which makes it particularly interesting to deepen and broaden studies of tensions around KPIs and system boundaries in dyads or even supply chains. The propositions can be tested in broader survey studies, to fulfill the final step of the Carney (1990) model or to be further investigated through deeper qualitative research. Such a study can take a point of departure from our suggested framework and develop it into an explanatory framework. This could extend to interactive research to understand how managers can accept, embrace and manage tensions over time and how tensions may take on new shapes or forms. Furthermore, the framework is also recommended for application in settings outside green transportation, as it is expected to transfer satisfactorily into other contexts.

Figures

Figure 1

Empirical examples and identified tensions

Figure 2

Suggested framework for increased understanding of paradoxical tensions hampering the greening of transportation in transport buyer–supplier dyads

Table 1

Company characteristics and respondents

Company	Company characteristics	Relationship characteristics	Respondents and information sources
Transport buyer (TB)	Large manufacturer of heavy vehicles Part of international group of companies (including headquarters and sister companies) Adopted science-based targets and ambitious transport-related scope 1–3 targets for CO2	Long-term, close relation with TS1, important transport supplier in a specific geographic area, inbound flows to manufacturing sites Long-term relation with TS2, relatively dependent on TS2 due to their unique coverage in northern Europe, inbound flows to manufacturing sites	Purchasing manager (TB:PM) Sourcing project manager (TB:SPM) Sustainability developer (TB:SD) TB’s sustainability reports 2021 and 2022 TB’s website (accessed May 2023)
Transport supplier 1 (TS1)	Specialized in road transportation Pan-European presence Approximately 200 vehicles, primarily own Bio-gas project together with fuel supplier, buyer and researchers	Goods from the buyer’s suppliers to manufacturing sites are often consolidated via cross-docks Long-term, mutually important partnership with close communication The buyer is one of the largest customers and a prestigious customer account Expresses dependency, but not solely on the buyer	Owner/Operations manager (TS1:OM) Key account manager (TS1:KAM) Sustainability manager (TS1:SM) TS1’s sustainability report 2022/2023 TS1’s website (accessed May 2023)
Transport supplier 2 (TS2)	Logistics service provider with a global presence, focus is northern Europe and road transportation Operates a large fleet of primarily subcontracted vehicles  Offers insetting - greening in the supplier’s transport system is sold to green buyers Adopted science-based targets	Goods from the buyer’s suppliers to manufacturing sites, often consolidated via cross docks Long-term, mutually important partnership with close communication. The buyer and buyer group are important long-term customers Expresses a joint dependency in the relation but acknowledges their own “interchangeability” lane by lane	Key account manager (TS2:KAM) Sustainability specialist (TS2:SS) Environmental specialist (TS2:ES) TS2’s sustainability report 2021 and 2022 TS2’s website (accessed May 2023)

Source(s): Table by authors

Table 2

Where (locus spectrum) and why (due to action, perspective or tension) tensions arise

	Locus 1: Internal → Supply chain	Locus 2: Sourcing → Supply	Locus 3: Strategic → Operational
Performing category	Hampering requirements: The large buyer’s complex requirements and routines cause tensions as it makes it difficult for suppliers and sub-contractors to adhere. (Action)	Hampering requirements: Buyer strategic level enforces a shift to control-based monitoring. Operational level is left to solve how monitoring should be realized, resulting in a resource shift from greening to verifying greening during supply, affecting both buyer and supplier. (Action)
	Contradictory KPI: Ambiguous buyer prioritization between delivery service and sustainability (inconsistent use of supplier selection criteria) results in suppliers bidding on false premises. (Action)	Contradictory KPI: In sourcing, tensions arise as the buyer fails to recognize the suppliers' diverse range of sustainability KPIs, causing tensions also in supply as the transport offered takes more sustainability aspects into account. (Tension)
	Parts-whole: Buyer’s decisions during sourcing resulting in suppliers losing volumes on certain lane(s) can lead to reduced environmental performance during supply due to unbalanced flows. (Action)
Belonging category			Hierarchical identity: The nature of the strategic KPI, with a focus on vehicle sustainability (e.g. better engines) hampers broader greening initiatives on operational level. (Perspective)
	Functional identity: Inconsistent values and perspectives regarding green transportation among the buyer’s functions lead to conflicting practices and conflicting signals about the buyer’s preparedness to pay. (Perspective)
Learning category	Inertia in purchasing process: The requirements for short contract durations hamper suppliers' greening initiatives and upkeep, as investments in sustainability become too risky. (Action)	Inertia in purchasing process: As sourcing requirements are fixed during contract periods, greening initiatives during supply are hampered. (Action)	Inertia in purchasing process: Headquarters and purchasing prioritize costs, whereas the operational sourcing and sustainability functions advocate for prioritizing sustainability. (Perspective)
	Inertia in green upkeep: The buyer’s full understanding and appreciation of insetting took a long time due to differing perspectives on, e.g. how to follow up and report CO2 improvements, hampering the supplier’s actual insetting initiative. (Perspective)	Inertia in green upkeep: Despite green sourcing, based on old knowledge suppliers offer less green solutions expecting a low buyer preparedness to pay. This tension affects supply where less green solutions are adopted. (Tension)	Inertia in green upkeep: The narrow perspective of the strategic KPI (see tension Hierarchical identity) does not encourage green upkeep and development at the operational level. (Perspective)
Organizing category		Controlled flexibility: Despite the buyer sourcing from a single transport supplier, they may encounter unknown sub-contractors for transporting their goods during the supply phase. (Action)	Headquarters involvement: Buyer group directive and reporting structures create tensions between operational and strategic levels, these tensions disseminate and become part of the functional identity tensions. (Tension)

Source(s): Table by authors

Appendix Interview guides

For the Transport Buyer

General questions

• 1.

  Describe your current position, title and “history” (both within the company and previous employment)

• 2.

  What characterizes the transport supply chain?

Questions on relations

• 3.

  How would you describe the relation with the transport supplier?

Probing questions on relations

• —

  How would you describe your dependency on the transport supplier? (special competence, more important than average buyer/supplier, degree of substitutability, switching costs)

• —

  How would you describe the transport supplier’s ability/willingness to perform as agreed, share relevant information, enhance your sustainability performance?

Questions on sustainable transport purchasing

How would you describe each sourcing and supply activity;

• 4.

  Define sustainability requirements, sustainability goals, logic of “division” of your logistics system (who’s involved, type of requirements, etc.)

• 5.

  Gather sustainability information from transport suppliers (type of information; methods applied?)

• 6.

  Select transport supplier (based on what, how, by whom?)

• 7.

  Write contract agreement, non-compliance clauses (any mutual agreements?)

• 8.

  Potential supplier development – or buyer development? (Examples of activities, what is developed, how, when, etc.)

• 9.

  What characterizes the green activities considering the ordering of transport services

• 10.

  What activities take place regarding monitoring sustainability performance? (Sustainability KPIs applied, including third-part revision, how often/when is revision made, same process for all suppliers, etc?)

Probing questions (for Questions 4–10)

• —

  Type of sustainability-related information exchange

• —

  Documents and tools used (type of documents, type of info documented?)

• —

  Type of info in different directions? (giving/receiving type of information, who’s involved, etc.) How well routinized? (is the information exchange routinized and structured vs more irregular and spontaneous) (can be both, what dominates, examples)

For Transport Suppliers

General questions

• 11.

  Describe your current position, title and “history” (within the company and previous employments)

• 12.

  What characterizes this transport supply chain)?

Questions on relation

• 13.

  How would you describe the relation with the transport buyer?

Probing questions on relation:

• —

  How would you describe your dependency on the buyer? (e.g. special competence, more important than average buyer/supplier, degree of substitutability, switching costs)

• —

  How would you describe the buyer’s ability/willingness to perform as agreed, share relevant information, enhance your sustainability capability?

• —

  Do you experience that the buyer has a coherent development agenda for your sustainability development/the sustainability developments of the supply chain and continuity of the development agenda (e.g. keep same person as contact, develop in line with previous aims)?

• —

  Is your ability to adapt to the requirements of the buyer affected (negatively/positively) by adaptations toward other buyers? (Ability to focus/streamline, use similar working methods, etc.). Please give some examples.

Questions on sustainable transport purchasing from the buyer

How would you describe each sourcing and supply activity;

• 14.

  Define sustainability requirements, sustainability goals, logic of “division” of your logistics system (who’s involved, type of requirements etc.)

• 15.

  Gather information from transport suppliers (type of information; methods applied?)

• 16.

  Select transport supplier (based on what, how, by whom?)

• 17.

  Write contract agreement, non-compliance clauses (any mutual agreements?)

• 18.

  Potential supplier development – or buyer development? (Examples of activities, what is developed, how, when, etc.)

• 19.

  What characterizes the green activities considering the ordering of transport services

• 20.

  What activities take place regarding monitoring sustainability performance? (Sustainability KPIs applied, including 3rd part revision, how often/when is revision made?)

• 21.

  Potential supplier development – or buyer development?

Probing questions on sustainable transport purchasing (for question 14–21)

• —

  type of sustainability-related information exchange

• —

  Documents and tools used (type of documents, type of info documented?)

• —

  Type of info in different directions? (giving/receiving type of information, who’s involved, etc.) How well routinized? (is the information exchange routinized and structured vs more irregular and spontaneous) (can be both, what dominates, examples)