Sustainable Freight Transport Lóránt Tavasszy and Maja Piecyk www.mdpi.com/journal/sustainability Edited by Printed Edition of the Special Issue Published in Sustainability Sustainable Freight Transport Sustainable Freight Transport Special Issue Editors Lóránt Tavasszy Maja Piecyk MDPI • Basel • Beijing • Wuhan • Barcelona • Belgrade Special Issue Editors Lóránt Tavasszy Delft University of Technology The Netherlands Maja Piecyk University of Westminster UK Editorial Office MDPI St. Alban-Anlage 66 Basel, Switzerland This is a reprint of articles from the Special Issue published online in the open access journal Sustainability (ISSN 2071-1050) in 2018 (available at: https://www.mdpi.com/journal/ sustainability/special issues/Sustainable Freight Transport) For citation purposes, cite each article independently as indicated on the article page online and as indicated below: LastName, A.A.; LastName, B.B.; LastName, C.C. Article Title. Journal Name Year , Article Number , Page Range. 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Contents About the Special Issue Editors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii Preface to ”Sustainable Freight Transport” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix L ́ or ́ ant Tavasszy and Maja Piecyk Sustainable Freight Transport Reprinted from: Sustainability 2018 , 10 , 3624, doi: 10.3390/su10103624 . . . . . . . . . . . . . . . . 1 Abiye Tob-Ogu, Niraj Kumar, John Cullen and Erica E. F. Ballantyne Sustainability Intervention Mechanisms for Managing Road Freight Transport Externalities: A Systematic Literature Review Reprinted from: Sustainability 2018 , 10 , , doi: 10.3390/su10061923 . . . . . . . . . . . . . . . . . . 5 Hongli Zhao, Ning Zhang and Yu Guan Safety Assessment Model for Dangerous Goods Transport by Air Carrier Reprinted from: Sustainability 2018 , 10 , 1306, doi: 10.3390/su10051306 . . . . . . . . . . . . . . . . 23 Kinga Kijewska and Mariusz Jedli ́ nski The Concept of Urban Freight Transport Projects Durability and Its Assessment within the Framework of a Freight Quality Partnership Reprinted from: Sustainability 2018 , 10 , 2226, doi: 10.3390/su10072226 . . . . . . . . . . . . . . . . 39 Inge Vierth, Samuel Lindgren and Hanna Lindgren Vehicle Weight, Modal Split, and Emissions—An Ex-Post Analysis for Sweden Reprinted from: Sustainability 2018 , 10 , 1731, doi: 10.3390/su10061731 . . . . . . . . . . . . . . . . 57 Franco Ruzzenenti The Prism of Elasticity in Rebound Effect Modelling: An Insight from the Freight Transport Sector Reprinted from: Sustainability 2018 , 10 , 2874, doi: 10.3390/su10082874 . . . . . . . . . . . . . . . . 72 Carlos Llano, Santiago P ́ erez-Balsalobre and Julian P ́ erez-Garc ́ ıa Greenhouse Gas Emissions from Intra-National Freight Transport: Measurement and Scenarios for Greater Sustainability in Spain Reprinted from: Sustainability 2018 , 10 , 2467, doi: 10.3390/su10072467 . . . . . . . . . . . . . . . . 85 Ronald A. Halim, Lucie Kirstein, Olaf Merk and Luis M. Martinez Decarbonization Pathways for International Maritime Transport: A Model-Based Policy Impact Assessment Reprinted from: Sustainability 2018 , 10 , 2243, doi: 10.3390/su10072243 . . . . . . . . . . . . . . . . 118 Jessica Wehner Energy Efficiency in Logistics: An Interactive Approach to Capacity Utilisation Reprinted from: Sustainability 2018 , 10 , 1727, doi: 10.3390/su10061727 . . . . . . . . . . . . . . . . 148 Heikki Liimatainen, Phil Greening, Pratyush Dadhich and Anna Keyes Possible Impact of Long and Heavy Vehicles in the United Kingdom—A Commodity Level Approach Reprinted from: Sustainability 2018 , 10 , 2754, doi: 10.3390/su10082754 . . . . . . . . . . . . . . . . 167 v Jesko Schulte and Henrik Ny Electric Road Systems: Strategic Stepping Stone on the Way towards Sustainable Freight Transport? Reprinted from: Sustainability 2018 , 10 , 1148, doi: 10.3390/su10041148 . . . . . . . . . . . . . . . . 185 Oskarbski Jacek and Daniel Kaszubowski Applying a Mesoscopic Transport Model to Analyse the Effects of Urban Freight Regulatory Measures on Transport Emissions—An Assessment Reprinted from: Sustainability 2018 , 10 , 2515, doi: 10.3390/su10072515 . . . . . . . . . . . . . . . . 201 Tharsis Teoh, Oliver Kunze, Chee-Chong Teo and Yiik Diew Wong Decarbonisation of Urban Freight Transport Using Electric Vehicles and Opportunity Charging Reprinted from: Sustainability 2018 , 10 , 3258, doi: 10.3390/su10093258 . . . . . . . . . . . . . . . . 219 J ́ an Liˇ zbetin, Martina Hlatk ́ a and Ladislav Bartuˇ ska Issues Concerning Declared Energy Consumption and Greenhouse Gas Emissions of FAME Biofuels Reprinted from: Sustainability 2018 , 10 , 3025, doi: 10.3390/su10093025 . . . . . . . . . . . . . . . . 239 Erik Johannes, Petter Ekman, Maria Huge-Brodin and Matts Karlsson Sustainable Timber Transport—Economic Aspects of Aerodynamic Reconfiguration Reprinted from: Sustainability 2018 , 10 , 1965, doi: 10.3390/su10061965 . . . . . . . . . . . . . . . . 250 vi About the Special Issue Editors L ́ óránt Tavasszy is Full Professor in Freight Transportation and Logistics Systems at the Delft University of Technology. He graduated as Transportation Engineer at TU Delft. He has worked with the Dutch national research institute TNO until 2016, holding part-time positions at Radboud University Nijmegen (2004–2009) and TU Delft (2009–2016). His main research topic is freight transportation modelling. Prof. Tavasszy is a fellow of the Netherlands research school TRAIL, member of US Transportation Research Board Freight committees, chair of the World Conference for Transport Research Society’s Scientific Committee, and vice chair on Sustainable Transport for the EU Logistics Platform ALICE. M aja Piecyk is a Reader in Logistics at the University of Westminster. She is a former Deputy Director of the Centre for Sustainable Road Freight, an EPSRC-funded research centre between Heriot-Watt and Cambridge Universities. Her research interests focus on the environmental performance and sustainability of freight transport operations. Much of her current work centres on the optimisation of supply chain networks, GHG auditing of businesses, and forecasting of long- term trends in energy demand and environmental impacts of logistics. Maja is a Chartered Member of the Chartered Institute of Logistics and Transport (UK), and a Fellow of the Higher Education Academy. vii Preface to ”Sustainable Freight Transport” This Special Issue of Sustainability reports on recent research focusing on the freight transport sector. This sector faces significant challenges in different domains of sustainability, including the reduction of greenhouse gas emissions and the management of health and safety impacts. In particular, the intention to decarbonise the sector’s activities has led to a strong increase in research efforts—this is also the main focus of the Special Issue. W e want to thank the authors, the numerous anonymous reviewers, and the publisher, who have contributed to the creation of this issue. L óránt Tavasszy, M aja Piecyk Special Issue Editors ix sustainability Editorial Sustainable Freight Transport L ó r á nt Tavasszy 1, * and Maja Piecyk 2 1 Faculty of Civil Engineering and Geosciences, Transport & Planning Department, Delft University of Technology, Stevinweg 1, 2628 CN Delft, The Netherlands 2 Faculty of Architecture and the Built Environment, Department of Planning and Transport, University of Westminster, 35 Marylebone Road, London NW1 5LS, UK; m.piecyk@westminster.ac.uk * Correspondence: l.a.tavasszy@tudelft.nl Received: 10 October 2018; Accepted: 10 October 2018; Published: 11 October 2018 1. Introduction This Special Issue of Sustainability reports on recent research focusing on the freight transport sector. This sector faces significant challenges in different domains of sustainability, including the reduction of greenhouse gas (GHG) emissions and the management of health and safety impacts. In particular, the intention to decarbonise the sector’s activities has led to a strong increase in research efforts, which is also the main focus of the Special Issue. Sustainable freight transport operations represent a significant challenge with multiple technical, operational, and political aspects; the design, testing, and implementation of interventions require multi-disciplinary, multi-country research. Promising interventions are not limited to introducing new transport technologies, but also include changes in framework conditions for transport, in terms of production and logistics processes [ 1 ]. Due to the uncertainty of impacts, the number of stakeholders and the difficulty of optimization across actors, understanding the impacts of these measures is not a trivial problem. Research, therefore, is not just needed on the design and evaluation of individual interventions, but also on the approach of their joint deployment through a concerted, public/private programme. This Special Issue addresses both dimensions, in two distinct groups of papers—the programming of interventions, and the individual sustainability measures themselves. The first 7 papers, besides offering insights about freight sustainability measures, also address progress in the different, typical stages of programme preparation: (1) defining the objectives and the problem; (2) learning from past experiences; (3) systematic generation of solutions; (4) understanding system behaviour; (5) scenario building; and (6) evaluation of policies. The second group of papers focuses on the evaluation of specific solutions to reduce the carbon content of transport. This concerns a wide range of measures, including improved capacity utilisation, electrification, regulatory measures, alternative fuels and vehicle aerodynamics. We introduce the contributions in more detail below. Within the first group, the opening paper of Abiye Tob-Ogu, Niraj Kumar, John Cullen and Erica Ballantyne reports on a systematic literature review of sustainability intervention mechanisms [ 2 ]. Two important findings are: (i) the identification of information and communication technology as an opportunity to drive changes towards sustainable transport; and (ii) the strong geographic compartmentalisation of the literature, confined to continental silos. The authors find that relatively few papers are based on collaborative work across continents. The contribution of Hongli Zhao, Ning Zhang and Yu Guan focuses on the identification of the relative importance of factors determining air cargo safety for dangerous goods [ 3 ]. They find that, besides regulation of dangerous goods acceptance, the capacity and quality of equipment and facilities also play a role. A potential implication of these results is that, in the area of safety, benefits of innovations in trade facilitation may be constrained by the available physical infrastructure. Kinga Kijewska and Mariusz Jedli ́ nski introduce the concept of policy durability for sustainable urban freight transport [ 4 ]. In urban freight transport, many policies are known to have been abandoned only Sustainability 2018 , 10 , 3624; doi:10.3390/su10103624 www.mdpi.com/journal/sustainability 1 Sustainability 2018 , 10 , 3624 a few years after their introduction. The authors analyse the causes and provide directions for more robust policy making, focusing on the inclusion of critical stakeholders that need to be involved to make measures succeed. In most roadmaps for decarbonisation in the freight transport sector, a shift of loads is advocated from current trucks to high-capacity vehicles or even other modes of transport. The recent experiences with these policies in Sweden are evaluated by Inge Vierth, Samuel Lindgren and Hanna Lindgren [ 5 ]. In their ex post analysis of the impacts of the introduction of longer and heavier vehicles in Sweden, they find that this measure has not had any discernible effect on modal split. The share of different types of emissions of road transport changed, however, leading to a higher share of GHGs. An important element of discussions about impacts of policy measures concerns the rebound effects of measures. Increased efficiency may reduce emissions per unit moved but may also increase the number of units moved, due to the demand effect, thus partly neutralising the effects of measures. Often, these rebound effects are assessed through the cost and time elasticities of freight transport. In an original contribution, Franco Ruzzenenti explains how elasticities as currently used can be misleading [ 6 ]. His main assertion is that tabulating flows as is done today neglects the complex interdependence between flows that is present in networks and that is essential for considering rebound effects. Therefore, he develops a new line of thinking using network theory that may prove important for sustainability analyses. Two further contributions take the perspective of practical solution scenarios at the country and sector level, respectively. For Spain, Carlos Llano, Santiago P é rez-Balsalobre and Julian P é rez-Garc í a develop scenarios for emission reduction of domestic freight transport [ 7 ]. They build up a consistent flow database, develop default emission projections, and study the impacts of a shift of freight from road to railways. Studies that link the analysis of modal shift potential to detailed flow databases are scarce, and may support the development of modal shift policies that take into account the supply chain context of goods flows. Reporting about Organization for Economic Cooperation and Development (OECD) research aimed at the decarbonisation of the maritime transport services sector, Ronald Halim, Lucie Kirstein, Olaf Merk and Luis Martinez develop pathways for emission reduction [ 8 ]. In a systematic study, using a global freight transport and emission model, they consider 4 different pathways. Mobilizing all available technologies, these could lead to a reduction of carbon emissions of up to 95% by 2035, well beyond the current commitment of 50% reduction by 2050. The paper describes the approach and assumptions behind this study, which contributed to the formulation of broadly supported decarbonisation targets by the maritime shipping world. The second group of papers discusses specific interventions that can be implemented to decarbonise the freight transport sector and approaches that can be applied to evaluate their likely effects. Jessica Wehner presents the analysis of opportunities to improve the energy efficiency of operations by increasing capacity utilisation in logistics systems [ 9 ]. Her research results in the categorisation of factors that cause unutilised capacity within the categories of activities, actors and areas. These factors are then linked to a number of mitigation measures, such as relaxing delivery schedules, training, and off-peak deliveries, among others. The paper also emphasises the need for a standardised approach to the measurement of environmental impacts of logistics to enable meaningful comparisons between companies. The potential effects of introducing longer and heavier vehicles (LHVs) in the United Kingdom are investigated by Heikki Liimatainen, Phil Greening, Pratyush Dadhich and Anna Keyes [ 10 ]. The authors estimate that if LHVs were used similarly in Finland in the transport of various commodities, significant savings could be achieved in truck kilometres, transport costs, and CO 2 emissions. Furthermore, lower road freight traffic volumes and reduced emissions are likely to more than offset the possible negative effects of modal shift from rail to road. Jesko Schulte and Henrik Ny focus on overhead line Electric Road Systems (ERS) as a way to improve the sustainability of transporting goods by road [ 11 ]. The research show that although ERS 2 Sustainability 2018 , 10 , 3624 may present some severe violations of the sustainability principles, especially in the raw material extraction, production and use phases, they could still be a valuable element in the transition towards a more sustainable freight transport system. Based on a case study of a Polish town Gdynia, Jacek Oskarbski and Daniel Kaszubowski investigate whether a mesoscopic urban transport model already in use there can be populated with urban freight transport data in order to improve evaluation of potential CO 2 reductions from the designation of dedicated delivery places [ 12 ]. They conclude that this approach produces satisfactory results if basic regulatory measures are considered. However, dedicated freight transport models that can take urban supply chain structure into account are more suitable to study more complex policy options. Tharsis Teoh, Oliver Kunze, Chee-Chong Teo and Yiik Diew Wong demonstrate that opportunity charging offers the potential to significantly reduce the lifecycle costs of using electric vehicles in urban freight transport without increasing related CO 2 emissions [ 13 ]. The authors also find that other factors also strongly influencing the lifecycle costs are the use of inductive technology, extension of service lifetime, and reduction of battery price. The use of inductive technology and the carbon intensity of electricity generation are the two other factors with a strong influence on CO 2 emissions from electric vehicles operating in towns and cities. J á n Ližbetin, Martina Hlatk á and Ladislav Bartuška discuss issues related to energy consumption and GHG emissions related to the use of fatty acid methyl esters (FAME) biofuels in road freight transport [ 14 ]. They conclude that even though FAME biofuels significantly reduce GHG emissions, their production is highly energy intensive, which translates into steeper fuel prices. Therefore, more research is needed into ways to reduce the energy requirements of FAME biofuels production in order to bring the prices down to an industry-acceptable level. In the final article, Erik Johannes, Petter Ekman, Maria Huge-Brodin and Matts Karlsson focus on aerodynamic improvements for timber trucks in Sweden [ 15 ]. While the aerodynamics provide the opportunity to reduce the transport cost of timber in Sweden, the changeover time is found to be the most important parameter to them being economically viable. Hence, in the Swedish timber transport sector aerodynamic kit that does not have to be manually installed is key to the profitability of the investment. Together the papers in this Special Issue paint a diverse and rich picture of opportunities in the freight transport sector for a transition towards sustainability. They confirm the theoretical availability of a significant and—from the perspective of the global sustainability targets—promising potential for decarbonisation. At the same time, they make us aware of important limitations of policy measures, caveats in our knowledge and weaknesses in our approaches to assess the impacts of policies. All these provide new directions to accelerate R&D, innovation and public policy in the required direction and ultimately create a more sustainable freight transport sector. Conflicts of Interest: The authors declare no conflict of interest. References 1. McKinnon, A. Decarbonizing Logistics: Distributing Goods in a Low Carbon World ; Kogan Page: London, UK, 2018. 2. Tob-Ogu, A.; Kumar, N.; Cullen, J.; Ballantyne, E.E.F. Sustainability Intervention Mechanisms for Managing Road Freight Transport Externalities: A Systematic Literature Review. Sustainability 2018 , 10 , 1923. [CrossRef] 3. Zhao, H.; Zhang, N.; Guan, Y. Safety Assessment Model for Dangerous Goods Transport by Air Carrier. Sustainability 2018 , 10 , 1306. [CrossRef] 4. Kijewska, K.; Jedli ́ nski, M. The Concept of Urban Freight Transport Projects Durability and Its Assessment within the Framework of a Freight Quality Partnership. Sustainability 2018 , 10 , 2226. [CrossRef] 5. Vierth, I.; Lindgren, S.; Lindgren, H. Vehicle Weight, Modal Split, and Emissions—An Ex-Post Analysis for Sweden. Sustainability 2018 , 10 , 1731. [CrossRef] 6. Ruzzenenti, F. The Prism of Elasticity in Rebound Effect Modelling: An Insight from the Freight Transport Sector. Sustainability 2018 , 10 , 2874. [CrossRef] 3 Sustainability 2018 , 10 , 3624 7. Llano, C.; P é rez-Balsalobre, S.; P é rez-Garc í a, J. Greenhouse Gas Emissions from Intra-National Freight Transport: Measurement and Scenarios for Greater Sustainability in Spain. Sustainability 2018 , 10 , 2467. [CrossRef] 8. Halim, R.A.; Kirstein, L.; Merk, O.; Martinez, L.M. Decarbonization Pathways for International Maritime Transport: A Model-Based Policy Impact Assessment. Sustainability 2018 , 10 , 2243. [CrossRef] 9. Wehner, J. Energy Efficiency in Logistics: An Interactive Approach to Capacity Utilisation. Sustainability 2018 , 10 , 1727. [CrossRef] 10. Liimatainen, H.; Greening, P.; Dadhich, P.; Keyes, A. Possible Impact of Long and Heavy Vehicles in the United Kingdom—A Commodity Level Approach. Sustainability 2018 , 10 , 2754. [CrossRef] 11. Schulte, J.; Ny, H. Electric Road Systems: Strategic Stepping Stone on the Way towards Sustainable Freight Transport? Sustainability 2018 , 10 , 1148. [CrossRef] 12. Oskarbski, J.; Kaszubowski, D. Applying a Mesoscopic Transport Model to Analyse the Effects of Urban Freight Regulatory Measures on Transport Emissions—An Assessment. Sustainability 2018 , 10 , 2515. [CrossRef] 13. Teoh, T.; Kunze, O.; Teo, C.-C.; Wong, Y.D. Decarbonisation of Urban Freight Transport Using Electric Vehicles and Opportunity Charging. Sustainability 2018 , 10 , 3258. [CrossRef] 14. Ližbetin, J.; Hlatk á , M.; Bartuška, L. Issues Concerning Declared Energy Consumption and Greenhouse Gas Emissions of FAME Biofuels. Sustainability 2018 , 10 , 3025. [CrossRef] 15. Johannes, E.; Ekman, P.; Huge-Brodin, M.; Karlsson, M. Sustainable Timber Transport—Economic Aspects of Aerodynamic Reconfiguration. Sustainability 2018 , 10 , 1965. [CrossRef] © 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). 4 sustainability Review Sustainability Intervention Mechanisms for Managing Road Freight Transport Externalities: A Systematic Literature Review Abiye Tob-Ogu 1 , Niraj Kumar 2 , John Cullen 1 and Erica E. F. Ballantyne 1, * 1 Faculty of Social Science, Sheffield University Management School, University of Sheffield, Sheffield S10 2TN, UK; a.tob-ogu@sheffield.ac.uk (A.T.-O.); john.cullen@sheffield.ac.uk (J.C.) 2 University of Liverpool Management School, Chatham Street, Liverpool L69 7ZH, UK; niraj.kumar@liverpool.ac.uk * Correspondence: e.e.ballantyne@sheffield.ac.uk Received: 30 April 2018; Accepted: 4 June 2018; Published: 8 June 2018 Abstract: With road freight transport continuing to dominate global freight transport operations, there is increasing pressure on the freight transport industry and its stakeholders to address concerns over its sustainability. This paper adopts a systematic review to examine the academic literature on road freight transport sustainability between 2001 and 2018. Using content and thematic analysis, the paper identifies and categorises sustainability intervention mechanisms providing useful insights on key research applications areas and continental distribution of sustainable road freight transport (SRFT) research. In addition to the six-overarching sustainability intervention mechanism themes identified: decoupling, Information and Communications Technology (ICT), modality, operations, policy, and other, future research can explore the effectiveness of different interventions mechanisms identified in this study to improve sustainable practices across different continents. Keywords: road freight; sustainability; intervention mechanisms; systematic review; externalities 1. Introduction Despite its importance to economic growth and prosperity, there are valid concerns relating to the sustainability of road freight transportation in terms of safety, efficiency, and health implications. These concerns are reflected in the contemporary road freight transport literature [1–6]. Accordingly, there is increasing pressure on stakeholders to address externalities emanating from freight transport operations across a variety of landscapes including urban, inter-urban, and rural landscapes. For example, in Europe, road freight transport sustainability is a priority for the European Commission (EC) with initiatives like MERCURIO, ERTRAC, KOMODA, and FIDEUS highlighting the commitment of the supranational and State level actors to addressing road freight transport sustainability. Academically, authors [ 6 – 8 ] have explored various sustainability initiatives in the road freight sector with insights on policy approaches, multi-stakeholder involvement, and modal integration planning. These initiatives represent some of the different mechanisms employed to intervene and tackle road freight externalities. For example, the literature investigates and discusses the idea of green corridor infrastructure for road freight transportation [ 9 ], other studies [ 1 , 10 , 11 ] have explored applications of information and communication technology (ICT) to aid sustainable road freight operations, whilst other studies discuss policy loopholes and freight energy management strategies [12]. Intervention mechanisms represent efforts, tools, and approaches that are theory or practice informed to address specific challenges. These capture not only the vitality of research inquiries into sustainable road freight transport but also highlight the complexity of the field. A resulting implication Sustainability 2018 , 10 , 1923; doi:10.3390/su10061923 www.mdpi.com/journal/sustainability 5 Sustainability 2018 , 10 , 1923 of this complexity is a lack of knowledge congruence which can negatively impact the development of research collaboration and efficiency [ 13 ]. Further, the literature is yet to address the impact of contextual limitations on the adoption of specific intervention mechanisms and this can have interesting impact for strategic planning amongst freight transport stakeholders. For example, green corridor initiatives can be considered as Pan-European, with conceptual and pragmatic acceptance across the European community. However, limitations relating to infrastructure or regional mobility may affect their adoption outside of Europe, for instance the absence of such regional cooperation in Africa or Southern America limits the pragmatism of such an initiative in these regions and thus highlights potential knowledge gaps concerning relationships between contexts and intervention mechanisms. The purpose of this paper extends to examining the focus of the literature as well as providing some guidance for optimising future research and practice across different regions. In this regard , the objective of this paper is to provide a synthesized account of the literature on sustainable road freight transport (SRFT) interventions offering some insight on the main SRFT research streams, taxonomies, as well as insights on the contextual implications for SRFT intervention mechanisms. Such outcomes can improve future research synergy and collaboration, support strategic planning and offer useful reference for future research. To achieve our objective, the following research questions were posed: 1. What are the main intervention mechanisms advanced in peer-reviewed publications on sustainable road freight transport? 2. What implications do regional contexts have on the adoption of different intervention mechanisms? Addressing these questions through a critical review of the literature will advance the significance of sustainable road freight transport as a critical area of research in the logistics and supply chain sustainability literature. Additionally, it will address current knowledge gaps on the relationship between intervention mechanisms and geographical contexts, with implications for future research and practice. The rest of this paper is organised as follows: Section 2 presents a discussion of systematic literature reviews in management research; Sections 3 and 4 describe the methodology and analysis approaches for the study; whilst Section 5 presents the study discussions. Finally, our concluding statements and directions for future research are presented in Section 6. 2. Systematic Literature Reviews The use of systematic reviews in the social sciences and specifically management research has significantly developed in the last decade with increasing acceptance across ontological and epistemological divides [ 14 ]. As knowledge converges and develops towards complementary methods in the social sciences, the pillars of reliability and apposition are increasingly important [ 15 ]. It has been advocated that systematic reviews help to map relevant intellectual territories that identify how and where the literature base can benefit from further studies, i.e., the identification of research gaps [ 14 ]. Whereas others take a more instructive approach [ 16 ], calling for systematic reviews to support the literature’s account of contextual factors that need to be integrated into management research. The importance of these issues is addressed by [ 17 ] who underline the use of systematic reviews to enable transparency, inclusivity, heuristics, and explanation in the review process. Accordingly, the importance of systematic reviews of the extant literature on SRFT related studies has been previously emphasized [ 4 ] who highlight the benefits to the development of research in this area. However, since Perego’s review [ 4 ], there has been little done to update the literature in this area and a recent review [ 18 ], focuses more on the general urban logistics function rather than road freight transport specifically. SRFT research requires targeted and collaborative synergies to address the ubiquitous challenges faced and a systematic review of the data can give useful funneling for identifying specific trends as well as collaborative scope in SRFT research. 6 Sustainability 2018 , 10 , 1923 3. Methodology The importance of a review protocol prior to conducting a systematic review of the literature and cited its usefulness for mitigating biases in the review process has been emphasised [ 17 ]. The literature review protocol was implemented in four stages, i.e., design, review, selection and analysis. 3.1. Design of Review Protocol Accordingly, 3 review team members jointly developed a protocol with inputs from discussions with academic and industry experts in road freight logistics within and outside the UK. The purpose of this was to enhance the rigour and evidence base of the review outcomes. The protocol tied the review objectives to the processes establishing the data sources, plausible databases, inclusion and exclusion criteria, search string techniques and acceptance schedule (Table 1). Table 1. Review Protocol. Inclusion and Exclusion Criteria Databases Data Sources Inclusion Exclusion Taylor & Francis Google Scholar Science Direct Web of Science Sage Emerald Online (Soft) Print (Hard) Timeframe Between 2001 and February 2018 Outside 2001–2018 Type Peer reviewed Non-peer reviewed, books, conference papers Topic Road freight transport, road logistics, sustainable road freight transport Non-sustainability, Non-road freight transport Language English or English Translate Non-English Reviewer’s Initials Paper no. Decision (Please tick) Accept/Rationale Reject/Rationale Search Technique Boolean, Verbatim and Word combinations: The protocol was not considered a rigid guide and iteration supported modification as the actual review process progressed. Although SRFT publications go back many decades, our focus was on identifying contemporary and updated intervention mechanisms. The cut off timeline for the review was initially set between the years 2001 and 2016 and later extended to 2018 (February), following further reviews and feedback. This period coincided with uptake in technology as well as commencement of the millennium development goals (MDGs), which underlined a global outlook to sustainability across different sectors. Practical constraints relating to time, feasibility, access to materials and review scope also informed the design and modification of the protocol. For example, although we are aware of useful grey publications, we omitted these from the review due to considerations on quality and reliability (peer-review process improves the value of the report) and practicality (impossible to review all publications or gain access to regional publications across different continents). 3.2. Review and Selection Following the review and affirmation of the agreed review protocol, six databases; ScienceDirect ® , Emerald ® , Taylor and Francis ® , Sage ® , Web of Science ® and Google Scholar ® , were identified as suitable for conducting the literature search. This was informed by learning from similar literature reviews and the need to represent the complexity of SRFT publications. Test searches revealed gaps in scope of individual databases and we observed that the incorporation of more databases offered greater opportunities for capturing the latitude of potential SRFT literature. Simple operator and Boolean search methods were combined to execute the search using different phrases and strings to implement the search. In the first instance, the review process was designed to follow a funneling procedure, moving from broad references to smaller and restrictive (Boolean) criterion as the review progressed. Search strings and keys works including: “sustainable freight”; “green freight”; “road freight”; “sustain* 7 Sustainability 2018 , 10 , 1923 freight”; “green freight*”; and “road freight*”, “sustain* logistics*”, were used to search these databases with a combined yield of 2265 hits in 2016 and an extra 88 hits in 2018. After a review of titles and over 300 abstracts from the first searches, a few adjustments were made to the protocol. For example, the phrase “road freight” was removed from the ‘list of search strings’ due to its extremely large sample when used by itself without ‘green’ or ‘sustainability’ included in the search. Boolean logic was applied to combine keywords like “Road freight” and “sustain*”, improving the focus of the returned results. In many instances, some of the results from these search strings failed to address any sustainability issues and included other issues besides road freight transport. This led to the rejection of 1158 papers, which were deemed irrelevant based on a 1st screen scanning of the titles and abstracts. An important learning from this process was the critical role that titles, abstracts and keywords play in influencing publication visibility and readership of peer-reviewed material. Following further searches and ‘hit’ reviews, a decision was made to exclude Google scholar from the ‘search database’ because of duplicity and source credibility. For example, a preliminary search conducted using the ‘sustainable freight’ string returned just over a thousand results with Google scholar accounting for over 90% of the results (Figure 1). Closer scrutiny of the results revealed that over 200 of the results from Google Scholar were repeated on several occasions within the database with varying citations from both peer-review and bogus sources. Furthermore, we established that much of the ‘peer-reviewed’ references within the Google Scholar batch were already reported by the other databases. Whilst it is plausible to suggest that the exclusion of the Google Scholar database may raise questions about the scope of the evidence incorporated in the review, it was also important that the review was conducted within robust but qualitative parameters. This is particularly important when the “peer review” inclusion criterion is taken into consideration. Figure 1. Chart illustrating initial database ‘hits’ for “Sustainable Freight” string. Progressively, search terms were replicated across the remaining databases with additional strings used to streamline the searches. As captured by the protocol, the focus was on peer-reviewed material in published sources and a total of 403 hits were returned across 8 re-organized searches. After screening for duplicates and relevance, a total of 168 materials were accepted for further review. A 3rd stage review of the abstracts, introduction and publication type saw an elimination of a further 54 materials which were books, conference proceedings or items that did not materially discuss the related subject of “sustainability in road freight transport”. A total of 98 journal articles from 44 different journal titles were finally accepted for inclusion in the review report (Figure 2 and Supplementary Materials: Appendix A1. 8 Sustainability 2018 , 10 , 1923 ͳ ͳ ʹ ͳ ͳ ͳ ͳ ͳͲ Ͷ ͵ ʹ ͳ Ͷ ͳ ͳ ͳ ͵ ͳ ͳ ͳ ͳ ͳ ͳ ͳ ͳ ͳ ʹ Ͷ ͳ ͳ ͳ ͳ Ͷ ͵ ͳ Ͷ ͳ Ͷ ͷ Ͷ ͳ Ͳ ʹ Ͷ ͅ ͳͲ ͳʹ
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Journals Figure 2. Final Journal Selection. 9