3.1. Reverse Logistics
The concept of reverse logistics has evolved in the last decades, and different authors have highlighted the evolutionary process being experienced by this discipline [31
]. According to Rubio and Jiménez-Parra [35
], the origins of RL date back to the seventies, where some contributions on raw material recycling were published (see, for example, Guiltinan and Nwokoye [36
]; and Ginter and Starling [37
]); however, these first papers used to employ terms such as reverse channels or reverse flows as a way of illustrate the movement of materials and products from consumers to recyclers, in the opposite direction to the traditional forward flow in the Supply Chain (SC). Then, in the nineties, the first definitions of RL appeared (see, for example, Rogers and Tibben-Lembke [34
]; Pohlen and Farris [38
]; Stock [39
]; and Kopicky et al. [40
]) at the same time, significant contributions from engineering and operations research fields provided a new approach to this concept (see, for example, the pioneer paper by Fleischmann et al. [41
]). Among the definitions for RL, one of the most acknowledged was provided by De Brito and Dekker [32
] who define reverse logistics as “the process of planning, implementing and controlling backward flows of raw materials, in process inventory, packaging and finished goods, from a manufacturing, distribution or use point, to a point of recovery or point of proper disposal”. Finally, a holistic and strategic approach became predominant in the 21st century, making an explicit recognition of the joint existence of forward flows (from producer to consumer) and reverse flows (form consumer to producer). This is the source of the closed-loop supply chain (CLSC) concept that can be defined as “a supply chain, or a supply network, where, in addition to the typical flows of materials from suppliers to end customers, there are return flows of products (post-consumption or use) to the manufacturers” [42
]. In this way, supply chain management is understood as a whole, where the links between traditional logistics operations (forward flows) and reverse logistics operations associated with return flows need to be considered.
As previously was mentioned, in a similar way to the growing academic interest in this field, reverse logistics and CLSC have enormous economic potential [4
]. Actually, currently, it is difficult to find supply chains with more or less presence of reverse logistics [45
], and enterprises, such as Apple, Canon, Caterpillar, Dell, Electrolux, Hewlett-Packard, IBM, and Kodak have already developed and implemented reverse logistics systems to collect and manage end-of-use products (EOU), end-of-life products (EOL), and commercial returns. This interest in implementing reverse logistics systems is usually attributed to three factors that act as drivers for companies: (1) Obtaining competitive advantages, (2) environmental legislation, and (3) the pressure exerted by different stakeholders [42
]. These factors are known as the triple bottom line: profit, planet, and people.
Firstly, from an economic viewpoint, companies may get a competitive advantage by using EOL products as inputs in their production process, generally with a less cost than the original raw materials, but also, by accessing to new market segments (as a way of increasing revenues) in which environmentally aware consumers are willing to meet their needs with re-manufactured, reused, or recycled EOL products. Secondly, from an environmental perspective, a strict legislation arises in order to be sure that waste generated and its management and proper disposal are priorities in our developed societies [47
]. In this sense, some initiatives carried out in the context of waste reduction can be considered as pioneers, namely the Dual System in Germany (1992) and the National Packaging Protocol in Canada (1990) [48
]. As a result, other measures were implemented by companies to cope with legislation requirements, such as the principle of extended producer responsibility (EPR) and the development of systems for collecting and properly managing EOL (see for example, Rubio et al. [49
]). Thirdly, from a social viewpoint, increasing awareness about the negative impact of human activity on the environment (e.g., causing shortages of raw materials, pollution, climate change, etc.), also leads to increasing pressure exerted by different stakeholders on companies and organizations to implement measures aimed at developing suitable systems for resource and waste management [46
]. Reverse logistics is, therefore, a key factor for the supply chain management and logistics activity [51
In order to provide a closer point of view to this topic a document searching process on the reverse logistics topic was carried out using the Scopus database. As options of searching, documents articles, book chapters, books, reviews, and editorials were employed, all of them in the English language. In order to refine the searching, two requirements were considered. Firstly, the term “reverse logistics” and/or its synonyms (“reverse flows”, “closed loop supply chain”, “reverse supply chains”, “product recovery”, and “commercial returns”) should be included in the field “tittle document”. Secondly, the term “literature” or “literature review” or “framework” or “challenges” should appear in the “title, abstract, or keywords” field. The search period used was from 1976 to 2018. As a result, a total of 528 documents were identified. Although, it is in the beginning of the 1990s when it seems to arise the number of documents publishes on that topic, the majority of them (89%) were published from 2008 to 2018. Regarding the country or region of origin, it is noted that around 65% of them were published by institutions located in ten countries: United States (16.8%), India (11.6%), China (8.4%), United Kingdom (5%), Iran (4.8%), Germany (4.1%), Brazil (3.8%), Canada (3.6%), France (3.5%), and Denmark (3.2%). Finally, regarding the type of document, most of them were articles (87.3%), followed by reviews (7.2%), book chapters (4.5%), books (0.6%), and editorials (0.4%).
In spite of this interest on RL, many authors agree that there are significant challenges that still require special attention and further research [11
]. Among these challenges, we could highlight those that are shown in Table 2
3.2. Urban Logistics
According to the United Nations Organization [56
], 55% of the world’s population lives in urban areas and it is estimated that this figure will reach 68% by 2050, for a total world population estimated around 7.75 billion people. Furthermore, it is necessary to highlight the existence of great disparity in urbanization levels by geographical area, with the regions of North America (82%), Latin America and the Caribbean (80%), and Europe (74%) being the most urbanized.
As the number of urban areas increases, this heightens certain economic and social problems caused by large population agglomerations, traffic congestion, and atmospheric pollution, which impacts on both the quality of life and health of the population and the efficiency of the logistic activities of companies [21
]. For instance, according to the European Environmental Agency (EEA) [58
], in 2016, the transport sector contributed 27% of total EU-28 greenhouse gas emissions, which represented a 26.1% higher relative to 1990. Similarly, the World Health Organization (WHO) is also warning about the ambient air pollution generated by transport in our cities. According to this entity, the transport sector is one of the main sources of air pollution, for which evidence on direct effects on mortality as well as on respiratory and cardiovascular disease is firmly established. Transport is a major source of emissions of urban air pollutants with 60% of cities in Europe exceeding WHO air quality guideline levels for particulate matter [59
Given this situation, it seems necessary to find a balance between the urbanization process and sustainable development, with special emphasis on city planning that promotes the economic and social development of cities whilst also searching for solutions to reduce the negative impact on the environment [60
]. In this regard, both the public authorities and companies must be able to work together to achieve the aims pursued by both parties; that is, to improve the quality of life of the citizens through good mobility management and the suitable and efficient management of commercial activity [61
]. Urban logistics can play a very important role in the search for that balance [21
Regarding this topic, a document searching process was also conducted. In this case, 136 documents were identified using the same database and the same options of searching as in the case of reverse logistics. The requirements taken into account to refine the searching were: (1) The term “urban logistics” and/or its synonyms (“city logistics”, “last mile delivery”, “urban freight”, and “urban delivery”) should be included in the field “tittle document”, and (2) the term “literature” or “literature review” or “framework” or “challenges” should appear in the “title, abstract, or keywords” field. The search period used was from 1984 to 2018. Approximately, it was in 2011 where it could be observed an increasing tendency in the number of documents published on that topic. However, the majority of them (81%) were published in the period 2013–2018. With respect to the country or region of origin, it can be highlighted that almost 60% of them were published by institutions located in Italy (12.9%), United States (7.9%), United Kingdom (6.7%), France (6.2%), Netherlands (6.2%), Sweden (6.2%), Belgium (5.1%), Canada (3.9%), and Germany (3.9%). Regarding the type of document, around 83% were articles, followed by book chapters (9.6%), reviews (7.4%), and editorials (0.7%).
Nevertheless, in recent years, some papers providing a general overview of the current state of the research on urban logistics were published. In this sense, Crainic et al. [15
] provide a brief history of urban logistics, highlighting milestones and defining fundamental concepts such as consolidation (related to the activities developed at the city distribution centers, CDC) and coordination of operations developed by different stakeholders at different levels of participation and engagement. A systematic review of literature on urban logistics was carried out by Lagorio et al. [24
], who analyzed 104 papers published in 24 different journals in the period 2000–2013. As a main result of this review, three main areas of possible investigation for the next future were identified: (1) stakeholder engagement, (2) urban logistics ecosystem, and (3) common frameworks and data sharing platforms. According to Savelsbergh and Van Woensel [20
], the challenges of city logistics change continually, so a review and discussion of these challenges is provided, namely population growth and urbanization, e-commerce, sharing economy, speed in deliveries, climate change, and sustainability. Additionally, some opportunities for research are identified: network design, omni-channels logistics, delivery systems, stakeholder cooperation, and sustainability. Finally, Rose et al. [62
] developed a systematic literature review, from different academic disciplines, highlighting the gaps regarding the defining features of urban logistics and proposing a framework of urban environmental factors affecting logistics operations. A remarkable contribution of this investigation is the definition of the concept of urban logistics in which an explicit mention to the existence of reverse flows occurring within urban systems is made. This way, according to Rose et al. [62
], urban logistics is defined as “that part of supply chain management that plans, implements, and controls the efficient, effective forward and reverse flow and storage of goods, services, and related information between the point of origin and point of consumption in order to meet customers’ requirements, as influenced by complex interactions among densely populated social systems and associated infrastructure”.
Recently, new trends in urban logistics have also been reported. For example, those related with the decentralization of logistics hubs and facilities (logistics sprawl) and its implications for land use planning, freight transport, and employment [63
]. Another relevant issue is related to freight transport management and the role played by public authorities to improve freight transport activity in urban areas. Holguín-Veras et al. [64
] highlight the “tremendous need to conduct research that assess the effectiveness, advantages and disadvantages” of public policies on freight transport, and analyze different initiatives carried out in different countries regarding infrastructure, parking/loading areas, vehicle-related strategies, traffic management, as well as financial approaches, logistical management, and demand/land use management [65
]. Certainly, the goal of the research and practice on urban logistics should be to achieve a city that is liveable and healthy for everyone; to create a human city, maybe not perfect or even smart, but warm and welcoming, where it is nice to live and visit [66
]. Obviously, although these challenges deserve further discussion, they are beyond the limits of this research.
As stated before, other terms commonly used to refer to urban logistics are city logistics and urban freight transport. However, the latter, along with the logistics activities around it, has acquired special relevance in recent times due to the fact that it forms an essential part of the GDP in developed economies and has very important effects on all sorts of companies [24
Regardless of the term used to refer to urban logistics, the appropriate management of the logistics activity in cities may contribute to creating an urban freight transport system that is more efficient, safer, and more respectful of the environment and human health [21
]. For years, this has been an issue of special interest both to researchers and to public authorities and companies [67
]. This interest has also increased recently due to several reasons [24
]: the development of new forms of consumption (e.g., e-commerce); changes in consumer attitudes, tastes, and preferences (e.g., greater awareness about environmental issues); and the growing evolution of technology that allows for new ways of supplying goods (e.g., the use of drones or electronic vehicles with greater autonomy). Table 3
summarizes different challenges existing in the field of urban logistics.