SYSTEMATIC LITERATURE REVIEW ON LAST MILE DISTRIBUTION

\label{systematic-literature-review-on-last-mile-distribution}
In this section, we present the steps of the systematic literature review developed and present the main results obtained.

Activity 1 – Planning

\label{activity-1-planning}
In this stage, the planning of the systematic literature review, which is the first activity determined by the research protocol, is described.

Stage 1.1: identifying the need for revision

\label{stage-1.1-identifying-the-need-for-revision}
The growth of urban centers is a phenomenon manifested in regions of all continents, concentrating thus the demand for supplies in smaller geographic spaces and then creating more dispute for road space and others problems, such as traffic congestion, pollutants emissions, noise and a gradual decrease in the quality of life of the local population (Oliveira et al., 2015a). For that reason, the last mile freight distribution has been discussed in the specialized literature as an important basis for: (1) reducing operating costs (2) improving the socio-environmental sustainability and (3) increasing competitiveness. As a result, it is necessary to identify alternative ways to perform the urban freight distribution in the last mile perspective.

Stage 1.2: the purpose of the literature review

\label{stage-1.2-the-purpose-of-the-literature-review}
The purpose of this paper is to identify, through a systematic literature review new forms of operations and technologies in urban freight transport, especially identifying the main type of vehicles used in last mile distribution. The secondary objectives include identifying the main characteristics of these vehicles, the barriers, opportunities and benefits (economic, social and environmental) related to their use, as well as the range of the distributions.

Stage 1.3: developing the protocol of the review

\label{stage-1.3-developing-the-protocol-of-the-review}
The identification activity used the following databases: Web of Science, SCOPUS, EBSCO, Science Direct, DOAJ, Springer Link and Compendex, as recommended by (Thomé et al., 2016) to use more than two databases in order to ensure the identification of a greater diversity of papers. A combination of the keywords – last mile and (urban freight or urban freight distribution or city logistics) and vehicles – was chosen to identify researches that propose different technologies adopted in last mile urban deliveries. This choice was based on a preliminary survey of the keywords of six papers related to the scope of the present study. The combination of terms: last mile and (urban freight or urban freight distribution or urban freight transportation or city logistics) allows identifying studies that deals with last mile in urban freight transport or urban logistics. The objective of complementing these terms with the Boolean operator ”and” plus the term ”vehicles” is to restrict the search to papers that actually focus on the vehicles adopted in this type of operation.
The search of the chosen keywords in the selected databases was directed to the title, abstract and keywords of the papers. Since the practice of urban logistics involves the use of technologies that evolve continuously, the last five years have been considered as publication period (2012 to 2016). It is understood that the topic is important for the economy of all countries, consequently it has not been adopted a specific delimitation in geographical comprehensiveness. Initially, the search (identification stage) was restricted to papers published in indexed and peer-reviewed international journals, as recommended by (Nord et al.,1995; Ngai and Wat, 2002; Oliveira et al., 2015a) to ensure the quality of the studies. The criterion for selection of identified studies was based exclusively on the language that the paper was written (English).
The inclusion and exclusion criteria of the selected papers was based on a content analysis. Duplicate works and papers which the content was related to last mile distribution and urban freight but not specifically on the type of vehicle adopted were not considered. In conclusion, the information obtained was recorded in a database, in order to facilitate the classification, investigation and evaluation of the studies used in this research.

Activity 2 – Realization

\label{activity-2-realization}
In this section, the steps of the systematic literature review activity itself (realization) are detailed.

Stage 2.1: identify, select and include papers

\label{stage-2.1-identify-select-and-include-papers}
The identification, selection and inclusion of papers followed the criteria presented in the sub-item 3.1.3. At first, 157 articles were identified, but the exclusion of duplicate papers (since the search was performed in more than one database) resulted in a list of 125 papers, whose abstracts were read by at least two authors, as recommended by (Thomé et al., 2016). The selection process was iterative, seeking agreement among co-researchers. It culminated in the selection of 46 papers for the complete reading. Of these, 26 studies were included for the development of the systematic literature review. The results of this stage are presented in Table 1.
Table 1: Synthesis of the stage of identification, selection and inclusion of papers.