Figure 2. Research process diagram for bibliometric analysis. Table 1. Citation analysis by year. Table 1 presents citation analysis for the previous twenty-two years. The results indicate that the largest number of articles were published in the year 2021 (212), followed by 2020 (162), 2019 (151), and 2018 (106). However, their number of citations is still relatively small compared with articles from other years. It can be seen in Figure 2 that papers from the year 2016 have the highest number of citations in the entire selected period. A total of 102 articles from the year 2016 have been cited 3020 times in the literature. Likewise, 70 articles from 2015 and 32 articles from 2006 have the second (2978) and third (2559) highest number of citations in the previous literature. It can also be observed in Figure 4 that the citation trend was positive from the year 2010 to 2016, whereas it significantly decreased in the most recent five years. Nevertheless, a growing number of articles in the last five years indicates that researchers’ attention toward ELV-related issues is expected to increase significantly with time. large quantity of ELV-related articles. Out of fifteen institutions, four are from the Peoples Republic of China, whereas three came from Japan. This indicates the high concern in China and Japan for this research area. Besides these two countries, the remaining top fifteen institutions are in France, the UK, USA, Malaysia, Belgium, Netherlands, Serbia, and Norway. Overall, it was found that the top fifteen institutions published two hundred and fourteen research articles targeting ELVs and their management. Table 2. Publications by countries. the results indicate that Chinese scholars have emphasized this research domain more in recent years. Figure 6. Influential institutions. “ Finally, this research identified various domains within ELV-related research by ana- yzing keywords clusters. The primary information contained in an article can be mainly represented by keywords, allowing us to comprehend the domain of the research topic through keyword analysis. This research specifically used VOSviewer to examine the author’s keywords. The original data were preprocessed, and comparable keywords were merged to make the data more understandable. Because most terms appeared only once, the top keywords were chosen based on a threshold of five occurrences. Hence, a total of 2,596 keywords were used; out of these, 881 keywords met the threshold with a minimum of five occurrences. The last two clusters basically represent socioeconomic aspects of the field. For instance, the yellow cluster primarily includes keywords relating to ELVs’ life cycle as- sessment and their environmental impacts, such as global warming potential, emissions, greenhouse gases, natural gases, hydrogen fuel, etc. In a similar manner, the light blue cluster represents literature covering the social side of the research. This cluster includes ar- ticles covering traffic accidents, moralities, human-specific factors, sleep disorder breathing, and positive end-expiratory pressure. Hence, these clusters cover ELV life cycle assess- ment, including their related socioeconomic problems. The results also indicate that the socioeconomic impacts have received more research attention in recent years. Figure 9. Timeline of various research areas. Table 3. Summary and scope of existing review studies. Table 3. Cont.
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