Fig. 3: Research topics and evolving trends in sustainable mobility and transport.
From: The landscape, trends, challenges, and opportunities of sustainable mobility and transport
a Keyword co-occurrence network. Each node indicates a keyword, and the node’s size and color indicate its average co-occurrence frequency and the research topic it belongs to, respectively. b Evolution trend of research topics in the past decade. The y-axis indicates the importance of each topic in the corresponding publication year. The curve fits the evolution trend of topic importance.
