Figure 5
The flowchart illustrates the progression of research themes in AI-enabled systems over several periods. From 2019 to 2023, the focus was on digital transformation, Industry 4.0, rail transportation, and railway operations. By 2024, the themes shifted towards information management, maintenance, and digitalization. In 2025, the research integrated advanced digital technologies within railway operations, emphasizing intelligent systems, decision-making, and sustainability. By 2026, the themes highlighted the growing importance of digital twin, sustainable development, information management, and change management, reflecting a transition towards more intelligent and integrated railway ecosystems.Thematic evolution. Source: Authors’ own work