Typological synthesis of cost overrun determinants in road construction using “K-means”: a narrative synthesis

Abstract

Road projects are indispensable for a country’s economic and social development. Despite the importance, road construction projects are vulnerable to cost overruns. Thus, the identification of causative factors is prudent to mitigate the risk of cost overruns. While previous studies have identified cost overrun factors in isolation even lack systematic clustering of factors. Furthermore, few studies have employed unsupervised clustering techniques to objectively classify cost overrun factors, whereas most have relied on subjective categorisation methods. This study conducted a data-driven typology of cost overruns in global road construction projects through a narrative synthesis. The data were extracted from peer-reviewed literature in the Scopus, Taylor & Francis and ProQuest databases, which provide comprehensive coverage of construction management and engineering literature from 2020 to 2025, to capture contemporary road cost overrun factors. Subsequently, hierarchical clustering was applied to determine the number of clusters, followed by K-means clustering to optimise the classification of cost overrun factors. Results identified 253 cost overrun factors, which were first organised into nine thematic categories and subsequently grouped into the three identified clusters. The most frequently cited factors across the literature were ‘political instability, supply chain disruptions, contractor’s incompetence, inaccurate cost estimation, project scope changes, claims due to uncertainty incidents, financial mismanagement by contractor, delays in obtaining permits, delays in contractor’s payments and inappropriate procurement systems. The unsupervised clustering offers a systematic classification of cost overrun factors that can be applied to different domains in future.