# What Causes Cost Overrun in Transport Infrastructure Projects?"

**Authors:** Bent Flyvbjerg, Mette K. Skamris Holm, Søren L. Buhl  
**arXiv:** [1304.4476](https://arxiv.org/abs/1304.4476)  
**Date:** 2013-04-16  
**Summary page:** https://www.summarizepaper.com/en/paper/1304.4476v1/

## Key points

- Study by Bent Flyvbjerg, Mette K. Skamris Holm, and Søren L. Buhl on cost overrun in transport infrastructure projects
- Analysis of 258 rail, bridge, tunnel, and road projects totaling US$90 billion
- Factors contributing to cost escalation: project implementation phase length, project size, type of project ownership
- Significant correlation between cost escalation and duration of implementation phase
- Importance of proactive decision-making and efficient planning to mitigate risks
- Trend towards larger projects over time; bridges and tunnels experience higher percentage cost escalations with increased project size
- Need for careful consideration when undertaking large-scale infrastructure projects
- Influence of project ownership on cost escalation: accountability mechanisms are critical determinants rather than public or private ownership
- Significance of addressing potential delays and escalating costs through proactive measures at all stages of transport infrastructure projects

## Summary

In their study titled "What Causes Cost Overrun in Transport Infrastructure Projects? ", authors Bent Flyvbjerg, Mette K. Skamris Holm, and Søren L. Buhl present findings from a comprehensive analysis of 258 rail, bridge, tunnel, and road projects totaling US$90 billion. The research focuses on identifying factors contributing to cost escalation in these infrastructure projects by examining the impact of project implementation phase length, project size, and type of project ownership. The study reveals a significant correlation between cost escalation and the duration of the implementation phase. Delays and extended timelines during this phase pose substantial risks for cost overruns. This highlights the importance of proactive decision-making and efficient planning to mitigate these risks. Furthermore, the research shows a trend towards larger projects over time with bridges and tunnels experiencing higher percentage cost escalations as project size increases. This emphasizes the need for careful consideration when undertaking large-scale infrastructure projects. The study also challenges common assumptions about the influence of project ownership on cost escalation. While it is often believed that private ownership may be more effective in controlling costs compared to public ownership, the findings indicate that accountability mechanisms play a more critical role in determining cost outcomes. Overall, this study underscores the significance of addressing potential delays and escalating costs through proactive measures during all stages of transport infrastructure projects. These findings have significant policy implications for stakeholders involved in infrastructure development and management.