# Cost Overrun Causative Factors in Road Infrastructure Projects: A Frequency and Importance Analysis
## 5 Conclusions  
This study presents a systematic review compound by five principal stages: (1) question formulation; (2) searching of relevant documents; (3) document selection; (4) evidence collection, analysis and synthesis; and 5) results' report. Thirty-eight cost overrun factors were identified and classified into 14 categories. According to the Influence Index, the ten most important and frequent cost overrun factors were: (1) 'failures in design', (2) 'price variation of materials', (3) 'inadequate project planning', (4) 'project scope changes', (5) 'design changes', (6) 'unrealistic contract duration', (7) 'inadequate bidding method', (8) 'legal issues', (9) 'late decision making by the owner', and (10) 'political situation'. On the one hand, these results show a strong influence of design and planning aspects on the occurrence of cost overruns in road projects, taking into account the high level of influence obtained for the factors 'failures in design', 'design changes' and 'inadequate project planning'. Therefore, the cost overrun phenomenon could be widely mitigated through modifications and greater controls to traditional processes developed in the project's early stages. On the other hand, the factors 'price variation of materials', 'inadequate bidding method', 'legal issues' and 'political situation' also have a strong influence; however, their mitigation is more complex due to the mitigation actions might require changes in legislation, in addition to economic and political events related to high volatility and uncertainty. Based on the findings, it is recommended that the mitigation of cost overruns in road projects be undertaken from the early stages. This due to the fact that several causal factors with high influence values are observed among the top-20 factors with the greatest influence, which are related to different processes that belong to the initial stages of the projects, factors that are under the control of the project stakeholders and therefore have high viability to be addressed. It is worth noting that the aspects related to design require profound changes, which could imply modification of design development methodologies and even the implementation of new technologies that allow solving the current deficiencies that are causing the cost overrun occurrence. The comparative analysis between studies (Table 10) shows that the factors and the importance level reported varies both from one region to another and from one country to another. In addition to this, it is observed that studies from the same country shows a low number of common factors within the top-10. Therefore, it follows that the factor importance level is affected by the project environment conditions and variables. However, the factors with the highest influence levels reported in Table 7 represent general deficiencies, on which it is feasible to base the shipment of high-impact solutions so that the cost overrun mitigation has a general perspective. Future works could focus on the following: (1) identifying cost overruns factors for road projects from countries where there are no studies, (2) studying the relationship between cost overruns factors and magnitudes, and (3) analyzing the relationship between reported factors and geographic location. Limitations of this study are: (1) the low number of studies of cost overruns factors in road infrastructure projects located in European and American countries, (2) the selection of the top-10 factors reported with a higher level of importance, instead of a greater number. **Supplementary Materials:** The following are available online at [[http://www.mdpi.com/2076-3417/10/16/5506/s1](http://www.mdpi.com/2076-3417/10/16/5506/s1)]([http://www.mdpi.com/2076-3417/10/16/5506/s1](http://www.mdpi.com/2076-3417/10/16/5506/s1)), Table S1: Database reviewer papers. **Author Contributions:** All authors participated in the evidence collection, analysis and synthesis, in addition to document writing. [PERSON] performed the network analysis of relationships between the identified factors.