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Purpose Extensive research towards identifying the attributable cost overrun factors globally has been conducted predominantly from a survey-oriented perspective, which disregard the contextual basis on which these triggers manifest. This study aims to explore the driving factors of cost overrun in highway projects, specific to the Nigerian context. Design/methodology/approach The research used a context-based approach to seek project stakeholders’ perspectives on the key drivers of cost overrun in highway projects in Nigerian. Semi-structured interviews were conducted with client, contractor and consultant organisations involved in the provision of highway infrastructure projects in Nigeria. The collected data was analysed using a developed coding framework grounded on a case study approach, principles of inductive thematic analysis and saliency analysis to identify the key drivers. Findings Findings from the analysis identified triggers from macroeconomic, societal, leadership and project management perspectives with synergistic relationships with each other based on prevalence and significance. Among the key triggers is a delay in work progress, political instability, adverse weather, social issues, delay in progress payment to contractors and modification of project scope. In conclusion, the triggers of cost overrun in highway projects are contextually driven by the complex nature of the project management, societal, macroeconomic and leadership triggers specific to the Nigerian context. Research limitations/implications The research was limited to only highway infrastructure projects in Nigeria. Furthermore, the findings are based on a small sample size, and thus, caution must be taken before applying the outcome of this study in a generalised way to other contexts. Practical implications Practically, the stakeholders i.e. client, contractors and consultants should acknowledge the contextual circumstances in which each of the triggers takes place, which will aid in developing pragmatic measures and make the right decisions towards addressing these triggers during any highway construction project in Nigeria and enhance the chances of project success. Originality/value The context-based approach applied in this study is expected to provide a new insight in understanding the triggers of cost overruns, especially in highway projects in Nigeria and indeed other developing countries with similar governance characteristics

Purpose Empirical evidence suggests that many triggers influence poor cost performance in highway projects, whereas previous studies about the cost overrun triggers stem from a positivist standpoint supported by conventional statistical techniques, thus disregarding the sophisticated interactions and overall dynamics of the triggers. This study contends for a paradigm shift in investigating and understanding cost overrun triggers by adopting a holistic perspective through the lens of system thinking. This study aims to contend for a paradigm shift in investigating and understanding cost overrun triggers by adopting a holistic perspective through the lens of system thinking. Design/methodology/approach Semi-structured interviews with industry stakeholders in Nigeria were conducted buttressed by textual data from literature sources and project documents. Data analysis based on a developed data compatible coding framework and causal relations from textual data sources was used to develop a causal loop diagram depicting the interactions of the triggers which were validated by experts. Findings The analysis of the causal loop diagrams (CLDs) allowed identification of action points used to suggest changes for improved cost-effective highway project delivery. Among the suggested interventions are ensuring the provision of adequate funding prior to contract award will result in timely delivery of projects and indeed delivering key projects at the contractual agreed budget. This can be achieved through ensuring strict adherence to the provisions of Section 4 (2) (b) of the Nigerian Public Procurement Act, 2007 which stipulates that no contract should be awarded if funds are not available from the onset. Research limitations/implications The study was limited to only highway infrastructure projects in Nigeria and as such caution must be taken before using the outcome of the study to other context within Nigeria and beyond. Practical implications From a practical point of view, the causal model demonstrates that this study is capable of being used to make pragmatic decisions regarding policy leverages about improving cost performance in highway projects provision in the Nigerian highway infrastructure sector of the construction industry. Moreover, it will aid a clear understanding of the key influencing triggers of cost overrun by the relevant stakeholders within the highway sector of the industry. Originality/value The hybrid-based approach applied in the development of CLDs in this study is expected to provide new insight into understanding the linkages, interactions, feedbacks and processes among the key cost overrun triggers and suggesting leverages for cost performance improvement within the philosophy of system thinking.

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A reduced-height and reduced-pressure (RHRP) INER (Institute of Nuclear Energy Research) Integral System Test (IIST) facility has been built for simulating the thermal hydraulics (T/H) behavior of Westinghouse three-loop pressurized water reactor (PWR). Experiments on loss of all feedwater (LOFW) with no operator action and with reactor coolant system (RCS) bleed and feed were conducted at the IIST facility. The experimental results not only explore the key (T/H) phenomena during LOFW transients but also show the validation of RCS bleed-and-feed procedures for mitigating the consequence of LOFW transient.