Significant factors affecting the New Zealand transportation infrastructure project cost – quantity surveyors' perception

PurposeCost overrun is one of the critical issues faced in construction projects, as nine out of ten projects will likely go over the budget. In particular, transportation infrastructure (TI) projects, such as roads and bridges, are vastly affected by cost overruns, which can delay the entire project. This research intends to identify the factors affecting the cost overruns in New Zealand (NZ) TI projects.Design/methodology/approachThe research was conducted using a questionnaire survey involving ninety-two participants experienced in infrastructure project estimation in NZ. Quantitative methods were used to analyse the data.FindingsFifty-three factors were identified through literature under ten categories. Based on the survey, ten significant factors were identified with a high grade of importance. The three most critical factors were “frequent design changes,” “poor planning and scheduling” and “inadequate tender documentation.” It was found that the cost overrun is primarily affected by the pre-contract stage causes.Research limitations/implicationsThe data were collected from professionals involved in NZTI projects. Therefore, the implications may be different for other contexts.Practical implicationsThe results will improve the current estimation practice by developing a new statistical model considering all the significant variables for NZTI projects.Originality/valueAlthough much research is done to identify these factors, they are only considered in a few statistical cost models. These new statistical models mainly focused on technical variable factors similar to the current standard estimation process. However, the results of this research, qualitative and quantitative factors, will be used for the future cost model.