Motorway tunnel construction: Is cost variance under control? A study of ten underground structure

Federal Roads Office

Key facts

Various international studies in transport infrastructure have shown that costs are underestimated in nine out of ten projects. On average, actual costs are 30% higher than estimated at the time of project approval. This systematic tendency to underestimate costs applies to all project types. Within infrastructure, the construction of underground structures is particularly costly and complex, especially with respect to managing risk and uncertainty. For this specific type of structure, risk of cost overrun is an even higher 35%.