In 2024, multiple tenders for infrastructure projects using Integrated Project Delivery (IPD) are issued.These models have recently been introduced in Germany and Austria. They aim to reduce cost andschedule overruns on major projects. IPD uses criteria such as partnership-based project managementwhich is based on a collaborative culture to select a contractor. Contract models, such as costreimbursement with bonus/malus mechanisms, are used to further reduce the impact of price. However,traditional calculation is not suitable for new remuneration models as it tends to hide extra profits. It istherefore not transparent enough for the successful implementation of IPD.The construction costs are usually determined in the award procedure by pricing a bill of quantities.However, in IPD there is no bill of quantities. Instead, the cost estimate is based on a probabilisticperformance calculation by the contractor. Costs for materials and machinery are recorded separatelyand independently. Risk management gives the cost calculation a range. Overheads and profit areadded based on pre-agreed mark-ups. A bonus/malus mechanism encourages cost reductions by thecontractor. This allows transparent control by the owner or a third party. Including scientific theories,such as systems theory, probability theory, principal agent theory and hold-up problem, in thedevelopment of the model ensures maximum transparency in cost estimation.This paper presents the basics of traditional calculation and shows the reasons why it is not suitable forestimating the costs of large construction projects. A new holistic and transparent model for probabilisticcost estimation is developed and presented. The focus is on the base costs. The paper concludes withan outlook on further research and an option of digitalization of the process transparency.    «

In 2024, multiple tenders for infrastructure projects using Integrated Project Delivery (IPD) are issued.These models have recently been introduced in Germany and Austria. They aim to reduce cost andschedule overruns on major projects. IPD uses criteria such as partnership-based project managementwhich is based on a collaborative culture to select a contractor. Contract models, such as costreimbursement with bonus/malus mechanisms, are used to further reduce the impact of price. However,traditio...    »