## 5 Conclusions  
The performance of construction projects depends largely on the efficiency of the operative management and decisions taken in the course of the project. The proposed method was intended to support decisions at the stage of designing the implementation of construction projects. It helps assess the chances of meeting the project due date and considers the effects of corrective measures (working overtime, hiring additional resources, etc.) in terms of both cost and time.  
The proposed approach is innovative: the existing methods of reactive scheduling respond to schedule disturbances by relocating resources and rescheduling the processes that have not started yet--in a way that minimizes the weighted sum of the differences between the updated and the baseline process starts [43]. The authors found only one study [45] that, in addition to the above, considers the problem of selecting the process acceleration measures.  
The authors assume that, due to risk, the process durations can be modeled as random values. In contrast to other approaches, the aim is not to build an optimized schedule after each disturbance. Instead, an optimal decision rule to pick the schedule acceleration measures is desirable. It is therefore not necessary to carry out an optimization procedure every time a disruption occurs. The quality of the decision rule is evaluated in the course of the simulations: its outcomes are assessed based on the distribution of results obtained in many simulation runs. Therefore, as the assumptions are different, the results obtained using the proposed method are not directly comparable with the results generated employing the methods proposed in the literature.  
The proposed method is intuitive. It does not involve complex optimization calculus which the site engineers might be not familiar with. The simulation model needs to be developed only once, and the simulation tests are repeated only when the parameters of the model are changed--the lag time. They can be performed using practically any simulation package available on the market. The data for the model are obtained based on expert opinions, as in PERT, which is widely established in the construction industry.  
Construction activity is considered particularly exposed to risk and uncertainty. Nevertheless, assumptions of full knowledge of work organization parameters and on the influence of disturbing factors are frequently made by construction schedulers. The reason may be the availability of software that supports only deterministic planning, or a natural human preference for exact numbers that define project dates. However, deterministic schedules tend to expire. The approach of subsequent updates in reaction to changes (incremental design strategy) is usually less efficient than the strategy of searching for an optimal solution in given conditions (proactive approach), yet it is commonly used in practice. Therefore, the direction of further research is to develop pro-active scheduling methods that account for the possibility to switch from one mode of operation to some other, selected out of a set of options differing in duration, cost, and even resources.  
Conceptualization, methodology, P.J. and S.B.; description of the problem, P.J.; simulation model programming, S.B.; validation, P.J. and S.B.; simulation experiments, S.B.; formal analysis, P.J. and S.B.; data collection, S.B.; writing--original draft preparation, writing--review and editing, P.J. and S.B. Both authors have read and agreed to the published version of the manuscript.  
This research was financially supported by the Ministry of Science and Higher Education in Poland within the statutory research number FN/63.  
The authors declare no conflict of interest.