## 2 Literature Review  
The estimation of construction duration is based on the assessment of the TOS for the construction project, for example, using the critical path method (CPM) [31; 32]. Considering the overall process of estimating construction duration based on the TOS, it is necessary to identify the components of this process [33; 34; 35]. The TOS is a set of activities with technological and organizational dependencies between each other and is located on the time scale of the project duration. The TOS also describes the possible risks that may affect the performance of this or that work. Figure 1 provides a graphical representation of the TOS. The smallest unit of any TOS is an individual construction activity--characterized by the following indicators: TOS, normative duration, and normative cost. In practice, the normative duration is determined based on averaged data of individual construction activities, for instance, in Poland, using KNR [19]. Additionally, external factors, such as the occurrence of risk events, can influence the duration and cost of each construction activity, either increasing or decreasing it [36; 37; 38; 39; 40; 41; 42; 43; 44]. The authors of this article consider risk events solely as negative occurrences that may prolong construction duration. Thus, the actual work duration or total activity duration is the sum of the normal (average) duration and risk lag time. A graphical representation of the impact of risks on individual activities and the actual work duration is shown in Figure 2.  
Figure 1: TOS model of the construction project. Figure 2: The impact of a risk event on an individual construction activity upon occurrence. From Figure 2, it can be concluded that the duration of each activity comprises two components: the duration determined based on averaged indicators (for example, based on estimates from KNR [19]) and an additional risk lag time [45; 46], which considers the probability and impact level of a risk event. Therefore, to accurately address the issue of actual construction duration, it is necessary to precisely determine the additional time by which the duration of an individual task may increase upon the occurrence of risk events associated with that specific task. Most construction projects are implemented using best management practices, for instance, employing methodologies such as PMBOK [20] or PRINCE2 [21]. Such management methods describe various approaches and techniques for handling risks and incorporating them into project implementation, including construction projects. For example, research [47; 48] indicates that an effective risk management tool is the use of a probability and impact matrix. However, there is also the problem of choosing a risk management methodology, illustrated by the example of railway construction [49]. A probability and impact matrix is a basis for rules and dependencies between probability and impact, as well as cumulative effects on threats. This matrix allows for ranking the level of risk threat based on the likelihood of occurrence of a risk event and its impact on work or the project as a whole. For instance, in PMBOK guidance [20] and related works, numerical values are used, which can be multiplied to provide a likelihood-impact score for each risk, enabling the evaluation of relative priority levels among individual risks within each priority level. By employing this approach, it is necessary to define two input parameters--the likehood and impact score for each risk. A probability and impact matrix is a basis for rules and dependencies between probability and impact, as well as cumulative effects on threats of a risk event occurring and the level of impact of this risk event on either the project as a whole or a specific project element. Additionally, a relationship is established between the input parameters and the output parameter--the threat level, which may occur upon the incidence of a risk event.