Introduction

It is widely recognised among professionals involved in delay disputes that various methods exist to assess delays during a project's lifecycle. These methods, collectively referred to as delay analysis methods, are essential tools for understanding the causes of delays, supporting or dismissing Extension of Time (EOT) claims and assisting in resolving disputes in litigation, arbitration or other alternative dispute resolution (ADR) processes. Among these methods, programme-based delay analyses, which rely on project schedules and software, are frequently employed. However, their effectiveness is frequently a subject of debate, with critics arguing that they have inherent limitations in their underlying methodologies.

Overview of Delay Analysis Methods

The Society of Construction Law (SCL) Delay and Disruption Protocol[1] outlines six recognised delay analysis methods. Similarly, the Association for the Advancement of Cost Engineering (AACE) provides guidelines[2] that describe delay analysis methods, which differ slightly from those in the SCL Protocol. Delay analysis methods can be broadly categorised into two groups:

1. Programme-Based Methods: These rely on project programmes and specialised software to assess delays. Frequently, events are inserted into the programmes to evaluate their impact, with the critical path determined based on the forecast durations of the activities.
2. Non-Programme-Based Methods: These methods do not heavily depend on software and often employ simpler, more straightforward techniques to analyse delays.

While some argue that all delay analysis methods produce similar results, it is widely recognised among delay experts that different methods can lead to significantly varied outcomes. For example, if they are not used correctly, programme-based methods such as Time Impact Analysis (TIA) and Impacted As-Planned Analysis are often perceived to favour contractors, as they can exaggerate the impact of events on the project schedule.

Moreover, the SCL Protocol highlights that all delay analysis methods may not be suitable for every situation, implicitly acknowledging that different methods may yield varying results depending on the specific conditions of a project.[3]

The Role of Programme-Based Delay Analyses

Programme-based delay analyses are commonly utilised by contractors to demonstrate the impact of employer-related delay events on project programmes. These methods are particularly valuable during the course of the works, as they provide a theoretical evaluation of delay events, enabling employers to make informed decisions regarding extensions of time (EOTs) and overall project management. In fact, during the execution of a project, programme-based methods may often be the only practical option for assessing the theoretical impact of a delay event.

When applied correctly, programme-based analyses can produce well-founded and justifiable EOT claims. However, since these analyses rely on programmes, it is essential that the programmes are accurate, and the SCL Protocol emphasises the importance of maintaining and regularly updating accurate programme data. Nevertheless, these analyses are often undermined by programming issues, such as unrealistic activity durations, incorrect logic links and overly generalised assessments, which can exaggerate the effects of delay events.

Furthermore, when used retrospectively (after project completion), programme-based analyses are often less reliable. This is sometimes due to their reliance on poorly developed programmes and, at other times, due to their inherent limitation of providing only a theoretical projection of a delay's impact on specific activities. Consequently, the calculated completion dates for these activities may not correspond with their actual completion dates.

Inherent Limitations of Programme-Based Delay Analyses

Programme-based delay analyses rely heavily on the Critical Path Method (CPM), a programming tool originally developed for project management to identify the critical path of a project. The critical path is defined as “the longest sequence of activities through a project network from start to finish, the sum of whose durations determines the overall project duration. A delay to progress of any activity on the critical path will, without acceleration or re-sequencing, cause the overall project duration to be extended.”[4]

It is therefore of the utmost importance for delay analysis to correctly identify the critical path, as any EOT claim will be based on whether or not the delay affected the critical path. Incorrect identification of the critical path can result in unreliable conclusions regarding the impact of delays on the overall project timeline.

While CPM revolutionised project management and remains one of the most reliable tools still widely used, it was not specifically designed for delay analysis. This fundamental limitation impacts on the reliability of programme-based analyses in several ways:

Dependence on Forecast Durations: The reliability of programme-based delay analyses is heavily influenced by the quality and accuracy of the data and assumptions used to build the programme. Simply put, a programme is only as reliable as the data and logic it is based on. Any inaccuracies or flaws in the input data, activity durations or programme structure can compromise the validity of the delay analysis and its conclusions.

In project scheduling, even when programmes are updated with actual progress data during the course of the project, the durations of future activities are still based on assumptions and best estimates. Since the calculation of the critical path depends heavily on these activity durations, any unrealistic or overly optimistic assumptions can result in an inaccurate identification of the critical path. This, in turn, undermines the reliability of the delay analysis and its outcomes.

For example, the programme will identify the critical path as the sequence of activities with the longest duration that determines the project’s completion date. However, if the durations of these activities are based on flawed or unrealistic assumptions, the critical path identified by the programme may not correspond to the actual sequence of work driving the project’s completion on-site. This misalignment can result in incorrect conclusions about which activities are genuinely critical to the project’s completion and may lead to inaccurate assessments of delays.

Inability to Automatically Adjust to New Conditions: CPM-based programmes are inherently static and cannot automatically adapt to changes in project logic or the resequencing of activities. This is because they rely on predefined relationships between activities (e.g., finish-to-start or start-to-start links) and do not account for alternative sequences or dynamic resequencing options. For instance, if access to a work area is delayed, the programme cannot automatically adjust to prioritise unaffected activities or propose alternative sequences to maintain the project timeline. Instead, such adjustments require manual intervention by the planner, who must modify the links between activities to reflect the changes. Consequently, a delay analysis that relies on a programme that is not updated to reflect the new on-site conditions is likely to produce inaccurate results, as it fails to capture the actual sequence of work and the potential for resequencing to mitigate delays.

Counterintuitive Results: CPM-based programmes can sometimes identify critical paths that do not reflect the practical realities of on-site construction. For example, they may indicate that the critical path runs through relatively minor activities, such as the electrical works in a single bathroom of a multi-story building. In reality, such activities are unlikely to govern the overall project timeline. However, a delay analysis based on such a programme might conclude that a delay in completing the electrical works in that specific bathroom would delay the entire project, which is counterintuitive and does not reflect the actual dynamics of construction.

These issues arise because the programme relies on predefined logic and relationships between activities, which cannot automatically adapt to the dynamic and evolving conditions on-site. Additionally, the structure of the programme can sometimes fail to present the broader context or "big picture" of the project, focusing instead on isolated activities without adequately reflecting their relative significance within the overall project timeline. While such inconsistencies may have a minimal impact on project management, where the focus is on overall progress and coordination, they pose significant challenges in delay analysis where accurately identifying the true critical path is crucial for determining the actual impact of delay events and for substantiating or refuting claims. Misidentifying the critical path can lead to flawed conclusions and undermine the reliability of the analysis.

This is why the SCL protocol states that “Critical path analysis is not limited to analysis conducted through the use of specialist programming software. While such software can provide a powerful analytical tool, the critical path to completion may on occasion be more reliably established through a practical analysis of the relevant facts or by analysis of production and/or resource data”.^[5]

Resource-Driven Projects: In projects where the critical path is primarily driven by the availability of resources-such as drainage networks and soil improvement projects, the critical path is often determined by resource availability rather than the sequencing of activities. For example, in a project involving soil improvement in a brownfield, the critical path will not necessarily run through a specific area but rather depend on the availability and allocation of essential resources, such as equipment, labor or materials, to carry out the work.

This means that delays in one area may not necessarily impact on the overall project timeline if resources can be reallocated to other areas, allowing work to continue uninterrupted. For instance, if archaeological findings delay work in one area that appears to be on the critical path in the programme, the contractor can often resequence activities to focus on other areas and return to the affected area once the issue is resolved. However, programme-based analyses may fail to account for this flexibility, as they are typically rigid in their logic and sequencing. This can lead to exaggerated claims and inaccurate assessments of the actual impact of delays.

It is important to note, however, that this does not apply to all projects. In many cases, resequencing may not be feasible, and certain delay events will critically and unavoidably impact the project’s completion.

Conclusion

Programme-based delay analyses are valuable tools for assessing delays during the course of a project, particularly when real-time evaluations are needed to inform decisions about Extensions of Time (EOTs). However, their inherent limitations stem from their reliance on the Critical Path Method (CPM), a methodology originally designed for project management rather than delay analysis. These limitations are rooted in the quality of the programme, the static nature of CPM, its dependence on forecast durations and its inability to adapt automatically to changing project conditions. Consequently, if these analyses rely solely on programme data without incorporating practical, evidence-based insights, they often struggle to fully capture the complexities of on-site construction. This can lead to the misidentification of critical paths and less accurate assessments of delays.

When applied retrospectively – after project completion – the limitations of programme-based analyses can become even more pronounced. Retrospective applications may rely on poorly developed or outdated programmes that fail to accurately reflect the actual sequence of work or the true impact of delay events. Additionally, such analyses may provide only a theoretical projection of delays, potentially resulting in calculated completion dates that do not align with the actual completion dates. However, when applied with care, supported by accurate input data, regular programme updates and skilled analysts, programme-based delay analyses can still potentially provide meaningful insights.

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