Geoff Bewsey, Partner HKA

Same Term, Two Paths

The Society of Construction Law Delay and Disruption Protocol (SCL Protocol) describes two delay analysis methods in which the critical path is determined ‘contemporaneously,’ and delay impact is determined ‘retrospectively.’ With no other explanation, both methods are said to identify ‘the contemporaneous or actual critical path.’

In this short paper, I propose how the contemporaneous critical path and the actual critical path are distinct yet inseparably connected.

“… the contemporaneous critical path exists in the forecast portion of a programme^[1]Or other planning for the works., whereas the actual critical path exists in the as-built portion, being developed from the sequential chain of contemporaneous critical activities over time.”

Understanding the Distinction

The SCL Protocol^[2]Society of Construction Law delay and Disruption Protocol, 2nd Edition, February 2017. describes two analysis methods in which the critical path is determined ‘contemporaneously,’ and delay impact is determined ‘retrospectively.’

The ‘Time Slice Windows Analysis’ is said, in the SCL Protocol, to use a series of time‑slice programmes to reveal “the contemporaneous or actual critical path in each time slice period as the works progressed and the critical delay status at the end of each time slice, thus allowing the analyst to conclude the extent of actual critical delay incurred within each window^[3]SCL Protocol, Guidance Part B, paragraph 11.6(c).

The ‘As-Planned versus As-Built Windows Analysis’ for which the SCL Protocol states: “The analyst determines the contemporaneous or actual critical path in each window by a common-sense and practical analysis of the available facts.… The incidence and extent of critical delay in each window is then determined by comparing key dates along the contemporaneous or actual critical path against corresponding planned dates in the baseline programme^[4]SCL Protocol, Guidance Part B, paragraph 11.6(d)”.

Both methods rely upon identifying what the Protocol calls the ‘contemporaneous or actual critical path’ to determine actual delay within each window.

This introduces the concept of the ‘actual critical path’ which is not otherwise explained in the SCL Protocol. I therefore explain below my understanding of the distinction between the contemporaneous critical path and the actual critical path.

Looking ahead: What is the Contemporaneous Critical Path?

To understand this point, I find the below extract from Walter Lilly & Co v Mackay (No 2)^[5]Walter Lilly & Co v Mackay (No 2) [2012] EWHC 1773 (TCC), [2012] BLR 503, to be most helpful:

‘Mr R [the claimant’s expert] had regard to the likely longest sequence of the outstanding work on a monthly basis as being the primary pointer to what was delaying the work at any one time. This was a wholly logical approach and, indeed is the approach used by most delay experts when there is a usable baseline programme from which to work. The logic is simply that if there are, say, two outstanding items of work, A and B, and A is always going to take 20 weeks to complete but B is only going to take 10 weeks, it is A which is delaying the work because B is going to finish earlier; overall completion is therefore dictated by the length of time needed for A. Put another way, it does not matter if B takes 19 weeks, it will be the completion of A which has prevented completion. Thus, if one is seeking to ascertain what is delaying a contractor at any one time, one should generally have regard to the item of work with the longest sequence^[6]Walter Lilly v Mackay, note 8, para [378]..

The above extract describes how ‘what was delaying the work at any one time’ should be determined, using the term ‘the likely longest sequence of the outstanding work on a monthly basis.’ Mr R’s analysis, was carried out on a monthly basis, thus providing an evolving, contemporaneous view of the critical path, this being ‘the likely longest sequence of the outstanding work’ at any time. The ‘likely longest sequence of the outstanding work’ at any time is thus the ‘contemporaneous critical path.’

Pointing in the right direction:

The key to the relationship between the contemporaneous critical path and the actual critical path is seen in the above extract from Walter Lilly v Mackay in the phrase ‘as being the primary pointer to what was delaying the work at any one time.’ In practice, this forward-looking, likely longest sequence of the outstanding work, i.e. the contemporaneous critical path, is ‘the primary pointer’ which enables the analyst to assess ‘what was delaying the work at any one time.’

For each month, or other analysis ‘window,’ ‘the primary pointer’ is the activity at the start of the contemporaneous critical path, i.e. the activity of the path that is currently in progress or immediately about to start ‘at the time.’ This is the ‘contemporaneous critical activity’ and is taken to fall on the actual critical path of the project at the time of each assessment.

Tracking and compiling these contemporaneous critical activities sequentially across all analysis windows enables the analyst to determine the actual critical path through the period of the analysis^[7]Where an analysis is based on monthly intervals, such as with a time slice windows analysis using monthly programme updates, the actual critical path may also include intermediate activities falling … Continue reading.

A Similar Yet Different Path

Whilst closely related, the contemporaneous critical path and the actual critical path are distinct, but inextricably linked operating in different parts of the programme.

The contemporaneous critical path exists in the forecast portion of a programme^[8]Or other planning for the works., starting at any point in time with the then-contemporaneous critical activity. It changes throughout the project and identifies what is expected to drive completion at that moment in time.

In contrast, the actual critical path exists in the as-built record of a programme. It is constructed retrospectively from the sequential compilation of contemporaneous critical activities identified through the period of an analysis.

Put simply, one path predicts, while the other path records what has happened.

Conclusion

Both the Time Slice Windows Analysis and the As-Planned versus As-Built Windows Analysis of the SCL Protocol, enable determination of the actual critical path of a project. This is dependent upon identifying the contemporaneous critical path across stages of the project. The activity driving each contemporaneous critical path, at any given time, is the then-contemporaneous critical activity. Sequential compilation of these contemporaneous critical activities through the analysis period forms the actual critical path.

Accordingly, the contemporaneous critical path and the actual critical path are distinct concepts but inextricably linked.

The Author

With more than 40 years’ industry experience, Geoff Bewsey is a leading expert in construction delay, disruption and programming. He has been appointed as an expert over 35 times, providing evidence in major international arbitrations and concurrent evidence sessions. Geoff combines deep engineering and contracting experience with advanced planning techniques to assess causes of delay and productivity loss. His work spans buildings, infrastructure, energy and industrial projects across Europe, Africa, Asia and the Middle East. A recognised Lexology Thought Leader, he regularly delivers training on time risk management and supports clients with project strategy, controls and dispute avoidance.

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