UK Construction Journal - Issue 1 - April 2026 - Flipbook - Page 24
Productivity-based methods
time to confidently determine a trend.
Cost-based methods
1. Project-speci昀椀c studies:
1. Estimated v incurred labour
(a) Measured mile analysis
2. Estimated v used cost
Another problem might be the identification of disruption
taking place. In my pipework installation example, the
measured mile would show that production is being achieved
therefore there is no disruption - it does not automatically
identify lower productivity.
(b) Earned value analysis
(c) Programme analysis
(d) Work or trade sampling
(e) System dynamics modelling
A better option, particularly during the ‘live’ works might be an
Earned Value calculation.
2. Project-comparison studies
3. Industry studies
What is Earned Value?
Earned value (generally referred to as Earned Value Analysis
‘EVA’ or Earned Value Management ‘EVM’) is a technique
used in project management to measure performance of a
project.
Well maybe not so easy. The clue to disruption lies in those
last four words of the SCL’s definition: “resulting in lower
efficiency” – that is to say, lower productivity.
When carrying out its regular progress update, a contractor
might find that it is on programme – there is no delay, and no
disruption – so all is good with the world. Well, that may not
be strictly correct.
The analysis combines project budget and the programme to
determine the value of work that has been completed to date.
It can be applied across the entire project, specific sections of
work or selected activities.
Consider this. What if the contractor had planned to install
100m of pipework per week and the progress update showed
that it had in fact installed 100m of pipework per week.
Traditionally that would be the end of the story. However,
what if the planned work was to be carried out using a single
two-person team but instead, two teams actually completed
the work – a total of four people not two?
A simplified EV equation is:
EV = % of work completed x budget
The EV method compares ‘earned’ hours (derived from the
budget) with actual hours to complete the work (EVA). The
difference is then used to determine any productivity loss and
the productivity (or performance) factor (‘PF’).
In this situation, the planned production was achieved but
productivity was not.
What is often not appreciated across the industry is the subtle
difference between production and productivity. Production is
a measurement of output whereas productivity measures the
labour hours required to achieve a unit of output.
How do we value disruption?
There are several ways of assessing disruption. The SCL
Protocol provides a summary table of the more common
methods of measuring disruption4.
It describes the productivity-based methods as being the
preferred methods and they are listed in order of preference.
The cost-based are considered to be the least robust and
are mostly used when lost productivity cannot be reliably
calculated.
The cost-based methods generally rely upon comparing
actual costs and estimated costs.
Of the productivity-based methods, probably the measured
mile is one that is most talked about. A reason for this is
perhaps that it is very easy to understand. It requires the
analyst to compare actual production during an undisrupted
period of work to the production rate achieved during a
disrupted period.
The measured mile is very good, however, as with most
methods, it does have its limitations. A limitation which is often
discussed is that it requires the analyst to ‘find’ a piece of the
same or similar work that has not been disrupted. Having
done that – and this is not as easy as it sounds by the way –
the undisrupted period must be over a reasonable length of
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