"Critical
path, Critical Chain, Critical time for completion, Critical thinking, Critical
slacking, Critical methods, ..." All these critical words aim to identify
and underscore the projects backbone or the minimum set of vital activities for
Project Management, not only in terms of time and durations, or linking tasks
with predecessors and successors but also in terms of constraints level,
manpower mobilization and other settings such as complexity index proper to
each work package or deliverables followed by Control Project Teams.
In fact, the
"Criticality approach" in Project Management reflects the real
obsession to control and monitor the work to be performed, since mid of the
1950's, when first Critical Path was issued by BOOZ ALLEN HAMILTON firm. But Models
and schedules, since that time, become more complex with the integration of new
settings to optimize workflow and productivity.
Why a
Critical Path?
Something
critical could be defined as crucial for the Management in Time. The Latin
roots of this word (criticus) suggest that the criticality approach is linked
to “crisis” and “solving the faced problems”. As Time dimension is a goal for
finishing a project, the critical path becomes a sort of compass to direct the
work. It helps to make a decision regarding a technical context and the scope
of work to be performed.
In Project Management,
a Critical Path is the sequence of project network activities which add up to
the longest overall duration. This determines the shortest time possible to
complete the project. Any delay of an activity on the Critical Path directly
impacts the planned project completion date.
Algorithm of
Critical Path is a pure Mathematical approach based upon:
- An identified
WBS including all activities to be performed within a Project
- Duration
tasks (Start / Finish)
- Dependencies linking
(Predecessors / Successors)
- Logical End
Points (Milestones / Deliverables items / Key Meetings for GO- NO GO)
The Algorithm
looks like a 4-D plot, gathering 4 levels of information. Otherwise, the
Critical Path is influenced by time for completion (durations) and a logical
network links. But if you add “allocated resources”, you get the Critical Chain
Approach. A
resource-leveled schedule may include delays due to resource bottlenecks,
because some of them are unavailable at the required time, they impact Project completion
date.
Definitely, the
reliability of the Critical approach in Project Management is a proof. Software
like Primavera, Ms Project … was inspired by this Algorithm to ease calculation
for time completion. The Critical Path Method is well-known, wide-shared and
completely deep-rooted.
KPI(s) of
Criticality?
In case of a first
Baseline Schedule, analysis must highlight indicators which proceed to show off
feasibility of the Project and help Managers making decisions.
After
identification of the Critical Path – stage zero, here are some major indicators:
- Critical Time for Completion
which means literally the Duration of the Longest Path. It aims to
determinate the Target Date for finishing.
- Volumes of Critical
activities : Number of Critical Activities regarding the entire Work to be
performed : (example : PRIMAVERA gives this information in the
SchedLog.txt)
- Percentage of
Critical Activities (PCA): % = Critical Workload (Hours) / Total Workload
Project (Hours). This indicator could be reached with an S-Curve using a
filter “critical”.If % of PCA <
50% or > 80%, accuracy of the schedule is not reliable.
- Critical Density:
This indicator focus on the period when the S-Curve of Critical Workload
is increasing fast. Very close to strategy for project execution.
- Critical Resources
or bottlenecks: Applicable to the multi-project Management, being unavailable
at the required time is a risk for delaying a Project. This indicator is
proper to the Critical Chain Method when allocation of resources is fixed
and controlled.
