Critical Path Analysis: Its Use and Limitations
Critical Path Analysis: Its Use and Limitations
Introduction As firms begin to realize the need to improve on their project management capabilities, many companies and software developers have charged to fill this need by offering tools and techniques for a variety of projects. Some are tools for portfolio management, and some focus on particular disciplines within the project management field.
Tools for resource planning, task and time management, communications management, resource allocation, or other project needs abound. Being a mature academic and practical course, Project Management has developed many tools and methodologies to assist in the planning, execution, evaluation and closeout of various types of projects. Varied tools can be used throughout many categories of project needs, while some tools are specific to certain types of projects.
Some of the benefits of using project management tools and techniques as opposed to general management procedures, as mentioned in this week’s lecture, are that they have been proven to work particularly in a project environment and the uniformity of terms and approaches allows for better understanding and communication between members of the project team and the stakeholders. Tools such as Decision Trees, Cost-Benefit Analysis and programs such as Agile and Prince2 have proven to be particularly useful in producing best practice and expert results for projects that have employed them.
CPA Utility and Limitations Critical Path Method (CPM) or Critical Path Analysis (CPA), as a project management tool, operates as the basis for a project work schedule, and likewise of resource planning illustrating shortest possible time to complete a project. The tool outlines critical events noting their sequencing, precedence relations, and strict timing requirements (Shtub, Bard and Globerson, 2005:395). The authors further note that PERT and CPA approaches treat ‘Finish to Start’ precedence relations using ‘zero’ as lag time between finish of last activity to start of next task along the critical path.
The CPA map shows what activities cannot begin without accomplishing the preceding task, it is dependent on and also defines parallel tasks or ‘non-dependent’ tasks which can be performed simultaneously. By plotting activities using circles to represent activities noting earliest start (EST) and end times (LFT), and arrows showing sequencing of tasks, CPA clearly defines the flow of tasks, timings and therefore resources that must be allocated to accomplish activities and timelines.
CPA has similarities to a GANTT chart as both tools show tasks that need to be done and the corresponding time to accomplish each. However, unlike a GANTT chart, CPA activity timings are not drawn to scale in that arrows represented with the same length may correspond to differing measures of time (e. g. same size arrows may represent 1, 2 or 4 weeks). A GANTT chart will have the tasks on a vertical axis while the time required for each task is easily identified along its horizontal axis.
For both GANTT and CPA, the plan’s ‘critical path’ is the longest and has no spare time or ‘slack’/’float’ in any of the tasks. If any delays between dependent tasks in the critical path are encountered, the whole project will be delayed unless the manager makes changes to bring the plan back on track. Bringing a project back on track may be done by possibly adding resources to cut delivery time of tasks (‘crashing’) affected by the delay. Obviously, adding or re-allocating resources usually mean additional costs to the project.
A sample for a 10-week computer project using a CPA map is as below. Upper left numbers within nodes represent the EST and lower left numbers on nodes represent LFT. Number on the right is the activity number and task description and duration is along the arrow lines: Source: www. mindtools. com In managing a project, a CPA map allows the project team to monitor attainment of goals and assists the project manager to see where corrective action is required to get the project back on course.
Shtub, Bard and Globerson (2005:381) reiterate preparation and use of the tool requires a complete understanding of the project’s goals and structures. As most projects will have a number of stakeholders with different requirements, it must be assumed that a thorough knowledge and understanding of all these requirements are known and considered by the project manager in order to utilize a CPA approach. Moreover, considerable expertise is required in order to estimate the duration of each project task as performance and resource allocation are dependent on the accuracy of the ame.
While CPA is recognized as an important part of project management, projects which may not benefit from use of this tool are those where there is a requirement for high flexibility in project tasks and schedules. ‘Project Flexibility’ is described by Maylor, (2010:86) as the capability of a project to adjust to changes. As CPA assumes that activity times are ‘deterministic’ – having a predictable outcome as all of its causes are clear and rigid, it is unlikely that the CPA tool can easily take in many adjustments during the execution stage without jeopardizing the project.
Since only parallel tasks are afforded time slack within the plan, a project may experience detrimental delays and spiralling costs should situations arise where the schedules are not met, or resources cannot be re-allocated to a later or earlier timeline. In particular, R&D projects, where results of new technology or a new drug cannot be easily predicted, or may need further testing and numerous changes, may suffer from a very rigid CPA map. Moreover, project work on innovations will not have the benefit of historical basis for correctly estimating time requirements of many tasks involved which is ssential in using the CPA.
The United States Food and Drug Administration (2004) comments, “A new product development toolkit — containing powerful new scientific and technical methods such as animal or computer-based predictive models, biomarkers for safety and effectiveness, and new clinical evaluation techniques — is urgently needed to improve predictability and efficiency along the critical path from laboratory concept to commercial product”. This lack of knowledge and systems in drug research and development negatively affects the proper implementation of a CPA as a project management tool.
Conversely, Construction industry projects benefit widely from the use of CPA maps as there is a considerable body of knowledge, experience, and repetition in many of the tasks performed in such projects. Another weakness in the utilisation of the CPA tool highlighted by Woolf (2008) is the observation that there is as yet no “universally accepted definition of the term ‘critical path’”. He argues that this lack of consensus poses a problem in determining what is critical, nearcritical, or non-critical in nature when preparing a CPA map.
Since parallel tasks falling outside of the critical path can still have grave effects on the total project should they fall behind in schedule, Woolf argues there is nothing ‘non-critical’ about a parallel activity which has -17weeks as float. It is suggested ‘criticality’ must be measurable and objective, free from comparisons which will make it subjective. Moreover, as a completed project is one unit, it is contended all tasks within the project are important/critical and contributes to its completion.
This agreement in understanding and measure of terms is an important issue as one of the advantages of utilising tools and methods is its universality of understanding. In the case of R&D and highly innovative tasks in projects, this question poses an issue as unknown tasks at the start of the project which may arise and have significant implications on the project would not have been accounted for in the ‘critical path’. Shtub, Bard and Globerson (2005:382) cite overdependence on the CPA as a potential threat to project success.
When pressure in sequential schedules is the primary focus, a team may cut short or totally exclude certain tasks in order to stay within timelines. This negative manner of management can be harmful to the project’s final outcome. This last observation though is not a weakness of the tool itself but is a case of weak project management.
Conclusion and Recommendation: As with any tool, the user’s skill is key to its effective employment and management. CPA has been proven to be a valuable tool in project management for determining:
Activities which must be performed, sequencing, prioritising, and timing Tasks which can be performed parallel to save time. The shortest time a project can be successfully delivered What and when resource will be required Remedial measures will be required and when during the performance of the project. As such, it is an integral part of the project management toolbox which can be harnessed efficiently in a variety of complex projects with proper inputs derived from experience, research, modelling and sound judgement.
University/College: University of Arkansas System
Type of paper: Thesis/Dissertation Chapter
Date: 4 October 2016
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