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Project Management tools: Line of Balance (LOB), Cost Optimisation, and PERT

Updated: Aug 13, 2022

Line of Balance (LOB)

The Line of Balance is a graphical production technique that can be used in conjunction with precedence diagrams. This graphical method gives a good understanding of how gangs go through work areas on a project. By analyzing the work carried out by individual gangs, using a line of balance the efficiency and delivery by work gangs can be significantly improved hence reducing errors or delays.

Line of balance can provide the information of how many operatives are available and the possibility to reduce the overall project time by efficiently moving gangs from one activity to the other by overlapping as the example in Figure below. LOB is useful for carrying out repetitive activities such as the basement walls and efficiently use gangs to complete them in a more efficient way.


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Cost optimization (Activities crushing)

Cost optimisation technique based on network planning seeks to reduce the total project time by reducing the duration of activities or otherwise crash activities on the critical path in order of least cost slope thus reduce float of non-critical path activities.

By carrying cost optimisation to reduce the project period, a time-cost relation is analysed. Indirect costs (e.g. site office expenses) reduce while direct costs such as labor or material costs increases as additional overtime hours and additional labor are required to finish the project in a shorter period than before.

By applying this technique to the critical path network is known as crashing. It should be noted that crushing non-critical activities will not reduce the total project time. When the critical path is crushed is worth noting that a re-analysis of the network should be done as non-critical activities can become critical. By crashing activities an extensive increase of labour hours and subsequently cost will be inevitable.

Program Evaluation and Review Technique (PERT)

PERT is type of milestone planning used in parallel with activity on arrow or precedence. PERT is a network analysis technique used to estimate project duration when there is a high degree of uncertainty for activities duration. By anticipating how long it will take to complete an activity, durations of pessimistic time, the longest it might take to complete, a most likely expected time and an optimistic time refers to the shortest possible duration as seen in the figure below are created.

By using the equation in the below figure an expected time of the activity could be determined based on the approximations of optimistic (o), most likely (m), pessimistic (p).

Duration groups of possible project/activities duration time used in PERT analysis
Duration groups of possible project/activities duration time used in PERT analysis

Advantages of PERT

Some advantages of the PERT chart analysis are that it incorporates data and information from multiple sources and can manage a number of complex activities. PERT analysis increases the capability of managers to correctly evaluate the time and resources necessary for the completion of a project and has tracking capabilities.

Furthermore, PERT is useful for creating what-if-analysis scenarios that may concern the flow of project resources and milestones such as in the pumping station of delivery of prefabricated members on-site on time.

Disadvantages of PERT

Some disadvantages of using the PERT system are that it is fairly complex, and its success depends on the management’s experience of using it. Also, due to the bulk of information and data, it can include unreliable data, such as unreasonable estimations for cost as it is a milestone-based approach.



Kopp, C. M., 2022. Program Evaluation Review Technique (PERT) Chart. [Online] Available at:


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