Whilst developing a schedule is critical for delivering projects on time, making sure people understand the schedule can be equally important.
To many programmes have been lost to the trash can due to complexity or poor presentation particularly when issued to field staff for implementation.
In this weeks blog, we will explore the various methods and tools available for presenting schedule information to field staff so they can clearly understand the work scope and planning aspects.
We will determine which are the best tools using an example construction project – SPJ jetty works (Container Berth Works) Which includes elements of unique sequence critical works as well as large sections of highly repetitious work activities.
We will consider the following options
- Bar/Gantt Charts
- Time Scaled Diagram
- Velocity Chart / Line of Balance
- Time – Location Diagrams
Development of the alternatives
- Bar chart/ Gantt Chart
A Bar Chart or Gantt Chart does not show logic links, only the bars. This is often used to compare actual progress against a baseline and is often used for management reporting, in particular to compare planned starts and finishes vs actual start and finishes.
Figure 1 above is taken from the “master or construction programme” broken down to level 4. Typically, the construction team will break this down further and develop a level 5 or 6 working schedule referred to as a 3 or 2 week look ahead. The programme is normally developed using a bar chart format and will attempt to co ordinate the works at a site level. It provides site engineers and supervisors with the flexibility to make the necessary refinements to planning which may not have been possible to foresee by planners when developing the master or baseline programme. An example is provided under Figure 2 below.
- Time Scaled Diagram
The diagram below indicates the same network but this time is presented in what is known as a Time Scaled Logic Diagram. Notice that the only change which has been made is to turn on the logic links. Otherwise, the durations, start and finish dates and critical path remain identical.
- Velocity Diagram / Line of Balance
The concept of the Line of Balance (LOB) technique (also referred to as Velocity Diagram) is to have a greater understanding and control of production rates (outputs) between various trades such that resource levels can be balanced and wastage (such as „standing time‟ between trades) can be kept to a minimum.
It is also sometimes referred to as a „lean construction‟ technique and is useful when repetitive cycles of activities are required
Figure 4 below allows us to understand that the production rates relative to each other element or activity. It will also allow site teams to know exactly where they need to be by a certain date and get a better feel for which activities are achieving higher than planned production and potential delays if a mis balance in activity productions are left to run without action.
- Time – Location Diagrams
The activities of a linear project are plotted on a grid where one axis is the time-scale and the other axis is the distance-scale and diagrams of the project (scans of maps, landscape cross-sections, etc.) are often included across the distance axis of the diagram to help orientate the reader to where physical attributes are located.
Figure 4 above provides similar information to the Velocity diagram however it allows the site teams to understand better the time (start and Finish) blocks which work must be completed as well as general rate of production. It summarises or rolls up multiple tasks
Each method shall be assessed based on the following
- Ease of Interpretation
- Definition of work scope at working level
- Definition of Activity and resource relationships
- Assessment of production targets / requirements
To help assess which method/s provide may be regarded as the most suitable for field staff to plan and execute works we will use the above criteria within a Non-compensatory decision model.
Comparison of Alternatives
Results are as follows
The time scaled chart fails to provide a clear and easily interpreted discerption of the works due to the presence of the
Time bar charts at either level 4 offer the site team the best opportunity to describe the works and short term working bar charts provide a format where adjustments and more tailored solutions can be made to reflect the field teams own sequence preferences.
Line of balance or velocity diagrams can be useful and easy to understand for understanding “where we need to be” by a certain date. Plotting the actual production and location data obviously gives field teams the ability to assess ongoing rates and predict delays or stoppages if crews are moving too fast or slow.
Selection of the preferred Alternative
Through the application of the Lexicograph analysis, the Gantt chart has been determined to be the best method of communicating schedule information to field teams.
The use of the bar chart to provide supervisors and engineers with an full understanding of the programme drivers and constraints can be greatly enhanced when accompanied with a Line of balance diagram to show the inter relationships between crews and resources as well as providing a high level indication of what average productions rates are required.
Further assessment and understanding of Time location diagrams need to be carried out. Software programmes such as TILOS can bridge the gaps identifited above with resource planning, works sequence and activity definition however it remains to be seen if the clarity and presentation will allow for distribution to field staff for implementation.
- Sullivan, G. W., Wicks, M. E., & Koelling, C. P.(2014). Engineering economy 16th Edition. Chapter 3 – DEcision making Considering Multiattributes., pp604-606.
- Chapter 7.1 – Introduction to Managing Planning & Scheduling – Guild of project controls compendium and reference (CaR) | Project Controls – planning, scheduling, cost management and forensic analysis (Planning Planet). Retrieved from http://www.planningplanet.com
- TILOS, Schedule with confidence retrieved 20 December 2017 from from https://www.tilos.org/sites/default/files/2017-04/022482-3430_TILOS_Bro_033016.pdf