Five steps in creating a robust schedule are:
- Producing WBS
- Estimating durations for executing work packages
- Preparing precedence diagram, and calculating floats
- Determining critical path
- Determining Project Milestones
1-Producing work break down structure is the first step in preparing robust schedule. WBS provides analysis to the activities (work packages) that will be carried out during the development phase of the project to produce the expected deliverables / products. WBS gives good idea about the amount and type of the activities (work packages) that will be executed during the project. For example, WBS for a project for sewage pumping station includes several work packages for Civil works activities, Mechanical works activities and Electrical works activities.
2-Estimating durations for executing work packages is the second step in preparing robust schedule. Estimated durations should be realistic and should account for the resources availability and capabilities. One can refer to actual records of similar projects, or to information from experienced peers. Accurate duration estimation enables ending with a realistic and achievable schedule. For example, estimated durations for the work packages for the mechanical works were based on the actual records from a similar project that was subject to delays due to the underestimation of planned activities durations.
3- Preparing Precedence diagram and calculating floats is the third step in preparing robust schedule. Precedence diagrams will evolve from the WBS and the estimated durations for work packages. The diagram will link the work packages according to their respective sequences and interdependencies (relations). That willenable indicating the early and late starts and finishes for each work package. It also enables assessing the impact of the delay of each work package on its successor as well as on the project end date (in other works, enables calculating the free floats and the total floats for each work package).For example, Precedence diagram showed the Finish to Start relations between the Civil work packages and the Mechanical work Packages in the project for the pumping station.
4-Determining Critical Path activities is the fourth step in preparing robust schedule. Work packages on the critical path are the ones with zero total float which if delayed will have impact on the successor activities and subsequently on the project end date. This process highlights to the PM the critical work packages. Durations and resources for the work packages on the critical path should be carefully estimated in order to avoid delays that with bump the project end date. For example, work package for producing electromechanical drawings is on the critical path. PM should carefully calculate the time required for producing the drawings and assign enough cad technicians to do the work.
5-Determining Project Milestones is one of the key steps in preparing robust schedule. Milestones are zero duration activities that represent projects significant events or commitments. PM will usually agree the Milestones with the project sponsor and at certain occasions with the users. Agreed milestones will be reported to the senior management of the organisation and audited during the stage reviews. PM has to be aware and attentive to all the Milestones in the project since delay of any is not allowed and may lead to imposing penalties or causing embarrassment to the Organisation senior managements. Examples for milestones are: the start dates end dates of the project, major material supply dates, tests and commissioning dates, etc.