Based on the triple constraints of time, cost and scope, projects are considered as successful, if they are completed within the agreed upon time (schedule), met the scope within budget. Though the definition of project success looks simple, more than 75% of the projects slips their deadlines. Just 25% of projects came within 10% of their original deadlines in the past 3 years, based on KPMG Global survey. Unrealistic schedules is one of the main root causes for this. A formal approach of Plan-Do-Check-Act or PDCA to schedule management will help us to develop and leverage realistic schedules for the success of projects.

Project scheduling provides a detailed plan that represents how and when the project will deliver the products, services and results defined in the project scope and serves as a tool for communication, managing stakeholder’s expectations, and as a basis for performance reporting (PMBOK Ver 6.0)

Schedules are classified into various levels based on the purpose and the level of details.

Schedule classification based of level of detail and purpose

Level 1: Level 1 schedules are high-level schedules that reflect key milestones by major phase, stage or summary activities of projects being executed specifically engineering, procurement, construction and start-up activities. Generally represented as gantt charts. Level 1 schedules provide high-level information that assist in the decision making.

Level 2 : Level 2 schedules are generally prepared to communicate the integration of work throughout the life cycle of a project. Level 2 schedules may reflect, at a high level, interfaces between key deliverables and project participants (contractors) required to complete the identified deliverables. Typically presented in Gantt (bar chart) format. Level 2 schedules provide high-level information that assist in the project decision-making process (re-prioritization and criticality of project deliverables).

Level3 : Level 3 schedules are generally prepared to communicate the execution of the deliverables for each of the contracting parties. The schedule should reflect the interfaces between key workgroups, disciplines, or crafts involved in the execution of the stage. Typically presented in Gantt or CPM network format and is generally the output of CPM scheduling software. Level 3 schedules provide enough detail to identify critical activities. Level 3 schedules assist the team in identifying activities that could potentially affect the outcome of a stage or phase of work, allowing for mitigation and course correction in short course. Audiences for this type of schedule include, but are not limited to program or project managers, CMs or owner’s representatives, superintendents, and general foremen.

Level4 : Level 4 schedules are prepared to communicate the production of work packages at the deliverable level. This schedule Level should reflect interfaces between key elements that drive completion of activities. Typically presented in Gantt or CPM network format Level 4 schedules usually provide enough detail to plan and coordinate contractor or multi‐discipline/craft activities. Audiences for this type of schedule include but are not limited to project managers, superintendents, and general foremen.

Level5 : Level 5 schedules are prepared to communicate task requirements for completing activities identified in a detailed schedule. Level 5 schedules are usually considered working schedules that reflect hourly, daily or weekly work requirements. Depending on these requirements, the Level 5 schedules are usually prepared a day or week in advance. 

Schedules can also be defined by their intended purpose:

A master schedule is a consolidated schedule incorporating multiple related projects (e.g., program management), or unrelated projects (e.g., a portfolio management of unrelated projects).

A baseline schedule: A fixed project schedule that reflects all formally authorized scope and schedule changes against which project performance is measured.

A schedule update: A statused version of the baseline schedule that reflects the most current information on the project.

A recovery schedule is a plan for recovering time lost on the project (i.e. slippage)

A look-ahead schedule includes a select set of activities for a short time-period, typically within the upcoming two- to six-week timeframe. This schedule highlights the near-term tasks projected to be performed in a given period of time to identify upcoming priorities for each of the project team 

Turn-around schedules are special schedules with short look-ahead time periods that are used to plan and monitor hourly or daily work at a detail level 

Steps involved in schedule development

  1. Plan schedule management – Establishes the policies, procedures and documentation for planning, developing, managing, executing, and controlling the project schedule resulting in the Schedule management plan
  2. Define activities – Decomposing the work packages into activities resulting in the activity lists, activity attributes
  3. Sequence activities – Sequencing the activities based on their relationships resulting in the project schedule network diagrams
  4. Estimate activity durations – Estimating the number of work periods needed to complete the individual activities with estimated resources
  5. Develop schedule – Analyzing the activity sequences, durations, resource requirements and schedule constraints, resulting in the schedule baseline
  6. Control schedule – Updating the project schedule to reflect the project’s status and managing changes to the schedule baseline

Let us elaborate these steps further;

Plan schedule management 

Involves creation of a schedule management plan to prepare and manage the project schedule. The key steps involved are;

  • Defining the method to be adopted for the development of the schedule. This is tightly linked to the project’s strategy. Some projects demand for end to end schedules, whereas some demands a rolling wave, iterative approaches. If the project organization gives more emphasis on integrated project delivery (IPD), then early inclusion of the associated stakeholders into the plan schedule management is important.
  • Defining the tools, number of licences to be used for schedule creation and updation
  •  Decision on the number of schedules and their types
  • Decision on the levels of accuracy for each type of schedule
  • Units of measure to be used in the schedules
  • Control thresholds
  • Rules of credit (rules of performance measurement for earned value reporting)
  • Reporting formats

Define activities 

Once the schedule management plan is prepared, the next step is to define the activities.

  • When we start the project, we start with the high level scope, which gets elaborated into detailed scope.
  • The detailed scope gets decomposed into  Work Breakdown Structure (WBS)
  • The work packages of the WBS gets decomposed further into activities
  • For each activity, activity attributes like successor, predecessor, technical specifications, resource requirements, quality standards etc are defined
  • Milestone list is prepared. Milestones are significant point or events in a project and do not have any duration by itself. When all the associated activities are completed, then the milestone is considered as achieved. A milestone list identifies all project milestones and indicates whether it is a mandatory contractual milestone or optional.

Sequence activities 

Once the activities are identified, the next step is to sequence them based on their dependencies. This step defines the logical sequence of work considering inter disciplinary constraints thus providing the greatest efficiency. Major chunk of the activity sequencing happens during planning and continues throughout the project. The output of ‘Sequence activities’ is the activity sequence diagrams. The key steps involved are;

Activity on Arrow (AOA) diagram
Precedence Diagramming Method (PDM)
The four types of dependencies (FS,FF,SS,SF)
  • Precedence diagramming method (PDM) or the Activity on Node (AON) diagrams (if the number of activities are very high)
    • The activities are represented by the nodes and are connected by arrows to show their logical dependencies like;
      • Finish to Start – Something has to finish for me to start something else
      • Finish to Finish – Something has to finish for me to finish something
      • Start to Start – Something has to start for me to start something else
      • Start to finish – Something has to start for me to finish something else
    • Dependencies can be either mandatory or discretionary
    • Can be highly scaled. PDM is the underlying logic for most of the software scheduling tools
  • Arrow diagramming method (ADM) or Activity on Arrow (AOA) diagrams (if the number of activities are very low)
    • In arrow diagramming, activities are represented by the arrows and connected at the nodes
    • Ideal for small projects where the number of activities are very less
  • The output of activity sequencing are the project schedule network diagrams
  • The network diagrams are further optimized through leads and lags. Leads represent parallelism between two activities where as lag represents waiting time. Adjusting leads and lags is one of the ways of optimizing schedule.

Estimate activity durations 

Once the activity sequences are established, the next logical step is to estimate the activity durations. The key techniques are;

  • Analogous estimation – based on comparison
  • Parametric estimation – based on averages / indexes
  • Three point estimates based on optimistic (tO), pessimistic (tP) and most likely (tM). Estimated time (tE) = (tO + tP + tM)/3

Develop schedule 

  • Schedule network analysis – an iterative process performed until a viable schedule model is arrived at and comprises of;
    • Critical path method
    • Resource optimization techniques
    • Modeling techniques
    • Assessing the need to aggregate schedule reserves at the points of path convergence, to reduce the probability of schedule slip
    • Critical path review to detect activities of long lead times, high risk activities
    • Analysis of near critical paths
Forward pass
Backward pass
  • Critical path method – Is the shortest possible time in which the project can be completed. The steps involved in determining the critical path are;
    • Forward pass through the network to identify the Early Start (ES), and the Early Finish (EF)
    • Backward pass to identify the Late Start (LS) and the Late Finish (LF)
    • Calculate the float for all activities on the network using the formula Float = LS-ES or LF-EF
    • Connect all the activities whose float = 0, and that is the critical path
    • Sometimes there can be multiple paths, whose float=0. That means the project has more than one critical path and will be complex to manage.
    • It is a good practice to track those paths whose float is very less. Technically they do not fall under ‘critical path’ but they are very close to critical path.
  • Resource optimization
    • Resource leveling
    • Resource smoothing
  • Leads and lags 
  • Schedule compression 
    • Fast tracking
    • Crashing
Lead
lag

Control schedule 

  • Status updates
  • Change management
  • Iteration burn down chart
  • Performance reviews
  • Trend analysis
  • Variance analysis
  • What if scenario analysis

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