Project Schedule Management

There is a triple constraint that exists in project management called the iron triangle. This triangle consists of 3 key project constraints. The project scope, project schedule, and project cost.

Projects are temporary endeavors with definite start and end dates, constrained to a fixed time duration, and it is expected that the project should be completed within the set schedule. This is where effective project schedule management is required.

When planning a project, developing and managing a realistic schedule is necessary for the successful execution of the project. The responsibility of developing a realistic project schedule plan and ensuring that the project actually follows this schedule falls on the project manager.

While there are project management software products that can be used for scheduling, project schedule management still often requires the hands-on approach of the project manager to take into account the unique nature of each scheduling process.

What is Project Schedule Management?

Project schedule management is a set of processes that aim to define the project activities, durations, dependencies, and assigned resources to deliver the project successfully within the given project schedule.

Throughout the project, monitoring is also ongoing to ensure the project is on track to meet the time deadlines and project schedule.

Project Schedule Management Processes

Project Schedule Management Processes

According to the Project Management Book of Knowledge (PMBOK) 6th Edition, there are 6 processes in the project schedule management knowledge area. These are:

  1. Plan schedule management.
  2. Define project activities.
  3. Sequence project activities.
  4. Estimate activities duration.
  5. Develop project schedule.
  6. Control project schedule.

Let’s explore each of these project management processes in detail.

Plan Schedule Management Process

1. Plan Schedule Management Process

The plan schedule management process defines how you will plan, manage, and control the project to align with the schedule baseline, and how to manage and control the variances that may arise as a project manager.

The project life cycle and development approach agreed on when developing the project management plan influences the schedule management planning. Enterprise Environment Factors (EEFs) are another input to this process.

Organizations could have a work authorization system in place, as well as project management software for scheduling activities and tasks too.

Other inputs to planning the project schedule management are the project charter, and Organizational Process Assets (OPAs). Tools and techniques include expert judgment, data analysis (alternative analysis), and meetings with stakeholders, the project sponsor, and the project team.

The key output from this process is the project schedule management plan. This plan is part of the project management plan, and it helps make estimating and the schedule development process faster.

The project schedule management plan should specify the following:

  1. The project scheduling methodology and the software to be used.
  2. The rules for how estimates are to be stated. If it is stated in hours, days, or weeks.
  3. A schedule baseline for measuring the project schedule performance and variance.
  4. A threshold for acceptable schedule variance.
  5. Performance measures to identify schedule variances as early as possible.
  6. A plan that determines how variances are to be managed.
  7. A process for determining whether a variance should be acted upon or not.
  8. Project schedule change control procedures.
  9. The types of reports related to the schedule required.
  10. The format and frequency of reports.
  11. The length of iterations and releases. This is if the project is using an adaptive or agile methodology.

Define Project Activities Process

2. Define Project Activities Process

This process entails the decomposition of deliverables and work packages in the Work Breakdown Structure (WBS) into the activities that are required to produce the work packages and deliverables.

The activities should be at a level small enough to estimate, schedule, monitor, and control them. Some project managers opt to do this process when creating the WBS.

The inputs to this process are the project schedule management plan, scope baseline (scope statement, WBS, and WBS dictionary), and Organizational Process Assets (OPAs).

The major output from this process is the project activity list. Other outputs are the milestone list, activity attributes, and change requests.

Rolling Wave Planning

Rolling wave planning is a useful technique when planning for projects where it is difficult to adequately decompose or break down the work packages and schedule at the beginning of the project.

It is a form of progressive elaboration that entails developing the plan at a high level and adding more details as the work goes on and more project insights are available.

Project Milestones

Milestones are significant events within the project schedule. Initial project milestones are documented in the project charter.

The project manager can also insert milestones as checkpoints for project control. The milestone list forms one of the project documents that is very important to the project.

Sequence Activities Process

3. Sequence Activities Process

After defining the project activities, you need to understand that to get the work done, the activities follow a certain sequence. Some activities need to be done before the next one can commence.

This process involves taking the project activities and arranging them sequentially in the order that the work will be performed.

This results in a project schedule network diagram that shows the dependencies between activities.

The inputs to this process are the project scope statement, project schedule management plan, activity list, activity attributes, milestones list, and Organizational Process Assets (OPAs).

The outputs for the sequence activities process are the project schedule network diagram, updates to the risk register, activity list, activity attributes, milestone list, and assumption log.

Relationships between Activities

There are 4 logical relationships between project activities.

  1. Finish-to-start (FS).
  2. Start-to-start (SS).
  3. Finish-to-finish (FF).
  4. Start-to-finish (SF).

Types of Dependencies in Project Activities

There are 4 different types of dependencies that exist among the project activities.

1. Mandatory Dependency

This is also referred to as hard logic. This is a dependency among activities that is inherent in nature or part of a contract.

2. Discretionary Dependency

This is reliant on the way an organization prefers to have things done An organization may prefer to always do a certain project activity before another.

3. External Dependency

This is a dependency based on the needs of an external party.

4. Internal Dependency

This is a dependency that is based on the project’s needs.

Note that more than one dependency can be identified for a project activity. The project team identifies mandatory and discretionary dependencies, while the project manager identifies external and internal dependencies.

Leads and Lags

When project activities are sequenced, we have predecessors and successors for most activities. A lead indicates that an activity can start before its predecessor is completed.

And a lag is the waiting time between activities. For example, when building a house, you may need the newly formed bricks to harden in 3 days before using them for the next activity. There is a lag of 3 days between these activities.

Project Schedule Network Diagram

The project schedule network diagram is a graphical representation of the flow of activities of the project in the order that they will be performed.

It is also referred to as a network diagram or activity network diagram and is a useful tool in project schedule management.

The network diagram helps to plan which activities can be done or completed in parallel, and see where leads or lags are required.

For large and complex projects, there is a tendency to have more activities overlapping.

When an activity has one or more activities directly preceding it, we have what is called a path convergence.

If the activity on the other hand has one or more successor activities directly following it, then we have a path divergence.

Path convergence and divergence are indicators of greater project risk within the impacted activities.

Project schedule network diagrams can be used in the following ways.

  1. Show the interdependencies of all activities and identify risky activities.
  2. Show the project workflow so that the project team will know the sequence of the entire project.
  3. Aid in effective planning, organizing, and controlling the project.
  4. Spot and identify opportunities to compress the project schedule during planning, and throughout the project life cycle.
  5. Show a visual representation of the progress of the project.

Methods for Drawing Schedule Network Diagram

There are different ways that the schedule network diagram can be represented.

In the past, techniques such as the arrow diagramming method (ADM), and graphical evaluation and review technique (GERT) were used.

Nowadays, the precedence diagramming method (PDM) is more popular. The precedence diagramming method uses boxes to represent the project activities.

Estimate Activities Duration Process

4. Estimate Activities Duration Process

After the project activities have been defined and sequenced, the duration of each activity should be estimated. The estimate is how long each activity is expected to last.

It is important to note the following before estimating the duration and costs of the activities.

  1. The project management plan provides the approach to be used for estimation.
  2. The project manager and the project team may use one or more techniques for estimation.
  3. Cost, duration, and resource estimates are interrelated.
  4. Identified risks must be considered when estimating duration, cost, and resources for the project.
  5. Estimating may uncover more unidentified risks.
  6. Estimating an activity should be done by the person who will do the activity or someone familiar with it.
  7. Estimates must be realistic and updated as more project information is available.
  8. Estimates can be impacted by reducing risks.
  9. Estimates are more accurate if smaller size work components are estimated.
  10. The project manager should periodically recalculate the Estimate to Completion (ETC) of the project to ensure that adequate time, funds, and resources are available.
  11. The project manager should not just accept constraints from management. The project needs should be analyzed, and estimates developed, with reconciliation of the differences to produce a realistic plan.

Inputs to this process include:

  1. Activity list and attributes.
  2. Assumption log.
  3. Project schedule management plan.
  4. Lessons learned register.
  5. Resource breakdown structure (RBS).
  6. Resource requirements.
  7. Resource calendar.
  8. Risk register.
  9. project team assignments.

During the estimating, the project manager should:

  1. Provide the team with enough information for proper estimation.
  2. Prevent schedule padding.
  3. Document assumptions.
  4. Formulate a reserve.
  5. Complete a sanity check of the estimates.


Padding is extra time or cost added to an estimate due to an inability to properly estimate an activity as a result of insufficient information. Any potential need for additional time or funds should be addressed by the reserves.

Estimating Techniques

There are different techniques that can be employed during the estimation of project activities.

1. One-Point Estimating

For this technique, the estimator submits one estimate per activity. This is through expert judgment, guessing, or history. While it is a fast technique, it is not the most accurate.

2. Analogous Estimating (Top-Down)

This is a form of one-point estimating that uses historical information. The level of accuracy depends on how closely the activity or project matches the historical data being used.

3. Parametric Estimating

This is a form of one-point estimating that creates mathematical equations using historical data or other related sources to create estimates.

An estimator may create parametric estimates using regression analysis (scatter diagram), learning curve, or heuristics.

The learning curve has improved efficiency when it comes to estimating, and heuristics is a generally accepted rule.

4. Three-Point Estimating

With this technique, estimators give an optimistic (O), pessimistic (P), and most likely (M) estimate for each activity.

The triangular distribution is given as (P+M+0)/3

The Beta distribution is given as (P+4M+O)/6

Beta activity standard deviation is given as (P-O)/6

The greater the standard deviation and range, the greater the risk.

5. Bottom-Up Estimating

This involves detailed analysis and creating detailed estimates for each activity. To use this technique, an accurate WBS is needed.

Tools and Techniques for Estimating Project Activities

These are other tools and techniques used for estimating the activities.

1. Data Analysis

The estimating activity duration process uses 2 forms of data analysis. Alternatives and reserve analysis.

Alternatives analysis is used when activity estimates are not acceptable within project constraints. Options are then considered, and the impact of each option on constraints is assessed.

Reserve analysis is used to reduce uncertainty in time and cost estimates. It includes the estimation of extra time and cost for the project schedule and budget in case of unexpected delay or cost overrun.

It is the responsibility of the project manager to create reserves to accommodate risks that remain after risk management processes are complete.

There are contingency and management reserves.

Contingency reserves are for known unknowns. They are for risks that have been identified and included in the project schedule baseline.

Management reserves are allocated for covering unforeseen risks.

During the risk management process, an initial reserve is estimated. After risk responses are planned to avoid, transfer, mitigate, or accept, the reserve is revised.

2. Decision-Making

When estimating, you have to make lots of decisions. Voting is a common method used to decide the amount of reserve needed.

For traditional or plan-driven projects, voting may result in decisions based on unanimity, plurality, or majority. For change-driven or agile projects, a method called ‘fist to first’ is often used.

Outputs from the activity estimation process include:

  • Activity estimates.
  • Reserves.
  • Updates to project documents (assumption log, lessons learned register, risk register, activity attributes).
  • Basis of estimates. This refers to how the estimates were derived, the assumptions, constraints, and risks that were taken into consideration, and the confidence level of the estimates.

Develop Project Schedule Process

5. Develop Project Schedule Process

It is the responsibility of the project manager to create a realistic schedule in this process. Developing the project schedule is an iterative process and can occur many times in the project life cycle.

To do this, it is important for you as a project manager to

  • First of all work with the stakeholders’ priorities.
  • Look for impacts on other projects.
  • Consider the skill level and availability of assigned resources.
  • Consider alternatives.
  • Apply leads and lags.
  • Compress schedule through crashing, fast tracking, and reestimation.
  • Adjust components of the project management plan as necessary.
  • Input data into the project scheduling software and determine the optimum schedule.
  • Simulate the project using the Monte Carlo simulation process and other analysis techniques to determine the likelihood of completing the process as scheduled.
  • Optimize resources.
  • Liaise with the stakeholders to approve the final schedule.


Inputs to developing a project schedule include:

  1. Project schedule management plan.
  2. Scope baseline.
  3. Historical records and lessons learned (OPAs).
  4. Activity list and attributes.
  5. Project schedule network diagram.
  6. Milestone list.
  7. Assumption log.
  8. Estimates of activities duration.
  9. Resource requirements.
  10. Resource breakdown structure.
  11. Resource calendar.
  12. Company calendar indicating working days.
  13. Project team assignments.
  14. Risk register.
  15. Agreements.

Schedule Network Analysis

This uses different techniques to create the schedule module to finalize the project schedule. These techniques include:

  1. Critical path method.
  2. Schedule compression.
  3. What-if/Monte Carlo analysis.
  4. Resource optimization.
  5. Agile release planning in sprints.

Critical Path Method

The critical path is the longest duration through the network diagram and is used to determine the shortest time to complete a project.

The critical path method involves determining the longest duration, and the earliest and latest an activity can start or finish.

The near-critical path is the closest in duration to the critical path.

Project Float

This is the project schedule flexibility and is the amount of time by which a project activity or task can be delayed before impacting the project deadline.

1. Total Float

This is the amount of time an activity can be delayed by without delaying the project end date or an intermediary milestone while adhering to any imposed schedule constraint.

2. Free Float

Free float is the amount of time an activity can be delayed without delaying the start of its successor while adhering to any imposed schedule constraints.

3. Project Float

Project float also known as the positive total float is the amount of time a project can be delayed without delaying externally imposed project completion date by management or customers.

The total float is the difference between the finish date of the last activity on the critical path and the project completion date.

Activities on the critical path have zero float. For critical path activities that are delayed, this can result in a negative float as each task on the critical path must be completed before the next activity can start.

If the critical path has a negative float, then corrective action is required to bring the project back on track.

Note that there can be more than one critical path on a project. This however increases the project risk.

Float = Late start – Early start (forward pass) or Late finish – Early finish.

The critical path helps to:

  1. Show how long the project will last.
  2. Determine activities with float.
  3. Help in schedule compression.
  4. Determine if delayed activities require immediate attention.
  5. Determine which activity has more associated risks.

Schedule Compression

This is one of the techniques used to shorten the project schedule. Two ways of compressing the schedule are fast-tracking and crashing.

For schedule compression, you use your choice of technique or a combination that has the least negative impact. The first option for schedule compression is reestimating by reviewing and reducing risk.


Fast-tracking involves performing activities on the critical path in parallel instead of sequentially. This is especially done when the activities have a discretionary dependency. Fast-tracking can increase project risk and result in reworks.


Crashing involves adding resources to compress the project schedule while maintaining the project scope. This results in increased project costs and may increase project risks.

Data Analysis

What-if analysis analyzes the effects of changes on the project schedule.

Monte Carlo analysis simulates the project outcome. This outcome can indicate overall project risk, the probability of project completion on any specific date, the probability of project completion for any specific cost, and the probability of any activity being on the critical path.

Monte Carlo analysis is also used in risk management to do a quantitative risk analysis.

Resource Optimization

This involves using resources as efficiently as possible and balancing resource demands based on their availability.

Resource Leveling

Resource leveling is the leveling of peaks of the use of resources between months. It could lead to an increase in schedule length and cost.

Resource Smoothing

In this technique, resources are leveled within the limits of float activities.

Agile Release Planning

This provides a high-level schedule that highlights the frequency of releases, and the number of iterations per release.


The main output of the develop project schedule process is the project schedule. The project schedule includes activities with an assigned date for each activity, and milestones inserted by the project manager or management.

It can be represented in formats like network diagrams, bar charts, or milestone charts.

Other outputs are the schedule baseline which is the version of the project schedule model used to measure project performance against, schedule data, change requests, and updates to project documents.

Control Schedule Process

6. Control Schedule Process

Controlling the schedule involves measuring the outcome against the project schedule.

It involves taking corrective and preventive measures regularly and continuously to ensure the project schedule is in line with the schedule baseline.

Also, it focuses on root cause analysis to determine factors causing changes and influencing the factors.

If the completion date is a key success criterion, and a project can no longer meet the completion date, then the project manager may recommend termination.

To control the project schedule,

  1. Access the project management information system (PMIS) for work performance data.
  2. Reestimate the remaining components of the project partway through project execution.
  3. Conduct performance reviews by formally analyzing the project performance.
  4. Perform data analysis (what-if, earned value, trend, and variance analysis).
  5. Confirming activities on the critical path are on schedule.
  6. Optimize resources to improve project performance.
  7. Identify the need for corrective and preventive actions.
  8. Follow change control processes.

For change-driven projects using an agile methodology,

  1. Compare the work completed in an iteration or sprint with what was predicted.
  2. Reprioritize the product backlog as necessary.
  3. Identify and manage changes as they arise.


Reestimating involves evaluating the remaining project work as the project during the project life cycle, ensuring that it is still possible to complete the project within the stipulated schedule and budget, and adjusting the project if you can not.

The outputs of this process include work performance information, schedule forecasts, and change requests.


It is important to have a project completed within the stipulated schedule. If this is not done, then the outcome project may not be needed in the end.

Project schedule management enables you as a project manager to get a realistic project schedule and stick to delivering the project within the schedule.

David Usifo (PSM, MBCS, PMP®)
David Usifo (PSM, MBCS, PMP®)

David Usifo is a certified project manager professional, professional Scrum Master, and a BCS certified Business Analyst with a background in product development and database management.

He enjoys using his knowledge and skills to share with aspiring and experienced project managers and product developers the core concept of value-creation through adaptive solutions.

Articles: 334

Leave a Reply

Your email address will not be published. Required fields are marked *