Project Management Chapter 6

Developing a Project Schedule

• A project network is a graphic flow chart that depicts project activities, their logical sequences, and interdependencies, and provides the basis for scheduling labor and equipment, enhancing communication among project stakeholders.
• It estimates project duration, provides the basis for budgeting cash flow, identifies critical activities, and helps managers get and stay on the project plan.

The Project Network Defined

• A project network is a graphic representation of project activities, their sequences, and interdependencies.
• It provides the basis for scheduling labor and equipment, enhances communication among project stakeholders, and estimates project duration.

Terminology

• Activity: an element of the project that requires time but may not require resources.
• Parallel activities: activities that can take place at the same time, if desired.
• Burst activity: an activity that has more than one activity immediately following it.
• Merge activity: an activity that has more than one activity immediately preceding it.
• Path: a sequence of connected, dependent activities.
• Critical path: the path with the longest duration through the network.

Basic Rules to Follow in Developing Project Networks

• Networks flow typically from left to right.
• An activity cannot begin until all preceding connected activities have been completed.
• Arrows on networks indicate precedent and flow and can cross over each other.
• Each activity should have a unique identification number.
• An activity identification number must be greater than that of any activities that precede it.
• Looping is not allowed.
• Conditional statements are not allowed.
• Where there are multiple starts, a common start node can be used to indicate a clear project beginning on the network.
• Similarly, a single project end node can be used to indicate a clear ending.

Network Computation Process

• Forward Pass: calculates early start and finish times for each activity.
• Backward Pass: calculates late start and finish times for each activity.
• Earliest times: how soon can the activity start (ES) and finish (EF).
• Latest times: how late can the activity start (LS) and finish (LF).
• Critical path: the longest path through the network, which determines the project duration.

Network Information

• Early start (ES) and finish (EF) times are calculated using the forward pass.
• Late start (LS) and finish (LF) times are calculated using the backward pass.
• Critical path is determined by finding the path with the least slack.
• Slack (or float) times: the amount of time an activity can be delayed without affecting the project end date.

Determining Slack (or Float) Times

• Total slack: the amount of time an activity can be delayed without affecting the project end date.
• Free slack: the amount of time an activity can be delayed without affecting any immediately following activity.

The Critical Path

• The critical path is the network path(s) that has the least slack in common.
• It is the longest path through the activity network, which determines the project duration.
• It is important because it impacts the project completion time.
• Activities on the critical path should be prioritized and closely monitored.

Sensitivity

• Network sensitivity is the likelihood the original critical path(s) will change once the project is initiated.
• A network schedule that has only one critical path and noncritical activities that enjoy significant slack would be labeled ‘insensitive’.

Practical Considerations

• Network logic errors, such as illogical loops, can occur.
• Activity numbering should be unique and consecutive.
• Computers can be used to develop networks and create Gantt charts.
• Calendar dates should be considered when developing project schedules.
• Multiple starts and multiple projects can be accommodated using network techniques.

Extended Network Techniques

• Laddering: breaking down activities into segments to reduce project duration.
• Lags: the minimum amount of time a dependent activity must be delayed to begin or end.
• Hammock activity: spans over a segment of a project and has a duration determined after the network plan is drawn.