What are lead and lag time in project management?

Date: 28/09/2021| Category: FAQ| Tags:

As part of the Project Schedule Management, ‘Lead and Lags’ is a technique that involves different processes. It refers to the potential advance or delay of the activities in the planning of the project, thus being fundamental in the management of the activities.

What is lead time?

The PMBoK defines lead time as: “Lead time is the amount of time whereby a successor activity can be advanced with respect to a predecessor activity.”

That is, when an activity is still running and at the same time the execution of another activity begins, the Lead Time indicates the overlap between the first and the second activity.

For example, in introducing order management software, the organisation may decide to begin the training phase of the employees who will be in charge of using the software. This happens while the test and development team is still carrying out testing activities on the software.

Lead time in project management

In the context of project management, the concept of Lead Time defines a finished project, a one-time project or the completion of an important part of the project.

Taking into consideration a Project Board (KANBAN board) that uses the subdivision between “To Do”, “Work in Progress” and “Work Waiting for Next Steps”, the Lead Time would extend to all three subdivisions. When the task is added to the Project Board its processing time is added to the Lead Time.

For this reason, identifying Lead Times can help the Project Manager re-plan activities so that they can make the most of that time. The early start of subsequent activities reduces the overall time required to complete a sequence of activities (e.g. in a project or work package).

In planning activities, lead time is generally indicated as negative, this is because it is considered as the time that is being saved compared to a finish-to-start planning.

A practical example: We have two activities, one that will take 4 days and the other will take 5, for a total of 9 days of work. Suppose that the second activity has two days of Lead Time, that is, we can start working on the second activity two days earlier than the conclusion of the previous activity. In this way the total duration of the processing will be 7 days instead of 9.

What is Lag Time?

The PMBoK defines lag time as: “the amount of time whereby a successor activity is required to be delayed with respect to a predecessor activity.”

In practice, when the first activity has been completed but there was a delay with the start of the second activity, the delay itself is called Lag Time. The expression was borrowed from the jargon relating to the delay of the internet connection and the Lag Time is rarely intentional or positive.

Lag Time in project management?

As part of project management, Lag Time is when two or more tasks that depend on each other are slowed down by an accident or an error in the processing path. When a task is blocked, the other must consequently also be stopped until the problem is resolved.

For this reason, Lags can cause delivery delays and budget problems.

Lead Time VS Lag Time

  • The Lead Time is an advance in carrying out the activities. The Lead Time corresponds to the time “saved”.
  • The Lag Time is a delay in carrying out activities.

Leads are the predicted measure of how long it will take to do something, while Lags measure how far a task or project phase is after it has begun. The main difference lies on a practical level: if the Lag Time is only a recording of what happened, the Lead Time is also able to influence the performances.

Lead and Lag indicators in project management

The Lead and Lag indicators help to evaluate performance: what went well and what did not. But above all Lead and Lag times are used to evaluate what should be improved.

Therefore, Lead and Lag time are two key elements when we are talking about continuous improvement. If the project team compares Lead and Lag Time of various projects on which it has worked, the team is able to understand its strengths and weaknesses to improve.

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