In this tutorial, I will provide an overview of the four different Critical Path and Driving Path functions that Project X-Ray provides and why each function is important. This tutorial builds off of the tutorial: Microsoft Project and the Critical Path. If you have not read that tutorial, I recommend you read it before moving forward with this tutorial. Let’s start our discussion with an overview of our sample schedule…

Our Sample Schedule

In the below sample schedule, we see several tasks that are organized into four distinctly different paths. We will be using this sample schedule to discuss the Critical Path features that Project X-Ray offers.

Project X-Ray Critical Path and Driving Path Functions

Project X-Ray includes four different Critical Path and Driving Path functions. These functions are found on the Project X-Ray ribbon menu and include:

  • Show True Critical Path
  • Show Constrained Critical Path
  • Show True Driving Path
  • Show Constrained Driving Path

Each of these functions can identify a unique path through the project schedule that provides valuable insight into the schedule drivers. Let’s take a look at each of these functions in more detail…

Critical Path Functions

The Critical Path functions are found under the Show Critical Path menu button as shown below:

Show True Critical Path

What This Button Does

This feature will rip through the project schedule and identify the path with the longest duration and the least amount of total slack to the end of the project.

Why this Feature is Important

This feature helps identify what is driving the forecasted completion date of the project. Tasks that are on the True Critical Path should be actively watched and managed to ensure that they start and finish on time so that the project end date is not impacted. The True Critical Path should be used in conjunction with the Constrained Critical Path to gain valuable insight into the tasks that are driving the forecasted completion date of the project. With this insight, schedule reduction techniques such as crashing, modifying task relationships, or reducing project scope can be applied as needed to get an acceptable project forecasted completion date.

Example

If we run the Show True Critical Path in our original sample schedule, Project X-Ray calculates that Path 2 is the True Critical Path. It is the path with the longest duration and the least amount of total slack. This path has the most potential impact on the project completion date. It is also the path with the least amount of total slack on it which means that this path needs to be actively managed to ensure the project completion date does not get delayed.

Show Constrained Critical Path

What This Button Does

This feature will rip through the project schedule and identify the path that is having the biggest impact on the forecasted completion date of the project. The Constrained Critical Path typically includes at least one task or milestone that has a date constraint applied to it that is pushing the completion date of the project into the future. While the method of calculating the Constrained Critical Path is different than the method used to calculate the True Critical Path, both paths often include the same tasks.

Why this Feature is Important

This feature helps identify what is driving the forecasted completion date of the project. Date constraints that are affecting tasks on the Constrained Critical Path should be scrutinized to ensure that they are valid and necessary, especially if you are looking for options to try to save time and complete the project earlier than current forecasts. The Constrained Critical Path should be used in conjunction with the True Critical Path to gain valuable insight into the tasks that are driving the forecasted completion date of the project. With this insight, schedule reduction techniques such as crashing, modifying task relationships, or reducing project scope can be applied as needed to get an acceptable project forecasted completion date.

Example

If we run the Show Constrained Critical Path in our original sample schedule, Project X-Ray calculates that Path 1 is the Constrained Critical Path. There are two Start No Earlier Than date constraints assigned to tasks on Path 1 that are causing Path 1 to drive the project completion date into the future. This path is not the longest duration path with the least amount of total slack, but it is currently the path that is having the biggest impact on the project completion date. Very useful information…

Driving Path Functions

The Driving Path functions are found under the Show Driving Path menu button as shown below:

Show True Driving Path

What This Button Does

This feature will rip through the project schedule and identify the path with the longest duration and the least amount of total slack to a selected task or milestone. You can think of the Driving Path as the Critical Path to a key event or milestone in the schedule that is earlier than the end of the project.

Why this Feature is Important

This feature helps identify what is driving the forecasted start or finish date of the selected key event or milestone. Tasks that are on the True Driving Path should be actively watched and managed to ensure that they start and finish on time so that the forecasted start or finish dates of the upcoming key event or milestone are not impacted. The True Driving Path should be used in conjunction with the Constrained Driving Path to gain valuable insight into the tasks that are driving the forecasted start or finish dates of the key event or milestone. With this insight, schedule reduction techniques such as crashing, modifying task relationships, or reducing project scope can be applied as needed to get acceptable forecasted start or finish dates of the key event or milestone that is being evaluated.

Example

Let’s assume that we want to look at the Driving Path to Milestone 2. We want to know the path with the longest duration and the least amount of total slack to our selected key milestone. If we run the Show True Driving Path in our original sample schedule, Project X-Ray calculates that Path 4 is the True Driving Path. It is the path with the longest duration and the least amount of total slack to Milestone 2. This path has the most potential impact on the completion date of Milestone 2. It is also the path with the least amount of total slack on it which means that this path needs to be actively managed to ensure that Milestone 2 does not get delayed.

Show Constrained Driving Path

What This Button Does

This feature will rip through the project schedule and identify the path that is having the biggest impact on the forecasted start or finish dates of a selected task or milestone. The Constrained Driving Path typically includes at least one task or milestone that has a date constraint applied to it that is pushing the start or finish dates of the selected task or milestone into the future. While the method of calculating the Constrained Driving Path is different than the method used to calculate the True Driving Path, both paths often include the same tasks.

Why this Feature is Important

This feature helps identify what is driving the forecasted start or finish dates of a key event or milestone. Date constraints that are affecting tasks on the Constrained Driving Path should be scrutinized to ensure that they are valid and necessary, especially if you are looking for options to try to save time and start or finish the key event or milestone earlier than current forecasts. The Constrained Driving Path should be used in conjunction with the True Driving Path to gain valuable insight into the tasks that are driving the forecasted start or finish dates of the key event or milestone. With this insight, schedule reduction techniques such as crashing, modifying task relationships, or reducing project scope can be applied as needed to get acceptable forecasted start or finish dates of the key event or milestone being evaluated.

Example

Let’s now assume that we want to get a better understanding of what is actually driving the completion date of Milestone 2. If we run the Show Constrained Driving Path in our original sample schedule, Project X-Ray calculates that Path 3 is the Constrained Driving Path. There is at least one date constrained on Path 3 that is driving the completion date of Milestone 2. This path is not the longest duration path with the least amount of total slack to Milestone 2, but it is currently the path that is having the biggest impact on the completion date of Milestone 2. Once again, very useful information…

Summary

In this tutorial, we learned about four different types of Critical Path and Driving Path tools that can help us identify schedule drivers that are affecting key dates in our project schedule. Referring back to our sample schedule, we learned why we need to be able to identify each of the four paths in our schedule. Each path is important.

Path 1: This is the Constrained Critical Path that currently has two date constraints applied to it and is having the biggest impact to the project completion date

Path 2: This is the True Critical Path. This is the path that has the longest duration and the least amount of total slack.

Path 3: This is the Constrained Driving Path to Milestone 2. This path currently has one date constraint applied to it and is having the biggest impact to the completion date of Milestone 2.

Path 4: This is the True Driving Path to Milestone 2.  This is the path that has the longest duration and the least amount of total slack to Milestone 2.

Now you are ready to really dive into your project schedules and take control of those tasks and activities that are driving the schedule!