Reading: Scheduling Tools

Photo of the Izmailovo Hotel complex at night.

Izmailovo Hotel complex, Moscow, Russia

As you might expect, operations managers find that complex processes involve complex planning and scheduling. Consider the Izmailovo Hotel in Moscow shown in the photograph at the right. Built to house athletes during the 1980 Olympics, the complex has 7,500 guest rooms and is the largest hotel in the world. Think about cleaning all those rooms—in four thirty-story-high towers—or checking in the thousands of guests. No small operation! Although the Izmailovo doesn’t produce a tangible good, it relies on many of the same operations management principles used in manufacturing to stay in business. To increase operational efficiency in complex processes like those of running a giant hotel, operations managers use three common planning tools: Gantt charts, PERT, and the critical path method (CPM).

Gantt Charts

A Gantt chart—named after the designer Henry Gantt—is an easy-to-use graphical tool that helps operations managers schedule the activities and determine the status of projects. Devised by Gantt in the 1910s, this chart illustrates the start and finish dates of the elements of a project. Modern Gantt charts also show the dependency relationships between activities. Although now regarded as a common planning technique, Gantt charts were considered revolutionary when they were first introduced.

Three different, ornate, brightly colored birdhouses.

Let’s look at a Gantt chart for producing a birdhouse. Suppose the following activities are required to build and package each birdhouse:

  1. Determine which birdhouse the customer has ordered
  2. Trace pattern onto wood
  3. Cut the pieces of wood from the birdhouse pattern
  4. Assemble the pieces into a birdhouse
  5. Paint birdhouse
  6. Attach decorations to the birdhouse
  7. Prepare a shipping carton
  8. Pack birdhouse into shipping carton
  9. Prepare customer invoice
  10. Prepare packing slip and shipping label
  11. Deliver carton to shipping department

Below is the corresponding Gantt chart:

Figure 1. Gantt Chart

As you can see, the tasks on the list are displayed against time. On the left of the chart are all the tasks, and along the top is the time scale. A bar represents each work task; the position and length of the bar indicate the start date, duration, and end date of the task. At a glance, we can determine the following:

  • What the various activities are
  • When each activity begins and ends
  • How long each activity lasts
  • Where activities overlap with other ones, and by how much
  • The start and end date of the whole project


Gantt charts are useful when the production process is simple and the activities are not interdependent. For more complex schedules, operations managers use PERT, which stands for “program evaluation and review technique.” This is a method of analyzing the tasks involved in completing a given project, especially the time needed to complete each task and to identify the minimum time needed to complete the total project. PERT was developed primarily to simplify the planning and scheduling of large and complex projects. The key to this technique is that it organizes activities in the most efficient sequence. It can also help managers determine the critical path, which is discussed below.

Critical Path Method (CPM)

The critical path method (CPM) is a step-by-step technique for process planning that identifies critical and noncritical tasks in order to prevent time-frame problems and process bottlenecks. The CPM is ideally suited to operations consisting of numerous activities that interact in a complex manner. It’s often used in conjunction with PERT.

The essential technique for using CPM is to construct a model of the project that includes the following:

  1. A list of all activities needed to complete the project
  2. The time that each activity will take to complete,
  3. The dependencies between the activities and,
  4. Logical end points such as milestones or deliverable items.

Using these values, CPM calculates the longest path of planned activities (expressed in time) to logical end points or to the end of the project, and the earliest and latest that each activity can start and finish without making the project longer. This process determines which activities are “critical” (i.e., on the longest path) and which can be delayed without extending the overall project duration. Take a look at Figure 2, below. What was the critical path in our construction of a birdhouse?

Figure 2. Critical Path

Our critical path was the path that took the longest amount of time! This was sequence of activities that included the customer invoice and packing and shipping label (from the start to G to H), which totaled 180 minutes. The problem is that even if we were able to assemble and decorate the birdhouse faster, the birdhouse would just and wait for the paperwork to be completed. In other words, we can gain efficiency only by improving our performance in one or more of the activities along the critical path. 

Did you know…?

PERT was developed by the U.S. Navy. The Navy’s Special Projects Office devised this statistical technique for measuring and forecasting progress while they were designing the Polaris-Submarine weapon system and the Fleet Ballistic Missile capability.

CPM was first used for major skyscraper development in 1966 for the construction of the former World Trade Center Twin Towers in New York City.[1]

  1. Kerzner, Harold (2003). Project Management: A Systems Approach to Planning, Scheduling, and Controlling (8th ed.)