We will use a series of graphical illustrations to show an overallocation problem and how to address the overallocation. The Gantt chart attached here shows the schedule and resource requirements for a simple project gantt-chart-for-movie-production. The diagram shows that the scriptwriter is needed on all three activities while the producer is needed for two. Two of the three tasks needing the scriptwriter are both scheduled for the period March 28-April 06. This means the scriptwriter is needed for both the “scriptwriting” and the “propose shoots” tasks. Since both tasks are occurring in the same time period, and there is only one scriptwriter, we have an overallocation problem. This is illustrated by the following graph overallocation-for-movie-production1
To remove the overallocation, we have to move one of those tasks out of the March 28-April 06. Which one of the two tasks should we move? The first option is which of these tasks has slack (i.e., not on critical path). The “propose shoots” fits this criterion and moving it till after the scriptwriting is done will remove the over allocation for the scriptwriter. The resultant resource diagram is shown here. Resource-Leveled_Scriptwriter
You will notice that the graph is leveled now ( very even across the entire period). Removing resource overallocation is also known as leveling.