Development of schedule involves analyzing numerous options and applying different techniques to meet the project (imposed) delivery date. Various schedule network analysis techniques are used to generate project schedule. Some of them are Critical path method, critical chain method, what-if analysis and resource leveling. More than one technique can be applied on project schedule to come up with expected schedule.
Estimation of activity resource is a vital process which involves
* Determining what resources will be required (labor, equipment, material)
* What quantity for each resource will be required.
* When are resources available to perform project activities
Resource requirements by time period, often in the form of a resource histogram. Resource histogram is
* A bar chart showing the amount of time assigned to a resource for the time interval.
* Resource availability is depicted as a line for comparison purposes.
* Resources assigned more work than available hours are considered ‘over-allocated’.
If supply is sufficient to meet the demand, then projects does not have any resource allocation issues. But this may not be the case in real time scenario – Demand will exceed supply & resource scarcity arises. Project manager uses a technique called ‘Resource leveling’.
Resource Leveling is a project management technique used to examine a project for an unbalanced use of resources (usually people) over time, and smoothen distribution of resource usage by resolving over-allocations or conflicts. With this technique PM ensures resource demand does not exceed resource availability.
Resource leveling is used:-
* to address schedule activities that need to be performed to meet specified delivery dates
* to address a situation where shared or critical required resources are only available at certain times or are only available in limited quantities
* to keep selected resource usage at a constant level during specific time periods of the project work
Resource leveling is applied to a schedule model that has that has a critical path identified. In critical path method calculation, preliminary early start & late start schedule is calculated which may need more resources in different time line. After resource leveling schedule, projected start and finish dates(which may be longer than the preliminary dates) are calculated to reflect resource availability and even there could be a change in critical path. There are issues with using the simple bar chart for resource leveling as the interdependency between activities is not available in them, which may result incorrect schedule plan.
Generally, there are two approaches to leveling and smoothing the resources required:
* Time-constrained approach – In this case importance will be given on completing the project within a specified (imposed) date. This date will usually have been determined by network analysis. Changes in the duration of any activity, and the resources required at a given time, must be undertaken within the float (slack) available. Obviously there can be no adjustment of activities which are on the critical path.
* Resource-constrained approach – In this approach, the project must be completed with limited available resources even if this means extending the project duration. If the total resource demand exceeds the resource availability at any time then some of the activities must be delayed until there is sufficient resource availability.
For both of the above approaches, information regarding the earliest & the latest start times and slack will be used to level resources.
Few options that can be used in resource leveling are:
* Allocating scarce resources to critical path activities first can be used to develop a project schedule that reflects such constraints.
* Common way to bring the project back on track is resource reallocation from non-critical to critical activities. This may at least bring schedule as close as possible to its originally intended overall duration.
* Resources working extra hours , weekends, or multiple shifts by authorizing overtime to reduce the durations of critical activities.
* Adding or substituting resources of equal or greater productivity to shorten durations that have extended the preliminary project schedule.
* Last but not the least, delaying or extending critical path tasks/task duration. :-(
Other than impact in duration, some of the above options have impact on project cost & risk also.