Once a reasonable project plan is in place we should swiftly focus on the resources. Simply, resource is something that is required for the execution of a task.
These can be divided, generally, into four main categories:
- Human Resources,
- Materials,
- Equipment and premises,
- Finance (cash) for subcontractors, for example.
The project manager will need to assess accurately all required resources in each category.
These, than, will be designated as either time-based or fixed-cost.
Time based implies that the cost is directly associated to the time period the resources are assigned to the project. This is often presented in a fixed hourly or daily rate.
In fixed cost the resource cost is fixed at the outset. These could be, for example, construction materials or any resource item for which the quantity is not calculated by the time of using them.
Once the detail list of resources have been identified, we need to decide on which component of the project the resource should be attached. Most of the time, the component is a task. However, human resources can be attached to other project components.
We can also generate Resource Histogram. It is a graphical representation of quantities of resources required over time, often separated on a weekly basis. This can gives us an important week by week information about the people and resources planned. This can be very useful for recruitment process.
If we carefully consider the resource requirements we can make accurate resource-based costing, and then calculating the set of project resource cost. This way, we create a comprehensive overall budget for the project.
This is called a 'bottom-up' approach. This means, that the process of developing the overall budget based on aggregation of multiple lower level estimates.
'Top-down' approach to budgeting implies the imposition of an overall budget for the project by the business. In either event, the project manager should undertake careful resource cost estimate to ensure that the project has necessary financial resources to meet its objectives.
The outcome of estimating a budget does not always mean that the tasks and project will be achieved within the budget. This information, however, will support the information about the project costs.
In order to accurately determine the budget for time-based resources we need to know in advance the duration of the task or activity, the nature and number of resources required and the rate of each resource.
Resource levelling
If we have created a coherent project plan and estimated resource requirements as accurately as possible, plus, attached them to appropriate tasks then, we have all the information necessary to create a week by week resource histogram. But, what if the pictogram show a peak, for example? This may be rather difficult to manage in practice.
That's where resource levelling concept comes to play. We can analyse whether the project plan can be adjusted without particular penalties in time or cost to level the diagram.
One primary way to achieve this is to level the principle of float on non-critical tasks and explore options that this knowledge presents. Some manipulations of non-critical tasks can lead to levelling of resource assignments.
As we might already know, float is the amount of time a task can be delayed without impacting the entire project schedule and completion date. By definition, all critical tasks have zero float.
Generally, the first step in developing a schedule is to assume that we have unlimited resources as this allows to determine the project durations. However, once we have established that the project deadline can be met, we now must see on whether the idea of limited resources has not overloaded the resources. We might find out that we have people double and triple scheduled. This clearly, will not work!
Example 1
As an example, let's consider the four tasks in figure above. Task A requires 2 workers to be completed in 3 weeks. Task B and C needs one person each. However, when it comes to do the project, we find out that there are only 3 workers available. It could be, that we have overloaded the resources and we must change something for it to work.
We could see whether any other task has enough float to allow it to be delayed until resources become available.
The solution can be presented in the below figure.
Another solution, could include reduction of scope, time limit or performance. But usually, performance should not be negotiable. Sometimes, however, we can reduce scope that might be acceptable to the business. We might also ask the manager who manage the resources to hire additional person. But, this might also be refused. Thus, we might find ourselves in a complex situation.
As we have used up the float on task C and it has now become a critical path task. Generally, when we tell a software to level resources it will want to known whether we want to schedule within the available float. If we say "yes' the task will run out of float and we call it "time-critical resource levelling".
Suppose, the answer is "no", and we basically telling the software to slide the task over, until the resources become available, even if it means slipping the end date. This is called "resource critical levelling". Sometimes the slip might even seem ridiculous and delay the entire project deadline.
Resource availability
Availability of a person to do a project work can be a major factor when dealing with resource allocation. Sometimes, organisations put a rule in place that a person is not available to work for more than 80% of the time. So, if we say we work 8 hours work, in reality it might be as much as 6.4. The 20% goes to PFD ( personal, fatigue, delay). People loose time due to personal breaks, rest, tiredness or even waiting for someone to complete the job etc. Even the 80% is also often tied for those who are tied to their workstations. For example, factory workers. In reality an office work only gets us to 50%.
Most software programs allow us to specify the number of working hours needed for a task and the percentage of a day that people will work on a task.
We also need to know the availability of the people to do project work. Otherwise we might produce unusable schedule.
Summary
The resource allocation and scheduling can be a challenging task. We must remember, however, that we should ignore resource limitations when we began developing the schedule. If two tasks logically can be done in parallel, we must draw them that way.
We also need to remember, that critical path is the longest and it has no float. We can have a project on which the task with the longest path is non-critical because it has a float. We must also remember, that no one is available to do more than 80% of work a day.
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