About Assignment Types

In DTS it is important to understand the different ways in which resources can be assigned to tasks. This has nothing to do with the type of resource, only with the way in which the resource is assigned to a task. Naturally, depending on the resource, some of these assignment types will be more suitable in practice than others. One thing to keep in mind is that these assignment types are available for all but the "Fixed Duration" tasks, which only support the "Required" assignment type.

In the context of this discussion, the term Number Of refers to the number of resources assigned to a task (other project scheduling programs may refer to this as "units"). A resource can be a generic resource such as "Trucks" (which refers to any one of the trucks you have in your fleet), or it could be a specific resource such as "Shovel-XYZ" (which refers to one single piece of equipment). Assigning Shovel-XYZ at a Number Of=0.5 would effectively indicate that this resource is only used for half of its time on a particular task. This does not have any effect on the production rate of the resource, i.e. it does not imply that the resource is working at half of its rated production speed. It simply means that this resource could work concurrently on another task, i.e. it has capacity to do more work.

Furthermore, if we speak of e.g. a "driving" resource, this does not actually mean that the resource is of this type. Rather it means that the assignment of the resource to a particular task has occurred in a "driving" manner. By virtue of the assignment type, we say that the resource is driving, but it only applies to this single task. The same resource could be assigned to another task in a different manner.

The three assignment types are the following:

• Driving: this means that the resource will determine how long it will work on the task until it has completed the prescribed production quantity. Hence the name "Driving" as it drives the production. Consequently it is suited to resources that in practice are the primary production resources, e.g. you would typically assign a shovel as a driving resource.

  To create a driving resource assignment, the number of resources assigned as well as the production rate must be specified. So it is quite possible that the task duration will change while you are making the assignment. In the example of a single specific shovel assigned to a task, the "number of" would typically be 1. Note also that if the task is a "Fixed Rate" task (which it would be in this case, otherwise you would not have been able to create a driving assignment), then the task will take on the production rate of this specific assignment.

  You can also assign more than one driving resource to the same task. In this case you would need to make a decision as to whether the driving resource assignments all contribute to the overall production rate of the task (i.e. the work load would be split, so the production is cumulative), or whether the slowest resource determines the overall production rate. The option called Rate of 'Fixed rate' tasks is determined by on the Resources page of the Task Information form is used for this purpose. The possible values you can select from are Combined rate of all 'Driving' resources and Lowest rate of all 'Driving' resources. If you only have a single driving resource assignment on a task, then this selection does not matter.

  An example of using the combined rate of all driving resources would be say 2 specific shovels assigned separately to the same task (working from different ends) - the production rate is the sum of the individual rates of both resources, as both resource assignments share the production quantity and each one consequently only processes a portion of this.

  An example of using the lowest rate of all driving resources would be say 1 shovel and 5 trucks assigned to the same task - one of these resource assignments will be the bottleneck that determines the overall production rate of the task, as both resource assignments have to process the entire production quantity.

• Required: this means that you specify how many resources are required for a task. The rate is irrelevant, in fact you cannot even fill this into the assignment details.

  This type of assignment is intended for overheads (e.g. supervisor, cost etc.), i.e. any resource that has to be available, but will not have any effect on the duration of the task. As with other assignment types you could assign this resource at a �number of� e.g. 0.33, meaning that this resource could be available for 3 tasks at the same time if working at a �number of� 0.33 on all of them. Leveling will naturally still have an effect on these resource assignments, so even though they do not affect the progress of a task, they can still cause a task to be delayed (or split) if this specific resource is over-allocated. To distinguish again between resources and assignments, you would not be leveling "required" resources, rather you would be leveling resources that happen to be assigned in a required manner, and could be assigned in any other manner to different tasks.

• Effort: this type of assignment will process the entire production quantity. It differs from a driving assignment in that you only specify the rate of production, and DTS will calculate how many resources you require in order to complete the work (at the specified production rate in the time specified by the task duration, which in turn could have been determined by other driving resource assignments).

  An example is a task with a single shovel assigned in a driving manner (i.e. the shovel determines how quickly the task will progress due to its own production rate), and (generic) trucks assigned in an effort driven manner. The trucks would be assigned at an average rate that accounts for travel, and DTS would then calculate the number of trucks required to support the shovel working at its rate. Naturally this specific example could be solved more accurately using DTS's Haulage facility, which calculates accurate travel times based on a road network, so that you do not need to estimate an effective production rate for your trucks.