In the previous posts, we reviewed Volume Lags and Point-to-Point dependencies to demonstrate that assigned resources may impact activity and lag durations. This is also an excellent example to demonstrate indirect resource dependencies.

We reviewed a scheduling fragment with two activities and one dependency. It is easy to imagine real examples when activity A performs preparation for activity B and must be continuously ahead with defined Volume: 20m, 10m3, 10 items, etc.

Technologically, without considering resource requirements, this example looks SIMPLE. Resource assignments add dimensions to the complexity of planning and execution of this fragment. 

Practically to be able to complete this work, it is essential to know:

• Volume of Work (We know that already: both activities are 100m)
• Technical dependency constraints (We know that already: SS + lag & FF + lag)
• Volume lag (We know that already: 40m)
• Required skills (equipment, people)
• Required materials (if any)
Technological resource constraints: minimum & maximum quantity, minimum % workload, teams, shifts, etc.
• Space constraints (if any)
• Activity Calendar constraints (if any)

• Resource quantity limits
• Resource Productivity Rates (For each skill)
• Resource Calendar Constraints
• Cost components (If cost has a high priority in planning this work)

Resource Dependencies
• Direct resource dependencies
• Indirect resource dependencies

These parameters and correlations between them are relatively easy to understand, document and add to the project delivery model. Of cause, if the project delivery tool allows that. All except Resource Dependencies. Direct Dependencies add a new layer of complexity, indirect another one. Let’s review how.

Scenario 1: (Without Resource Dependency)
• Activities A & B require the same skill S1
• Resources (R1) with skill S1 have productivity of 2.5 m/h
Two identical resources are available
• Each activity requires a minimum of one resource
• Maximum one resource could be assigned to each activity
• Activities & Resources have 5d*8h calendar

Work takes 7 days, and there is no opportunity to accelerate delivery.

Scenario 2 (Direct Resource Dependency)
The same as above, except:
• Only one resource is available

Work takes 10 days, and there is no opportunity to accelerate delivery.

Scenario 3 (Indirect Resource Dependency)
Activity A
• Activities A requires skill S1
• Activity A requires a minimum of one resource
• Maximum one resource could be assigned
• Two resources with skill S1 have productivity of 2.5m/h (R1) and 5m/h (R2)

Activity B
• Activities B requires skill S2
• Activity A requires a minimum of one resource
• Maximum two resources could be assigned
• All resources with skill S2 have same productivity of 2.5m/h (R3)

• Activities & Resources have 5d*8h calendar

Scenario 3a
Resource R1 and one resource R3 are assigned to activities A & B.

Work takes 7 days, the same as in scenario 1. Is it an opportunity to accelerate delivery now?

Scenario 3b
Resource R2 is twice more productive as resource R1. Let’s replace them!

While the duration of activity ‘A’ is reduced to 2.5 days, the overall duration is reduced by 1 day only. This is due to the reduced duration of the SS lag. Refer to Volume Lag post for details.

Scenario 3c
The previous scenario doesn’t give us the expected result. Let’s add additional resource to activity ‘B’ instead.

While the duration of activity ‘B’ is reduced from 5 to 2.5 days, the overall duration of work hasn’t changed. It is still 7 days. This is due to the required FF lag between activities.

Scenario 3d
The additinal resoucre assigned to activity B also doesn’t give us the expected result. What if we combine scenarios 3b and 3c: replace R1 with R2 and add additional R3 resource?

It gives acceleration bigger than two scenarios applied separately (one day in scenario 3b and zero days in scenario 3c)! Appling together, the duration of work reduces to 3.5 days!

Yes! 1+0=3.5

Project planning is more complex than simple math. 

Visible Resource Dependencies

These scenarios demonstrate that technological resource requirements and supply constraints impact the schedule in several ways:
• R1 & R2 resources have the same skills with different productivity rates. It impacts the duration of activity A (scenario 3b).
• R3 resources have the same productivity rate. Activity B can be performed with a different quantity of R3 resources, It impacts the duration of Activity B (scenario 3c).
• The resource constraint (scenario 2) doesn’t impact the activity durations but creates additional Resource Dependency.

There are all visible dependencies that are relatively easy to identify and analyse. Relatively, as we only analysed the impact of two activities without the context of the overall project. If analysed resources are required to perform other activities at the same time when this work is planned, it may trigger further changes.

Hidden Resource Dependencies
In scenario 3d we identified indirect dependency. There is no visible dependency between Resources R1/R2 and R3. These resources have different skills and are assigned to different activities.
However, work was significantly accelerated only when the correlation between these resources was identified. These resources are dependent indirectly.

Project acceleration
Resources may have direct and indirect dependencies with other resources in the project in many other ways. A small change in one assignment may trigger a ‘domino’ effect and cause significant delay. This is one of the main reasons why projects are late.

However, the effect works in both ways! The project may have an acceleration opportunity through direct and indirect resouce dependencies, but it is not easy to identify them manually. Applying a project delivery tool with advanced scheduling methods and good resource levelling algorithms could significantly accelerate project delivery and reduce project cost.

Alex Lyaschenko

PMO | Portfolio Planning & Delivery | PMP | P3O Practitioner | AgilePM Practitioner | Six Sigma