Activity planning

Time is natures way of stopping everything happening at once.

The objectives of activity planning

• Feasability assessment
  • Is the project possible within the required timescales and resources?
• Resource allocation
  • What are the most effective ways of allocating resources? When should the resources be available?
• Detailed costing
  • How much will the project cost? After producing an activity plan, we can obtain more detailed estimates of costs.
• Motivation
  • Providing targets and monitoring progress can motivate staff.
• Coordination
  • When do the staff need to be transfered between projects to increase efficiency?

Activity networks

           ____  
          |____| 
    ____ /      \ ____
-->|____|        |____|-->
         \ ____ /
          |____|

Activity networks can be used to assess the feasability of the projects completion date, identify when resources are needed, calculate when costs incur, and to coordinate the staff between tasks.

Defining activities

An activity includes:

• Start and end-time
• Resource requirements
• Duration
• Dependencies

Identifying activities

There are three approaches to identifying the activities or tasks:

• Activity based planning

  • Creating a list of all the activities that the project needs. Can be done by creating a Work Breakdown Structure (WBS, filled with verbs). This involves identifying the main tasks that are needed for the project and then breaking them down into lower-level tasks. Too great depth will result in a large number of small tasks that will be diffcult to manage. Too shallow project provides insufficient detail.

• Product-based approach

  • Consists of producing a Product Breakdown Structure (PBS, filled with nouns) and a Product Flow Diagram (PFD). The PFD idicates for each product which other products are required as inputs. With the help of a PFD you can easily create an ordered list of activities by identifying the order of products and which acitivies are needed for them.

• Hybrid approach

  • The hybrid approach is a mix of both. Instead of creating a WBS that is based on the projects activities, you create a WBS that is based on the projects products.

Network planning models

• Program Evaluation Review Technique (PERT)
  • Activity on arrow
• Critical Path Method (CPM)
  • Activity on arrow
• Precedence network
  • Activity on node
  • most common

Rules for precedence networks:

• Should have only one start node.
• Should have only one end node.
• Every node has a duration.
• Links normally don't have a duration.
• Precedence are the immediate preceding activities.
• Time moves from left to right.
• A network may not contain loops.
• No dangling activities.

Lagged activities

   ____        ____        ____                                     
  |____|----->|____|----->|____|                                                
            1/ ____ \2                                 
             \|____|/                                   

Lagged acitivites are dependent on other activities but are initiated with a lag. In the above example, the second-row activity is started 1 day after the dependent activity and completed 2 days after the dependent activity has completed.

Start and finish time of activities

• Earliest start (ES)
• Earliest finish (EF) = ES + duration
• Latest finish (LF) = latest task that can be completed without affecting project end.
• Latest start = LF - duration

Forward and backward pass

• Forward pass

  • A forward pass calculates the earliest dates on which each activity may be started and completed.
  • It does this by going through the dependencies from start to finish and sorting the activities accordingly.

• Backward pass

  • A backward pass calculates the latest date at which each activity may be started and completed.
  • It does this by going backwards and looking at the duration of each activity.

Critical path and float

The float of an activity is defined as the difference between its earliest start date and latest start date (or earliest finish - latest finish). It is a measure of how much the start or completion of an activity may be delayed without affecting the end of the project.

• Free float
  • The time by which an activity may be delayed without affecting any subsequent activities.
• Interfering float
  • The difference between total float (Vad är total float, berätta för mig / Andrée) and free float. Indicates how much the activity can be delayed without delaying the project end date.

The critical path shows the path of activities in a project that define the duration of the whole project. Any delay in these activities will delay the whole project, which means these activities have no float.

If a project duration needs to be reduced it is the critical path that needs to be shortened.