Risk management header
products page

Risk management - Ways to modify plans

Ways to modify plans

Reduce to only one critical path

If you have more than one critical path you will need to eliminate one of them.

By its very nature the critical path contains all of the tasks, which can affect the completion date of the project should they alter.
In the real world most tasks are dependent on others completing before they can start. The amount of time that a task can be delayed before it affects another is called ‘float or slack’. There are two basic types:

Free slackThis is the time the task can be delayed before it affects the next task that relies on it.
Total slackThis is the time the task can be delayed before it affects the completion date of the project i.e. before it becomes a critical task

Note: That for tasks with no dependencies free and total slack are the same in terms of definition because their delay can only affect the project end date. On the assumption that they have to be completed before the project can end, otherwise there would be little point in having them in the schedule. Strictly speaking these tasks would have only one dependency and that would be the project end date.
The special criteria for tasks on the critical path is that they have zero slack. Any change will affect the completion date.
On this basis the critical path is always the longest in the schedule.

A project should only have one critical path. The Project Manager does not want to be focussing on more than one critical path. Simplistically, there are a few ways to eliminate one of these paths affording only one critical path.

You can modify the tasks to achieve only one critical path by:

Changing one or more task durations:

Either reducing tasks (so that they are no longer critical, for the path not desired) or extending them (so that the tasks remain critical, for the desired path). By definition extending any task on an already critical path will extend the project completion date.

Extending the completion date:

This would have the effect of removing both critical paths and introducing ‘slack’. It should be carried out along with extending one or more tasks to restore a single critical path (see first approach above).

Reassessing the dependencies:

It may be appropriate to review these. If a particular dependency is modified this will have the effect of removing one path or promoting the other to become critical.

Clearly, any modification which extends the completion date would need to be considered very carefully.

Examine the critical path

You may wish to consider the following when eliminating one critical path and reviewing the remainder:

  • Activities: More activities may mean more risk.
  • Skill level of people: The least skilled path may hold more risk.
  • Technical risk: The path with the highest technical risk may need more float.
  • Weather/uncontrollable: Give more float to uncontrollable activities.
  • Cost: Consider giving float to activities that cost more.
  • Historical data: For tasks supported by the least data or previously gave a problem give more float.
  • Backup plan: Give more float to areas of the plan with no obvious backup plan.
  • Business cycle: Give float to those areas likely to become hectic.
  • Difficulty: Give more float to the most difficult activities.

Modifying task durations

  • Increasing efficiency: Apply more productive/skilled personnel.
  • Reducing the scope: Do less, alter the product or task specification.
  • Applying extra effort: Increase resources, number, overtime. You can also increase the resource initially reducing this as the task gets back on track.
  • Change the process: How and what is done within the activities.

When the amount of work done decreases without an increase in mistakes, it is possibly due to people carrying them out at their own speed.
When mistakes increase it is often due to tiredness.

Modifying task dependencies

You may need to review task dependencies and see if more tasks can be done in parallel. This may mean extra resource in terms of modified cash flow or more equipment.

General

You may need to draft contracts and term and conditions to allow more flexibility so as not to interrupt the work pattern.
Additional or more modern equipment may improve efficiency.