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Every project is unique with its own set of contractual requirements, and each carries with it a definitive scope and objectives.

A thorough schedule analysis will provide you with a better program that models the progress of your project accurately to enable successful results. This is incredibly important as we discussed last week.

When GBA Projects undertakes an assessment of a program, we ask two very important questions:

  • Quality of program: Can the schedule correctly model progress?
  • Technical accuracy: Is the schedule realistic based on a review of the sequencing, remaining duration and resources?

We use a combination of Primavera P6 (or Microsoft Project) and Acumen Fuse to filter the program and detect issues with quality. The following key elements are examined:

Missing logic

All activities, with exception of the first and last in the schedule, should have at least one driving predecessor and one successor. Failure to do so results in an incomplete program and incorrect float calculations.

Critical path

There should be one clear, definitive critical path driving the project’s duration. The critical path must be technically correct to ensure project duration accuracy.

Near critical path

The near critical path should be realistic and achievable. If logic is missing from the near critical path or durations are incorrect (for example), then the overall critical path could shift. Knowing what the near critical path is for a project is key to ensuring risk is well managed.

Constraints

Constraints (such as ‘must start on…’, ‘start no earlier than’ or ‘must finish on…’) should be avoided as they affect the calculation of early and late dates. But if you do have to use a constraint do so with caution and consider flagging it for others to interpret..

Negative float

Negative float is the result of an artificially accelerated or constrained schedule. Negative float indicates that a schedule is not achievable based on the current completion dates.

Long durations

Activities with a high duration relative to the duration of the project are generally an indication that a plan is too high level for adequate planning and controls. Consider further developing the schedule by adding more detailed activities.

Lag

Check the total number of activities that have lags in their predecessors. This number should not exceed 5 per cent and, if in use, the lag duration must be controllable (i.e. no greater than two to three reporting periods). Lags are often hidden to end viewers of schedule reports, so use them sparingly!

Lead

'Negative lag’ leads are often used to bring the successor task’s start or end date forward relative to its predecessor. Some schedulers use this ‘lazy technique’ to help crash the schedule by overlapping finish-to-start relationships rather than using a start-to-start relationship. During execution, this logic can result in the successor starting before the predecessor.

SF predecessors

Start-to-finish (SF) links should be used very rarely. Having a successor activity happen before the predecessor activity is generally a poor practice when planning.

Open start

Check your schedule to see if there are any activities that do not have a finish-to-start or start-to-start predecessor. If an activity does not have at least one of these relationships, then it is possible that the start of the activity will not be correctly driven by preceding tasks.

Open finish

Just like checking for open starts, perform a check on your activities to ensure that they have at least one finish-to-finish or finish-to-start relationship. If an activity exists where it cannot ‘drive’ the start and/or finish of a successor, then it is at risk of failing to model delay.

High float 

Activities with high float (usually greater than two reporting periods) are often considered as low-risk. However, if a task is missing a successor, it could also mean that the total float calculated is incorrect. Before establishing your baseline review activities with total float (or total slack) greater than two reporting periods, ask yourself: “if those activities were to be delayed by the total float value, would it impact the schedule?”

Resources

Best practice scheduling requires that resources are assigned to activities within the program to assist in resource levelling and optimising the schedule. As a bare minimum, critical resources should be allocated to ensure some form of optimisation is performed.

Redundant logic

In theory, if your schedule contains too much logic it can be considered risky and complex. That is why reviewing Logic density is important. Density can be created due to additional redundant logic links that should have been removed from the schedule. Removing ‘unnecessary logic’ within a schedule network, can ensure the critical path is clearly and readily traversable and can increase the ‘maturity’ of the schedule. Redundant logic can affect the critical path calculations if out-of-sequence progressing is noted.

Out-of-sequence progress

This happens when the task status has been applied contrary to the logic used to plan it. For example if a finish to start relationship was actually executed in a start to start manner. It can create calculation issues in both Primavera and Microsoft Project if not noted or fixed. Mature schedules do not have out-of-sequence logic.

Linked summaries

Summary tasks (particularly in Microsoft Project) should not have logic associated with them. The logic of the ‘child’ tasks should determine the dates applicable to the ‘parent’ (roll up calculation).

 

By Matt Betros

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