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12 Best Practices for Preventing Project Schedule Overruns

May 11, 2020 |   | 
Øyvind Røberg

Øyvind Røberg

A sobering 9 out of 10 projects experience cost overrun, and experience tells us that schedule overrun is a common occurrence too.

To counter this, project professionals must ensure their project schedule is reliable, meets project requirements, and contains all necessary work.

What’s more, schedules should be built according to acknowledged best practices, such as the US Government Accountability Office’s Schedule Assessment Guide and the DCMA 14 Point Assessment. Regular health checks are another powerful tool in a project manager's arsenal, used worldwide by many businesses and governments to assess the credibility of the project schedule.

To that end, we’ve identified 12 key scheduling best practices. Does your schedule pass these tests?

1. Reflect the Project Execution Strategy in the Schedule

The project schedule must align with the project execution strategy. These two documents should clearly show how the work will be executed and define the sequence and timing of each step.

Project teams will rely on the schedule to plan for upcoming work, understand resource requirements, and to identify risks that may occur during execution. So, unless the schedule clearly reflects the project execution strategy, it's of little value to these teams.

2. Capture the Entire Scope of Work

The schedule should reflect all the activities and work needed to accomplish the project’s objectives and meet all the requirements of the contract. When it comes to project execution, controlling the scope of work and its impact on your schedule is crucial.

Learn how schedule risk analysis can be the key to project management success  with our free guide. Click here to download today. 

3. Set Reasonable Activity Durations

The schedule should clearly set out how long each activity will take. These activity durations should be reasonably short, meaningful, controllable, and allow for discrete progress measurement. 

When defining activity durations, the quantity of work and resources needed should also be taken into account.

4. Logically Sequence and Link All Activities

To ensure critical project milestones are met, activities must be logically sequenced and linked. For example, a predecessor activity must finish before its successor.

All too often in projects, date constraints and lags – i.e the extension of activity durations – are used to fix a start or finish date.

The issue with this is that using negative lags extensively – to allow activities to be planned in parallel or squeeze the required work into an unrealistic time frame to meet project milestones – results in a less reliable schedule.

What’s more, if the duration of the predecessor is shortened, the successor may end up starting before its predecessor. So, best practice dictates that when sequencing activities, you should look out for high-value lags and aim to have Finish-to-Start as the dominant dependency type.

5. Keep Date Constraints to a Minimum

The use of constraints and lags hinder free flowing paths and prohibit accurate float calculations and critical path identification. They can also lead to inaccurate project start and finish dates being set.

For these reasons, though they're sometimes necessary, the use of constraints and lags should be kept to a minimum.

6. Avoid Dangling Activities

When building your project schedule, you should avoid dangling activities – i.e. activities with no or incomplete logic.

To produce an accurate critical path schedule, the implications of changes to an activity's duration must be reflected in its successor and the project as a whole – without the need for extra manual work.

If there are dangling activities, their float values will not be accurate, meaning the critical path may not be identified correctly. As a result, you may end up formulating a completely inaccurate project completion date.

7. Check the Critical Path Makes Sense

The schedule should identify both the project’s critical path(s) and longest path. Be mindful that critical paths often change during project execution as a result of progress updates.

Establishing a valid critical path is essential as it allows you to examine the effects of slippage as the project progresses.

Since the critical path determines the project’s earliest possible completion, extra focus, energy, and attention should be spent on critical activities. If your critical path runs through your management activities, the schedule should be carefully examined and challenged.

8. Check the Schedule Contains Reasonable Float

The schedule should identify float – i.e. the amount of time an activity can slip before the project end date or any part of delivery is delayed. Try to look out for excessively high float as it can be an indicator of missing logic and avoid using too many activity date constraints as they can cause inaccurate float calculations.

9. Assign Resources to All Activities

Project schedules should reflect the resources needed to complete the project successfully. Remember that every activity in the schedule should be resource-loaded, except for milestones.

Activities represents work that must be done to satisfy the project contract. This can't be done without consuming resources. Therefor, any activities without assigned resources shouldn't be in your schedule.

Ultimately, the reason resource-loaded schedules are so useful is that manpower requirements can be planned in advance, allowing for any manpower conflicts or problems to be mitigated and resolved ahead of time.

10. Verify the Resource Plan

With the activity durations set, the right logic in place, and a free-flowing resource-loaded schedule, you can now check whether the resource plan is executable. Ask yourself:

  • Do we have the right amount of resources required at the required time?
  • Are there any density conflicts from concurrent activities and work at the location?

After answering these questions, you may well decide to make schedule adjustments, thereby improving your chances of executing the project successfully.

11. Run a Schedule Risk Analysis

Project schedules are built using single point estimates of activity durations. But when you take risk uncertainty into account, end dates, criticality, and level of confidence are likely to change. Therefore, the starting point for a solid schedule risk analysis should always be a clear and accurate critical path schedule.

However, as the activity duration is a single (deterministic) value and not a range of possible outcomes, the end date is also forecasted as a single value. In real life, the duration of an activity may vary, but that single value should be considered your best estimate.

To understand how uncertainty and risk affect your project and project schedule, run a schedule risk analysis. This statistical model can determine the impact of risk and uncertainty on confidence levels for meeting the project’s completion date.

A schedule risk analysis also helps you define the contingency or reserve of time needed for a certain level of confidence and to identify and focus on high priority risks.

Be sure to include the results of your schedule risk analysis and mitigations when constructing an executable baseline.

12. Set Your Baseline

The project baseline is the defined benchmark for evaluating your project performance. You should set the baseline after the schedule has been challenged and verified, but before any work starts on the project and progress starts to be reported.

Since the baseline acts as a contract with the project team and determines when work will take place, extra care should be taken in getting it right.

Aim to set the baseline in stone and don't change it unless authorized to do so. To do this, you need to ensure that changes to the scope of work are captured through a change control process and the impact of any changes to the baseline are assessed in terms of resources required, cost, and time.

During project execution, measure progress against the baseline to determine if you’re behind or ahead of schedule and whether any schedule variance that crops up affects down-stream work. During this analysis, take extra care in examining any out of sequence updates.

The Importance of Accurate Project Schedules

Project professionals need to ensure the schedule is accurate and credible – it’s crucial to project success. Following these 12 points will provide a great head start, but remember that a schedule health assessment should be done prior to setting the initial baseline and after every major update to the baseline.

With Safran Project, you can establish and maintain several alternative schedule scenarios, together with a practically unlimited number of baselines and variations. The schedule risk analysis tool is fully compatible with this functionality, giving users the ability to conduct comprehensive impact analysis in a single program.

This activity, known as What-If analysis, is just one of the many techniques we discuss in our recent guide. We also examine the Monte Carlo method and how it can be applied to project planning, as well as discussing the major elements of risk within project schedules and how to mitigate them.