LBMS controlling theory focuses on preventing production alarms from becoming production problems on site. Buffers allow some time for control actions to take effect before a problem happens. In reality the lag times to implement control actions to alarms are unacceptably long. In the US, we have observed on large construction projects that it can take four weeks to implement a control action in response to an alarm. In Finland, the lag has also been unacceptably long at around 2-3 weeks.
Why does it take so long? In many cases it is because the parallel CPM schedule is showing that the activity is not on the critical path or is not delayed from schedule yet. However, LBMS works on production trends. A delay will happen in the future if something is not done now. Industry, which has for a long time been focused on firefighting, is not used to reacting to future delays if there are none at the present. However, for LBMS to create optimum results, actions should be taken immediately. Data collection, validation, discussions, and action should all happen in the same week.
Control actions take time before they are effective. For example, if the control action is to add resources to an undermanned crew, it is unlikely that all the required resources would show up on the next day. It often takes some time because those people are working on other projects and the subcontractor needs to finish work elsewhere to free up the resources. It often takes a few weeks to mobilize resources. If the lag to DECIDE on a control action is four weeks and the time required to fully implement is two weeks, six weeks have been lost on the project.
A good way to implement faster actions is to implement a Control Action Log as a project deliverable. The Control Action Log reports any production rate deviations and actions and includes:
- Date found
- Explanation of issue
- Date control action made (or decision to not do anything)
- Control action description (or why control action was not made)
This report makes it easy to calculate lead times from production alarm to control action. In some projects it has been added as an Owner deliverable to monthly reports and reviewed with the Owner weekly to show that action is being taken to address any production issues. A sample from a control action log is shown below:
Effective production control can decrease project durations by 10% or more and increase subcontractor productivity. It certainly decreases the risk in the project. If you are an Owner or an Executive in a construction company would you not want to see any production problems addressed in real time to get these benefits?
See the Control Action Log and three other reports every Owner should have and how to produce them in the Production Controller video training series.
Also, be sure to catch up with the other best practice articles in this series:
Part 1: Beyond Start Dates
Part 2: Get the Subs Involved
Part 3: Manpower and Suspensions
Part 4: Control Actions
Part 5: Planning the LBS
Part 6: Clarifying Scope
Part 7: Look-Ahead Plans
Part 8: Running Parallel Schedules
Part 9: Resource Graphs
Part 10: Production Rates and Location Sequence
Part 11: Using 5D with LBMS in Subcontractor Meetings
Part 12: Deliveries and Lay-Down Areas
Part 13: Starting As Early As Possible Will Hurt Your Project
Part 14: Buffers Are Important for Production Control