jueves, 18 de septiembre de 2008

Last Planner System

Last Planner System
The Last Planner System (LPS) improves both design and construction schedule/programme predictability – work completed as and when promised. It is a system of inter-related elements – full benefits come when all are implemented together, over time. Based on simple paper forms, it can be administered using Post-it notes, paper, pencil, eraser and photocopier. A spreadsheet can help.
LPS begins with collaborative scheduling/programming engaging the main project suppliers from the start. Risk analysis ensures that float is built in where it will best protect programme integrity and predictability. Where appropriate the process can be used for programme compression too. In this way, one constructor took 6 weeks out of an 18-week programme for the construction of a 40 bed hotel. Benefits to the client are enormous.
Figure 1: intense discussion during a programme compression workshop
Before work starts, team leaders make tasks ready so that when work should be done, it can be. Why put work into production if a pre-requisite is missing? This MakeReady process continues throughout the project.
Figure 2: part of a MakeReady form for documenting the process of making tasks ready (this one for use in design)
There is a weekly work planning (WWP) meeting involving all the last planners – design team leaders and/or trade supervisors on site. It is in everyone’s interest to explore inter-dependencies between tasks and prevent colleagues from over-committing.
Figure 3: part of a Weekly Work Plan form used by trade foremen on site or design team leaders to prepare for the WWP meeting.
This weekly work planning processes is built around promises. The agreed programme defines when tasks should be done and acts as a request to the supplier to do that task. The last planners (that is the trade foremen on site or design team leaders in a design process) only promise once they have clarified the conditions of satisfaction and are clear that the task can be done.
Figure 4: the promise cycle (after Fernando Flores)
Once the task is complete the last planner responsible declares completion so that site management or the next trade can assure themselves that it is complete to an appropriate standard.
A key measure of the success of the Last Planner system is PPC. This measures the Percentage of Promises Completed on time. As PPC increases. project productivity and profitability increase, with step changes at around 70% and 85%. This score is measured site-wide and displayed around the site. Weekly measures are used by the project and by individual suppliers as the basis for learning how to improve the predictability of the work programme and hence the PPC scores.
A key part of the continual improvement process is a study of the reasons why tasks promised in the WWP are delivered late. The following chart shows typical reasons:
Figure 5: example of a reasons Pareto chart
Recording the reasons in a Pareto chart like the one above makes it easy to see where attention is most likely to yield the most results. Using tools like 5 Why analysis and cause-effect diagrams will help the team understand how they can improve the clarity of information and ensure that there are sufficient operatives.
Last Planner benefits don’t stop at project predictability, profit and productivity; it contributes to positive changes in other industry KPIs. Danish research shows almost half the accidents and up to 70% less sickness absence on LPS managed sites.
Last Planner System development continues under the direction of Lean Construction Institute Directors
Professor Glenn Ballard and Greg Howell with support from users around the world. For more information about the development process see Ballard (1994, 2000) and Ballard & Howell (2004) for example
For a more detailed description and list of benefits
see here For more on Learning how to implement Last Planner see here