Solution Summary: Last Planner® System
The Last Planner System (LPS) is a production planning and control system implemented on construction projects to improve planning and project performance. It epitomizes the following planning practices:
- Detailed planning before the commencement of site operations.
- Development of the work plan with project team members.
- Identification and removal of work constraints proactively to make work ready and increase reliability of work plans.
- Making reliable promises and driving work execution based on coordination and active negotiation with trade partners and project parties.
- Learning from planning failures by identifying root causes and taking preventive actions.
The last planners ‒ usually the trade foreman and project site management team ‒ are responsible for product unit control at the operational level. Last planners make the final assignment of tasks to specific performers and equip them with the necessary materials, tools, and information for successful project execution. They also manage the relationships and commitments necessary for collaborative production planning decisions at the lowest level possible. Communication and correspondence are promoted among the parties to the project before issues become critical. Regular exchange of information promotes healthy relationships and collaboration which facilitates a smooth flow of operations.
The last planner system comprises four main planning processes:
Master Scheduling: This is done at the beginning of a project and is the first step in front-end planning. It involves developing logistics plans and work strategies of long lead items prior to setting project milestones.
Phase / Pull Scheduling: It builds on the milestones set in master scheduling to define milestone deliverables, breakdown milestones into work segments, perform collaborative reverse phase scheduling, identify operational conflicts and adjust the schedule to meet the specified project duration.
Lookahead Planning: This also knows as make work ready planning and is the first step in production planning. The six-week lookahead planning requires planners to evaluate constraints to upcoming tasks identified during phase planning. It starts by taking a lookahead filter from the phase schedule. Processes are broken down into operations, and constraints to the smooth flow of activities are identified and addressed. Lookahead planning ensures that work is made ready for installation or re-planning as necessary.
Weekly Work Planning: Weekly work planning allows teams to collaborate and carefully plan, sequence, and synchronize activities for the following week It drives the production process by developing reliable weekly work plans and triggers preparation for planned activities. Plan reliability at the weekly work planning level is promoted by making only quality assignments and reliable promises to shield production units from variability in upstream tasks. Learning is done by a measure of the percent of plan completed (PPC) as planned, a deep dive into reasons for failure is carried out and lessons learnt are implemented in the next plan.
Daily huddles present opportunities for learning through coordinated meetings, team check-ins and regular discussions to confirm that work is executed according to plan and adjustments are made where necessary if any variations are identified.
Prior to the commencement of construction, activities that SHOULD be done are defined and scheduled in the master plan of the project. However, due to resource constraints, resources are re-allocated among competing tasks. Activities that should have been done hitherto are scaled down to those than CAN be done given limited resources.
LPS enables the planning crew to identify what part of the work that SHOULD be done CAN be done and commit to the part of the work that WILL be done. The modified schedule thus reflects what WILL be done, CAN be done, and not simply what SHOULD be done. This shields the production crew from uncertainties and variability in work flow.
The benefits of LPS implementation are smooth work flow, predictable work plans, reduced cost, reduced time of project delivery, improved productivity and greater collaboration with project team members.
Work flow variability is an important source of waste in lean. Fluctuations and uncertainties in work processes cause disruptions in workflow, significantly impacting project cost, duration, quality, productivity, resource assignment, flow path, sequencing and project performance. The consequences of deviations from planned activities have a negative effect on the production system and results in adverse outcomes like lost production resources, wasted capacity, increased cycle times, high levels of inventory, long lead times, poor quality, and dissatisfied clients. As a result, understanding and managing variability is essential to improving construction. If variability is not reduced, the efficiency of the system will be affected and will result in failure to meet the overall project objectives. Maintaining consistency in production facilitates proper matching of labor and other resources to workload and shields production from uncertainties in construction operations, thus improving productivity.
The last planner system (LPS) of control is also applicable to resource management. Getting work done on construction sites depends on the availability of resources. One of the challenges workers face during the course of a project is coping with discrepancies between anticipated, actually needed, and available resources. Factors such as ambiguity in design drawings, errors in measurement, rework, transportation delays and damage during handling of materials affect the smooth flow of resources on construction projects. LPS aids the clarification of work tasks, identification of constraints, checking constraint satisfaction and the efficient allocation of resources. It has been successfully implemented on construction projects to increase the reliability of planning, improvement production performance, and the establishment of predictable workflow regardless of uncertainties in design and construction operations.
How Risks are Reduced:
To improve the quality of planning and avoid the adverse effects of unreliable workflow, construction activities should be protected from variability in the system. Accordingly, the Last Planner System (LPS) for production planning and control was developed to reduce the negative impact of variability and increase reliability of workflow and has been successfully implemented on construction projects to improve planning and production performance. Forecasting, buffering, smoothing and rationing are some of the techniques used in LPS to address variability. Forecasting is done to anticipate uncertainties in construction processes. Uncertainties in the project environment is usually compensated for by the addition of buffers to task inputs and performance. Buffering is done to safeguard production from the harmful consequences of variability and disruptions to the flow of activities. Buffers of different types can be introduced to reduce instability in a system’s operations and they include money, time, capacity, inventory, space and information.
Smoothing is used to reduce variability in inputs and internal operations to avoid the extra costs and the resultant reduced performance of system buffers.
Rationing limits the allocation of resources to uncertain work tasks. Work processes are shielded from fluctuations in the system by restricting the allocation of resources to uncertain activities. Shielding workers from project uncertainties by means of proper planning is essential to maintaining productivity.
In addition, prior to the release of work packages to the site for construction, they are subjected to constraint analysis to satisfy last planner’s quality criterion for execution and soundness. Constraint analysis is a technique used for tracking and close monitoring of work tasks for production level planning. This expedites the removal of obstructions to the successful execution of work tasks. It improves safety performance of target operations by identifying and removing safety risks and hazards. It also ensures the active management of the production and delivery of goods and services by suppliers. The last planner is provided with an early warning of potential problems with sufficient lead time to plan and address issues as required. Typical constraints on construction tasks are incomplete design or prerequisite work and non-availability of materials, information, directives, and labor or equipment resources. After successful constraint analysis, weekly work plans are formed from workable backlog, which improves the productivity of workers who receive the assignments and increases the reliability of work flow to the next phase of the works.
Last Planner® system uses a variety of approaches to achieve the required level of safety on site. Production control brought about by process stability and work flow predictability creates fewer opportunities for accidents. Construction planners are informed of safety risks at all levels of planning decisions. Risk levelling is done to ensure that safety risks are planned and filtered in Last Planner assignments and safety management resources are pulled to the places they are most required.
Effects on Productivity:
The last planner system facilitates transparency of the design process through the metrics of the percentage of plan completed (PPC). PPC is the standard against which control is exercised at the production unit level, using quality plans, project schedules, execution strategies and budget unit rates. The impact of change orders and design modifications to the schedule are proactively analyzed which improves design management by allowing for benchmarking, setting targets and monitoring the progress of the project. A high PPC means that more of the appropriate tasks were accomplished with the available resources and translates to greater productivity and progress.
The lookahead process aids work flow control by coordinating the flow of design, supply, and installation through production units. It creates an adequate schedule planning framework which structures the definition and flow of activities, develops efficient methods for executing work tasks, improves communications between trades and matches load and capacity. Matching load to capacity within a production system is necessary for productivity of the production units through which work flows in the system, and efficiency of system cycle time. Materials or other resources necessary to complete a task in a production process are then pulled to areas where needed.
LPS focuses on increasing the quality of the weekly work plan assignments when combined with the lookahead process. These plans are used by crew foremen to schedule work packages and allocate available labor and equipment resources which encourages the systematic monitoring of resource availability for production planning and control. Construction data from various sources are also integrated in the work plan for easy visual management of project resources.
Utilizing the CHASTE Model
Construction workers are frequently endangered by activities performed by themselves or other workers on site. In the complex, dynamic and unpredictable construction environment, risk levels fluctuate due to changes in the physical environment, different work activities, and the turnover of crews and equipment.
In the Last Planner system, safety-conscious work filtering can be achieved using the Construction Hazard Assessment with Spatial and Temporal Exposure (CHASTE) model. CHASTE is a conceptual model that enables the forecast and evaluation of safety risks in construction projects for different trades and enhances the reliability for planning and managerial purposes through automation. It conceptually defines the required knowledge and data, the mechanisms for manipulating the data, and the parameters that affect risk levels.
With the aid of a digital building model, project plan and schedule, CHASTE utilizes a detailed knowledge base of a variety of construction methods and their potential loss-of-control scenarios for short and long-term forecasting of safety risk levels for work teams with minimal efforts and greater accuracy. Risks are analyzed in advance and continuously monitored as work progresses for each phase and at each location. Additionally, risk levelling, which ensures that risks remain within tolerable levels by the application of mitigation efforts, can be achieved by running a CHASTE analysis of the proposed master plan. As the peaks of risk levels inherent in construction activities are revealed, tasks that have hazardous effects on the project can be rescheduled. Adjustments may be made to the duration of activities or construction methods to avoid assigning risky combinations or sequencing of tasks which expedites the development of a weekly work plan with lower risk levels. The CHASTE model is a novel approach for predicting risk levels that can be used to enhance existing safety management practices at construction sites. It is a time- and - space-dependent model that quantifies risk levels using automated calculations, which facilitates the efficient management of construction safety. With a reliable and moderately precise prediction of safety risk levels, construction managers will be able to level risks by rescheduling tasks or by other means to reduce risks to acceptable levels.
Other software packages available for the Last Planner system are KaiNexus, Pipefy, vPlanner, Touchplan, LeanProject and Villego.
Behzad Esmaeili, PhD - George Mason University
Olugbemi Aroke - George Mason University
Babak Memarian, PhD - CPWR The Center for Construction Research and Training
Hyun Woo “Chris” Lee, PhD - University of Washington, Department of Construction Management
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