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.

(Photo courtesy of ELCOSH)

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.

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