A relook at plan reliability measurements in lean construction and new metrics from digitized practical implementation

Abstract

Lean construction is increasingly being adopted in many countries as a means to improve construction project performance and productivity. Measuring the various improvements towards achieving the outcomes of reliability, preparedness, commitment and collaborative culture is crucial for a sustained successful practical implementation of Lean. Among various Lean techniques and tools, the Last Planner System (LPS) method has been widely used in construction projects for its simplicity and applicability to the construction environment. With LPS, the plan reliability is measured by Percent Plan Complete (PPC). The PPC as a single metric has been found to be insufficient in providing actionable information in understanding the root cause of challenges faced in different projects nor in improving the reliability nor in getting valid commitment of key project parties. It is also ineffective to symbolize as the metric to represent the preparedness, capacity or performance of the different sub-contractors. This paper aims to provide an in-depth review of PPC and other reliability measurements and their advantages and shortfalls for practical implementation. It reviews the symbolic representation of PPC to improvement through the application of Lean methods in construction from a planning and management perspective. From these analysis, this paper introduces a framework for practical implementation of Lean construction. It also proposes new metrics to supplement PPC to accurately represent plan reliability for better understanding of the root causes. The proposed indices are validated using data obtained from the digital application of Lean construction processes using Lean PlanDo. Lean PlanDo is digital tool embedded with Lean principles for construction planning and management based on LPS with a key emphasis on Value Stream Mapping (VSM) and constraint management. The proposed indices will provide the project teams with practical measurements and to build upon their understanding of Lean, measure the effectiveness of planning and the application of Lean methods in the project.