Improving construction workflow- The role of production planning and control.

摘要

The Last Planner(TM) System (LPS) has been implemented on construction projects to increase work flow reliability, a precondition for project performance against productivity and progress targets. The LPS encompasses four tiers of planning processes: master scheduling, phase scheduling, lookahead planning, and commitment / weekly work planning. This research highlights deficiencies in the current implementation of LPS including poor lookahead planning which results in poor linkage between weekly work plans and the master schedule. This poor linkage undermines the ability of the weekly work planning process to select for execution tasks that are critical to project success. As a result, percent plan complete (PPC) becomes a weak indicator of project progress.The purpose of this research is to improve lookahead planning (the bridge between weekly work planning and master scheduling), improve PPC, and improve the selection of tasks that are critical to project success by increasing the link between Should, Can, Will, and Did (components of the LPS), thereby rendering PPC a better indicator of project progress.The research employs the case study research method to describe deficiencies in the current implementation of the LPS and suggest guidelines for a better application of LPS in general and lookahead planning in particular. It then introduces an analytical simulation model to analyze the lookahead planning process. This is done by examining the impact on PPC of increasing two lookahead planning performance metrics: tasks anticipated (TA) and tasks made ready (TMR). Finally, the research investigates the importance of the lookahead planning functions: identification and removal of constraints, task breakdown, and operations design.The research findings confirm the positive impact of improving lookahead planning (i.e., TA and TMR) on PPC. It also recognizes the need to perform lookahead planning differently for three types of work involving different levels of uncertainty: stable work, medium uncertainty work, and highly emergent work.The research confirms the LPS rules for practice and specifically the need to plan in greater detail as time gets closer to performing the work. It highlights the role of LPS as a production system that incorporates deliberate planning (predetermined and optimized) and situated planning (flexible and adaptive).Finally, the research presents recommendations for production planning improvements in three areas: process related- (suggesting guidelines for practice), technical- (highlighting issues with current software programs and advocating the inclusion of collaborative planning capability), and organizational improvements (suggesting transitional steps when applying the LPS).