between the phases was represented by sharing one module between
two subsequent phases. Production control and lean
work structuring were both shown to extend throughout the
five main phases. Learning was introduced to underscore the
need to document lessons learned from one engagement to
another.
The LPDS model consists of 15 modules, 11 organized in 4
interconnecting triads extending from project definition to design
to supply and assembly, plus 2 production control modules
and work structuring module, both conceived to extend
through all project phases, and the post-occupancy evaluation
module, which links the end of one project phase to the beginning
of the next: (1) Project Definition: (a) Needs and Values
Determination; (b) Design Criteria; and (c) Conceptual Design;
(2) Lean Design: (a) Conceptual Design; (b) Process Design;
and (c) Product Design; (3) Lean Supply: (a) Product
Design; (b) Detailed Engineering; and (c) Fabrication/Logistics;
(4) Lean Assembly: (a) Fabrication/Logistics; (b) Site
Installation; and (c) Testing/Turnover; and (5) Production
Control: (a) Work Flow Control; and (b) Production Unit
Control. Work Structuring and Post-Occupancy Evaluation
are thus far only single modules. Essential features of LPDS
are as follows [45]: (1) Structure and management of a project
are aimed at creating value; (2) Cross-functional teams, involved
in front end planning and design, include members
from all areas of production process; (3) Project control would
be a tool executed throughout the project as opposed to reliance
on after the fact variance detection; (4) Optimization efforts
are focused on making work flow reliable and not to
focus on improving productivity; (5) Pull techniques are used
to govern the flow of materials and information; (6) Capacity
and inventory buffers are used to absorb variability in the production
process; (7) Feedback loops incorporated at every level,
are aimed at a rapid system adjustment and learning;
and (8) Work structuring of the entire process increases value
and reduces waste at the project delivery level. Efforts to improve
performance at the planning level increases performance
at project level.
8.2. Last Planner System (LPS)
One of the most effective ways to increase efficiency of construction
industry is to improve planning and control process.
In Lean Construction, planning and control are considered to
be complementary and dynamic processes maintained during
the course of the project. Planning defines the criteria and creates
strategies required to reach project objectives, control
makes sure that each event will occur following the planned sequence.
Re-planning must be done when the previously established
sequences are no longer applicable or convenient.
Feedback facilitates learning when the events do not occur
as planned [15,45]. One of the best known Lean techniques is
the Last Planner System which has been demonstrated to be
a very useful tool for the management of construction process,
and continuous monitoring of the planning efficiency, to assist
in developing foresight, smoothing workflow variations, and
reducing/removing uncertainties plaguing construction processes.
It consists of work flow control and production unit
control. Work flow control is accomplished primarily through
the look-ahead process, while production unit control is
accomplished primarily through weekly work planning.