A Comparison of Takt Time and LBMS Planning Methods

Olli Seppänen1

1Postdoctoral Researcher, Aalto University and Director of VDC Services, Trimble NavigationLimited, olli_seppanen@trimble.com

Abstract

Takt time and LBMS are getting increased attention from practitioners of LeanConstruction. The takt time approach focusses on designing work locations withsimilar quantities and plans on the same duration for each task without any buffers.To achieve level resource utilization takt time projects require substantial workbacklog tasks or locations to absorb periods of low production demand. The LBMSapproach plans on using consistent resources through all the locations. Buffers areadded to absorb the risk of deviations and durations are allowed to vary based onquantity of work. This results in significantly longer schedules but decreases the needfor workable backlog areas and the risk of demobilizations.To compare these two methods, three schedules planned with LBMS methodologywere reformed into takt time schedules by forcing each task to have the same durationin each location. This was achieved by changing the crew size in each location toachieve a duration shorter than or equal to the takt time. The resulting schedules werecompared in terms of total project duration, total project manhours and the risk ofduration and manhours evaluated using Monte Carlo simulation.The results indicate that takt time achieves substantially shorter schedules but themanhours required in work backlog areas are much higher than in LBMS approach.In projects where quantities are similar between locations, takt time performs well ifthe resources are not demobilized when they run out of work. If the resourcesdemobilize, the risk of return delays makes takt time a risky strategy.

Keywords

LBMS, takt time, variability, buffers

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Reference

Seppänen, O. 2014, 'A Comparison of Takt Time and LBMS Planning Methods' In:, Kalsaas, B.T., Koskela, L. & Saurin, T.A., 22nd Annual Conference of the International Group for Lean Construction. Oslo, Norway, 25-27 Jun 2014. pp 727-738

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