Managing the “Receding Edge”

Abstract

So much attention is paid to starting construction activities, and starting new work at regular time intervals to a beat (aka. takt) that-not surprisingly-work to finish those very activities may fall behind. This paper focuses, not on the start-, the "leading edge, "but on the end of activities, the "receding edge." The receding edge articulates when work is "done-done" and the successor contractor may start their work, unimpeded by their predecessors' unfinished work or "leftovers" (e.g., areas left dirty and cluttered with remnants). This paper describes receding-edge activities related to forming, placing, and finishing post-tensioned, cast-in-place concrete slabs, observed on a project in San Francisco, California. The researchers went to the gemba, described the current situation, and exchanged ideas with the contractor on means to keep the receding edge progressing at the pace of the leading edge, that is: to improve the cycle time from start, to not just finished or "done," but to "done-done" completion of each slab. Findings include the need to define standard processes (e.g., for clean-up work) as those observed appeared defective (one of Ohno's 7 wastes) or none existed, and to designate resources to accomplish them. This paper contributes to knowledge by articulating the receding edge concept, describing challenges in managing it, and documenting lean methods as countermeasures to those challenges. When managed considering the production impact of receding-edge work on the contractor responsible for it and on follow-on contractors, the case for cycle time reduction is easy to make and worth the money.

Handoffs Between Takt Train Wagons: a Systematic Literature Review

“…All of this can contribute to what they call a parade of delays. Salem et al (2018) saw a similar effect. They observed that work that was not 100% finished but handed off to the next wagon created costly additional work.…”

“…While conducting an extensive bibliographic analysis is outside the scope of this paper, we made some overarching observations regarding who has written anything about takt handoffs. Although there are many different contributors from around the world to the general field of takt, the papers we identified regarding handoffs cluster primarily around three international communities: The American -affiliated with Berkley (Frandson et al, 2013(Frandson et al, , 2014Frandson et al, 2015;Frandson & Tommelein, 2016;Linnik et al, 2013;Salem et al, 2018;Tommelein & Emdanat, 2022), the Finnish -affiliated with Aalto University (Keskiniva et al, 2021(Keskiniva et al, , 2022Kujansuu et al, 2020;Lehtovaara et al, 2021Lehtovaara et al, , 2022 and the Norwegian affiliated with NTNU (Dahlberg & Drevland, 2021;Gardarsson et al, 2019;Haugen et al, 2020). Interestingly, while the German community behind the Takt Planning and Takt Control approach has been prolific in producing papers on takt, none of their publications directly concerned the handoff of takt areas.…”

“…Several authors point to reliable and predictable handoffs as principles derived from the Last Planner® System (LPS) (Haugen et al, 2020;Kalsaas et al, 2014;Lehtovaara et al, 2022;Salem et al, 2018;Tommelein & Emdanat, 2022). In the context of LPS, takt planning will be a method used to stabilize production and make work events more predictable (Kujansuu et al, 2020;Lehtovaara et al, 2021;Linnik et al, 2013).…”

“…According to Salem et al (2018), some people consider their work "done" when they have done enough to allow them to continue in the next workspace. In other words, this does not include the work a wagon must do for subsequent wagons to work unhindered.…”

“…This thinking illustrates the difference between being "done" and "done-done." Salem et al (2018) found several causes of not being "done-done". In one of the case projects they refer to, no individuals were held responsible for post-work clean-up, and there were no processes to ensure that the areas were tidied after the work was completed.…”