Location-based scheduling methods are not new. In some countries such as Finland, the adoption of line of balance schedules is widespread and used for decades. However, in the United States these schedules have remained unpopular. Location-based scheduling has come under the guise of many names: Vertical Production Method, Linear scheduling, Repetitive Scheduling Method, Line of Balance scheduling, Even Flow Production, and Flowline Scheduling are a few of the more popular names. In general, a location-based schedule could be any schedule that aims to develop a schedule and communicate the schedule with space as a resource.
It’s important to think about space as a resource because construction is a type of production where the workers move through the work (as opposed to manufacturing where the work predominantly moves to the workers). As such, if a schedule fails to consider space then it is all too easy to create schedules that are full of problems. What sort of problems? Think about trades working on top of one another, or a subcontractor being scheduled to work for a week, then off for two weeks, then come back with three crews.
One of the first cases in the US that used a location-based schedule, with multiple paced sets of work, was on the construction of the Empire State Building in 1930. Willis and Friedman authored a wonderful book in 1998 documenting the construction of the building using the notes of the superintendent and other personnel on site4. The superintendent controlled the project using a schedule that closely resembles a line of balance schedule. The schedule clearly outlines the necessary pace for steel erection, fabrication, and design throughout the job. The general contractor was closely tied with the architect to make sure that this was a possible feat. The result: the tallest building in the world for decades, built under budget and ahead of schedule in a little over a year.
Aside from the Empire State Building, the most common usage of line of balance schedules was for manufacturing purposes. The nature of the scheduling method was perfect for the clear, linear structure of the production system. Goodyear in the 1940s was known for using line of balance schedules. Germany began to use a similar pacing concept for airplane manufacturing a decade earlier in the 1930s. Planes were built at certain beats (takts) to maintain a consistent, stable production system. The plane manufacturing method spread to Japanese plane manufacturing, which later made it into automobile manufacturing. Today, the Toyota Production System is known for using both the phrase and the concept in their car manufacturing. If you’re interested in learning more about the origins of Takt time, see the wonderful blog post by Michel Baudin.
Unfortunately the use of line of balance schedules fell out of practice in the US because they were critiqued for not having the same analytical power as the Critical Path Method. Line of balance schedules were just seen as a visual way of communicating the schedule. Researchers soon disproved this idea in the 1980s, but it was too late: CPM scheduling had won the battle. The past 30 years has seen some use of line of balance schedules on linear projects, but overall the scheduling method has remained dormant in the US for commercial construction.
Roughly seven decades later, pacing construction work using set beats has made its way back to construction in the US. The US Government utilized a paced, location-based schedule called "Short Interval Production Scheduling" to deliver the renovation of the Pentagon in 20022. Research in the UK built upon that research and called it "week beat scheduling"1. In that same year Olli Seppänen completed his dissertation on the Location-based Management System3. Now, case studies are exploring the use of Takt time for less repetitive types of construction with various takt times. An effective way to communicate a Takt time plan is through the use of a location-based schedule, like a line of balance schedule. Whether the space is shown in one dimension, two dimensions, or more, it certainly is a critical resource to communicate in any construction schedule.
1. Court, P.F. (2009). “Transforming traditional mechanical and electrical construction into a modern process of assembly”. Eng. D. Dissertation, Loughborough University, United Kingdom.
2. Horman, M.J., Messner, J.L., Riley, D.R. and Pulaski, M.H. (2002). “Using buffers to manage production: A case study of the pentagon renovation project.” Proc. 10th Annual Conf. of the Int’l Group for Lean Constr. (IGLC 10), Gramado, Brazil.
3. Seppänen, O. (2009). “Empirical research on the success of production control in building construction projects.” Ph.D. Dissertation, Helsinki University of Technology.
4. Willis, C. and Friedman, D. (1998). Building the Empire State Building, W.W. Norton and Company, New York.