Abstract: Determining the controlling path is of great importance to the repetitive projects scheduling. Although several methods for determining controlling path are proposed, none of them is commonly accepted. This paper presents a convenient and correct way to identify the controlling path by the delayed step function. Ferstly, various types of activities and constraint lines in repetitive projects are expressed by the delayed step function. Then the controlling path is identified by a forward tracing and a backward tracing. Through the forward tracing, the potential controlling points are calculated and determined. Through the backward tracing the controlling path is determined. A highway project is presented to demonstrate its validity. Compared with the existing methods, the proposed method is more suitable for the engineering situations, and provides a mathematical foundation for the computer processing.

Key words: controlling path, delayed step function, repetitive project, controlling activities