124 ■ Transportation Research Record 1761 Paper No. 01-3291 A general model is presented for efficient scheduling and resource man- agement in construction projects that involve a high degree of repetition, such as highways and pipelines. The proposed model has three main fea- tures: (a) it fully integrates the critical path method for network analysis and the line of balance technique for linear scheduling, (b) it allows real- istic schedule development considering project deadline and resource constraints, and (c) it incorporates improved schedule presentation that shows crews’ movements along the repetitive units and their detailed work assignments. The detailed formulation of the proposed model is described, and an example application is presented. The proposed model is demonstrated to offer significant advantages as a resource-driven approach. Future extensions to the proposed model are then outlined. Time and cost control must be based on a schedule. There is no way that project managers can determine and report what is accom- plished unless they first know what is expected. The clearer, more complete, and more realistic the schedule, the more effective con- trol can be done. In construction, the critical path method (CPM) for network analysis has traditionally been used for planning and scheduling of nonrepetitive projects. However, the widely recog- nized disadvantages of using this technique in linear and repetitive projects, particularly related to resource management, have led to the development of various linear scheduling techniques, including the line of balance (LOB), that have been used extensively in Europe and the Middle East (1–3). These techniques allow the syn- chronization of resources and maintain work continuity along the repetitive units. The use of linear scheduling techniques in Canada and the United States, however, has been limited, irrespective of their advantages and the potential of merging their capabilities with those of network techniques to offer better planning and schedul- ing tools for complex construction projects (1, 4). Traditional techniques for scheduling repetitive projects such as the LOB technique assume purely sequential activities and have a sim- plistic formulation to maintain crew work continuity. One notable effort to combine the benefits of the CPM and the LOB techniques is the model developed by Suhail and Neale as a framework for CPM- LOB integration, which is expanded in the current developments (5). The objective of CPM-LOB scheduling is to achieve uninterrupted utilization of resources, maintain logical work relationships, and meet a predefined project deadline. The framework developed by Suhail and Neale, however, works well only when the calculated number of crews is not rounded to integer numbers. Moreover, it does not con- sider resource constraints. In an effort to provide generalized and flexible formulation of combined CPM-LOB, this paper presents a scheduling model that is practical and possibly more attractive for use in repetitive con- struction projects such as highways and pipelines. The model observes the network of relationships in each unit and determines the proper work schedule considering time and resource constraints. Details of the scheduling model are described and its capabilities demonstrated through an example project. Future enhancements are then outlined. BASIS OF CPM-LOB INTEGRATION: RESOURCE BALANCING The objective of CPM-LOB integration is to achieve a resource- balanced schedule by determining the suitable crew size and num- ber of crews to employ in each repetitive activity. This is done such that (a) the units are delivered with a rate that meets a pre- specified deadline, (b) the logical CPM network of each unit is respected, and (c) crews’ work continuity is maintained. The analysis also involves determining the start and finish times of all activities in all units and the crews’ assignments. The CPM-LOB formulation that achieves the above objective has four components, which are discussed in detail: meeting a given dead- line duration, crew synchronization, determining resource needs, and drawing the schedule. Meeting Deadline Duration A basic objective in CPM-LOB calculations is to meet a given dead- line for finishing a number of repetitive units (n), each with its own CPM network of component activities. As shown in Figure 1, the end of the project (Time T L ) is the date at which the last activity in the last unit is finished. When the first unit is finished at time (T 1 ), the remaining time till the deadline is taken to finish the remaining n - 1 units. Accordingly, to meet the deadline, a desired rate (R d ) of finishing the various units can be calculated as follows: where T L is the deadline duration of the project and T 1 is the CPM duration of the first unit. The delivery rate determined from Equa- tion 1 is, in fact, the minimum rate required to meet the desired deadline. R n T T d L = - - 1 1 1 () Critical Path Method–Line of Balance Model for Efficient Scheduling of Repetitive Construction Projects Tarek Hegazy Civil Engineering Department, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1.