Stephen E. Bechtold

A study of the reduction of fatigue impact on productivity through optimal rest break scheduling.

The variable-k with penalty (VKP) model was developed to determine optimal individual rest break policies. The goal is to maximize worker output over a specified time horizon. A rest break policy consists of the number, duration, and placement of rest breaks. This study examined the validity of the VKP model in an experiment that involved 10 subjects engaged in the demanding physical task of riding an ergometer. In separate sessions, the subjects first used a self-determined rest break policy and then the models policy. A comparison of the results indicated that, on the average, work output increased by nearly 13% when the subjects used the models policy.

Working set generation methods for labor tour scheduling

Abstract Working set methods in labor scheduling generally consist of a generation and implementation phase. The generation phase involves the selection of a subset of work schedules from the complete (master) set of all allowed work schedules. In the implementation phase, either heuristic or integer optimal solutions are obtained upon the basis of the schedules in the working set. We classify previous working set generation procedures as being either structural, demand-based, or refinement. Two new working set procedures within the first category and one new procedure within the second category are developed. Subsequently, we compare the efficacy of the new and previously published generation procedures within the context of a discontinuous tour scheduling environment where the sole objective is minimization of total labor hours scheduled. All comparative analysis was based upon the global integer optimal solutions to problems posed by the master set associated with 36 different labor requirements distributions. The second of the new structural methods resulted in the best performance for all working set sizes. In particular, it resulted in global integer optimal solutions, for all test problems, with working set sizes of 40 and 50. The new demand-based method resulted in the second best performance at a working set size of 50. We conclude with a discussion of the implications of the results for future research and practice.

The equivalence of general set-covering and implicit integer programming formulations for shift scheduling

In a recent article we demonstrated that implicit optimal modeling for shift scheduling (P2) has inherent size and execution time advantages over the general set-covering formulation for shift scheduling (P1) [11, 13]. We postulated that the absence of extraordinary overlap (EO) was a requirement for the equivalence of P1 and P2. We have defined EO as the condition in which the earliest and latest starts for a break in one shift are earlier and later than the earliest and latest starts for a break in any other shift(s). In this article, we prove that our earlier postulate was accurate. Additionally, we discuss research extensions and note other scheduling problems for which implicit modeling may be appropriate.

An interactive, optimization-based decision support system for scheduling part-time, computer lab attendants

The labor tour scheduling problem has attracted much recent research, focusing on the development and evaluation of optimal and heuristic methods to minimize labor costs while satisfying demand for labor. Researchers typically assume that a sufficient labor pool is available. However, service organizations such as fast-food restaurants, grocery stores, and video rental stores, as well as not-for-profit organizations using volunteer workers, typically use a large number of part-time employees with limited availabilities for work. This study presents an interactive decision support system that addresses the conflicting objectives of efficient labor scheduling and accommodating employee needs. The system uses a linear programming model to provide sets of optimal shifts from which employees can construct acceptable weekly schedules; the manager may override the schedule if necessary. The decision support system is used to schedule student computer lab attendants at a major university in an efficient and equitable manner.

A microcomputer-based heuristic for tour scheduling of a mixed workforce

Abstract Labor tour scheduling research has recently addressed environments which allow both full- and part-time employees with varying cost and productivity levels. Mathematical programming representations of the associated scheduling problems have most frequently been based upon the general set-covering formulation originally suggested by Dantzig. A number of heuristic solution methods appropriate for these problems utilize the LP solution of the general set-covering formulation. However, these methods typically require substantial amounts of CPU time for large problems. Continued increases in problem size may result in mathematical programming formulations which are essentially intractable, regardless of the hardware and software used. In this research, a two-stage heuristic for mixed-workforce tour scheduling problems was implemented on a 386 microcomputer. The performances of the new heuristic were compared to those associated with single-phase linear programming-based procedures on mini computers in two test environments. Using considerably lower CPU times, our new method resulted in mean labor scheduling costs which were only 0.36 above and 0.19% below those obtained by the competing methods for these two environments, respectively. The latter result was especially impressive since the problems in the second test set were considerably more difficult than those in the first test set. These results are likely to be important to service operations managers who are often limited to the use of microcomputer hardware and software.

Optimal Scheduling of a Flexible-Duration Rest Period for a Work Group

All previous modeling research involving optimization of performance associated with work-rest cycles has focused upon individual employees working independently. We extend this earlier research by considering the choices of placement for and duration of a single rest period that must be taken simultaneously by all employees in a work group. Assuming linear work-rate decay and recovery functions for individual employees within the group, we show that an appropriate model can be formulated as a mixed-binary, cubic programming problem. We develop an efficient optimal solution procedure with a computational time that appears to be a linear function of the number of employees considered. We report on a preliminary simulation experiment that evaluates the productivity loss that occurs when the rest break policy is determined based on the work characteristics of a randomly selected subset of employees in the work group, and provides an initial exploration of the nature of optimal policy variables. Finally, we offer suggestions for future research.

Improvement of Labour Utilisation in Shift Scheduling for Services with Implicit Optimal Modelling

Using labour efficiently in service organisations is an important management objective since labour frequently accounts for more than 70 per cent of total operating costs. While most service organisations can use flexible scheduling rules to improve the utilisation of labour, selecting a good or “best” set of work schedules from a large set of alternatives has proved to be a formidable task. A new modelling procedure is described which allows optimal decisions to be made when the desired level of scheduling flexibility results in a very large population of possible schedules. Flexibility in shift scheduling is increased primarily through increasing the number of different shift lengths and allowing flexible placement of breaks. The power of the new modelling approach was used in an experiment described here to assess the relative impact of shift‐length and break‐placement flexibility on labour utilisation. The results indicated that, while either type of flexibility can improve labour utilisation, there w...

Microcomputer‐based Workforce Scheduling

Service operations managers often attempt to improve labour‐scheduling efficiency through the use of one or more types of scheduling flexibility. Part‐time labour, for example, is one type of scheduling flexibility which is used in many service operations. The use of part‐time workers increases productivity by providing a closer match between the forecast labour requirements and the amount of labour actually scheduled. Demonstrates the feasibility of implementing a microcomputer‐based approach to workforce‐scheduling problems which contain a substantial degree of scheduling flexibility. This approach has particular application to small service firms which may have, or can obtain, microcomputers to schedule their operating personnel. The actual scheduling procedure is designed to produce daily and weekly work schedules simultaneously (i.e. tour schedules) for workers assumed to be of homogeneous skill and ability, such as those employed in a fast‐food restaurant. The application of such an approach in the ...

Microcomputer‐based working set generation methods for personnel scheduling

Presents a new approach to working set generation for personnel scheduling problems. In full‐time (FT) and mixed‐workforce (MW) experiments, generates the schedules in the working sets from the use of two‐phase heuristic labour scheduling solution procedures. The solution procedures were implemented on a 386 microcomputer and did not require the specification of the size of the working sets in advance. In the FT experiment, the general set‐covering formulations (GSCFs) associated with the produced working sets were solved with integer programming. The new working set procedure yielded optimal integer solutions for all 36 test problems in the FT experiment. Owing to the size and complexity of the problem data in the MW experiment, the GSCFs associated with the working sets were solved with linear programming, and heuristic rounding procedures were applied to obtain feasible integer solutions. The mean labour costs of these solutions averaged 0.69 per cent less than the mean cost of solutions obtained via t...

Antecedents of employee satisfaction in a hospital environment.

Employee satisfaction may be important both because of its possible relationship to turnover and absence rates and because of its potential impact upon employee productivity.