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Showing papers on "Service level published in 1977"


Journal ArticleDOI
TL;DR: This paper introduces a more realistic assumption-customers are assumed to wait a fixed amount of time before cancelling their orders, incorporated in the S-1, S inventory model, which is appropriate for slow-moving items.
Abstract: Existing models of inventory control assume that when a stockout occurs customers either wait as long as necessary or not at all for the replenishment to arrive. This paper introduces a more realistic assumption-customers are assumed to wait a fixed amount of time before cancelling their orders. The new assumption is incorporated in the S-1, S inventory model, which is appropriate for slow-moving items. Statistical and economic measures of performance for the model are developed on the basis of certain queuing results. We then use optimization techniques to derive a minimum-cost inventory policy with or without constraints on service levels. We also derive an optimal policy for trade-offs between inventory levels and replenishment rates and provide computational approaches.

35 citations


Journal Article
TL;DR: In this article, a case in which various service policies are evaluated, for parametrically varied demand levels, by using a combination of manual and automated procedures is examined, and it is shown that significant economies of scale develop at relatively low levels of increased transit use and that major redesign of system operating policies is required to sustain desirable service levels and costs.
Abstract: Dramatic increases in transit patronage will require a major restructuring of present transit and paratransit operations to achieve integrated regional systems capable of changing as traffic increases and new markets are penetrated. The integration of new public transportation options such as dial-a-ride, jitney, and subscription bus with conventional mass transit promises significantly improved overall levels of service without increased total system costs. Integrated systems and expansion policies require that the individual service and cost attributes of each system component be modeled and the synergisms that result from various service combinations must be evaluated. Integrated system design is significantly more complex than the conventional bus routing and scheduling problem because of the increased number and complexity of available modes. This paper examines a case in which various service policies are evaluated, for parametrically varied demand levels, by using a combination of manual and automated procedures. Major conslusions are that significant economies of scale develop at relatively low levels of increased transit use and that major redesign of system operating policies is required to sustain desirable service levels and costs.

9 citations


01 Dec 1977
TL;DR: In this article, the authors developed a method for estimating patronage of demand responsive transportation (DRT) systems, which requires as inputs a description of the intended service area, current work trip patterns, characteristics of the served population, and the major design choices, such as the vehicle fleet size, changes in fleet size over the day, types of vehicles being used (buses or taxis), and the fare level.
Abstract: This study has developed a method for estimating patronage of demand responsive transportation (DRT) systems. This procedure requires as inputs a description of the intended service area, current work trip patterns, characteristics of the served population, and the major design choices, such as the vehicle fleet size, changes in fleet size over the day, types of vehicles being used (buses or taxis), and the fare level. Using these data, the model predicts patronage and service levels for each user-specified interval during the day. The modern system has been developed as a software package which includes a set of disaggregate demand models, a set of analytic supply models, and an equilibration procedure. In addition, a simple sketch planning procedure has been developed which can be used for quick, preliminary analysis of DRT sites. /GMRL/

6 citations


17 Mar 1977
TL;DR: A unified reliability standard is needed for the combined bulk power system and the distribution network, which is responsible for nearly all customer power failure as mentioned in this paper, and areas for improvement include underground and alternate lines, better maintenance, improved substation equipment, sectionalized circuits to isolate faults, and dispersed generation and storage.
Abstract: Power systems designed to meet customer service quality standards are proposed as a way to provide reliable power without increasing the generating capacity. A unified reliability standard is needed for the combined bulk power system and the distribution network, which is responsible for nearly all customer power failure. Criteria for setting acceptable reliability levels vary for different groups of customers, hospitals requiring the highest quality. Utilities under this system will guarantee a certain service level and prices will be geared accordingly. Costs can be charged directly (i.e., extra charges to cover the cost of higher quality or the customer can install his own back-up arrangements) or indirectly through rebates to the customers receiving lower-quality service. Improvements in distribution systems will require additional investment, but should be looked at as alternatives to new plant investment. Areas for improvement include underground and alternate lines, better maintenance, improved substation equipment, sectionalized circuits to isolate faults, and dispersed generation and storage. Ways to improve the bulk power system portion are also identified as alternatives to new construction. A utility wishing to try these alternatives must first analyze the present quality of its composite bulk power and distribution system to determine the true level ofmore » existing reliability. (DCK)« less

2 citations