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Lab Report, 2010-11

K. Mamasis, I. Minis, G. Dikas

Managing a Vehicle Breakdown Incident During Urban Distribution of a Single Product, Under Review in JORS, 2010

This paper addresses a case in which a vehicle, member of a fleet distributing a common single product, is immobilized permanently while executing its distribution plan. The other, active, vehicles of the fleet are then rerouted to serve the remaining non-served clients. We model this re-planning problem as a variation of the Team Orienteering Problem constraining all vehicle routes to an upper time, or distance, limit and taking into account the limited capacity of the fleet vehicles. We propose an efficient heuristic to provide solutions in almost real-time. The heuristic progressively constructs new routes for each active vehicle taking into account that a vehicle may replenish its load by visiting the warehouse or the immobilized vehicle. We solve the replenishment sub-problem by developing a fast labelling algorithm. To test the effectiveness of the proposed heuristic, we have developed a Genetic Algorithm (GA) that obtains high quality (but computationally expensive) solutions and compare them to those obtained by the heuristic.
Keywords: Team Orienteering Problem, Urban Distribution, Distribution Vehicle Breakdown, Vehicle Routing, City Logistics

Post date: Tuesday, January 24, 2012 - 08:56
Lab Report, 2010-10

G. Ninikas, Th. Athanasopoulos, V. Zeimpekis, I. Minis

Routing in Hybrid Courier Operations, Technical Report, December 2010

We present the design and evaluation of an enhanced fleet management system that supports planners and dispatchers of courier operations in two significant current issues: a) Planning mass deliveries over a multiple-day horizon, and b) allocating, in real-time, dynamic requests that occur during service execution. In the former case, we proposed a method to assign service requests with some flexibility in a multi-period horizon, taking into account typical routes expected to be executed within this horizon. For the allocation of dynamic requests, we propose an intelligent insertion heuristic to provide efficient solutions within reasonable computational times. Both methods have been implemented in a commercial fleet management platform, and have been tested in a Greek courier operator. The results indicate that the system, enhanced by the proposed methods, may improve significantly the pickup and delivery operations of a courier company.
Keywords. Express logistics, fleet management systems, replanning in vehicle routing, multi-period vehicle routing

Post date: Tuesday, January 24, 2012 - 08:49
Lab Report, 2010-09

G. Ninikas, Th. Athanasopoulos, V. Zeimpekis, I. Minis

Routing Problem in Hybrid Courier Operation, Under Review in Journal of Operation Research Society, 2010

We present the design and evaluation of an enhanced fleet management system that supports planners and dispatchers of courier operations in two significant current issues: a) Planning mass deliveries over a multiple-day horizon, and b) allocating, in real-time, dynamic requests that occur during service execution. In the former case, we proposed a method to assign service requests with some flexibility in a multi-period horizon, taking into account typical routes expected to be executed within this horizon. For the allocation of dynamic requests, we propose an intelligent insertion heuristic to provide efficient solutions within reasonable computational times. Both methods have been implemented in a commercial fleet management platform, and have been tested in a Greek courier operator. The results indicate that the system, enhanced by the proposed methods, may improve significantly the pickup and delivery operations of a courier company.
Keywords. Express logistics, fleet management systems, replanning in vehicle routing, multi-period vehicle routing

Post date: Tuesday, January 24, 2012 - 08:32
Lab Report, 2010-08

I. Minis, K. Mamasis, V. Zeimpekis

Real-Time Management of Vehicle Breakdowns in Urban Freight Distribution, under review in Journal of Heuristics, 2010

This paper deals with situations in which an unexpected event immobilizes a vehicle of a distribution fleet permanently, and the remaining vehicles are rerouted to serve some of the clients of the failed vehicle. We model this problem as a variation of the Team Orienteering Problem (TOP), constraining all vehicle routes to an upper time, or distance, limit. The problem requires an effective solution in almost real time. We propose a new heuristic to provide efficient solutions within this strict computational time constraint. To test the quality of the heuristic, we have developed and validated a Genetic Algorithm (GA) that obtains high quality (but computationally expensive) solutions and compare them to those obtained by the heuristic. The latter has also been tested successfully in a real-time fleet management system.

Keywords: Team Orienteering Problem, Freight Distribution, Distribution Vehicle Breakdown, Vehicle Routing, City Logistics

Post date: Monday, January 23, 2012 - 10:47
Lab Report, 2010-07

V. Gliatis, I. Minis, K. M. Lavasa

The Impact of Failures in Service Operations, Under Review in Journal of Service Management, 2010

Purpose – Failures represent an important source of variability in service operations and a major performance challenge. As a consequence, the effective management of failures is a prerequisite to achieve lean services. In this paper we focus on the operational perspective of failures; that is we attempt to quantify the impact of critical failure parameters on key system performance measures, such as cycle time and work-in-process. We also examine various operational concepts, or management practices, that service organizations use to address the effects of failures.
Design/methodology/approach – We use discrete event simulation to model the behavior of a typical two-stage service system (front-office, back-office), and design of experiments to estimate the impact of significant parameters that characterize service failures, on key system performance measures. In a final experiment we analyze three of the most common practices used by management to address failures, and the impact of these practices on system performance under different conditions.
Findings – The results of this study suggest that failures and rework degrade the performance of service systems. The impact is reinforced, if specific inputs of the system deteriorate, such as the ability of the service organization to deliver appropriate quality, to detect failures early and to be capable enough to recover timely and efficiently from failures. In addition, the results show that the various management practices have strengths and weaknesses depending on the characteristics of failures. If this is not taken into consideration, the above managerial practices may lead only to short-term improvements, while the main causes of failures will remain unsolved.
Originality/value – Monitoring and assessing failures in a real service environment is a challenging task. In this paper, we complement the existing literature on service failures by focusing on the operational aspect. With the use of simulation, we manage to quantify and hence visualize failures and their impact on the behavior of a service system. We also provide useful insight into the parameters that determine the effectiveness of various management practices used to address failures.
Keywords: lean services, service failures, quality in service operations

Post date: Monday, January 23, 2012 - 09:54

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