An adaptive large neighborhood search heuristic for multi-commodity two-echelon vehicle routing problem with satellite synchronization

<p style='text-indent:20px;'>In considering route optimization from multiple distribution centers called depots via some intermediate facilities called satellites to final customers with multiple commodities request, we introduce the Multi-Commodity Two-Echelon Vehicle Routing Problem with Satellite Synchronization (MC-2E-VRPSS). The MC-2E-VRPSS involves the transportation from multiple depots to satellites on the first echelon and the deliveries from satellites to final customers on the second echelon. The MC-2E-VRPSS integrates satellite synchronization constraints and time window constraints for satellites on the two-echelon network and aims to determine cost-minimizing routes for the two echelons. The satellite synchronization constraints which trucks from the multiple depots to some satellites need to be coordinated guarantee the efficiency of the second echelon network. In this study, we develop a mixed-integer programming model for the MC-2E-VRPSS. For validating the model formulation, we conduct the computational experiments on a set of small-scale instances using GUROBI and an adaptive large neighborhood search (ALNS) heuristic which we develop for the problem. Furthermore, the computation experiments for evaluating the applicability of the ALNS heuristic compared with large neighborhood search (LNS) on a set of large-scale instances are also conducted, which proved the effectiveness of the ALNS.</p>

Randomized greedy algorithm for helicopter optimization in the energy industry: a practical approach to model development and solution deliverance

Purpose The global energy industry transports supplies and personnel via helicopter to offshore locations and is increasingly focusing on optimizing upstream logistics. This paper aims to and achieves a mutually beneficial balance between research and practice by providing generalizable methods to a problem routinely encountered in practice. Overall, the development and execution of the heterogeneous capacitated helicopter routing problem with split deliveries and multiple depots is validated by the networks’ results. Design/methodology/approach Using a unique sample of deepwater and ultra-deepwater permanent offshore locations in the Gulf of Mexico, transportation networks consisting of 57 locations operated by 19 firms are optimized via a randomized greedy algorithm. The study’s randomized greedy algorithm yields depot assignment, vehicle assignment, passenger assignment and routing. All data processing techniques and iterative algorithm processes are defined and explained. Findings Results show that the model effectively solves the complex transportation networks consisting of subject firms’ offshore nodes and eligible depots. Specifically, average load factors related to seat capacity and effective vehicle capacity of 87.7 and 95.7% are realized, respectively. The study’s model is a unique contribution to the extant literature and provides researchers and practitioners a practical approach to model development and solution deliverance. Research limitations/implications The extant literature encompasses works that inadequately observe the complexity associated with the transportation of personnel. Specifically, this research, unlike many works in the extant literature, uses a heterogeneous versus homogeneous fleet, includes multiple depots versus a single depot and allows split deliveries. Also, the current research ensures all relevant aircraft capabilities and limitations are observed. In particular, the paper takes into account vehicles’ seat capacities, effective capacities via maximum gross takeoff weights and reserve fuel requirements. The current model, which is built upon a heterogeneous capacitated helicopter routing problem with split deliveries and multiple depots (HCHRPSDMD), sufficiently provides a practical approach to model development and solution deliverance while promoting future research endeavors. Future research may use these findings for other geographical regions and similar transportation networks and could adopt firm-specific actual cost parameters instead of the estimated average hourly costs of operating different helicopters. Furthermore, future endeavors may employ other techniques for the derivation of solutions. Future works may be enhanced with actual cost data in lieu of estimations. In the current study, cost data were not available; however, estimations do not inherently proscribe sound interpretations of the models’ outputs. Also, future research endeavors including manual method results may enable comparative results to establish cost variance analysis. Although the current study is, to some extent, limited, the practicality for practitioners and contribution to researchers is comprehensible. Due to the idiosyncrasies and complexity prevalent in modern transportation networks, optimization is and will continue to be a rich opportunity for implementation and research. Practical implications As described by previous researchers, energy firms may more efficiently use their contracted aircraft via implementation of a decision-making mechanism for passenger assignment, aircraft selection, depot selection and aircraft routing. Most energy firms possess numerous and spatially segregated offshore facilities and, therefore, are unable to efficiently and effectively make such decisions. Ultimately, the efficient use of firms’ contracted helicopters can enhance profitability via reduced costs without compromising operational performance. Reduced costs are likely to be realized by a potential workforce or workload reduction, reduced flight hours and enhanced bargaining power with commercial helicopter operators. Specifically, enhanced bargaining power may be realized as a result of minimized depots from which the aircraft are operated and an overall reduction of aircraft via increased asset utilization. In essence, the efficient use of commercial helicopters may yield systemic efficiencies that can be shared among all stakeholders, contracting energy firms and commercial helicopter operators. The achievement of operational efficiencies, ultimately, may determine the realization of target performance or solvency of a plethora of firms in the future (Krishnan et al., 2019). Social implications For economies, communities and industries depending on crude oil and natural gas production, people’s livelihoods are significantly impacted due to price fluctuations (Rostan and Rostan, 2020; Solaymani, 2019). Based on a unique set of inputs and outputs, the International Energy Agency region (IEA), which includes the current study’s sample set, was found to achieve greater overall production efficiency relative to the Organization of the Petroleum Exporting Countries (OPEC) and the Organization of Arab Petroleum Exporting Countries (OAPEC) (Ohene-Asare et al., 2018). Therefore, enhanced logistics efficiency within the energy industry’s transportation sector across the globe is reasonably likely. For countries relying on these commodities’ exportation, production efficiency is and will continue to be a priority. With limited resources available in industry and society, efficiency is prone to yield advantageous results for all stakeholders. Furthermore, in the context of this study, a reduction of carbon dioxide and noise pollution in air, above water and on land will contribute to society’s drive to protect the environment and preserve our natural resources for future generations. Originality/value The current study represents the lone or one of few research endeavors to evaluate the heterogeneous capacitated helicopter routing problem with split deliveries and multiple depots. Furthermore, research pertaining to transportation via helicopter in the Gulf of Mexico’s offshore basin is unprecedented. Lastly, this work yields actionable knowledge for practitioners while enhancing current and promoting future research endeavors.

Integrated Train Timetabling and Rolling Stock Circulation Planning for a Metro Line with Multiple Depots

With the expansion of metro networks, it is common that a metro line is equipped with multiple depots. The operation costs of rail operators and the passenger satisfaction are highly dependent on train timetables and rolling stock circulation plans, which are closely related to each other. Therefore, it is important to investigate the integrated train timetabling and rolling stock circulation planning problem for metro lines with multiple depots. A mixed integer linear programming formulation is proposed to generate train timetables and rolling stock circulation plans simultaneously for a metro line with multiple depots, in which the capacity of each depot and the rolling stock balances between depots are considered. Several numerical experiments based on real-world data of Beijing Subway Line 5 and Beijing Subway Line 6 are carried out to demonstrate the effectiveness of the presented model.

Implementing Horizontal Cooperation in Public Transport and Parcel Deliveries: The Cooperative Share-A-Ride Problem

The static share-a-ride problem (SARP) consists of handling people and parcels in an integrated way through the same vehicle, which provides a shared trip between an origin and a destination, in response to requests received in advance. When multiple providers compete on the same market (for instance, within the same city or region), horizontal cooperation can be an efficient strategy to consolidate all requests and to optimize the total payoff. This situation gives rise to the cooperative SARP (coop-SARP). In this problem, multiple depots and heterogeneous vehicles must be considered and different cooperation levels may be agreed upon by service providers. In this paper, we propose a new mathematical programming formulation for cooperative SARP along with theoretical bounds. Moreover, through numerical experiments and ad hoc statistics, we analyze the benefits of different levels of horizontal cooperation between service providers. The results show that cooperation leads to reduced travel times and to improved vehicle occupancy rates, service levels, and profits, which make such a cooperative system even more appealing for service providers.

Asymmetric Multidepot Vehicle Routing Problems: Valid Inequalities and a Branch-and-Cut Algorithm

In “Asymmetric Multidepot Vehicle Routing Problems: Valid Inequalities and a Branch-and-Cut Algorithm,” Uit het Broek, Schrotenboer, Jargalsaikhan, Roodbergen, and Coelho present a generic branch-and-cut framework to solve routing problems with multiple depots on directed graphs. They present new valid inequalities that eliminate subtours, enforce tours to be linked to the same depot, and enforce bounds on the number of customers in a vehicle tour. This is embedded in a branch-and-cut scheme that also contains generalized and adapted versions of valid inequalities that are well known for related routing problems. The authors show that the new inequalities tighten root node relaxations considerably. In combination with a simple but effective upper-bound procedure, only requiring a MIP solver and a smart reduction of the problem size, the authors show that the overall framework solves instances of considerably larger size to optimality than have been reported in the literature.

Survey on Ten Years of Multi-Depot Vehicle Routing Problems: Mathematical Models, Solution Methods and Real-Life Applications

A crucial practical issue encountered in logistics management is the circulation of final products from depots to end-user customers. When routing and scheduling systems are improved, they will not only improve customer satisfaction but also increase the capacity to serve a large number of customers minimizing time. On the assumption that there is only one depot, the key issue of distribution is generally identified and formulated as VRP standing for Vehicle Routing Problem. In case, a company having more than one depot, the suggested VRP is most unlikely to work out. In view of resolving this limitation and proposing alternatives, VRP with multiple depots and multi-depot MDVRP have been a focus of this paper. Carrying out a comprehensive analytical literature survey of past ten years on cost-effective Multi-Depot Vehicle Routing is the main aim of this research. Therefore, the current status of the MDVRP along with its future developments is reviewed at length in the paper.