Nathalie Perrier

A survey of models and algorithms for winter road maintenance. Part IV: Vehicle routing and fleet sizing for plowing and snow disposal

This is the last part of a four-part survey of optimization models and solution algorithms for winter road maintenance planning. The two first parts of the survey address system design problems for winter road maintenance. The third part concentrates mainly on vehicle routing problems for spreading operations. The aim of this paper is to provide a comprehensive survey of optimization models and solution methodologies for the routing of vehicles for plowing and snow disposal operations. We also review models for the fleet sizing and fleet replacement problems.

A survey of models and algorithms for winter road maintenance. Part III: Vehicle routing and depot location for spreading

Winter road maintenance planning involves a variety of decision-making problems related to the routing of vehicles for spreading chemicals and abrasives, for plowing roadways and sidewalks, for loading snow into trucks, and for transporting snow to disposal sites. These problems are very difficult and site specific because of the diversity of operating conditions influencing the conduct of winter road maintenance operations and the wide variety of operational constraints. As the third of a four-part survey, this paper reviews optimization models and solution algorithms for the routing of vehicles for spreading operations. We also review models for the location of vehicle and materials depots and for the assignment of crews to vehicle depots. The two first parts of the survey address system design problems for winter road maintenance. The fourth part of the survey covers vehicle routing problems for plowing and snow disposal operations.

A survey of models and algorithms for winter road maintenance: part I: system design for spreading and plowing

Winter road maintenance operations involve a host of decision-making problems at the strategic, tactical, operational, and real-time levels. Those operations include spreading of chemicals and abrasives, snow plowing, loading snow into trucks, and hauling snow to disposal sites. As the first of a four-part survey, this paper reviews optimization models and solution algorithms for the design of winter road maintenance systems for spreading and plowing operations. System design problems for snow disposal operations are discussed in the second paper. The two last parts of the survey mainly address vehicle routing, depot location, and fleet sizing models for winter road maintenance. The present paper surveys research on determining the level of service policy and partitioning a region or road network into sectors for spreading and plowing operations. We also describe the applied setting in which these problems arise.

A survey of models and algorithms for winter road maintenance. Part II: system design for snow disposal

This is the second part of a four-part survey of optimization models and solution algorithms for winter road maintenance planning. The first part addresses system design problems for spreading and plowing operations. The aim of this paper is to provide a comprehensive survey of optimization models and solution methodologies for the design of systems for snow disposal operations. These problems include partitioning a region or road network into sectors, locating snow disposal sites, allocating sectors to snow disposal sites, and allocating sectors to private companies or governmental agencies. The two last parts of the survey mainly concentrate on vehicle routing for winter road maintenance.

Vehicle Routing for Urban Snow Plowing Operations

Winter road maintenance planning involves a variety of decisions related to the routing of vehicles for spreading chemicals and abrasives, plowing roadways and sidewalks, loading snow into trucks, and transporting snow to disposal sites. In this paper, we present a model and two heuristic solution approaches based on mathematical optimization for the routing of vehicles for snow plowing operations in urban areas. Given a district and a single depot where a number of plows are based, the problem is to determine a set of routes, each performed by a single vehicle that starts and ends at the districts depot, such that all road segments are serviced while satisfying a set of operational constraints and minimizing a time objective. The formulation models general precedence relation constraints with no assumption on class connectivity, different service and deadhead speed possibilities, separate pass requirements for multilane road segments, class upgrading possibilities, and vehicle road segment dependencies. Several extensions, such as turn restrictions, load balancing constraints, and tandem service requirements, which are required in a real-life application, are also discussed. Two objectives are considered: A hierarchical objective and a makespan objective. The resulting model is based on a multicommodity network flow structure to impose the connectivity of the route performed by each vehicle. The two solution strategies were tested on data from the City of Dieppe, New Brunswick, Canada.

Review: A survey of models and algorithms for emergency response logistics in electric distribution systems. Part II: Contingency planning level

This is the second part of a two-part survey of optimization models and solution algorithms for emergency response planning in electric distribution systems. The first part of the survey addresses reliability planning problems with fault considerations related to electric distribution operations. The aim of this second part is to provide a comprehensive survey of optimization models and solution methodologies for contingency planning problems related to electric distribution operations. These problems include the restoration of service, the sequencing of switching operations, the routing of repair vehicles, the scheduling of repair crews, and the assignment of crews to repair sites.

Review: A survey of models and algorithms for emergency response logistics in electric distribution systems. Part I: Reliability planning with fault considerations

Emergency response operations in electric distribution systems involve a host of decision-making problems at the reliability and contingency planning levels. Those operations include fault diagnosis, fault location, fault isolation, restoration, and repair. As the first of a two-part survey, this paper reviews optimization models and solution methodologies for reliability planning problems with fault considerations related to electric distribution operations. Contingency planning problems of emergency distribution response are discussed in the second part. The present paper surveys research on determining a distribution substation single-fault capacity, reallocating excess load, configuring distribution systems, partitioning a geographical area into service territories, and locating material stores and depots.

The sector design and assignment problem for snow disposal operations

Winter road maintenance operations involve a host of decision-making problems at the strategic, tactical, operational, and real-time levels. Those operations include spreading of chemicals and abrasives, snow plowing, loading snow into trucks, and hauling snow to disposal sites. In this paper, we present a model and two heuristic solution approaches based on mathematical optimization for the problem of partitioning a road network into sectors and allocating sectors to snow disposal sites for snow disposal operations. Given a road network and a set of planned disposal sites, the problem is to determine a set of non-overlapping subnetworks, called sectors, according to several criteria related to the operational effectiveness and the geographical layout, and to assign each sector to a single snow disposal site so as to respect the capacities of the disposal sites, while minimizing relevant variable and fixed costs. Our approach uses single street segments as the units of analysis and we consider sector contiguity, sector balance and sector shape constraints, hourly and annual disposal site capacities, as well as single assignment requirements. The resulting model is based on a multi-commodity network flow structure to impose the contiguity constraints in a linear form. The two solution approaches were tested on data from the city of Montreal in Canada.

CIGI2011: A heuristic method for resource-constrained project scheduling with activity overlapping

The overlapping of activities is a common practice to accelerate the execution of engineering projects. This technique consists in executing in parallel two activities, normally executed in a sequential way, by allowing the downstream activity to start before the end of the upstream activity based on preliminary information. In this paper, we propose a constructive heuristic for the resource-constrained project scheduling problem with overlapping modes (RCPSP-OM). Given a set of activities to execute, the RCPSP-OM consists in determining the order of execution in time of a set of activities so as to minimize the total project duration, while respecting precedence relations, resource constraints and overlapping possibilities. The heuristic implies that rework tasks related to overlapping are added to downstream activities and that the consumption of the resources is constant throughout the execution of the project (including rework). The method also considers that the possible overlapping modes for every couple of activities and the duration of rework tasks associated with every mode are known in advance. Results show that, when the objective consists in minimizing the project duration, the consideration of the costs associated to activity overlapping allows to significantly reducing the cost of reworks. On the other hand, when the objective consists in maximizing the gains related to the project execution, the search for the best trade-off between acceleration and increase of project costs enables to avoid losses.

Time-cost trade-offs in resource-constraint project scheduling problems with overlapping modes

In companies, overlapping is commonly regarded as a promising strategy to accelerate project execution. Overlapping consists in executing in parallel two sequential activities by allowing a downstream activity to start before the end of an upstream activity based on preliminary information. However, overlapping can entail reworks in downstream activity, caused by information updates until finalised information is available, and additional coordination and communication, which both require additional time and costs. In this paper, we present a model for the resource-constrained project scheduling problem with feasible overlapping modes. The makespan minimisation and the gain maximisation problems are formulated as linear integer programmes. Time-cost tradeoffs between project duration and overlapping costs are also discussed. An example of a 30-activity project is provided to illustrate the utility and efficiency of the model. Our results highlight the closed interaction between resource constraints and overlapping modes and suggest the relevance of jointly considering them.