Identifying Best Practices for Snowplow Route Optimization

Well-designed winter maintenance routes result in snow and ice control service that is both more effective, because roads are cleared more rapidly, and more cost efficient, because deadheading, route overlap and other inefficiencies are reduced or eliminated. There are an increasing number of computerized tools to facilitate the routing process, but these tools are not yet widely used by winter maintenance practitioners. The purpose of this report is to provide practitioners with an overview of computerized route optimization processes and concrete recommendations about how to ensure that route improvement efforts produce actionable results. Recommendations are synthesized from nine recent and ongoing snowplow routing projects using a variety of computerized routing tools. Project descriptions, based on interviews with project personnel, focus on project goals, optimization software features used, and lessons learned. Multiple route optimization projects report route length reductions on the order of 5% to 10%, with reductions as high as 50% reported in one case. These snowplow route optimization projects show that route optimization is a powerful tool for improving routing efficiency but that it does not replace the need for expert judgment in the route design process. Successful route optimization projects rely on close cooperation between experienced winter maintenance professionals and the individuals conducting the route optimization as well as a highly accurate, snowplow-routing specific representation of the road network. Successful projects also include time to review and revise new routes to identify potential problem spots prior to implementation

Optimization of vehicle routing and scheduling with travel time variability - application in winter road maintenance

This study developed a mathematical model for optimizing vehicle routing and scheduling, which can be used to collect travel time information, and also to perform winter road maintenance operations (e.g., salting, plowing). The objective of this research was to minimize the total vehicle travel time to complete a given set of service tasks, subject to resource constraints (e.g., truck capacity, fleet size) and operational constraints (e.g., service time windows, service time limit). The nature of the problem is to design vehicle routes and schedules to perform the required service on predetermined road segments, which can be interpreted as an arc routing problem (ARP). By using a network transformation technique, an ARP can be transformed into a well-studied node routing problem (NRP). A set-partitioning (SP) approach was introduced to formulate the problem into an integer programming problem (I PP). To solve this problem, firstly, a number of feasible routes were generated, subject to resources and operational constraints. A genetic algorithm based heuristic was developed to improve the efficiency of generating feasible routes. Secondly, the corresponding travel time of each route was computed. Finally, the feasible routes were entered into the linear programming solver (CPL EX) to obtain final optimized results. The impact of travel time variability on vehicle routing and scheduling for transportation planning was also considered in this study. Usually in the concern of vehicle and pedestrian\u27s safety, federal, state governments and local agencies are more leaning towards using a conservative approach with constant travel time for the planning of winter roadway maintenance than an aggressive approach, which means that they would rather have a redundancy of plow trucks than a shortage. The proposed model and solution algorithm were validated with an empirical case study of 41 snow sections in the northwest area of New Jersey. Comprehensive analysis based on a deterministic travel time setting and a time-dependent travel time setting were both performed. The results show that a model that includes time dependent travel time produces better results than travel time being underestimated and being overestimated in transportation planning. In addition, a scenario-based analysis suggests that the current NJDOT operation based on given snow sector design, service routes and fleet size can be improved by the proposed model that considers time dependent travel time and the geometry of the road network to optimize vehicle routing and scheduling. In general, the benefit of better routing and scheduling design for snow plowing could be reflected in smaller minimum required fleet size and shorter total vehicle travel time. The depot location and number of service routes also have an impact on the final optimized results. This suggests that managers should consider the depot location, vehicle fleet sizing and the routing design problem simultaneously at the planning stage to minimize the total cost for snow plowing operations

Mixed Integer Programming Approaches to Novel Vehicle Routing Problems

This thesis explores two main topics. The first is how to incorporate data on meteorological forecasts, traffic patterns, and road network topology to utilize deicing resources more efficiently. Many municipalities throughout the United States find themselves unable to treat their road networks fully during winter snow events. Further, as the global climate continues to change, it is expected that both the number and severity of extreme winter weather events will increase for large portions of the US.We propose to use network flows, resource allocation, and vehicle routing mixed integer programming approaches to be able to incorporate all of these data in a winter road maintenance framework. We also show that solution approaches which have proved useful in network flows and vehicle routing problems can be adapted to construct high-quality solutions to this new problem quickly. These approaches are validated on both random and real-world instances using data from Knoxville, TN.In addition to showing that these approaches can be used to allocate resources effectively given a certain deicing budget, we also show that these same approaches can be used to help determine a resource budget given some allocation utility score. As before, we validate these approaches using random and real-world instances in Knoxville, TN.The second topic considered is formulating mixed integer programming models which can be used to route automated electric shuttles. We show that these models can also be used to determine fleet composition and optimal vehicle characteristics to accommodate various demand scenarios. We adapt popular vehicle routing solution techniques to these models, showing that these strategies continue to be relevant and robust. Lastly, we validate these techniques by looking at a case study in Greenville, SC, which recently received a grant from the Federal Highway Administration to deploy a fleet of automated electric shuttles in three neighborhoods

Arc routing problems: A review of the past, present, and future

[EN] Arc routing problems (ARPs) are defined and introduced. Following a brief history of developments in this area of research, different types of ARPs are described that are currently relevant for study. In addition, particular features of ARPs that are important from a theoretical or practical point of view are discussed. A section on applications describes some of the changes that have occurred from early applications of ARP models to the present day and points the way to emerging topics for study. A final section provides information on libraries and instance repositories for ARPs. The review concludes with some perspectives on future research developments and opportunities for emerging applicationsThis research was supported by the Ministerio de Economia y Competitividad and Fondo Europeo de Desarrollo Regional, Grant/Award Number: PGC2018-099428-B-I00. The Research Council of Norway, Grant/Award Numbers: 246825/O70 (DynamITe), 263031/O70 (AXIOM).Corberán, Á.; Eglese, R.; Hasle, G.; Plana, I.; Sanchís Llopis, JM. (2021). Arc routing problems: A review of the past, present, and future. Networks. 77(1):88-115. https://doi.org/10.1002/net.21965S8811577

Optimizing Vancouver’s Snow Plow Route System

The snow plow routing problem (SPRP) is an optimization problem that specifes designatedroutes for snow plows to follow. Like any major cities in the US and Canada, Vancouver has alreadyadopted a snow plow routing plan, however, after their response this winter season, we have cometo conclude that it is insuficient as many roads were left unplowed and unsalted for days aftersnowfall.The SRPR minimizes either the total cost or the total time required to clear a network ofstreets. Given the heavy snowfall that has hit Vancouver this past winter, and the City of Vancouver’sunpreparedness, our model focuses on the latter. We hope to improve service withoutincreasing the costs too much. We solve the SPRP for a network of major roads in Vancouver;under the constraints of fleet size and specifications

Optimisation de tournées de véhicules en viabilité hivernale

RÉSUMÉ : Cette thèse développe des outils mathématiques et informatiques pour améliorer les opérations de viabilité hivernale. En particulier, la confection des tournées de déneigement est traitée comme un problème de tournées sur les arcs avec plusieurs contraintes. Une métaheuristique est d’abord développée pour la confection de ces tournées. Par la suite, des modifications majeures sont apportées à cet algorithme pour tenir compte des caractéristiques spécifiques aux problèmes de tournées sur les arcs (arc routing problem) (ARP) sur des réseaux routiers réels. Finalement, un second problème combinant les tournées de déneigement et d’épandage avec la mise en commun de certains véhicules pour les opérations est traité. La solution développée permet de tirer parti des caractéristiques de chaque véhicule. Tout au long de la thèse, un accent particulier est porté sur l’utilisation des données réelles ainsi que sur le développement de méthodes pour faciliter l’importation et l’exportation de ces données. Les travaux entourant cette thèse débutent avec la confection de tournées de déneigement pour une ville au Québec, soit Dolbeau-Mistassini (DM). De nombreux problèmes ont été rencontrés avec l’utilisation d’une méthode tirée de la littérature. Parmi ceux-ci, on compte : — de nombreux demi-tours difficiles à exécuter par les véhicules ; — le faible respect des priorités accordées aux rues à l’échelle du réseau ; — de nombreux véhicules parcourent de longues distances pour se rendre dans les coins reculés du réseau ; — le déséquilibre des tâches de travail en raison des différentes vitesses d’opération des véhicules ; — le fait que la méthode ne tient pas compte des ruelles qui peuvent être traitées dans une direction ou dans l’autre en un seul passage. À la suite de nombreux ajustements manuels pour corriger les tournées obtenues, force a été de constater que des améliorations pouvaient être apportées à ce type de méthode. Les travaux concernant la première contribution de cette thèse ont donc porté sur le développement d’une méthode de création de tournées de déneigement. En raison du grand nombre de variables et de contraintes considérées dans le problème, le choix s’est porté sur une méthode heuristique. Ce type de méthode offre un bon équilibre entre le temps de traitement et la qualité des solutions obtenues. Plus précisément, le choix s’est arrêté sur une métaheuristique de type algorithme de recherche à voisinage adaptatif large (adaptive large neighborhood search) (ALNS), en raison du succès remporté récemment par ce type de méthode. Le premier article a permis de constater que l’algorithme développé permet de créer des tournées pour les véhicules de déneigement. Les contraintes suivantes sont respectées : équilibrage des tournées, couverture partielle du réseau, vitesses hétérogènes, restrictions de virages, restrictions rue/véhicule et hiérarchie du réseau. Pour la deuxième contribution de thèse, le problème a d’abord été formalisé par l’intermédiaire d’un programme linéaire en nombres entiers (mixed integer programming) (MIP). Le problème a été formulé comme un problème des k-postiers ruraux avec objectif minmax (min-max k-vehicles rural postman problem) (MM K-RPP) avec hiérarchies, pénalités sur virages, vitesses d’opération hétérogènes et tournées ouvertes sur un graphe mixte. Tel qu’anticipé, la résolution devient rapidement impossible à traiter avec un solveur commercial en utilisant seulement 20 segments de rue. Il a été décidé de poursuivre l’approfondissement de l’algorithme développé en première partie. Cette décision a été prise notamment en raison du très long temps de traitement qui réduit l’utilité du premier algorithme. Cette décision repose aussi sur le fait que visuellement, on constate que les tournées obtenues peuvent être améliorées. Dans cette optique, une collaboration a été initiée avec messieurs Fabien Lehuédé et Olivier Péton du laboratoire des sciences du numérique de Nantes (LS2N) à IMT Atlantique. Leur expertise avec la méthode ALNS a effectivement permis d’améliorer grandement les résultats obtenus. Parmi les améliorations apportées, on note une transformation du réseau permettant de tenir compte des pénalités sur virages lors du calcul des plus courts chemins. Cette transformation permet également de mieux prendre en compte les ruelles qui requièrent un seul passage dans une direction ou dans l’autre. De plus, la possibilité d’appliquer plusieurs fois un opérateur de destruction avant de passer à la construction est ajoutée. Cette contribution a également été l’occasion de développer et tester de nouveaux opérateurs de voisinage, développer une méthode de groupement des arcs et revoir et simplifier le code de la métaheuristique. L’algorithme a été appliqué à la première étude de cas ainsi qu’a deux nouvelles études de cas, Baie-Comeau (BC) et Plateau-Mont-Royal (PMR). Des tests ont également été exécutés en comparant les nouvelles tournées obtenues à des tournées conçues quelques années plus tôt ainsi qu’aux résultats obtenus par un solveur commercial. Les résultats obtenus démontrent que la méthodologie améliore les tournées conçues précédemment. Il est aussi possible de conclure que la méthode de groupage des arcs améliore la qualité des solutions obtenues et l’efficacité des nouveaux opérateurs développés varie selon le réseau utilisé. Pour la troisième contribution, nous sommes revenus sur le cas d’étude initial tel que décrit par les intervenants de la première étude de cas. Il a été dit que les charges de travail doivent être équilibrées, mais que certains véhicules doivent également épandre des fondants ou des abrasifs en plus de déneiger. Pour tenir compte de cette contrainte, certaines tournées avaient délibérément été gardées plus courtes dans les premières solutions. Pour le troisième article, il a été décidé de traiter cette problématique de front. Ce qu’il faut savoir est que certains véhicules sont équipés pour l’épandage et le déneigement alors que d’autres sont équipés pour le déneigement seulement. Lorsque les premiers traitent un segment de rue, ils exécutent les deux opérations simultanément. Lorsque les deuxièmes traitent un segment de rue, il faut planifier un second passage par les premiers véhicules pour qu’ils puissent épandre des fondants ou des abrasifs. L’algorithme développé précédemment a donc été modifié dans cette optique. En plus, la considération des contraintes de restrictions rue/véhicule a été ajoutée dans l’algorithme. Les résultats démontrent que l’algorithme permet effectivement de concevoir des tournées qui respectent les contraintes de la nouvelle étude de cas. Cet outil permet donc de tirer profit de l’interaction entre les divers types de véhicules. La contribution souligne également l’utilité d’un tel outil pour supporter l’analyse des besoins justifiant l’achat de nouveaux véhicules. En parallèle aux développements algorithmiques, des méthodes d’importation et d’exportation des données provenant des cas d’étude réels sont aussi développées. Dès le départ, il a été choisi d’utiliser des fichiers de type Shapefile comme source de données en raison de sa grande disponibilité et de la compatibilité avec les système d’information géographique (SIG). Une méthode pour passer du réseau géographique vers un réseau mathématique a donc été améliorée au cours des travaux. Alors qu’au début des travaux de la thèse, il fallait passer par un chiffrier Microsoft ExcelTM pour ensuite importer les données dans le code, à la fin, une méthode automatisée permet l’importation directe à partir des fichiers Shapefiles vers le code de la métaheuristique. Quant aux résultats obtenus, ils furent obtenus dans les premières étapes sous forment de représentations géographiques dans un SIG ainsi que des feuilles d’instructions indiquant les étapes, coin de rue par coin de rue, aux opérateurs de véhicules. De ce côté, les développements ont permis d’obtenir des fichiers de type KML. Ce type de fichier est compatible avec plusieurs logiciels et applications, dont Google EarthviewTM et des applications de guidage routier sur des appareils mobiles.----------ABSTRACT : In this thesis, we develop mathematical and computerized tools to improve winter viability operations. More precisely, the snow routing design problem is treated as an problème de tournée sur les arcs (arc routing problem) (ARP). In a first effort to solve the problem, a metaheuristic procedure is designed. Then, some major modifications are made to the algorithm to improve the consideration of specific characteristics of real road networks. Finally, a second problem combining the routing of the snowplow and the spreading vehicles are addressed. The objective is to fully take advantage of the characteristics of the different type of vehicles. In parallel with the algorithmic development, this thesis also develops some methodologies to facilitate the importation and exportation of the real world data. Works concerning this thesis were initiated with a mandate to design snowplow routes for a city in the province of Québec, namely DM. The problem was addressed by using a methodology found in the literature, however, several difficulties were encountered. Among others: — the routes contained several U-turns which are difficult to perform by the snow plowing vehicles; — little consideration of the priorities at the network level; — several vehicles have to travel to some remote streets in the same sector of the city where we would expect only one vehicle to go; — unbalanced sectors due to the different speeds of operation of the vehicles; — no consideration for back alleys that needs to be serviced only once in either direction. In respond to these problems, several manual modifications of the routes were undertaken to make them feasible. It was found that the methodology fails to solve the problem as it is encountered. Therefore, works concerning the first contribution of this thesis focused on the development of a methodology to design snowplow routing. Due to numerous variables and constraints, it was decided to develop a metaheuristic algorithm. This type of methodology offers a good balance between runtime and the quality of the solution obtained. In particular, an ALNS is selected because of its recent success cited in the literature. Thus, the first article concludes that the algorithm can design snowplow routing. The following constraints are considered: workload balance, partial area coverage, heterogeneous vehicle speeds, road/vehicle dependencies, network hierarchies and turn restrictions. In the second contribution of this thesis, the problem was modeled as a mixed integer program. It is formulated as a min-max k-rural postmen problem with hierarchies, turn penalties, open tours and heterogeneous speed on a mixed graph. As expected, the formulation is intractable even for a number of arcs as low as 20. It was then decided to pursue the development of the ALNS algorithm. This decision was taken considering the long runtime of the first algorithm and the fact that the routes obtained can be visually improved. A collaboration with Fabien Lehuédé and Olivier Péton from the Laboratoire des Sciences du Numérique de Nantes (LS2N), IMT Atlantique was undertaken. Their expertise with ALNS greatly helped to improve the results obtained. Among other improvements brought to the algorithm, one can cite the transformation of the graph which allows to better take into account turn penalties during the computation of the shortest paths. This transformation also allows to better take into account the back alleys which only need one service in either direction. This contribution also allowed to develop and test new neighborhood operators and an arc grouping methodology. Both of these innovations improve the quality of the solutions obtained. However the efficiency of the new operators varies with the network. For the third contribution, we took back the case study as it was described by the collaborator in DM. It was said that the workload needs to be balanced among the vehicles. However some vehicles must also perform winter spreading in addition to plowing. For the first set of routes produced, some of the routes were deliberately left with a lower workload to allow them to perform winter spreading. For the third article, it was decided to consider the spreading and the plowing directly during the construction and the improvement steps. Thus this problem was tackled more directly in the third article. It must be noted that some vehicles are equipped to perform both winter spreading and snow plowing and some others can only perform plowing. When the former service a street, they can perform both plowing and spreading at the same time. When the latter service a street, a second passage is required to spread salt or abrasives. The algorithm developed for the second contribution was then adapted for this new problem. Moreover, the street/vehicle restriction constraints were also added. The result shows that the algorithm can produce a set of routes respecting the constraints of the new problem. It can take advantage of the interaction between the various types of vehicles. The article also shows that such tool can be beneficial in analyzing the requirements for new vehicles. In parallel with the development of the algorithms, data importation and exportation techniques from real road networks are also developed. It was chosen to use Shapefiles because of its good relative availability and because of its compatibility with Geographic Information System (GIS). A method to transfer from a geographical to a mathematical network is improved during the thesis. At the beginning, a Microsoft ExcelTM datasheet is used to transfer the data from the GIS to the metaheuristic. At the end, it is possible to fetch the data directly from the Shapefiles to the metaheuristic. As for the results obtained, at the beginning, they were provided in the form of a Shapefile for visualization and indications on sheets of paper for the operators. At the end, the results can be exported to the KML format. This type of file is compatible with several software such as Google EarthviewTM and application Global Positioning System (GPS) applications on mobile devices