SAMU ambulance positioning using MALP model

One of the constitutional principles of the public health care system in Brazil is universality, which turns health into a fundamental right and ensures that all citizens shall have access to health service whenever required. The purpose of this study is to assess the positioning of ambulances in Duque de Caxias-RJ, and find new arrangements to maximize the covered population. The configuration of a network that provides such service is indeed significant since small deviations may lead to users’ death. Therefore, four scenarios were built in order to represent different network arrangements, according to the manager’s strategy or the budget limitations of the city.  An Integer Programming model for servers’ positioning was used in each scenario. Indicators such as percentage of coverage population and total cost were then used to compare and choose the best solution. Results have shown that the current coverage could be doubled by just relocating facilities that already exist, without adding any costs. It is important to notice that this solution is rather different from the current positioning.

A mathematical programming approach for dispatching and relocating EMS vehicles.

We consider the problem of dispatching and relocating EMS vehicles during a pandemic outbreak. In such a situation, the demand for EMS vehicles increases and in order to better utilize their capacity, the idea of serving more than one patient by an ambulance is introduced. Vehicles transporting high priority patients cannot serve any other patient, but those transporting low priority patients are allowed to be rerouted to serve a second patient. We have considered three separate problems in this research. In the first problem, an integrated model is developed for dispatching and relocating EMS vehicles, where dispatchers determine hospitals for patients. The second problem considers just relocating EMS vehicles. In the third problem only dispatching decisions are made where hospitals are pre-specified by patients not by dispatchers. In the first problem, the objective is to minimize the total travel distance and the penalty of not meeting specific constraints. In order to better utilize the capacity of ambulances, we allow each ambulance to serve a maximum of two patients. Considerations are given to features such as meeting the required response time window for patients, batching non-critical and critical patients when necessary, ensuring balanced coverage for all census tracts. Three models are proposed- two of them are linear integer programing and the other is a non-linear programing model. Numerical examples show that the linear models can be solved using general-purpose solvers efficiently for large sized problems, and thus it is suitable for use in a real time decision support system. In the second problem, the goal is to maximize the coverage for serving future calls in a required time window. A linear programming model is developed for this problem. The objective is to maximize the number of census tracts with single and double coverage, (each with their own weights) and to minimize the travel time for relocating. In order to tune the parameters in this objective function, an event based simulation model is developed to study the movement of vehicles and incidents (911 calls) through a city. The results show that the proposed model can effectively increase the system-wide coverage by EMS vehicles even if we assume that vehicles cannot respond to any incidents while traveling between stations. In addition, the results suggest that the proposed model outperforms one of the well-known real time repositioning models (Gendreau et al. (2001)). In the third problem, the objective is to minimize the total travel distance experienced by all EMS vehicles, while satisfying two types of time window constraints. One requires the EMS vehicle to arrive at the patients\u27 scene within a pre-specified time, the other requires the EMS vehicle to transport patients to their hospitals within a given time window. Similar to the first problem, each vehicle can transport maximum two patients. A mixed integer program (MIP) model is developed for the EMS dispatching problem. The problem is proved to be NP-hard, and a simulated annealing (SA) method is developed for its efficient solution. Additionally, to obtain lower bound, a column generation method is developed. Our numerical results show that the proposed SA provides high quality solutions whose objective is close to the obtained lower bound with much less CPU time. Thus, the SA method is suitable for implementation in a real-time decision support system

IMPROVING QUALITY OF SERVICE IN EMS SYSTEMS BY REDUCING DISPARITIES BETWEEN SERVICE ZONES

Emergency medical service (EMS) systems respond to emergency or urgent calls so as to provide immediate care, such as pre-hospital care and/or transportation, to hospitals. Care must be provided in a timely manner; in fact quality of service is usually directly associated with response time. To reduce the response time, the number and location of vehicles within the service area are important variables. However with limited capacity, increasing the number of vehicles is often an infeasible alternative. Therefore, a critical design goal is to decide at which facilities stations should be located in order to serve as much demand as possible in a reasonable time, and at the same time maintain equitable service between customers. This study aims to focus on locating ambulances which respond to 911 calls in EMS systems. The goals are to find the optimal base station location for vehicles so that the number of calls or customers served is maximized while disparity between those customers is minimized, to consider the survival rate of patients directly in the model, and develop appropriate meta-heuristics for solving problems which cannot be solved optimally

STRATEGIES TO IMPROVE THE EFFICIENCY OF EMERGENCY MEDICAL SERVICE (EMS) SYSTEMS UNDER MORE REALISTIC CONDITIONS

Emergency medical service (EMS) systems provide medical care to pre-hospital patients who need rapid response and transportation. This dissertation proposes a new realistic approach for EMS systems in two major focuses: multiple unit dispatching and relocation strategies. This work makes recommendations for multiple-unit dispatch to multiple call priorities based on simulation optimization and heuristics. The objective is to maximize the expected survival rate. Simulation models are proposed to determine the optimization. A heuristic algorithm is developed for large-scale problems. Numerical results show that dispatching while considering call priorities, rather than always dispatching the closest medical units, could improve the effectiveness of EMS systems. Additionally, we extend the model of multiple-unit dispatch to examine fairness between call priorities. We consider the potentially-life-threatening calls which could be upgraded to life-threatening. We formulate the fairness problem as an integer programming model solved using simulation optimization. Taking into account fairness between priorities improves the performance of EMS systems while still operating at high efficiency. As another focus, we consider dynamic relocation strategy using a nested-compliance table policy. For each state of the EMS systems, a decision must be made regarding exactly which ambulances will be allocated to which stations. We determine the optimal nested-compliance table in order to maximize the expected coverage, in the binary sense, as will be later discussed. We formulate the nested-compliance table model as an integer program, for which we approximate the steady-state probabilities of EMS system to use as parameters to our model. Simulation is used to investigate the performance of the model and to compare the results to a static policy based on the adjusted maximum expected covering location problem (AMEXCLP). Additionally, we extend the nested-compliance table model to consider an upper bound on relocation time. We analyze the decision regarding how to partition the service area into smaller sub-areas (districts) in which each sub-area operates independently under separate relocation strategies. We embed the nested-compliance table model into a tabu search heuristic algorithm. Iteration is used to search for a near-optimal solution. The performance of the tabu search heuristic and AMEXCLP are compared in terms of the realized expected coverage of EMS systems

Tabu search heuristic for the single source capacited facility location problem

Orientador: Vinicius Amaral ArmentanoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de ComputaçãoResumo: Localização de facilidades é uma das atividades da área de logística que envolve decisões do número, localização e tamanho das facilidades a serem usadas. A localização de facilidades é uma questão central no planejamento estratégico de empresas públicas e privadas e está associada à variação da população em uma região, capital de investimento e estimativa de clientes que podem ser servidos. Este trabalho aborda o problema de localização de facilidades com restrições de capacidade e fonte única para atender a demanda de clientes. A fonte única impõe que um cliente seja atendido por uma única facilidade, e o objetivo é minimizar os custos de instalação e atendimento dos clientes. Este problema tem diversas aplicações, incluindo a localização de concentradores em redes de telecomunicações. Trata-se de um problema complexo de otimização combinatória, em que métodos exatos não produzem uma solução ótima em tempo viável, e portanto o uso de métodos heurísticos é pertinente. O objetivo deste trabalho é o desenvolvimento e implementação de um algoritmo de busca tabu para o problema, e comparação de seu desempenho com outros métodos apresentados na literatura. Palavras-chave: Localização de Facilidades, Otimização Combinatória, Heurística, Busca TabuAbstract: Facility location is a logistic problem that involves the decision on the number, location and capacity of facilities to be opened. Facility location is an important area in the strategic planning of public and private companies and is associated with population changes, money availability for investment and the estimation of the number of customers to be served. This work addresses on single source capacitated facility location problem. Single source imposes that each customer must be assigned to only one facility, and the objective is to minimize the installation and transportation costs. This problem has several applications, including the network concentrator location problem. It is a complex combinatorial optimization problem, which cannot be solved by exact methods in small computational times; therefore, heuristics methods are indicated. The objective of this thesis is the development and implementation of a tabu search algorithm for the problem and a comparative analysis with other methods available in the literature. Keywords: Facility location, Combinatorial Optimization, Heuristic, Tabu SearchMestradoAutomaçãoMestre em Engenharia Elétric

Approaches for optimal location of emergency response vehicles

Police, fire and emergency medical systems are all concerned with improving public safety, and share the common objective of responding to citizen calls for assistance as quickly as possible to reduce loss of life and injury. Optimization of emergency response vehicles location is a research area which is concerned with the location of one or more vehicles so as to satisfy objective function requirements such as providing fast and reliable service to customers. The most important decision facing any emergency response service is how many emergency vehicles to have, and on which site to locate them. A vast literature has developed out of the significant research interest in meeting this challenge. The literature review is separated into three sections depending on the objective function of the location models: Covering models, P-median models, and Center models. In the next chapter 3, we describe characteristics and performance criteria of emergency response services. The assumption is that if calls are answered and serviced quickly, then this will lead to customer satisfaction and compliance to regulatory standards for response time performance. The decision-maker is confronted with the elements of time and distance simultaneously. The time taken to get to an incident is necessarily dependent upon the distance to be travelled and the conditions experienced during the journey. Timeliness, cost minimization, coverage equity maximization and labor equity maximization are the most important objectives of emergency service systems. In this thesis we also, focused on the description of some methods to estimate travel distance and travel time. A crucial issue in locating emergency response vehicles is data availability. Collection and analysis of the available data point out one of the main problems of the system. Mathematical models may be very useful in dealing with emergency response vehicle location. In chapter 4, location models are classified according to their objectives, constraints, solutions, and other attributes. There has been an important evolution in the development of emergency vehicles location and relocation models over the past years. In this thesis, we attempted to provide an overview of emergency vehicles location models dedicated to capturing the complex time and uncertainty characteristics of most real-world problems. Chapter 5 concerns an elaborate description of the basic emergency response vehicles location models, mostly, in discrete space or networks, that are related to the public sector, such as ambulances, fire vehicles, police units. Static and deterministic location models assume that the nearest unit to a call for service is always available. Dynamic models can be used to periodically update emergency vehicles positions throughout the day. Probabilistic models deal with the stochastic nature of real-world systems. In these systems, models capture the stochastic aspects of facility location through explicit consideration of the probability distributions associated with modeled random quantities. Parameters, such as travel times, the location of clients, demand and the availability of servers are treated as random variables. The objective is to determine robust server/facility locations that optimize a given utility function, for a range of values of the parameters under consideration. Finally, in chapter 6 we present two applications of P- Median and Hypercube models. The solution of Hypercube model is the state probabilities and associated system performance measures such as workloads. As far as it concerns the P-Median model, the aim is to locate a fixed number of vehicles so as to minimize the weighted travel time of the system. In the end, we solve P-Median model for fixed number of servers and we implement the hypercube model using the assignment resulted from P-Median problem

Metodologia de definição de rede de suprimentos para armazenagem de commodities agrícolas

Tese (doutorado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Civil e Ambiental, 2020.A agricultura brasileira está entre as mais importantes do planeta, ocupando posição de destaque na exportação das commodities agrícolas de grãos como soja e milho. O fato das áreas de produção serem distantes dos portos e a sua velocidade de expansão territorial ser maior que a velocidade de instalação de novas estruturas de movimentação e armazenagem, emergem impactos negativos no sistema logístico. A ausência de um sistema logístico eficiente e com capacidade de armazenagem suficiente para todo o volume de colheita força os agricultores a venderem suas colheitas imediatamente, provocando uma redução de preços das commodities por excesso de oferta e a venda em um momento de preços em queda. Diante deste cenário, o presente estudo tem por objetivo principal desenvolver uma metodologia para definição de rede de suprimentos para armazenagem e escoamento de commodities agrícolas. Para alcançar tais objetivos foi desenvolvida uma metodologia composta de sete passos metodológicos que abrangem as etapas de execução da metodologia segundo um conjunto de restrições de definições teóricas para a aplicação do mesmo. De modo a validar a metodologia foi realizado um estudo de caso em que foram utilizados os mapas de estimativas das safras de soja e de milho do município de Nova Ubiratã no Estado do Mato Grosso – MT para determinar a configuração da rede suprimentos para o município que supra o déficit de capacidade estática por armazenagem para a safra 2017/2018 e que minimize o custo total da rede de suprimento. Para esse estudo de caso foram usados mapas da infraestrutura logística envolvida (rodovias e de armazenagem) para o escoamento destas safras, rede de suprimento e de localização p-mediana, linguagens de programação R e Python, e Sistemas de Informações Geográficas (SIG). Os resultados mostraram que a rede de suprimento com menor custo de transporte e armazenagem fora aquela que utilizou unidades de armazenamento de 162 mil toneladas de capacidade e com cobertura da produção de 120%. A metodologia possibilitou analisar a rede de suprimento atual sob a ótica de oferta-demanda e calcular as localizações e o número de instalações de facilidades logísticas necessárias para suprir o déficit da região do estudo de caso. Ademais, a metodologia demonstrou capacidade de tratar problemas de localização e otimização da rede de suprimentos em escala regional com agilidade e a eficiência preconizada.The Brazilian agriculture is one of the most important on the planet, with a prominent position in the agricultural commodities export of soybeans and corn. As the crop production areas are far from the ports and the speed of territorial expansion is greater than the speed of installation of new storage structures, important negative impacts on the logistics system emerge. The absence of an efficient logistical system with enough storage capacity for the entire harvest season forces farmers to sell their crops immediately after the harvest, causing a reduction in commodity prices due to oversupply and with sales at a time of falling prices. In this scenario, the main objective of this thesis was to develop a methodology for defining the supply network for the storage and flow of agricultural commodities. To achieve those objectives, the methodology developed consist of seven methodological steps that encompass the stages of the modeling execution according to a set of restrictions and definitions for its application. In order to validate the methodology, a study case was carried out using crop estimatives maps for soybean and corn in the municipality of Nova Ubiratã in the State of Mato Grosso – MT, Brazil. This maps to determine the configuration of the supply network for the municipality that overcomes the shortage of static storage capacity for the harvest of 2017/2018 and minimizes the total cost of the supply chain. For this case study, maps of the logistics infrastructure involved (highways and storage) were used for the flow of these crops, network model and p-median location, programming languages R and Python, and Geographic Information Systems (GIS). The results showed that the supply network with the lowest transport and storage cost was that one with storage units of 162 thousand tons of capacity and with production coverage of 120%. The model made it possible to analyze the current supply network from the perspective of supply-demand and calculate the locations and the number of logistical facilities necessary to supply the deficit of the region of the study case. In addition, the methodology demonstrated the ability to address problems of localization and optimization of the supply network on a regional scale with agility and the expected efficiency

Ανάπτυξη προτύπου προσομοίωσης για την πρόβλεψη και τη διαχείριση έκτακτων συμβάντων σε δίκτυα αυτοκινητόδρομων

177 σ.Research on road safety has been of great interest to engineers and planners for decades. Regardless of modeling techniques, a serious factor of inaccuracy - in most past studies - has been data aggregation. Nowadays, most freeways are equipped with continuous surveillance systems making disaggregate traffic data readily available; these have been used in few studies. In this context, the main objective of this dissertation is to capitalize highway traffic data collected on a real-time basis at the moment of accident occurrence in order to expand previous road safety work and to highlight potential further applications. To this end, we first examine the effects of various traffic parameters on type of road crash as well as on the injury level sustained by vehicle occupants involved in accidents, while controlling for environmental and geometric factors. Probit models are specified on 4-years of data from the A4-A86 highway section in the Ile-de-France region, France. Empirical findings indicate that crash type can almost exclusively be defined by the prevailing traffic conditions shortly before its occurrence. Increased traffic volume is found to have a consistently positive effect on severity, while speed has a differential effect on severity depending on flow conditions. We then establish a conceptual framework for incident management applications using real-time traffic data on urban freeways. We use dissertation previous findings to explore potential implications towards incident propensity detection and enhanced management.Η Οδική Ασφάλεια αποτελεί πεδίο ερευνητικού ενδιαφέροντος για μηχανικούς κατά τις τελευταίες δεκαετίες. Ανεξάρτητα από τις εφαρμοζόμενες μεθόδους προτυποποίησης, σημαντικός παράγοντας ανακρίβειας πρότερων διερευνήσεων είναι η ομαδοποίηση δεδομένων. Ωστόσο, οι περισσότεροι αυτοκινητόδρομοι είναι πλέον εξοπλισμένοι με συστήματα παρακολούθησης, τα οποία καθιστούν διαθέσιμα μη ομαδοποιημένα κυκλοφοριακά δεδομένα. Η διαθεσιμότητα των δεδομένων αυτών δεν έχει επαρκώς αξιοποιηθεί ερευνητικά. Στόχος της διατριβής είναι η αξιοποίηση των κυκλοφοριακών δεδομένων αυτοκινητόδρομων που συλλέγονται σε πραγματικό χρόνο κατά τη στιγμή εκδήλωσης ατυχήματος. Για το σκοπό αυτό, μελετήθηκε η επίδραση διάφορων κυκλοφοριακών παραμέτρων στον τύπο οδικού ατυχήματος, αλλά και στο επίπεδο σοβαρότητας τραυματισμού των επιβαινόντων. Παράλληλα, ελήφθησαν υπόψιν παράγοντες σχετιζόμενοι με το περιβάλλον και τη γεωμετρία. Εφαρμόστηκαν μοντέλα probit σε τετραετή δεδομένα συμβάντων από το κοινό τμήμα των αυτοκινητόδρομων Α4-Α86 στην περιοχή Ile-de-France της Γαλλίας. Τα εμπειρικά αποτελέσματα καταδεικνύουν ότι ο τύπος ατυχήματος μπορεί –σχεδόν αποκλειστικά- να εκτιμηθεί από τις επικρατούσες κυκλοφοριακές συνθήκες. η αύξηση του κυκλοφοριακού φόρτου φαίνεται να ασκεί σταθερή επίδραση στη σοβαρότητα των ατυχημάτων, ενώ η επίδραση της ταχύτητας διαφοροποιείται ανάλογα με το επίπεδο του κυκλοφοριακού φόρτου. Στη συνέχεια, αναπτύσσεται πλαίσιο για την ένταξη κυκλοφοριακών δεδομένων πραγματικού χρόνου στη διαχείριση συμβάντων. Τέλος, τα πορίσματα της διατριβής χρησιμοποιούνται στη διερεύνηση εφαρμογών με απώτερο στόχο τον περιορισμό της προδιάθεσης πρόκλησης συμβάντων και τη βελτιωμένη διαχείρισή τους.Ζωή Δ. Χριστοφόρο