Heuristic method for a mixed capacitated arc routing problem : A refuse collection application

The capacitated arc routing problem (CARP) is known to be NP-hard. The aim of this paper is to present a new heuristic method to generate feasible solutions to an extended CARP on mixed graphs, inspired by the household refuse collection problem in Lisbon. Computational experience was done to compare the method with some well-known existing heuristics, generalised for a different extended CARP by Lacomme et al. [Fast algorithm for general arc routing problems, Presented at IFORS 2002 Conference, Edinburgh, UK], namely, the Path-Scanning, the Augment-Merge and the Ulusoy’s algorithms. The results reveal a good performance of the proposed heuristic method. Generally providing a good use of the vehicles capacity, the resulting sets of feasible trips may also be considered good. The test instances involve more than 300 randomly generated test problems with dimensions of up to 400 nodes and 1220 links.info:eu-repo/semantics/publishedVersio

Lower-bounding and heuristic methods for a refuse collection vehicle routing problem

A set of routes that minimizes the total collecting cost of the household refuse in a quarter of Lisbon may be obtained solving a Capacitated Arc Routing Problem (CARP) with side constraints. The CARP is known to be an NP-hard problem. We present two lower-bounding methods, both based on the transportation model, in which we have been able to incorporate some of the side constraints. We also present a three-phase heuristic to generate a near-optimal solution from the solution obtained with the first lower-bounding method. For the relative gap between the heuristic solution value and its associated lower bound value we give a theoretical worst-case bound and computational experience obtained with a set of test problems.info:eu-repo/semantics/publishedVersio

An updated annotated bibliography on arc routing problems

The number of arc routing publications has increased significantly in the last decade. Such an increase justifies a second annotated bibliography, a sequel to Corberán and Prins (Networks 56 (2010), 50–69), discussing arc routing studies from 2010 onwards. These studies are grouped into three main sections: single vehicle problems, multiple vehicle problems and applications. Each main section catalogs problems according to their specifics. Section 2 is therefore composed of four subsections, namely: the Chinese Postman Problem, the Rural Postman Problem, the General Routing Problem (GRP) and Arc Routing Problems (ARPs) with profits. Section 3, devoted to the multiple vehicle case, begins with three subsections on the Capacitated Arc Routing Problem (CARP) and then delves into several variants of multiple ARPs, ending with GRPs and problems with profits. Section 4 is devoted to applications, including distribution and collection routes, outdoor activities, post-disaster operations, road cleaning and marking. As new applications emerge and existing applications continue to be used and adapted, the future of arc routing research looks promising.info:eu-repo/semantics/publishedVersio

Lower bounds for the mixed capacitated arc routing problem

Capacitated arc routing problems (CARP) arise in distribution or collecting problems where activities are performed by vehicles, with limited capacity, and are continuously distributed along some pre-defined links of a network. The CARP is defined either as an undirected problem or as a directed problem depending on whether the required links are undirected or directed. The mixed capacitated arc routing problem (MCARP) models a more realistic scenario since it considers directed as well as undirected required links in the associated network. We present a compact flow based model for the MCARP. Due to its large number of variables and constraints, we have created an aggregated version of the original model. Although this model is no longer valid, we show that it provides the same linear programming bound than the original model. Different sets of valid inequalities are also derived. The quality of the models is tested on benchmark instances with quite promising results..info:eu-repo/semantics/publishedVersio

Arc routing with trip-balancing and attractiveness measures : A waste collection case study

This work focuses on a household (or door to door) waste collection problem in the Portuguese municipality of Seixal, which is modelled as a generalisation of a mixed capacitated arc routing problem (MCARP). The MCARP is known to be NP-hard. The proposed methodology uses: i) a GIS (geographic information system), for input/output and to reduce problem dimensions; ii) a matheuristic that iteratively solves a new hybrid model; and iii) two versions of a two-phase matheuristic. The latter pursues the generation of connected and compacted trips. During the first phase, called initial assignment, some links requiring service are assigned to vehicle services. In the second phase, the hybrid model finishes the assignment and generates a feasible set of trips. The quality of the generated solutions is assessed through the total time, as well as by some attractiveness measures. These measures evaluate the adequacy of the solutions for the real case-study, a crucial aspect for trips that need to be accepted by practitioners. With this purpose, a new attractiveness measure that introduces space dependent penalisation of overlaps, named weighted hull overlap, is also proposed. Computational results with 18 Seixal instances, with 265–1223 nodes and 492–2254 links, point to the good performance of the proposed.info:eu-repo/semantics/publishedVersio

Dissimilar arc routing problems

Money collection presents particular problems in terms of effective vehicle routing. Planning the collection or distribution of money for ATMs or parking meters gives rise to two problems: while the total collecting time should be minimized, tours on successive days should be different to prevent robberies. The combination of these two problems is named as the Dissimilar Routing Problem. When the safes to be collected are located along the streets, it corresponds to an arc routing problem, which we call DARP, and when the money is from ATMs, it corresponds to a vehicle routing problem, usually referred to as the peripatetic routing problem. The former problem arises in a Portuguese company in charge of street parking in Lisbon. The firm needs to define tours to collect safes from parking meters, minimizing the total collecting time. To avoid robberies these tours cannot be repeated or somehow anticipated. For this new problem, we present a mixed integer linear programming (MILP) model and develop a matheuristic. Preliminary experiments are provided with data that mimic the real confidential data. Results point to a good performance of the matheuristic, while the smaller instances can be solved to optimality with the MILP model and a commercial solver.info:eu-repo/semantics/publishedVersio

Profitable mixed capacitated arc routing and related problems

Mixed Capacitated Arc Routing Problems (MCARP) aim to identify a set of vehicle trips that, starting and ending at a depot node, serve a given number of links, regarding the vehicles capacity, and minimizing a cost function. If both profits and costs on arcs are considered, the Profitable Mixed Capacitated Arc Routing Problem (PMCARP) may be defined. We present compact flow based models for the PMCARP, where two types of services are tackled, mandatory and optional. Adaptations of the models to fit into some other related problems are also proposed. The models are evaluated, according to their bounds quality as well as the CPU times, over large sets of test instances. New instances have been created from benchmark ones in order to solve variants that have been introduced here for the first time. Results show the new models performance within CPLEX and compare, whenever available, the proposed models against other resolution methods.info:eu-repo/semantics/publishedVersio

Profitable mixed capacitated arc routing and related problems

Mixed Capacitated Arc Routing Problems (MCARP) aim to identify a set of vehicle trips that, starting and ending at a depot node, serve a given number of links, regarding the vehicles capacity, and minimizing a cost function. If both profits and costs on arcs are considered, the Profitable Mixed Capacitated Arc Routing Problem (PMCARP) may be defined. We present compact flow based models for the PMCARP, where two types of services are tackled, mandatory and optional. Adaptations of the models to fit into some other related problems are also proposed. The models are evaluated, according to their bounds quality as well as the CPU times, over large sets of test instances. New instances have been created from benchmark ones in order to solve variants that have been introduced here for the first time. Results show the new models performance within CPLEX and compare, whenever available, the proposed models against other resolution methodsinfo:eu-repo/semantics/publishedVersio

Comparative effectiveness and predictors of response to tumour necrosis factor inhibitor therapies in rheumatoid arthritis

Funding Information: positions on two Pfizer sponsored trials and has directed an educational course supported by Bristol Myers Squibb. He serves as an epidemiology consultant to CORRONA. J.A.P.S. has received honoraria as a speaker or consultant and benefited from research support from several pharmaceutical companies involved in the production of biologic agents (Abbott, Amgen, MSD, Pfizer and Roche), always at sums less than E10 000. All other authors have declared no conflicts of interest. Funding Information: Funding: This work was supported by a grant from Harvard-Portugal Program HMSP-ICS/SAU-ICT/0002/ 2010.Objectives: Adalimumab, etanercept and infliximab are effective TNF inhibitors (TNFis) in the treatment of RA, but no randomized clinical trials have compared the three agents. Prior observational data are not consistent. We compared their effectiveness over 1 year in a prospective cohort.Methods: Analyses were performed on subjects' first episode of TNFi use in the Rheumatic Diseases Portuguese Register, Reuma.pt. The primary outcome was the proportion of patients with European League Against Rheumatism good response sustained at two consecutive observations separated by 3 months during the first year of TNFi use. Comparisons were performed using conventional adjusted logistic regression, as well as matching subjects across the three agents using a propensity score. In addition, baseline predictors of treatment response to TNFi were identified.Results: The study cohort included 617 RA patients, 250 starting etanercept, 206 infliximab and 161 adalimumab. Good response was achieved by 59.6% for adalimumab, 59.2% for etanercept and 51.9% for infliximab (P = 0.21). The modelled probability of good response did not significantly differ across agents (etanercept vs adalimumab OR = 0.97, 95% CI 0.55, 1.71; etanercept vs infliximab OR = 1.25, 95% CI 0.74, 2.12; infliximab vs adalimumab OR = 0.80, 95% CI 0.47, 1.36). Matched propensity score analyses also showed no significant treatment response differences. Greater educational attainment was a predictor of better response, while smoking, presence of ACPA, glucocorticoid use and worse physician assessment of disease activity at baseline each predicted a reduced likelihood of treatment response.Conclusion: Over 1 year, we found no difference in effectiveness between adalimumab, etanercept and infliximab.publishersversionpublishe

Arc routing for parking enforcement officers : exact and heuristic solutions

This paper presents exact and approximate methods for constructing daily walking tours for parking enforcement officers the Parking Enforcement Routing Problem (PERP), a problem faced by EMEL, a municipal company that manages parking in Lisbon. Parking Enforcement Officers (PEO) must ensure that the users of the street parking lots pay the corresponding fee, and that they also comply with the parking rules imposed by the legislation in force. The duration of the tours must be compatible with the PEO daily work schedules. A street cannot be supervised more than once in consecutive hours, nor supervised simultaneously by two PEOs. The PERP is a new generalisation of an Arc Routing Problem with profits aiming to maximise the total criticality, a concept defined to represent the need for enforcement of the street segments, related to the number of vehicles parked in transgression. Moreover, parking rules lead to some specificities regarding the underlying network, which needs to be built with additional unusual characteristics. A flow-based mixed integer linear programming model and heuristics which return two daily trips for each PEO are proposed. Computational results carried out on 50 instances based on real data show that it was appropriate to propose both types of methods, exact and heuristic. Furthermore, PEOs working for EMEL reacted positively to the trips corresponding to the generated solutions. A Decision Support System built on the heuristics was also developed to be easily used by practitioners in EMELinfo:eu-repo/semantics/publishedVersio