Dynamic railway junction rescheduling using population based ant colony optimisation

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Efficient rescheduling after a perturbation is an important concern of the railway industry. Extreme delays can result in large fines for the train company as well as dissatisfied customers. The problem is exacerbated by the fact that it is a dynamic one; more timetabled trains may be arriving as the perturbed trains are waiting to be rescheduled. The new trains may have different priorities to the existing trains and thus the rescheduling problem is a dynamic one that changes over time. The aim of this research is to apply a population-based ant colony optimisation algorithm to address this dynamic railway junction rescheduling problem using a simulator modelled on a real-world junction in the UK railway network. The results are promising: the algorithm performs well, particularly when the dynamic changes are of a high magnitude and frequency

Ant Colony Optimisation for Dynamic and Dynamic Multi-objective Railway Rescheduling Problems

Recovering the timetable after a delay is essential to the smooth and efficient operation of the railways for both passengers and railway operators. Most current railway rescheduling research concentrates on static problems where all delays are known about in advance. However, due to the unpredictable nature of the railway system, it is possible that further unforeseen incidents could occur while the trains are running to the new rescheduled timetable. This will change the problem, making it a dynamic problem that changes over time. The aim of this work is to investigate the application of ant colony optimisation (ACO) to dynamic and dynamic multiobjective railway rescheduling problems. ACO is a promising approach for dynamic combinatorial optimisation problems as its inbuilt mechanisms allow it to adapt to the new environment while retaining potentially useful information from the previous environment. In addition, ACO is able to handle multi-objective problems by the addition of multiple colonies and/or multiple pheromone and heuristic matrices. The contributions of this work are the development of a junction simulator to model unique dynamic and multi-objective railway rescheduling problems and an investigation into the application of ACO algorithms to solve those problems. A further contribution is the development of a unique two-colony ACO framework to solve the separate problems of platform reallocation and train resequencing at a UK railway station in dynamic delay scenarios. Results showed that ACO can be e ectively applied to the rescheduling of trains in both dynamic and dynamic multi-objective rescheduling problems. In the dynamic junction rescheduling problem ACO outperformed First Come First Served (FCFS), while in the dynamic multi-objective rescheduling problem ACO outperformed FCFS and Non-dominated Sorting Genetic Algorithm II (NSGA-II), a stateof- the-art multi-objective algorithm. When considering platform reallocation and rescheduling in dynamic environments, ACO outperformed Variable Neighbourhood Search (VNS), Tabu Search (TS) and running with no rescheduling algorithm. These results suggest that ACO shows promise for the rescheduling of trains in both dynamic and dynamic multi-objective environments.Engineering and Physical Sciences Research Council (EPSRC

Railway platform reallocation after dynamic perturbations using ant colony optimisation

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Train delays at stations are a common occurrence in complex, busy railway networks. A delayed train will miss its scheduled time slot on the platform and may have to be reallocated to a new platform to allow it to continue its journey. The problem is a dynamic one because while reallocating a delayed train further unanticipated train delays may occur, changing the nature of the problem over time. Our aim in this study is to apply ant colony optimisation (ACO) to a dynamic platform reallocation problem (DPRP) using a model created from real-world train schedule data. To ensure that trains are not unnecessarily reallocated to new platforms we introduce a novel best-ant-replacement scheme that takes into account not only the objective value but also the physical distance between the original and the new platforms. Results showed that the ACO algorithm outperformed a heuristic that places the delayed train in the first available time-slot and that this improvement was more apparent with high-frequency dynamic changes

Ant colony optimization for simulated dynamic multi-objective railway junction rescheduling

open access articleMinimising the ongoing impact of train delays has benefits to both the users of the railway system and the railway stakeholders. However, the efficient rescheduling of trains after a perturbation is a complex real-world problem. The complexity is compounded by the fact that the problem may be both dynamic and multi-objective. The aim of this research is to investigate the ability of ant colony optimisation algorithms to solve a simulated dynamic multi-objective railway rescheduling problem and, in the process, to attempt to identify the features of the algorithms that enable them to cope with a multi-objective problem that is also dynamic. Results showed that, when the changes in the problem are large and frequent, retaining the archive of non-dominated solution between changes and updating the pheromones to reflect the new environment play an important role in enabling the algorithms to perform well on this dynamic multi-objective railway rescheduling problem

Ant colony optimization with immigrants schemes for the dynamic railway junction rescheduling problem with multiple delays

Train rescheduling after a perturbation is a challenging task and is an important concern of the railway industry as delayed trains can lead to large fines, disgruntled customers and loss of revenue. Sometimes not just one delay but several unrelated delays can occur in a short space of time which makes the problem even more challenging. In addition, the problem is a dynamic one that changes over time for, as trains are waiting to be rescheduled at the junction, more timetabled trains will be arriving, which will change the nature of the problem. The aim of this research is to investigate the application of several different ant colony optimization (ACO) algorithms to the problem of a dynamic train delay scenario with multiple delays. The algorithms not only resequence the trains at the junction but also resequence the trains at the stations, which is considered to be a first step towards expanding the problem to consider a larger area of the railway network. The results show that, in this dynamic rescheduling problem, ACO algorithms with a memory cope with dynamic changes better than an ACO algorithm that uses only pheromone evaporation to remove redundant pheromone trails. In addition, it has been shown that if the ant solutions in memory become irreparably infeasible it is possible to replace them with elite immigrants, based on the best-so-far ant, and still obtain a good performance

Improving access to psychological therapies (IAPT) for people with bipolar disorder:summary of outcomes from the IAPT demonstration site

Access to structured psychological therapy recommended for bipolar disorder (BD) is poor. The UK NHS Improving Access to Psychological Therapies initiative commissioned a demonstration site for BD to explore the outcomes of routine delivery of psychological therapy in clinical practice, which this report summarises. All clinically diagnosed patients with BD who wanted a psychological intervention and were not in acute mood episode were eligible. Patients were offered a 10-session group intervention (Mood on Track) which delivered NICE congruent care. Outcomes were evaluated using an open (uncontrolled), pre-post design. Access to psychological therapy increased compared to preceding 6 years by 54%. 202 people began treatment; 81% completed >5 sessions; median 9 sessions (range 6–11). Pre-post outcomes included personal recovery (primary outcome), quality of life, work and social functioning, mood and anxiety symptoms (secondary outcomes). Personal recovery significantly improved from pre to post-therapy; medium effect-size (d = 0.52). Secondary outcomes all improved (except mania symptoms) with smaller effect sizes (d = . 20–0.39). Patient satisfaction was high. Use of crisis services, and acute admissions were reduced compared to pre-treatment. It is possible to deliver group psychological therapy for bipolar disorder in a routine NHS setting. Improvements were observed in personal recovery, symptoms and wider functioning with high patient satisfaction and reduced service use

Animal escapology I: theoretical issues and emerging trends in escape trajectories

Escape responses are used by many animal species as their main defence against predator attacks. Escape success is determined by a number of variables; important are the directionality (the percentage of responses directed away from the threat) and the escape trajectories (ETs) measured relative to the threat. Although logic would suggest that animals should always turn away from a predator, work on various species shows that these away responses occur only approximately 50–90% of the time. A small proportion of towards responses may introduce some unpredictability and may be an adaptive feature of the escape system. Similar issues apply to ETs. Theoretically, an optimal ET can be modelled on the geometry of predator–prey encounters. However, unpredictability (and hence high variability) in trajectories may be necessary for preventing predators from learning a simple escape pattern. This review discusses the emerging trends in escape trajectories, as well as the modulating key factors, such as the surroundings and body design. The main ET patterns identified are: (1) high ET variability within a limited angular sector (mainly 90–180deg away from the threat; this variability is in some cases based on multiple peaks of ETs), (2) ETs that allow sensory tracking of the threat and (3) ETs towards a shelter. These characteristic features are observed across various taxa and, therefore, their expression may be mainly related to taxon-independent animal design features and to the environmental context in which prey live – for example whether the immediate surroundings of the prey provide potential refuges

Adjustment in adolescents with cleft lip and palate: A preliminary investigation into experiences of shame and bullying

For some young people, the experience of having a facial disfigurement such as a cleft lip and palate can result in negative social interactions, often originating from the stereotyping reaction of others. Using the social rank theory of shame, the effects of bullying and teasing were investigated in a patient group of 16, 12-18 year olds with cleft lip or cleft lip and palate. The patient group were compared with a group of 16 of their peers with regards to their experiences of bullying and teasing, shame-proneness and the focus of their shame. The interactional effects of shame and bullying were also investigated in order to test a shaming-loop model of negative social interaction. The investigation necessitated two separate studies. The first study involved 215 adolescents from a secondary school and was required for the development of a focus of shame scale and the gathering of data for establishing its psychometric properties. It also enabled data to be collected regarding the experiences of shame and bullying in adolescents without cleft lip and palate, in order that a random sample of 16 school adolescents matched with the patient sample on age and gender, may act as a comparison group. Participants completed self-report questionnaires concerning shame-proneness and focus of shame, and a semi-structured interview regarding their experiences of bullying. The second study involved the administration of the same measures to the patient sample. Results showed high levels of bullying for both groups although there was no overall difference between the groups. Differences were seen in focus of shame scores, with the patient group having higher scores on shame related to facial appearance than their comparisons. No overall differences were seen on scores of shame-proneness. The implications of the findings are discussed and limitations of the study acknowledged

Adjustment in adolescents with a cleft lip and palate : a preliminary investigation into experiences of shame and bullying

For some young people, the experience of having a facial disfigurement such as a cleft lip and palate can result in negative social interactions, often originating from the stereotyping reaction of others. Using the social rank theory of shame, the effects of bullying and teasing were investigated in a patient group of 16, 12-18 year olds with cleft lip or cleft lip and palate. The patient group were compared with a group of 16 of their peers with regards to their experiences of bullying and teasing, shame-proneness and the focus of their shame. The interactional effects of shame and bullying were also investigated in order to test a shaming-loop model of negative social interaction. The investigation necessitated two separate studies., The first study involved 215 adolescents from a secondary school and was required for the development of a focus of shame scale and gathering of data for establishing its psychometric properties. It also enabled data to be collected regarding the experiences of shame and bullying in adolescents without cleft lip and palate, in order that a random sample of 16 school adolescents matched with the patient sample on age and gender, may act as a comparison group. Participants completed self-report questionnaires concerning shame-proneness and focus of shame, and a semi-structure interview regarding their experiences of bullying. The second study involved the administration of the same measures to the patient sample. Results showed high levels of bullying for both groups although there was no overall difference between the groups. Differences were seen in focus of shame scores, with the patient group having higher scores on shame related to facial appearance than their comparisons. No overall differences were seen on score of shame-proneness. The implications of the findings are discussed and limitations of the study acknowledged