Online Bus Speed Prediction With Spatiotemporal Interaction: A Laplace Approximation-Based Bayesian Approach

This study proposes a novel Bayesian hierarchical approach for online bus speed prediction by explicitly accounting for the spatiotemporal interaction (STI) of speed observations. The use of Laplace approximation can expedite the estimation of Bayesian models and enable the implementation of online prediction. Large numbers of trials are carried out to identify significant predictors and the optimal length of the look-back time window to achieve the highest prediction accuracy. The spatiotemporal interacting patterns are also explored, and results show that the Type IV model assuming the structured spatial effect interacts with the structured temporal effect can best accommodate the bus speed data. Besides, prediction errors of the Type IV model randomly distribute over time and space. The proposed model can achieve high prediction accuracy and computational efficiency without compromising the interpretability of the contributing factors and the unobserved spatiotemporal heterogeneity. The proposed model can be used to assist public transit operation and management, such as bus scheduling, congestion warning, and the development of proactive measures to mitigate bus delays

Luotettavuuden indikaattorien valintaprosessin määrittäminen: Case Helsingin seudun liikenne

It is important to have information on the day-to-day operational level events and planning objectives in public transport. Performance indicators are needed to inform related decisions in these domains. As one aspect of public transport level of service, problems with reliability appear to passengers as delays in different parts of the journey, such as increasing overall travel times or adding extra waiting time at transfer points. Factors affecting reliability can be classified in many different ways, but the factors mainly consist of decisions and choices at the planning and operational level, as well as environmental variables. This work considers that reliability consists of four components: punctuality, regularity, waiting time, and cancellation. As Helsinki Region Transport (HSL) is under-going a continuous effort of developing performance indicators, the aim of this thesis was to develop a process for defining and selecting reliability performance indicators for HSL case. Development in this thesis. starts with defining alternative performance indicators for punctuality, regularity and waiting time. The selection of a single indicator to describe the reliability was performed using the analytical hierarchy process (AHP). The AHP method was used to create an assessment framework consisting of a subjective and an objective part. The purpose of the evaluation framework was to help assess the superiority and suit-ability of the different indicator alternatives. The objective part evaluated the technical and computational details of the indicators, while the subjective part evaluated the indicators from the perspective of the user’s needs. Based on the evaluation, the selected indicators were subjected to spatio-temporal analysis to find the most effective aggregates. The analysis also outlined possible graphical visualizations for the indicators. In addition, a workshop was organized for users to define the criteria for subjective evaluation and to evaluate the indicator options. The workshop was evaluated as positive for its involvement and information sharing, as well as development wishes for the way the assessment was collected and for exploring the alternatives in advance. In general, the AHP method and assessment framework were found to work well as part of the selection process. Performed spatio-temporal analysis yielded the desired result, but the analysis was also found to need improvement in certain points. For example, the partial combination of analysis with a workshop was found to be a necessary addition. Overall, the indicator selection process outlined in this work can be considered successful, as details of the process are almost at the level where they can be implemented in the ongoing HSL processes.On tärkeää saada tietoa joukkoliikenteen päivittäisistä operatiivisen tason tapahtumista ja suunnittelutavoitteista. Suorituskykyindikaattoreita tarvitaan avuksi näihin asioihin liittyvissä kysymyksissä. Yhtenä julkisen liikenteen palvelutason näkökulmana luotettavuusongelmat näyttäytyvät matkustajille viivästyksinä matkan eri osissa, kuten kasvavina kokonaismatka-aikoina tai ylimääräisenä odotusaikana vaihdoissa. Luotettavuuteen vaikuttavat tekijät voidaan luokitella monin eri tavoin, mutta tekijät koostuvat pääasiassa suunnittelu- ja toimintatason päätöksistä ja valinnoista sekä ympäristömuuttujista. Työssä katsottiin, että luotettavuus koostuu neljästä osasta: täsmällisyydestä, säännöllisyydestä, odotusajasta ja ajamattomuudesta. Koska Helsingin seudun liikenne (HSL) pyrkii jatkuvasti kehittämään suoritusindikaattoreita, tämän työn tavoitteena oli kehittää prosessi luotettavuuden suorituskykyindikaattorien määrittelemiseksi ja valitsemiseksi. Tämän työ alkaa vaihtoehtoisten suorituskykyindikaattorien määrittämisellä täsmällisyydelle, säännöllisyydelle ja odotusajalle. Yksittäisen indikaattorin valinta luotettavuuden kuvaamiseksi suoritettiin käyttämällä analyyttistä hierarkia prosessia (AHP). AHP-menetelmää käytettiin luomaan arviointijärjestelmä, joka koostui subjektiivisesta ja objektiivisesta osasta. Arvioinnin tarkoituksena oli auttaa arvioimaan eri indikaattorivaihtoehtojen paremmuutta ja soveltuvuutta. Objektiivisessa osassa arvioitiin indikaattorien teknisiä ja laskennallisia yksityiskohtia, kun taas subjektiivisessa osassa arvioitiin indikaattoreita käyttäjän tarpeiden näkökulmasta. Arvioinnin perusteella valituille indikaattoreille tehtiin spatio-temporaalinen analyysi tehokkaimpien koosteiden löytämiseksi. Analyysi hahmotteli myös indikaattorien mahdollisia graafisia visualisointeja. Lisäksi tuleville käyttäjille järjestettiin työpaja subjektiivisen arvioinnin perusteiden määrittelemiseksi ja indikaattorivaihtoehtojen arvioimiseksi. Työpajaa arvioitiin positiivisesti sen osallistamisesta ja tiedon jakamisesta. Kehitystarpeita nähtiin arvioinnin keräystavassa ja tunnistettiin tarve saada tutkia vaihtoehtoja etukäteen. Yleisesti AHP-menetelmän ja arviointikehyksen todettiin toimivan hyvin osana valintaprosessia. Suoritettu spatio-temporaalinen analyysi tuotti halutun tuloksen, mutta analyysin todettiin myös tarvitsevan parannusta tietyissä kohdissa. Esimerkiksi analyysin osittainen yhdistäminen työpajaan todettiin olevan välttämätön lisä. Kaiken kaikkiaan tässä työssä hahmotettua indikaattorivalintaprosessia voidaan pitää onnistuneena, koska prosessin yksityiskohdat ovat melkein sillä tasolla, missä ne voidaan toteuttaa osana meneillään olevassa HSL:n suorituskykyindikaattorien kehittämisprosessia

Relaxing door-to-door matching reduces passenger waiting times: a workflow for the analysis of driver GPS traces in a stochastic carpooling service

Carpooling has the potential to transform itself into a mass transportation mode by abandoning its adherence to deterministic passenger-driver matching for door-to-door journeys, and by adopting instead stochastic matching on a network of fixed meeting points. Stochastic matching is where a passenger sends out a carpooling request at a meeting point, and then waits for the arrival of a self-selected driver who is already travelling to the requested meeting point. Crucially there is no centrally dispatched driver. Moreover, the carpooling is assured only between the meeting points, so the onus is on the passengers to travel to/from them by their own means. Thus the success of a stochastic carpooling service relies on the convergence, with minimal perturbation to their existing travel patterns, to the meeting points which are highly frequented by both passengers and drivers. Due to the innovative nature of stochastic carpooling, existing off-the-shelf workflows are largely insufficient for this purpose. To fill the gap in the market, we introduce a novel workflow, comprising of a combination of data science and GIS (Geographic Information Systems), to analyse driver GPS traces. We implement it for an operational stochastic carpooling service in south-eastern France, and we demonstrate that relaxing door-to-door matching reduces passenger waiting times. Our workflow provides additional key operational indicators, namely the driver flow maps, the driver flow temporal profiles and the driver participation rates

Unsplittable Load Balancing in a Network of Charging Stations Under QoS Guarantees

The operation of the power grid is becoming more stressed, due to the addition of new large loads represented by Electric Vehicles (EVs) and a more intermittent supply due to the incorporation of renewable sources. As a consequence, the coordination and control of projected EV demand in a network of fast charging stations becomes a critical and challenging problem. In this paper, we introduce a game theoretic based decentralized control mechanism to alleviate negative impacts from the EV demand. The proposed mechanism takes into consideration the non-uniform spatial distribution of EVs that induces uneven power demand at each charging facility, and aims to: (i) avoid straining grid resources by offering price incentives so that customers accept being routed to less busy stations, (ii) maximize total revenue by serving more customers with the same amount of grid resources, and (iii) provide charging service to customers with a certain level of Quality-of-Service (QoS), the latter defined as the long term customer blocking probability. We examine three scenarios of increased complexity that gradually approximate real world settings. The obtained results show that the proposed framework leads to substantial performance improvements in terms of the aforementioned goals, when compared to current state of affairs.Comment: Accepted for Publication in IEEE Transactions on Smart Gri

An information-based traffic control in a public conveyance system: reduced clustering and enhanced efficiency

A new public conveyance model applicable to buses and trains is proposed in this paper by using stochastic cellular automaton. We have found the optimal density of vehicles, at which the average velocity becomes maximum, significantly depends on the number of stops and passengers behavior of getting on a vehicle at stops. The efficiency of the hail-and-ride system is also discussed by comparing the different behavior of passengers. Moreover, we have found that a big cluster of vehicles is divided into small clusters, by incorporating information of the number of vehicles between successive stops.Comment: 8 pages, 15 figure

The role of public transport in addressing sustainable mobility for the elderly population in Malta

Over the past few years, several countries have continued experiencing a growth in their elderly population. Similarly, a number of towns and villages in Malta registered a high elderly population in the last census (NSO, 2012). The elderly people are one of the dominant ‘transport disadvantaged’ groups in the community. This research aims to analyse whether the current public transport system in Malta is providing effective and efficient mobility for elderly in the town of Luqa. In order to analyse this, the study analysed spatial accessibility, sought to identify barriers encountered by the elderly when using public transport and determine temporal accessibility to medical care. Data was collected using telephone surveys, travel time and bus frequency surveys. Statistical analysis was carried out using IBM SPSS 20 and Geographic Information Systems. The study showed that proximity to bus stops in Luqa does not affect public transport use amongst the elderly. The main barriers that elderly encounter when using public transport are mainly related to long waiting times, lack of comfort on bus stops and inaccessible travel information. Finally, temporal accessibility from Luqa to the State’s general hospital, Mater Dei, still requires improvements as it does not meet the desired time budgets of elderly people. By identifying the main concerns this study seeks to encourage policy makers and planners to target future development in public transport taking into consideration the requirements of the growing elderly population.peer-reviewe