65 research outputs found
A hybrid strategy for real-time traffic signal control of urban road networks
The recently developed traffic signal control strategy known as traffic-responsive urban control (TUC) requires availability of a fixed signal plan that is sufficiently efficient under undersaturated traffic conditions. To drop this requirement, the well-known Webster procedure for fixed-signal control derivation at isolated junctions is appropriately employed for real-time operation based on measured flows. It is demonstrated via simulation experiments and field application that the following hold: 1) The developed real-time demand-based approach is a viable real-time signal control strategy for undersaturated traffic conditions. 2) It can indeed be used within TUC to drop the requirement for a prespecified fixed signal plan. 3) It may, under certain conditions, contribute to more efficient results, compared with the original TUC method
A Time-varying Shockwave Speed Model for Trajectory Reconstruction using Lagrangian and Eulerian Observations
Inference of detailed vehicle trajectories is crucial for applications such
as traffic flow modeling, energy consumption estimation, and traffic flow
optimization. Static sensors can provide only aggregated information, posing
challenges in reconstructing individual vehicle trajectories. Shockwave theory
is used to reproduce oscillations that occur between sensors. However, as the
emerging of connected vehicles grows, probe data offers significant
opportunities for more precise trajectory reconstruction. Existing methods rely
on Eulerian observations (e.g., data from static sensors) and Lagrangian
observations (e.g., data from probe vehicles) incorporating shockwave theory
and car-following modeling. Despite these advancements, a prevalent issue lies
in the static assignment of shockwave speed, which may not be able to reflect
the traffic oscillations in a short time period caused by varying response
times and vehicle dynamics. Moreover, energy consumption estimation is largely
ignored. In response, this paper proposes a novel framework that integrates
Eulerian and Lagrangian observations for trajectory reconstruction. The
approach introduces a calibration algorithm for time-varying shockwave speed.
The calibrated shockwave speed of the CV is then utilized for trajectory
reconstruction of other non-connected vehicles based on shockwave theory.
Additionaly, vehicle and driver dynamics are introduced to optimize the
trajectory and estimate energy consumption. The proposed method is evaluated
using real-world datasets, demonstrating superior performance in terms of
trajectory accuracy, reproducing traffic oscillations, and estimating energy
consumption
Time-to-Green predictions for fully-actuated signal control systems with supervised learning
Recently, efforts have been made to standardize signal phase and timing
(SPaT) messages. These messages contain signal phase timings of all signalized
intersection approaches. This information can thus be used for efficient motion
planning, resulting in more homogeneous traffic flows and uniform speed
profiles. Despite efforts to provide robust predictions for semi-actuated
signal control systems, predicting signal phase timings for fully-actuated
controls remains challenging. This paper proposes a time series prediction
framework using aggregated traffic signal and loop detector data. We utilize
state-of-the-art machine learning models to predict future signal phases'
duration. The performance of a Linear Regression (LR), a Random Forest (RF),
and a Long-Short-Term-Memory (LSTM) neural network are assessed against a naive
baseline model. Results based on an empirical data set from a fully-actuated
signal control system in Zurich, Switzerland, show that machine learning models
outperform conventional prediction methods. Furthermore, tree-based decision
models such as the RF perform best with an accuracy that meets requirements for
practical applications
Antifragile Perimeter Control: Anticipating and Gaining from Disruptions with Reinforcement Learning
The optimal operation of transportation networks is often susceptible to
unexpected disruptions, such as traffic incidents and social events. Many
established control strategies rely on mathematical models that struggle to
cope with real-world uncertainties, leading to a significant decline in
effectiveness when faced with substantial disruptions. While previous research
works have dedicated efforts to improving the robustness or resilience of
transportation systems against disruptions, this paper applies the cutting-edge
concept of antifragility to better design a traffic control strategy for urban
road networks. Antifragility sets itself apart from robustness and resilience
as it represents a system's ability to not only withstand stressors, shocks,
and volatility but also thrive and enhance performance in the presence of such
adversarial events. Hence, modern transportation systems call for solutions
that are antifragile. In this work, we propose a model-free deep Reinforcement
Learning (RL) scheme to control a two-region urban traffic perimeter network.
The system exploits the learning capability of RL under disruptions to achieve
antifragility. By monitoring the change rate and curvature of the traffic state
with the RL framework, the proposed algorithm anticipates imminent disruptions.
An additional term is also integrated into the RL algorithm as redundancy to
improve the performance under disruption scenarios. When compared to a
state-of-the-art model predictive control approach and a state-of-the-art RL
algorithm, our proposed method demonstrates two antifragility-related
properties: (a) gradual performance improvement under disruptions of constant
magnitude; and (b) increasingly superior performance under growing disruptions.Comment: 32 pages, 13 figure
A rolling-horizon quadratic-programming approach to the signal control problem in large-scale congested urban road networks
The paper investigates the efficiency of a recently developed signal control methodology, which offers a computationally feasible technique for real-time network-wide signal control in large-scale urban traffic networks and is applicable also under congested traffic conditions. In this methodology, the traffic flow process is modeled by use of the store-and-forward modeling paradigm, and the problem of network-wide signal control (including all constraints) is formulated as a quadratic-programming problem that aims at minimizing and balancing the link queues so as to minimize the risk of queue spillback. For the application of the proposed methodology in real time, the corresponding optimization algorithm is embedded in a rolling-horizon (model-predictive) control scheme. The control strategy’s efficiency and real-time feasibility is demonstrated and compared with the Linear-Quadratic approach taken by the signal control strategy TUC (Traffic-responsive Urban Control) as well as with optimized fixed-control settings via their simulation-based application to the road network of the city centre of Chania, Greece, under a number of different demand scenarios. The comparative evaluation is based on various criteria and tools including the recently proposed fundamental diagram for urban network traffic
Harmonizing and improving European education in prescribing: An overview of digital educational resources used in clinical pharmacology and therapeutics
Aim: Improvement and harmonization of European clinical pharmacology and therapeutics (CPT) education is urgently required. Because digital educational resources can be easily shared, adapted to local situations and re-used widely across a variety of educational systems, they may be ideally suited for this purpose. Methods: With a cross-sectional survey among principal CPT teachers in 279 out of 304 European medical schools, an overview and classification of digital resources was compiled. Results: Teachers from 95 (34%) medical schools in 26 of 28 EU countries responded, 66 (70%) of whom used digital educational resources in their CPT curriculum. A total of 89 of such resources were described in detail, including e-learning (24%), simulators to teach pharmacokinetics and/or pharmacodynamics (10%), virtual patients (8%), and serious games (5%). Together, these resources covered 235 knowledge-based learning objectives, 88 skills, and 13 attitudes. Only one third (27) of the resources were in-part or totally free and only two were licensed open educational resources (free to use, distribute and adapt). A narrative overview of the largest, free and most novel resources is given. Conclusion: Digital educational resources, ranging from e-learning to virtual patients and games, are widely used for CPT education in EU medical schools. Learning objectives are based largely on knowledge rather than skills or attitudes. This may be improved by including more real-life clinical case scenarios. Moreover, the majority of resources are neither free nor open. Therefore, with a view to harmonizing international CPT education, more needs to be learned about why CPT teachers are not currently sharing their educational materials
EurOP2E – the European Open Platform for Prescribing Education, a consensus study among clinical pharmacology and therapeutics teachers
Purpose
Sharing and developing digital educational resources and open educational resources has been proposed as a way to harmonize and improve clinical pharmacology and therapeutics (CPT) education in European medical schools. Previous research, however, has shown that there are barriers to the adoption and implementation of open educational resources. The aim of this study was to determine perceived opportunities and barriers to the use and creation of open educational resources among European CPT teachers and possible solutions for these barriers.
Methods
CPT teachers of British and EU medical schools completed an online survey. Opportunities and challenges were identified by thematic analyses and subsequently discussed in an international consensus meeting.
Results
Data from 99 CPT teachers from 95 medical schools were analysed. Thirty teachers (30.3%) shared or collaboratively produced digital educational resources. All teachers foresaw opportunities in the more active use of open educational resources, including improving the quality of their teaching. The challenges reported were language barriers, local differences, lack of time, technological issues, difficulties with quality management, and copyright restrictions. Practical solutions for these challenges were discussed and include a peer review system, clear indexing, and use of copyright licenses that permit adaptation of resources.
Conclusion
Key challenges to making greater use of CPT open educational resources are a limited applicability of such resources due to language and local differences and quality concerns. These challenges may be resolved by relatively simple measures, such as allowing adaptation and translation of resources and a peer review system
Key Learning Outcomes for Clinical Pharmacology and Therapeutics Education in Europe: A Modified Delphi Study.
Harmonizing clinical pharmacology and therapeutics (CPT) education in Europe is necessary to ensure that the prescribing competency of future doctors is of a uniform high standard. As there are currently no uniform requirements, our aim was to achieve consensus on key learning outcomes for undergraduate CPT education in Europe. We used a modified Delphi method consisting of three questionnaire rounds and a panel meeting. A total of 129 experts from 27 European countries were asked to rate 307 learning outcomes. In all, 92 experts (71%) completed all three questionnaire rounds, and 33 experts (26%) attended the meeting. 232 learning outcomes from the original list, 15 newly suggested and 5 rephrased outcomes were included. These 252 learning outcomes should be included in undergraduate CPT curricula to ensure that European graduates are able to prescribe safely and effectively. We provide a blueprint of a European core curriculum describing when and how the learning outcomes might be acquired
Hierarchical control for large-scale urban road traffic networks
In the current work we focus on the development of hierarchical control structures to tackle the problem of signal control for large-scale urban networks. A recently developed perimeter control regulator, which integrates model-based optimal control and online data-driven learning/adaptation, is utilized for the upper-level layer. Another lower-level control layer utilizes the max-pressure regulator, which has been also proposed recently and constitutes a local feedback control law, applied in coupled intersections, in a distributed systems-of-systems (SoS) concept. Different approaches are discussed about the design of the hierarchical structure of SoS, i.e. mutual interactions between the two control layers, activation/deactivation of each layer, mutually related objectives of the regulators, online versus offline selection of critical intersection for the lower-level control layer. A hierarchical control approach that combines local and network level characteristics is expected to treat better uncertainties in demand and behavioural characteristics of drivers moving towards a more reliable performance of all users in the system
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