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Sökning: L773:0191 2615 OR L773:1879 2367 > (2020-2024)

  • Resultat 1-11 av 11
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1.
  • Čičić, Mladen, 1991-, et al. (författare)
  • Front-tracking transition system model for traffic state reconstruction, model learning, and control with application to stop-and-go wave dissipation
  • 2022
  • Ingår i: Transportation Research Part B. - : Elsevier BV. - 0191-2615 .- 1879-2367. ; 166, s. 212-236
  • Tidskriftsartikel (refereegranskat)abstract
    • Connected and Autonomous Vehicles is a technology that will be disruptive for all layers of traffic control. The Lagrangian, in-the-flow nature of their operation offers untapped new potentials for sensing and actuation, but also presents new fundamental challenges. In order to use these vehicles for traffic state reconstruction and control, we need suitable traffic models, which should be computationally efficient and able to represent complex traffic phenomena. To this end, we propose the Front-tracking Transition System Model, a cell-free modelling approach that can incorporate Lagrangian measurements, and has a structure that yields itself to on-line model learning and control. The model is formulated as a transition system, and based on the front-tracking method for finding entropy solutions to the Lighthill-Whitham-Richards model. We characterize the solution of this model and show that it corresponds to the solution of the underlying PDE traffic model. Algorithms for traffic state reconstruction and model learning are proposed, exploiting the model structure. The model is then used to design a prediction -based control law for stop-and-go wave dissipation using randomly arriving Connected and Autonomous Vehicles. The proposed control framework is able to estimate the traffic state and model, adapt to changes in the traffic dynamics, and achieve a reduction in vehicles' Total Time Spent.
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2.
  • Eliasson, Jonas, et al. (författare)
  • Costs and benefits of parking charges in residential areas
  • 2022
  • Ingår i: Transportation Research Part B. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0191-2615 .- 1879-2367. ; 166, s. 95-109
  • Tidskriftsartikel (refereegranskat)abstract
    • We develop a model for empirical evaluation of the social costs and benefits of street parking charges. From the model, we derive an expression for optimal parking charges and occupancy levels: in optimum, parking search costs are balanced against the loss of consumer surplus from unused parking spaces. Contrary to rules-of-thumb common in practice, optimal occupancy levels are not constant but depend on parking turnover rates and parking search costs. We demonstrate the model's applicability in a case study from Stockholm, where parking charges were recently introduced in suburban residential areas. The charges had considerable effects on parking de-mand, but our analysis shows that the overall welfare effect was a substantial welfare loss. Using parameters and demand functions estimated from the case study, we calculate optimal parking charges and occupancy levels, and show that the welfare loss arises because the introduced charges were considerably higher than the optimal ones.
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3.
  • Engelson, Leonid, et al. (författare)
  • Scheduling preferences and the value of travel time information
  • 2020
  • Ingår i: Transportation Research Part B. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0191-2615 .- 1879-2367. ; 134, s. 256-265
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we derive the value of a signal obtained by a traveller prior to the choice of departure time. The signal does not have to be a perfect prediction of the travel time. It is sufficient that it carries information about the travel time. The traveller may then consider the distribution of travel time conditional on the signal to increase her expected utility by making a better informed choice of departure time. We show that a signal always increases the expected utility compared to the situation without any signal. For a broad class of signals, the expected utility is monotone with respect to signal strength. Furthermore, we demonstrate that even perfect travel time information does not necessarily eliminate the cost of travel time variability and we establish necessary and sufficient conditions for when it does. We find that the predictable part of travel time variability may or may not be costly, depending on the shape of the traveller's scheduling utility at the origin of the trip. Using estimates of scheduling preferences from the literature, we show that the cost of predictable travel time variability may constitute a substantial part of the total cost of travel time variability. In a particular case of scheduling preferences, travel time distribution and noise distribution, we establish an analytic relationship between the strength of the signal and the expected utility of the trip and evaluate the marginal cost of signal weakness. This knowledge may facilitate design and cost-benefit analysis of traveller information systems and policies decreasing travel time variability. (C) 2020 Elsevier Ltd. All rights reserved.
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4.
  • Moustaid, Elhabib, et al. (författare)
  • Macroscopic model of multidirectional pedestrian network flows
  • 2021
  • Ingår i: Transportation Research Part B. - : Pergamon-Elsevier Science Ltd. - 0191-2615 .- 1879-2367. ; 145
  • Tidskriftsartikel (refereegranskat)abstract
    • Pedestrian flow models are useful for the design and operation of pedestrian spaces. This article describes a macroscopic model of pedestrian flows through networks composed of bidirectional corridors that are connected by multidirectional intersections. The proposed model builds on an existing pedestrian bidirectional fundamental diagram to define bidirectional sending and receiving flows, and it relies on the incremental transfer principle to model bidirectional flows across nodes with an arbitrary number of adjacent links. The model is solved in a cell-transmission formulation that is in all of its unidirectional properties consistent with the kinematic wave model. (C) 2021 The Authors. Published by Elsevier Ltd.
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5.
  • Basso, Rafael, 1979, et al. (författare)
  • Electric Vehicle Routing Problem with Machine Learning for Energy Prediction
  • 2021
  • Ingår i: Transportation Research Part B: Methodological. - : Elsevier BV. - 0191-2615. ; 145, s. 24-55
  • Tidskriftsartikel (refereegranskat)abstract
    • Routing electric commercial vehicles requires taking into account their limited driving range, which is affected by several uncertain factors such as traffic conditions. This paper presents the time-dependent Electric Vehicle Routing Problem with Chance- Constraints (EVRP-CC) and partial recharging. The routing method is divided into two stages, where the first finds the best paths and the second optimizes the routes. A probabilistic Bayesian machine learning approach is proposed for predicting the expected energy consumption and variance for the road links, paths and routes. Hence it is possible to consider the uncertainty in energy demand by planning charging within a confidence interval. The energy estimation is validated with data from electric buses driving a public transport route in Gothenburg-Sweden as well as with realistic simulations for 24 hours traffic in the city of Luxembourg connected to a high fidelity vehicle model. Routing solutions are compared with a deterministic formulation of the problem similar to the ones found in the literature. The results indicate high accuracy for the energy prediction as well as energy savings and more reliability for the routes.
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6.
  • Como, Giacomo, et al. (författare)
  • On the well-posedness of deterministic queuing networks with feedback control
  • 2021
  • Ingår i: Transportation Research. Part B: Methodological. - : Elsevier BV. - 0191-2615. ; 150, s. 323-335
  • Tidskriftsartikel (refereegranskat)abstract
    • We study the well-posedness of a class of dynamical flow network systems describing the dynamical mass balance among a finite number of cells exchanging flow of traffic between themselves and with the external environment. Dynamical systems in the considered class are described as differential inclusions whereby the routing matrix is constant and the outflow from each cell in the network is limited by a control that is a Lipschitz continuous function of the state of the network. This framework finds application in particular within traffic signal control, whereby it is common that an empty queue can be allowed to have more outflow than vehicles in the queue. While models for this scenario have previously been presented for open-loop outflow controls, our result ensures the existence and uniqueness of solutions for the network flow dynamics in the case Lipschitz continuous feedback controllers.
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7.
  • Cui, Shaohua, 1995, et al. (författare)
  • Delay-throughput tradeoffs for signalized networks with finite queue capacity
  • 2024
  • Ingår i: Transportation Research Part B: Methodological. - 0191-2615. ; 180
  • Tidskriftsartikel (refereegranskat)abstract
    • Network-level adaptive signal control is an effective way to reduce delay and increase network throughput. However, in the face of asymmetric exogenous demand, the increase of network performance via adaptive signal control alone is at the expense of service fairness (i.e., phase actuation fairness and network resource utilization fairness). In addition, for oversaturated networks, arbitrary adaptive signal control seems to have little effect on improving network performance. Therefore, under the assumption that the mean routing proportions/turn ratios of vehicles at intersections are fixed, this study investigates the problem of optimally allocating input rates to entry links and simultaneously finding a stabilizing signal control policy with phase fairness. We model the stochastic optimization problem of maximizing network throughput subject to network stability (i.e., all queue lengths have finite means) and average phase actuation constraints to bridge the gap between stochastic network stability control and convex optimization. Moreover, we further propose a micro-level joint admission and bounded signal control algorithm to achieve network stability and throughput optimization simultaneously. Joint control is implemented in a fully decomposed and distributed manner. For any arrival rate, joint control provably achieves network throughput within O(1/V) of optimality while trading off average delay with O(V), where V is an adjusted control parameter. Through a comparative simulation of a real network with 256 O-D pairs, the proposed joint control keeps network throughput at maximum, guarantees service fairness, and fully utilizes network capacity (i.e., increases network throughput by 17.54%).
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8.
  • Pereira, Mike, 1992, et al. (författare)
  • Parameter and density estimation from real-world traffic data: A kinetic compartmental approach
  • 2022
  • Ingår i: Transportation Research Part B: Methodological. - : Elsevier BV. - 0191-2615. ; 155, s. 210-239
  • Tidskriftsartikel (refereegranskat)abstract
    • The main motivation of this work is to assess the validity of a LWR traffic flow model to model measurements obtained from trajectory data, and propose extensions of this model to improve it. A formulation for a discrete dynamical system is proposed aiming at reproducing the evolution in time of the density of vehicles along a road, as observed in the measurements. This system is formulated as a chemical reaction network where road cells are interpreted as compartments, the transfer of vehicles from one cell to the other is seen as a chemical reaction between adjacent compartment and the density of vehicles is seen as a concentration of reactant. Several degrees of flexibility on the parameters of this system, which basically consist of the reaction rates between the compartments, can be considered: a constant value or a function depending on time and/or space. Density measurements coming from trajectory data are then interpreted as observations of the states of this system at consecutive times. Optimal reaction rates for the system are then obtained by minimizing the discrepancy between the output of the system and the state measurements. This approach was tested both on simulated and real data, proved successful in recreating the complexity of traffic flows despite the assumptions on the flux-density relation.
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9.
  • Varga, Balázs, et al. (författare)
  • Public transport trajectory planning with probabilistic guarantees
  • 2020
  • Ingår i: Transportation Research Part B: Methodological. - : Elsevier BV. - 0191-2615. ; 139, s. 81-101
  • Tidskriftsartikel (refereegranskat)abstract
    • The paper proposes an eco-cruise control strategy for urban public transport buses. The aim of the velocity control is ensuring timetable adherence, while considering upstream queue lengths at traffic lights in a probabilistic way. The contribution of the paper is twofold. First, the shockwave profile model (SPM) is extended to capture the stochastic nature of traffic queue lengths. The model is adequate to describe frequent traffic state interruptions at signalized intersections. Based on the distribution function of stochastic traffic volume demand, the randomness in queue length, wave fronts, and vehicle numbers are derived. Then, an outlook is provided on its applicability as a full-scale urban traffic network model. Second, a shrinking horizon model predictive controller (MPC) is proposed for ensuring timetable reliability. The intention is to calculate optimal velocity commands based on the current position and desired arrival time of the bus while considering upcoming delays due to red signals and eventual queues. The above proposed stochastic traffic model is incorporated in a rolling horizon optimization via chance-constraining. In the optimization, probabilistic guarantees are formulated to minimize delay due to standstill in queues at signalized intersections. Optimization results are analyzed from two particular aspects, (i) feasibility and (ii) closed-loop performance point of views. The novel stochastic profile model is tested in a high fidelity traffic simulator context. Comparative simulation results show the viability and importance of stochastic bounds in urban trajectory design. The proposed algorithm yields smoother bus trajectories at an urban corridor, suggesting energy savings compared to benchmark control strategies.
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10.
  • Wang, Tingsong, et al. (författare)
  • A two-stage stochastic nonlinear integer-programming model for slot allocation of a liner container shipping service
  • 2021
  • Ingår i: Transportation Research Part B: Methodological. - : Elsevier BV. - 0191-2615. ; 150, s. 143-160
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, we propose a container slot allocation problem for a liner shipping service. A liner containership provides a regular shipping service with a fixed itinerary and schedule. In practice, the liner containership may not be fully loaded, which results in a loss of revenue. We therefore segment shippers into two classes: contract shippers and spot shippers. A contract shipper has a contract with the shipping company and negotiates a fixed minimum quantity, so that the shipping company can secure a steady revenue. The remaining containership slots are open to spot shippers, allowing the shipping company to obtain ad hoc revenue. The container slot allocation problem is investigated in this study using a two-stage stochastic mixed-integer nonlinear programming model. We use the sample average approximation based on Lagrangian relaxation and dual decomposition techniques to effectively solve the model. Finally, we conduct a case study to evaluate the applicability and effectiveness of the proposed model and the solution algorithm.
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11.
  • Wu, Jiaming, 1989, et al. (författare)
  • Emergency vehicle lane pre-clearing: From microscopic cooperation to routing decision making
  • 2020
  • Ingår i: Transportation Research Part B: Methodological. - : Elsevier BV. - 0191-2615. ; 141, s. 223-239
  • Tidskriftsartikel (refereegranskat)abstract
    • Emergency vehicles (EVs) play a crucial role in providing timely help for the general public in saving lives and avoiding property loss. However, very few efforts have been made for EV prioritization on normal road segments, such as the road section between intersections or highways between ramps. In this paper, we propose an EV lane pre-clearing strategy to prioritize EVs on such roads through cooperative driving with surrounding connected vehicles (CVs). The cooperative driving problem is formulated as a mixed-integer nonlinear programming (MINP) problem aiming at (i) guaranteeing the desired speed of EVs, and (ii) minimizing the disturbances on CVs. To tackle this NP-hard MINP problem, we formulate the model in a bi-level optimization manner to address these two objectives, respectively. In the lower-level problem, CVs in front of the emergency vehicle will be divided into several blocks. For each block, we developed an EV sorting algorithm to design optimal merging trajectories for CVs. With resultant sorting trajectories, a constrained optimization problem is solved in the upper-level to determine the initiation time/distance to conduct the sorting trajectories. Case studies show that with the proposed algorithm, emergency vehicles are able to drive at a desired speed while minimizing disturbances on normal traffic flows. We further reveal a linear relationship between the optimal solution and road density, which could help to improve EV routing decision makings when high-resolution data is not available.
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