| 1. |
- Chi, Pengnan, et al.
(författare)
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Difforecast : Image Generation Based Highway Traffic Forecasting with Diffusion Model
- 2023
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Ingår i: Proceedings - 2023 IEEE International Conference on Big Data, BigData 2023. - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 608-615
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Konferensbidrag (refereegranskat)abstract
- Monitoring and forecasting of road traffic conditions is a common practice for real traffic information system, and is of vital importance to traffic management and control. While dynamic traffic patterns can be intuitively represented by space-time diagrams, this study proposes a new concept of space-time image (ST-image) to incorporate physical meanings of traffic state variables. We therefore transform the forecasting problem for time-series traffic states into a conditional image generation problem. We explore the inherent properties of the ST images from the perspectives of physical meaning and traffic dynamics. An innovative deep learning based architecture is designed to process the ST-image, and a diffusion model is trained to obtain traffic forecasts by generating the future ST-images based on the historical patterns.
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| 2. |
- Chi, Pengnan, et al.
(författare)
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Short-Term Traffic Prediction on Swedish Highways: A Deep Learning Approach with Knowledge Representation
- 2023
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Konferensbidrag (refereegranskat)abstract
- Accurate prediction of highway traffic is of vital importance to proactive traffic monitoring, operation and controls. In the data mining of highway traffic, abstracting temporal knowledge is often prioritized than exploring topological relationship. In this study, we propose a deep learning model, called Knowledge-Sequence-to-Sequence (K-Seq2Seq), to solve the short-term highway traffic prediction problem in two stages: representing temporal knowledge and predicting future traffic. Through computational experiment in a road section of a Swedish motorway, we show that our model outperforms the conventional Seq2Seq model significantly, more than 20% when predicting information of longer time step.
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| 3. |
- Deng, Qichen, et al.
(författare)
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A fast algorithm for planning optimal platoon speeds on highway
- 2014
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Ingår i: Elsevier IFAC Publications / IFAC Proceedings series. - : IFAC Papers Online. - 1474-6670. - 9783902823625 ; 19, s. 8073-8078
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Tidskriftsartikel (refereegranskat)abstract
- To meet policy requirements on increased transport energy efficiency and reduced emissions, smart control and management of vehicles and fleets have become important for the development of eco-friendly intelligent transportation systems (ITS). The emergence of new information and communication technologies and their applications, particularly vehicle-to-vehicle and vehicle-to-infrastructure communication, facilitates the implementation of autonomous vehicle concepts, and meanwhile serves as an effective means for control of vehicle fleet by continuously providing support and guidance to drivers. While convoy driving of trucks by longitudinal automation could save 5-15% of fuel consumption due to the reduction of airdrag resistance, this study attempts to investigate the energy saving potential of truck platoons by intelligent speed planning. Assuming that real-time traffic information is available because of communication, an efficient speed control algorithm is proposed based on optimal control theory. The method is faster than the conventional dynamic programming approach and hence applied in the study to analyze energy saving potential of simple platoon operations including acceleration and deceleration. The numerical result shows significant improvement on energy saving due to speed planning during platooning. It can be further applied for more complex platooning operations.
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| 4. |
- Eilers, S., et al.
(författare)
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COMPANION-Towards Co-operative Platoon Management of Heavy-Duty Vehicles
- 2015
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Ingår i: IEEE Conference on Intelligent Transportation Systems, Proceedings, ITSC. - : IEEE. - 9781467365956 ; , s. 1267-1273
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Konferensbidrag (refereegranskat)abstract
- The objective of the EU project COMPANION is to develop co-operative mobility technologies for supervised vehicle platooning, in order to improve fuel efficiency and safety for goods transport. The potential social and environmental benefits inducted by heavy-duty vehicle platoons have been largely proven. However, until now, the creation, coordination, and operation of such platoons have been mostly neglected. In addition, the regulation and standardization of coordinated platooning, together with its acceptance by the end-users and the society need further attention and research. In this paper we give an overview over the project and present the architecture of the off-board and onboard platforms of the COMPANION cooperative platoon management system. Furthermore, the consortium reports on the first results of the human factors for platooning, legislative analysis of platooning aspects, clustering and optimization of platooning plans and prediction of congestion due to planned special events. Finally, we present the method of validation of the system via simulation and trials.
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| 5. |
- Grumert, Ellen, 1983-, et al.
(författare)
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Analysis of a cooperative variable speed limit system using microscopic traffic simulation
- 2015
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Ingår i: Transportation Research Part C. - : Elsevier. - 0968-090X .- 1879-2359. ; 52, s. 173-186
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Tidskriftsartikel (refereegranskat)abstract
- Variable speed limit systems where variable message signs are used to show speed limits adjusted to the prevailing road or traffic conditions are installed on motorways in many countries. The objectives of variable speed limit system installations are often to decrease the number of accidents and to increase traffic efficiency. Currently, there is an interest in exploring the potential of cooperative intelligent transport systems including communication between vehicles and/or vehicles and the infrastructure. In this paper, we study the potential benefits of introducing infrastructure to vehicle communication, autonomous vehicle control and individualized speed limits in variable speed limit systems. We do this by proposing a cooperative variable speed limit system as an extension of an existing variable speed limit system. In the proposed system, communication between the infrastructure and the vehicles is used to transmit variable speed limits to upstream vehicles before the variable message signs become visible to the drivers. The system is evaluated by the means of microscopic traffic simulation. Traffic efficiency and environmental effects are considered in the analysis. The results of the study show benefits of the infrastructure to vehicle communication, autonomous vehicle control and individualized speed limits for variable speed limit systems in the form of lower acceleration rates and thereby harmonized traffic flow and reduced exhaust emissions.
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| 6. |
- Grumert, Ellen, 1983-, et al.
(författare)
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Characteristics of variable speed limit systems
- 2018
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Ingår i: European Transport Research Review. - : SPRINGER HEIDELBERG. - 1867-0717 .- 1866-8887. ; 10:2
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Tidskriftsartikel (refereegranskat)abstract
- The control algorithm used for deciding on the speed limit in variable speed limit systems is crucial for the performance of the systems. The algorithm is designed to fulfil the purpose of the variable speed limit system, which can be one or several of the following aspects: increasing safety, increasing efficiency and decreasing environmental impacts. Today, many of the control algorithms used in practice are based on fixed thresholds in speed and/or flow. Therefore, they are not necessarily reflecting the current traffic conditions. Control algorithms with a greater level of complexity can be found in the literature. In this paper, four existing control algorithms are investigated to conclude on important characteristics affecting the performance of the variable speed limit system. The purpose of the variable speed limit system and, consequently, the design of the control algorithm differ. Requirements of the investigated control algorithms are that they should be easy to interpret and the execution time should be short. The algorithms are evaluated through microscopic traffic simulation. Performance indicators related to traffic safety, traffic efficiency and environmental impacts are presented. The results show that the characteristics of the variable speed limit system and the design of the control algorithm will have effect on the resulting traffic performance, given that the drivers comply with the variable speed limits. Moreover, the time needed to trigger the system, the duration and the size of speed limit reductions, and the location of the congestion are factors of importance for the performance of variable speed limit systems.
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| 7. |
- Grumert, Ellen, 1983-, et al.
(författare)
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Effects of a Cooperative Variable Speed Limit System on Traffic Performance and Exhaust Emissions
- 2013
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Ingår i: TRB 92nd Annual Meeting Compendium of Papers.
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Konferensbidrag (refereegranskat)abstract
- Variable Speed Limit Systems (VSLS) where variable message signs show speed limits based on traffic or road conditions exist on motorways in many countries. The purpose of the VSLS is to decrease the number of accidents while increasing efficiency of traffic system. Cooperative systems are a type of intelligent transport system that has received increasing interest lately. The central part of a cooperative system is communication between vehicles and/or vehicles and the infrastructure. In this paper, a cooperative systems extension of a VSLS is proposed and evaluated by means of microscopic traffic simulation. In the proposed cooperative VSLS, communication between the vehicles and the infrastructure is made available via a roadside unit communicating the speed limits to vehicles upstream on the road. Both aggregate and micro-scale emission models are used to estimate emission from vehicle states in traffic flow. The results of the study show that the cooperative VSLS has a potential to contribute to flow harmonization and to reduce environmental impacts. The emission estimates in the study are dependent on the emission models being applied.
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| 8. |
- Grumert, Ellen, 1983-, et al.
(författare)
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Evaluation of Four Control Algorithms Used in Variable Speed Limit Systems
- 2016
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Ingår i: TRB 95th Annual Meeting Compendium of Papers. - Washington : Transportation Research Board.
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Konferensbidrag (refereegranskat)abstract
- Control algorithms used for deciding on the speed limits in variable speed limit systems are crucial for the performance of the system. Today, many of the control algorithms used are based on fixed thresholds in speed and/or flow for lowering and increasing the speed limit. The algorithms are not necessarily reflecting the conditions on the road, which might lead to low traffic efficiency. Our hypothesis is that by use of a simple and efficient control algorithm that is better in reflecting the conditions on the road, both traffic efficiency and traffic safety could be increased. In this study, four control algorithms used in variable speed limit systems, and fulfilling the above criteria, are evealuted through microscopic traffic simulation. Performance indicators related to traffic safety, traffic efficiency and environmental impacts are presented. The results show that the design of, and the objective with, the control algorithm have a great impact on the performance. Moreover, the time needed for incident detection, the duration of and the size of the speed limit reduction and the location of the congestion are of importance for the performance of the control algorithms. These results will be of importance for design and implementation of future efficient variable speed limit systems.
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| 9. |
- Guan, Wei, et al.
(författare)
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Advanced Dynamic Simulations in Transportation
- 2015
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Ingår i: Discrete dynamics in nature and society. - : Hindawi Publishing Corporation. - 1026-0226 .- 1607-887X. ; 2015
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Tidskriftsartikel (refereegranskat)
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| 10. |
- Hong, Beichuan, 1989-, et al.
(författare)
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Modeling of dynamic NOx emission for nonroad machinery : a study on wheel loader using engine test data and on-board measurement
- 2016
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Konferensbidrag (refereegranskat)abstract
- Quantification of nonroad machinery emissions is of high importance for improving heavy construction processes especially concerning environmental sustainability. In comparison to the substantial research effort on modeling dynamic emissions for road transport, there is, however, lack of knowledge on how to quantify dynamic emissions during construction operations. This paper proposes an approach to model dynamic NOx emission for nonroad construction machinery using recent experimental data collected by a wheel loader operated in the Chinese environment. In the experiment, emissions were measured during different operational cycles for wheel loader and the data is used for both model calibration and validation. Starting from an initial emission map built from in-lab engine bench test, the model prediction of dynamic NOx emission is calibrated by three real-time engine performance parameters highly correlated to the NOx generation. Considering the characteristics of the nonroad equipment, a dynamic module is added to represent engine state transition due to frequent switching of an operational mode in construction activities, making the whole model more accurate in predicting instantaneous emission levels. Compared to the validation data randomly selected from three different cycle tests, the model shows good performance concerning prediction accuracy and with the capacity of handling drastic changes of the working condition of the machine. While the study focuses on the engine-out NOx emission the resulting methodology can be generalized for emission modeling of other nonroad construction machines.
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