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Using Connected Vehicles in Variable Speed Limit Systems:: System Design and Effects
Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.ORCID iD: 0000-0001-5531-0274
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Motorway traffic management systems are useful for improving the traffic conditions on urban motorways. One of the most common motorway traffic management systems are variable speed limit systems. These systems adapt the speed limits based on the prevailing traffic conditions measured by roadside detectors and recommended or compulsory speed limits are shown on variable message signs installed on gantries over the road.Thesystems consist of three parts; the control algorithm used to determine which speed limit to be displayed, a method for estimating the traffic conditions to be used as input for the control algorithm and the infrastructure for application of the variable speed limits. The goal of the systems is often to increase safety or efficiency.

Recent development in the field of connected vehicles have opened up for a new type of data source, as the status of a connected vehicle and its surroundings can be communicated at arbitrary locations. Hence, by the use of connected vehicles in variable speed limit systems there is a potential of reducing the amount of roadside equipment. It is even possible to control the connected vehicles towards the current speed limit without the use of variable message signs. This allows for the application of variable speed limits at arbitrary locations.

The aim of this thesis is to examine how connected vehicles can be used to improve the efficiency of variable speed limit systems. The thesis contribute with new and improved methods using connected vehicles in all three parts of a variable speed limit system. The suggested methods are evaluated by microscopic traffic simulation. The overall conclusion is that the use of connected vehicles in variable speed limit systems can contribute to improvements in traffic efficiency compared to existing systems.

The six papers included in the thesis can be summarized as follows. First, it is shown that traditional variable speed limit systems can be effective for improving the traffic conditions on the motorway and the results can be comparable to more costly alterations by reconstruction of the infrastructure to increase the capacity. Next, the usefulness of connected vehicles for application and control of the speed limits in an existing variable speed limit system is investigated. It is concluded that the design of the control algorithm and the accuracy of the estimated traffic conditions have a great effect on the final outcome of the system. The design of the control algorithm is then examined by evaluation of a number of control algorithms with respect to safety, efficiency and environmental impacts. The main benefits and drawbacks of the algorithms are highlighted and desirable characteristics to include when designing a control algorithm are identified. In two studies, methods making use of connected vehicles for estimating the traffic conditions are proposed. The results show that connected vehicles are useful for improving the accuracy of the estimated traffic conditions through the inclusion of more detailed information and information at locations where detector measurements are not available. Finally, a variable speed limit system is proposed in which connected vehicles play a central role in the estimation of the traffic conditions, as well as in the control algorithm and for application of the speed limit. The system is shown to be useful for improving traffic efficiency during an incident at an arbitrary location along the controlled road.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2018. , p. 80
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1919
National Category
Transport Systems and Logistics
Identifiers
URN: urn:nbn:se:liu:diva-147049DOI: 10.3384/diss.diva-147049ISBN: 9789176853412 (print)OAI: oai:DiVA.org:liu-147049DiVA, id: diva2:1196452
Public defence
2018-04-20, K3, Campus Norrköping, Norrköping, 13:15 (English)
Opponent
Supervisors
Available from: 2018-04-10 Created: 2018-04-10 Last updated: 2019-09-30Bibliographically approved
List of papers
1. Analysis of a cooperative variable speed limitsystem using microscopic traffic simulation
Open this publication in new window or tab >>Analysis of a cooperative variable speed limitsystem using microscopic traffic simulation
2015 (English)In: Transportation Research Part C: Emerging Technologies, ISSN 0968-090X, E-ISSN 1879-2359, Vol. 52, p. 173-186Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Elsevier, 2015
Keywords
Cooperative systems;Intelligent transport systems;Infrastructure to vehicle communication;Variable speed limit;Microscopic traffic simulation; Emission model
National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:liu:diva-115013 (URN)10.1016/j.trc.2014.11.004 (DOI)000352252400012 ()
Available from: 2015-03-06 Created: 2015-03-06 Last updated: 2018-04-10
2. Traffic State Estimation Using Connected Vehicles and Stationary Detectors
Open this publication in new window or tab >>Traffic State Estimation Using Connected Vehicles and Stationary Detectors
2018 (English)In: Journal of Advanced Transportation, ISSN 0197-6729, E-ISSN 2042-3195, article id UNSP 4106086Article in journal (Refereed) Published
Abstract [en]

Real-time traffic state estimation is of importance for efficient traffic management. This is especially the case for traffic management systems that require fast detection of changes in the traffic conditions in order to apply an effective control measure. In this paper, we propose a method for estimating the traffic state and speed and density, by using connected vehicles combined with stationary detectors. The aim is to allow fast and accurate estimation of changes in the traffic conditions. The proposed method does only require information about the speed and the position of connected vehicles and can make use of sparsely located stationary detectors to limit the dependence on the infrastructure equipment. An evaluation of the proposed method is carried out by microscopic traffic simulation. The traffic state estimated using the proposed method is compared to the true simulated traffic state. Further, the density estimates are compared to density estimates from one detector-based method, one combined method, and one connected-vehicle-based method. The results of the study show that the proposed method is a promising alternative for estimating the traffic state in traffic management applications.

Place, publisher, year, edition, pages
WILEY-HINDAWI, 2018
National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:liu:diva-144890 (URN)10.1155/2018/4106086 (DOI)000423031600001 ()
Note

Funding Agencies|Swedish Transportation Administration (Trafikverket)

Available from: 2018-02-09 Created: 2018-02-09 Last updated: 2018-04-10

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Using Connected Vehicles in Variable Speed Limit Systems:: System Design and E‚ects(662 kB)354 downloads
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Grumert, Ellen F.

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