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  • 1.
    Allström, Andreas
    et al.
    Linköpings universitet.
    Barceló, Jaume
    Universitat Politècnica de Catalunya.
    Ekström, Joakim
    Linköpings universitet.
    Grumert, Ellen
    Linköpings universitet.
    Gundlegård, David
    Linköpings universitet.
    Rydergren, Clas
    Linköpings universitet.
    Traffic management for smart cities2016In: Designing, developing, and facilitating smart cities: urban design to IoT solutions / [ed] Vangelis Angelakis, Elias Tragos, Henrich C. Pöhls, Adam Kapovits and Alessandro Bassi, Switzerland: Springer, 2016, p. 211-240Chapter in book (Other academic)
    Abstract [en]

    Smart cities, participatory sensing as well as location data available in communication systems and social networks generates a vast amount of heterogeneous mobility data that can be used for traffic management. This chapter gives an overview of the different data sources and their characteristics and describes a framework for utilizing the various sources efficiently in the context of traffic management. Furthermore, different types of traffic models and algorithms are related to both the different data sources as well as some key functionalities of active traffic management, for example short-term prediction and control.

  • 2.
    Grumert, Ellen
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Cooperative systems: an overview2011Report (Other academic)
    Abstract [en]

    The objective of this report is to give an introduction to the subject of cooperative systems and an overview of projects related to cooperative systems. Issues related to cooperative systems are also discussed in the report. Two areas of great importance for cooperative systems are the standardization process of cooperative systems in Europe and the communication frequency used for cooperative systems. These two subjects are therefore discussed in more detail in the report. The objective of this report is to give an introduction to the subject of cooperative systems and an overview of projects related to cooperative systems. Issues related to cooperative systems are also discussed in the report. Two areas of great importance for cooperative systems are the standardization process of cooperative systems in Europe and the communication frequency used for cooperative systems. These two subjects are therefore discussed in more detail in the report.

    The report has been focusing on cooperative systems, which is a part of the wider concept Intelligent Transport Systems (ITS). The 'traditional' Intelligent Transport Systems use technology, inside or outside of the vehicle, to give the driver some kind of information. The driver gets the opportunity to act upon the given information. Along with the increased amount of new technology the use of information and communication in the transport area has increased. Today cooperative systems are well-known in the transport area. The idea is to extend the more traditional Intelligent Transport Systems and build systems that are able to communicate with each other. These systems could be located inside the vehicle or as a road-side unit outside of the vehicle. The benefit with cooperative systems is the ability to send and receive real-time information and to use this information in order to increase safety, efficiency and environmental impacts on the roads.

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  • 3.
    Grumert, Ellen
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics. Linköpings universitet, Kommunikations- och transportsystem.
    Cooperative Variable Speed Limit Systems: Modeling and Evaluation using Microscopic Traffic Simulation2014Licentiate thesis, monograph (Other academic)
    Abstract [en]

    During the last decades the road traffic has increased tremendously leading to congestion, safety issues and increased environmental impacts. As a result, many countries are continuously trying to find improvements and new solutions to solve these issues. One way of improving the traffic conditions is by the use of so called intelligent transport systems, where information and communication technologies are being used for traffic management and control. One such system commonly used for traffic management purposes are variable speed limit systems. These systems are making use of signs to show speed limits adjusted to the prevailing road or traffic conditions. The rapid development in telecommunication technologies has enabled communication between vehicles, and between vehicles and the infrastructure, so called cooperative systems. This opens up for  the possibility to further improve the performance of a standard variable speed limit system by adding cooperative system features.

    The overall aim of this thesis is to investigate the potential benefits of incorporating infrastructure to vehicle communication and autonomous control to an existing variable speed limit system. We show how such a cooperative variable speed limit system can be modeled and evaluated by the use of microscopic traffic simulation. Results from the evaluation indicate increased flow harmonization in terms of narrowing of the acceleration rate distribution and reduced exhaust emissions.

    Further, we compare four control algorithms for deciding on speed limits in variable speed limit systems. Differences in the resulting traffic performance between the control algorithms are quantified by the use of microscopic traffic simulation. It is concluded that the dened objective for the algorithms have a decisive influence on the effects of the variable speed limit system.

    The results from this thesis are useful for further development of variable speed limit systems, both with respect to incorporating cooperative features and by improving the speed setting control algorithms.

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  • 4.
    Grumert, Ellen
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics. Linköping University.
    Evaluation of Four Control Algorithms Used in Variable Speed Limit Systems2016In: TRB 95th Annual Meeting Compendium of Papers, Washington, 2016, article id 16-2880Conference paper (Refereed)
    Abstract [en]

    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.

  • 5.
    Grumert, Ellen
    et al.
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Bernhardsson, Viktor
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Ekström, Joakim
    Linköpings universitet.
    Tvingande variabla hastighetsstyrningssystem: design utifrån föreskrifter och empiriska studier2021Report (Other academic)
    Abstract [en]

    The Swedish Transport Administration is continuously improving the existing motorway control system in major Swedish cities. During 2018–2020, work is underway to increase flexibility regarding the choice of variable speed limit in the existing motorway control system, by allowing site-specific control strategies that are dependent on infrastructure and the traffic situation at the site. The control strategy should be able to be written as a traffic regulation to enable mandatory speed limits (red ring), instead of the commonly used recommended speed limits. 

    This study contributes to the work of Swedish Transport Administration by providing research and evidence-based support for how such control strategy should be designed. Previous studies on the effects of variable speed limits are, together with output from workshops and internal discussions with various units at the Swedish Transport Administration, used to ensure that the control strategy should comply with the Swedish traffic regulation and at the same time show benefits in terms of traffic efficiency.

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  • 6.
    Grumert, Ellen
    et al.
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Bernhardsson, Viktor
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Ekström, Joakim
    Linköpings universitet.
    Gundlegård, David
    Linköpings universitet.
    Ringdahl, Rasmus
    Linköpings universitet.
    Tapani, Andreas
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Variabla hastighetsgränser för Stockholms motorvägsnät: effekter av alternativa algoritmer och möjligheter till styrning genom estimerade trafiktillstånd2019Report (Other academic)
    Abstract [en]

    Variable speed limits are commonly used on Stockholm’s urban motorways, and it is part of the Stockholm Motorway Control System (MCS). The goal of today’s system is to reduce the risk of accidents during congested conditions, traffic jams etc. This is done by updating the speed limits shown on variable message signs based on a measured average speed at fixed detectors. As the demand for travel in Stockholm during peak-hours exceeds the available capacity in the road network, the need for an efficient traffic system is high. Variable speed limit systems have the possibility to contribute to increased efficiency, but since today’s system aims to increase safety, effects that lead to increased efficiency are limited. Further, in todays’ variable speed limit systems there are a large dependency of precise and available measurements from stationary detectors to be able to display speed limits that reflects the current traffic conditions. The purpose of this report is to investigate alternative control algorithms to decide on the variable speed limits to be displayed at variable message signs on the urban motorway of Stockholm.

    The goal is to increase efficiency compared to today's system. Two different road stretches with different complexity and different traffic conditions, resulting in two different types of congestion, are studied. Thereby, the studied control algorithms on the two road stretches are chosen based on the possibility of solving a specific problematic traffic situation in the best way. Hence, the studied control algorithms might differ for the two road stretches. Furthermore, for one of the roads stretches it is investigated if estimation of the traffic state can be used as input to the control algorithm as a complement to missing and erogenous measurements from stationary detectors in order to improve the calculations of the variable speed limits. The control algorithms are evaluated with microscopic traffic simulation and the method developed in the project Mobile Millenium Stockholm (MMS), using a macroscopic traffic flow model together with a Kalman filter, is used for estimation of the traffic state.

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  • 7.
    Grumert, Ellen
    et al.
    Swedish National Road and Transport Research Institute, Traffic and road users, Traffic Safety and Traffic System. Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Bernhardsson, Viktor
    Trafikverket.
    Gundlegård, David
    Linköpings universitet.
    Förslag på metodik för systematisk utvärdering av ITS i motorvägsmiljö: en sensorbaserad ansats2023Report (Other academic)
    Abstract [en]

    This report is one of two reports that describe the results from the project Evaluation of improved motorway control – a case study. The aim of the project is to develop a methodology for evaluation of before-after studies for ITS measures in a motorway environment and to apply the methodology to a use case on the E4 at Södertälje to evaluate the applicability of the method as well as effects on traffic efficiency, safety and the environment. When the goal is to study changes due to ITS measures on road sections with densely located sensors, there are good opportunities for evaluations by making use of data before and after the implementation of the ITS measure. Currently, such comprehensive studies with availability of data from densely located sensors are rare, and hence, knowledge about how such before and after studies should be designed to make fair comparisons are uncommon. 

    The purpose of this report is to propose a methodology for evaluation of the impacts on traffic efficiency, traffic safety and the environment data when closely located sensors are available. The report proposes justifiable methods to be able to make fair comparisons of the before and after situation. An important aspect is to identify days with similar traffic conditions in the before and after periods to avoid comparing days with different traffic situations, and thus, in practice non-comparable days when evaluating the effects of the ITS measure. Another report presents the results from the evaluation on the use case at Södertälje. 

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  • 8.
    Grumert, Ellen
    et al.
    Swedish National Road and Transport Research Institute, Traffic and road users, Traffic Safety and Traffic System. Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Bernhardsson, Viktor
    Trafikverket.
    Gundlegård, David
    Linköpings universitet.
    Utvärdering av styrning med variabla hastighetsgränser med fokus på framkomlighet: en fallstudie på E4 vid Södertälje2023Report (Other academic)
    Abstract [en]

    This report is one of two reports that describe the results from the project Evaluation of improved motorway control – a case study (funded by the Swedish Transport Administration through Center for Traffic Research). The aim of the project is to develop a methodology for evaluation of before-after studies for ITS measures in a motorway environment and to apply the methodology to a use case on the E4 at Södertälje to evaluate the applicability of the method as well as effects on traffic efficiency, safety and the environment. When the goal is to study changes due to ITS measures on road sections with densely located sensors, there are good opportunities for evaluations by making use of data before and after the implementation of the ITS measure. Currently, such comprehensive studies with availability of data from densely located sensors are rare, and hence, knowledge about how such before and after studies should be designed to make fair comparisons are uncommon. 

    The purpose of this report is to apply the methodology that has been developed in the project and evaluate effects on traffic efficiency, traffic safety and the environment through a case study at Södertälje. On the study area, a new control strategy for choosing variable speed limits has been implemented. Densely located sensors were installed at 150–300 meters also before the new control strategy was in place. Thereby there are good opportunities to measure the traffic conditions at the study area, which is giving a unique opportunity to compare traffic conditions before and after the control strategy is implemented. The results from the evaluation does, in addition to assessing the applicability of the methodology, contribute to knowledge about how before-after studies should be designed, as well as evaluation of variable speed limits impact on the traffic situation when the goal is to improve traffic conditions in the event of accessibility problems.

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  • 9.
    Grumert, Ellen
    et al.
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Bernhardsson, Viktor
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Strömgren, Per
    Movea.
    Gundlegård, David
    Linköpings universitet.
    Olstam, Johan
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Ekström, Joakim
    Linköpings universitet.
    Ringdahl, Rasmus
    Linköpings universitet.
    Effects of incidents on motorways: a proposed methodology for estimating and predicting demand, duration and capacity for incident management2021Report (Other academic)
    Abstract [en]

    Effective traffic incident management is important to minimize negative impacts of congestion caused by incidents. Predictions of the traffic state at the incident site and its surrounding road network, together with an estimate of incident duration, can be used to get increased knowledge about current and future incident characteristics. 

    The aim is to propose methods for estimating capacity, duration and demand profiles in case of an incident, and to explore how the level of detail and the possibility to identify explanatory variables for incidents with similar characteristics given currently available data sources affects the proposed methods. The knowledge obtained within the project is intended to be used for incident management. 

    The report presents a methodology for predicting capacity, traffic demand, and incident duration, when none of the parameters are known. The proposed methods can be used as input to traffic models, when the purpose is to perform scenario-based analysis and real-time predictions to be used in the decision-making processes for traffic management/control, but also for predicting travel times which can be communicated to road users.

    A motorway use-case study area south of Stockholm is used to propose methods for predicting incident duration, capacity and demand profiles based on the availability of data. The methodology is evaluated by using the predicted variables as input in a scenario-based analysis with two queue models.

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  • 10.
    Grumert, Ellen
    et al.
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics. Linköping University.
    Gundlegard, David
    Linköping University.
    Clustering breakdown observations of speed-flow relations for capacity estimation2020In: Transportation Research Procedia, Amsterdam: Elsevier B.V. , 2020, Vol. 52, p. 637-644Conference paper (Refereed)
    Abstract [en]

    Capacity estimation at bottleneck locations along urban motorways are of importance for traffic management purposes. If the capacity is known, bottlenecks with observed low capacity can be identified and improvements, such as active control strategies or infrastructure modifications, can be initiated to reduce the number of breakdowns. In this paper, we propose a methodology for estimating the capacity distribution for clusters with similar speed-flow relations before a breakdown for large data sets. Explanatory variables are identified to show that the proposed methodology can be used to categorize each cluster based on the bottleneck characteristics. The methodology consist of the following steps: (1) an automated process to identify breakdowns, (2) a clustering method to cluster breakdown days and locations with similar capacity levels, and (3) a statistical approach for estimating the capacity distribution for each cluster. Further, we illustrate how the proposed methodology can be used to identify bottleneck characteristics with the greatest impact on the capacity level by using one year of empirical observations of speed and flow from an urban motorway stretch south of Stockholm in Sweden. The results show that the proposed methodology has potential to identify bottlenecks with frequently observed low capacity and to find bottleneck characteristics with a large impact on breakdown capacity. © 2020 The Authors. Published by ELSEVIER B.V.

  • 11.
    Grumert, Ellen
    et al.
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics. Linköpings universitet, Kommunikations- och transportsystem.
    Ma, Xiaoliang
    Kungliga tekniska högskolan (KTH).
    Tapani, Andreas
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics. Linköpings universitet.
    Analysis of a cooperative variable speed limit system using microscopic traffic simulation2015In: Transportation Research Part C: Emerging Technologies, ISSN 0968-090X, E-ISSN 1879-2359, Vol. 52, p. 173-186Article in journal (Refereed)
    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.

  • 12.
    Grumert, Ellen
    et al.
    Swedish National Road and Transport Research Institute, Traffic and road users, Traffic Safety and Traffic System.
    Nusia, Jiota
    Swedish National Road and Transport Research Institute, Traffic and road users, Traffic Safety and Traffic System.
    Measures to prevent and reduce the impact of collisions involving wildlife: Potential of advanced driver assistance systems and ITSs in infrastructure2023Report (Other academic)
    Abstract [en]

    Despite measures to reduce the number of wildlife-vehicle collisions (WVCs) in Sweden, the trend is pointing in the wrong direction. The number of WVCs has increased by 37% between 2010 and 2021. Besides the fluctuating numbers of wildlife, the increase in the number of WVCs on Swedish roads is due to an increase in traffic, as well as high speeds on the parts of the road network where wildlife is common. More than half of WVCs occur on roads used by 4,000 or more vehicles per day and with speed limits above 80 km/h. For wild boar, fallow deer and red deer, increased distribution in Sweden and growing populations are also contributing to the increase in WVCs.

    Speed is a crucial factor in the occurrence of WVCs and their effects. Detection of wildlife, advanced driver support systems in vehicles and infrastructural Intelligent Transport System (ITS) measures such as warnings indicating wild animals and variable speed limits at strategically riskful locations are important enablers to reduce the number of WVCs. Research and technology development regarding the design of roadside areas, animal behaviour and ecology, and so forth, is therefore necessary.

    The purpose of this prestudy is to identify both existing and new driver support systems and systems in infrastructure that can help to prevent or reduce the impact of WVCs on parts of the road network where the proportion of WVCs per road user is high and where physical measures cannot be justified. Knowledge from authorities, industry and the academic community has been gathered with a view to identifying opportunities for solutions that could reduce the number of WVCs.

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  • 13.
    Grumert, Ellen
    et al.
    Swedish National Road and Transport Research Institute, Traffic and road users, Traffic Safety and Traffic System.
    Nygårdhs, Sara
    Swedish National Road and Transport Research Institute, Traffic and road users, The Human in the Transport system..
    Trafiksäkerhet vid vägarbete: läsavstånd och efterlevnad av skylten Körfält upphör med lysande VMS i jämförelse med reflexfolie2024In: Sammanställning av referat från Transportforum 2024 / [ed] Fredrik Hellman; Mattias Haraldsson, Linköping: Statens väg- och transportforskningsinstitut , 2024, p. 270-271Conference paper (Other academic)
    Abstract [sv]

    Vägmärken används i stor utsträckning vid vägarbeten som en förberedande upplysning för att öka uppmärksamheten och förhindra uppkomsten av olyckor. Lysande Variabla Meddelande Skyltar (VMS) som visar olika vägmärken blir allt vanligare vid vägarbeten. Vid användning av lysande VMS är det viktigt att man uppnår en likvärdig läsbarhet som med reflexfolie för att säkerställa att läsbarheten, beteendet som resultat av skyltningen och därmed potentiellt trafiksäkerheten, inte minskar vid vägarbeten. Storleken på VMS:en begränsar vilka mått ett vägmärke kan ha och vilken textstorlek det kan vara på dess tilläggstavla. De krav som ställs idag på reflexfolie är att storleken stor (1,5 x 1,2 meter) används vid arbete på väg. Dessa krav gäller även för lysande VMS, men det skulle kunna vara så att måtten kan minskas och fortfarande uppfylla kraven på läsbarhet. Det saknas idag kunskap och underlag för att kunna avgöra huruvida så är fallet. Ett vanligt förekommande vägmärke vid arbete på väg är F25 - Körfält upphör. I det här projektet undersöker vi vilka mått ett lysande vägmärke som visar F25 (Körfält upphör) behöver ha för att ha minst samma läsbarhet som ett vägmärke utfört med reflexfolie i storlek stor. 

    För att utvärdera vilka faktorer som påverkar läsbarheten av lysande VMS har en mindre litteraturstudie genomförts. Därefter genomfördes en kontrollerad läsbarhetsstudie med 12 försökspersoner. Försökspersonerna närmade sig en lysande VMS skylt i fordon där utförandet varierades. Den kontrollerade läsbarhetsstudien utfördes med svart symbol på orange bakgrund då det är den utformning som är vanligast idag i Sverige vid vägarbeten. Även reflexfolie av storleken stor visades för att kunna fastställa vid vilket avstånd läsbarheten av VMS:er med olika storlekar är likvärdiga med reflexfolie. En verifieringsstudie genomfördes sedan på en motortrafikled med ett befintligt vägarbete för att studera om den lysande VMS med jämförbart utförande som reflexfolie påverkade beteendet hos förarna/fordonen vid skyltningen.

    Preliminära resultat från den kontrollerade studien visar att storleken på lysande VMS kan minskas med samma läsbarhet som reflexfolie i mörker. Analys av verifieringsstudien pågår och förväntar ytterligare kunna bidra till ökad kunskap om ifall andra storlekar kan användas för lysande VMS och fortfarande ge likvärdigt beteende i vägarbetsmiljö för vägmärket körfält upphör.

  • 14.
    Grumert, Ellen
    et al.
    Swedish National Road and Transport Research Institute, Traffic and road users, Traffic Safety and Traffic System.
    Olstam, Johan
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics. Linköping University.
    An Automated Process for Identification of Bottlenecks in the Traffic System Using Large Data Sets2023In: Journal of transportation engineering Part A - Systems, ISSN 2473-2907, Vol. 149, no 3, article id 04022156Article in journal (Refereed)
    Abstract [en]

    Traffic breakdowns are frequently observed phenomena on roads in larger cities, especially during peak hours. Locations along a road stretch with frequently observed breakdowns are known as recurrent bottlenecks. Knowledge about bottleneck locations are important for improvement of traffic conditions at these locations. Bottleneck locations can be identified through manual inspection of data. However, due to the comprehensive amount of data that are available today, it becomes impractical to manually identify breakdowns and instead, an automated process can be used. We propose such an automated method. The proposed method is applied to a use case south of Stockholm in Sweden. One month of data collected at densely spaced detectors is used to investigate the sensitivity of the parameter settings. After calibration of the threshold values, 100% of the larger breakdowns and 40% of the medium size breakdowns are identified. Smaller breakdowns, not giving significant impact on the traffic conditions, are only detected in 10%-20% of the cases. Thereafter, the method is applied to 1 year of data to illustrate the applicability of the method on a larger data set. The results show that the method is promising to use for identification of recurrent bottleneck locations.

  • 15.
    Grumert, Ellen
    et al.
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Pereira, Iman
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics. VTI.
    Connected vehicles in traffic signals: effects in Swedish traffic signal conditions2021Report (Other academic)
    Abstract [en]

    Connected vehicles can be used in two ways in traffic signal control: (1) as a complement to, or for removing of, stationary detectors and to give more detailed information about position, speed, etc. of individual vehicles with the goal to optimize the traffic signal control strategy or (2) to receive information about the traffic signal status for optimization of the connected vehicles movements when traversing the intersection or for optimization of the traffic system. In Sweden, a traffic actuated control strategy is commonly used, where the traffic signal status is adjusted based on detection of individual vehicles. It is today unclear if connected vehicles can be used in the current Swedish traffic signal control settings or if the control strategy must be adapted to better take advantage of connected vehicle information.

    The purpose with this report is to investigate how, and if, connected vehicles can be incorporated in the current Swedish traffic signals when the goal is to improve the traffic performance in the intersection. The report presents results from the review of existing systems and in field tested connected traffic signals together with results from a workshop with experts in the field of Swedish traffic signals.

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  • 16.
    Grumert, Ellen
    et al.
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Pereira, Iman
    Region Östergotland, Sweden.
    Heads-Up Green in Connected Traffic Signals2022In: IEEE transactions on intelligent transportation systems (Print), ISSN 1524-9050, E-ISSN 1558-0016, p. 1-12Article in journal (Refereed)
    Abstract [en]

    Information-sharing between traffic signals and connected vehicles can enhance the traffic conditions in signalized intersections. We propose a straightforward application, heads-up green, with the aim to inform queuing connected vehicles about a switch from red to green. In this way, the drivers' reaction time is expected to be reduced and the number of vehicles that can pass the intersection during a cycle is thereby increased. Unlike the applications Green Light Optimal Speed Advisory (GLOSA), time-to-green and time-to-red, there is no need for predictions of future traffic signal states. Therefore, heads-up green can be used in traffic actuated and adaptive control strategies in signalized intersections without loss in precision. A simulation-based evaluation of a typical Swedish intersection with a traffic actuated controller is performed to evaluate the traffic performance. The main goal as been to show on the potential to use heads-up green to increase traffic efficiency in signalized intersections. Additionally, different reaction times to the information from heads-up green has been investigated. The results show that with heads-up green it is possible to improve the travel time by up to 15% at high demand levels when queues are frequently observed. The improvements are largest with 100% connected vehicles, but significant improvements of 5-15% are observed also for lower shares of connected vehicles. At high demand levels, travel times are decreased already at small reductions in the reaction time. Hence, there is a potential to improve traffic efficiency already when small changes in reaction time can be achieved with heads-up green.

  • 17.
    Grumert, Ellen
    et al.
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Tapani, Andreas
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Bottleneck mitigation through a variable speed limit system using connected vehicles2020In: Transportmetrica A: Transport Science, ISSN 2324-9935, E-ISSN 2324-9943, Vol. 16, no 2, p. 213-233Article in journal (Refereed)
    Abstract [en]

    Variable speed limit (VSL) systems are used to improve the traffic conditions by adjusting the speed limits based on the current traffic situation. Advances in vehicle technology have made it possible to use connected vehicles in VSL systems. Connected vehicles can continuously transmit information about their speed and location, which can be used to estimate the current traffic conditions at arbitrary locations. In this study, we propose a VSL system based on connected vehicles. The aim is to also allow application of VSLs for non-recurrent bottleneck mitigation at arbitrary locations, unlike today's systems which require densely placed detectors or are limited to beforehand known bottleneck locations. The proposed system is evaluated by microscopic traffic simulation. The results indicate that the VSL system manage to improve traffic efficiency in a simulated incident scenario.

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  • 18.
    Grumert, Ellen
    et al.
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Tapani, Andreas
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Impacts of a Cooperative Variable Speed Limit System2012In: Procedia - Social and Behavioral Sciences, ISSN 1877-0428, E-ISSN 1877-0428, Vol. 43, p. 595-606Article in journal (Refereed)
    Abstract [en]

    Variable Speed Limit Systems (VSLS) where variable message signs show speed limits based on, for example,traffic volume or road conditions exists on motorwaysin many countries. The purpose of the VSLS is to decrease the number of accidents and to increase traffic efficiency. 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 traffic simulation. By adding cooperative systems functionality to an existing VSLS there is a potential for further increase in traffic efficiency and also to reduce the environmental impacts of the traffic on the road. 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. The results of the study show that the cooperative VSLS has a potential to contribute to flow harmonization and to reduce environmental impacts.

  • 19.
    Grumert, Ellen
    et al.
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Tapani, Andreas
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics. Linköpings universitet, Kommunikations- och transportsystem.
    Microscopic traffic simulation for evaluation of a cooperative variable speed limit system2013In: 1st SUMO User Conference 2013. Proceedings, Berichte aus dem DLR-Institut für Verkehrssystemtechnik, Band 21, Berlin: Deutsches Zentrum für Luft- und Raumfahrt e.V. Institut für Verkehrssystemtechnik, Berlin-Adlershof , 2013, p. 147-164Conference paper (Refereed)
    Abstract [en]

    Variable Speed Limit Systems (VSLS) where gantries are showing speed limits based on, for example, traffic volume or other road or traffic conditions exists on motorways in many countries. The aim of the VSLS is usually to improve traffic efficiency. Lately, cooperative intelligent transport systems allowing for communication between vehicles and/or vehicles and the infrastructure has received increasing interest. A cooperative VSLS, utilizing communication between vehicles and the infrastructure, could possibly result in further improved traffic efficiency and decreased exhaust emissions and fuel consumption. In this paper, a cooperative VSLS is evaluated by the use of a microscopic traffic simulator. The cooperative VSLS is described together with a discussion on how the modeling of the cooperative VSLS and the assumptions made regarding vehicles behavior will impact the final results of the evaluation. Results from the simulations are presented with in terms of traffic efficiency and exhaust emissions.

  • 20.
    Grumert, Ellen
    et al.
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Tapani, Andreas
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Traffic State Estimation Using Connected Vehicles and Stationary Detectors2018In: Journal of Advanced Transportation, ISSN 0197-6729, E-ISSN 2042-3195, article id UNSP 4106086Article in journal (Refereed)
    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.

  • 21.
    Grumert, Ellen
    et al.
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Tapani, Andreas
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Using connected vehicles in a variable speed limit system2017In: Transportation Research Procedia, Elsevier B.V. , 2017, p. 85-92Conference paper (Refereed)
    Abstract [en]

    Variable speed limit systems are used to improve the traffic conditions on specific road stretches. This is done by adjusting the speed limits according to current traffic situations. A variable speed limit system usually consist of stationary detectors to estimate the traffic state and variable message signs at predefined locations for the application of new speed limits. Advances in vehicle technology have made it possible to use connected vehicles to improve existing variable speed limit systems. Connected vehicles can continuously transmit information about speed and location. This can be used to get more detailed information about the traffic state. By including information from connected vehicles in a variable speed limit system there is a potential to identify bottlenecks also in between stationary detectors. Further, it is possible to use direct control of the connected vehicles to adjust vehicle speeds towards the new traffic situation. In this study, we propose such a variable speed limit system based on connected vehicles. The aim is to allow for application of variable speed limits in connection with non-recurrent bottlenecks. The proposed system is evaluated with respect to traffic efficiency using microscopic traffic simulation. An incident is simulated as an example of a non-recurrent bottleneck. The traffic performance when the proposed VSL system is applied is compared to the performance without the system. The results indicate that the VSL system manage to improve traffic efficiency in a majority of the simulated cases.

  • 22.
    Grumert, Ellen
    et al.
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Tapani, Andreas
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Ma, Xiaoliang
    KTH.
    Characteristics of variable speed limit systems2018In: European Transport Research Review, ISSN 1867-0717, E-ISSN 1866-8887, Vol. 10, no 2, article id 21Article in journal (Refereed)
    Abstract [en]

    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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  • 23.
    Grumert, Ellen
    et al.
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics. Linköpings universitet, Kommunikations- och transportsystem.
    Tapani, Andreas
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics. Linköpings universitet, Kommunikations- och transportsystem.
    Ma, Xiaoliang
    Kungliga Tekniska Högskolan (KTH), Stockholm.
    Effects of a Cooperative Variable Speed Limit System on Traffic Performance and Exhaust Emissions2013In: TRB 92nd Annual Meeting Compendium of Papers, 2013Conference paper (Refereed)
    Abstract [en]

    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.

  • 24.
    Gundlegård, David
    et al.
    Department of Science and Technology, Linköping University, Norrköping, Sweden.
    Grumert, Ellen
    Swedish National Road and Transport Research Institute, Traffic and road users, Traffic Safety and Traffic System.
    Clustering in Before-After Studies of ITS Measures2024In: 2023 IEEE 26th International Conference on Intelligent Transportation Systems (ITSC), IEEE, 2024, p. 2671-2676Conference paper (Other academic)
    Abstract [en]

    Intelligent Transport System (ITS) measures are becoming more and more common on urban motorways. Different methods can be used to evaluate the effectiveness of the ITS measure, for example traffic simulation, cost-benefit analysis and before-after studies. A fundamental part of a before-after study is the choice of days for comparison of the before and after periods. Many previous before-after studies of ITS measures are based on simple methods for choosing comparable days, similar to the benchmark method used in this paper. For the chosen case study, a modified Variable Speed Limit (VSL) control strategy, we have used clustering to 1) quickly find similar days for evaluation, 2) identify type days with different characteristics and 3) identify deviating days that are non-representative for the before-after study. From the case study, it is clear that the choice of the days for evaluation are important and can generate different inference, and the clustering method provides promising results compared to the benchmark.

  • 25.
    Gustafsson, Susanne
    et al.
    Swedish National Road and Transport Research Institute, Traffic and road users, Traffic safety, society and road-user.
    Jägerbrand, Annika
    Swedish National Road and Transport Research Institute, Society, environment and transport, Environment.
    Grumert, Ellen
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Hastighetsdämpande åtgärder: en litteraturstudie med fokus på nya trafikmiljöåtgärder och ITS-orienterade lösningar2011Report (Other academic)
    Abstract [en]

    A literature survey has been conducted regarding international traffic calming measures that could have a potential use in Sweden and other Nordic countries. Focus has been on measures in new traffic environments and ITS (Intelligent Transport System) based solutions. Information has been obtained through searches in literature databases and on different homepages, as well as from contacts in networks. Initially, we describe common traffic calming measures used today in Swedish traffic environments. For example, different forms of vertical and horizontal measures, and different types of surfaces, road markings and paintings. In the case of existing ITS solutions, we mention speed reminder signs, variable message signs and Motorway Control System (MCS).

    New kinds of physical measures that have most potential for use are e.g. modifications of speed bumps and the construction of small curves that enforce lower speed. Such curvatures can be used at entrances to communities or before roundabouts.

    Different concepts of "shared space" (e.g. walking speed zones) are something that could be used more extensively, even at intersections and other locations in urban areas. In such cases, all traditional road equipment is removed and a synergy between different user groups is created, leading to lower speeds.

    Different types of road markings and paintings can be used to visually narrow the road, but also in order to create an optical illusion that makes one feel as if the speed is high. However, such measures are not fully effective during winter conditions. Applications in 3D can also be used to create the illusion of obstacles in the roadway and result in reduced speeds. It is important to consider the overall picture and to combine various measures in a correct way. This report gives some examples on how to implement speed reduction measures in communities with thoroughfares. Furthermore, we give example on how strategic approaches and policy design may help to efficiently implement different kinds of traffic calming measures.

    ITS-solutions, where a two-way communication between vehicles and between vehicles and the infrastructure is used, have gained momentum in Europe and internationally. Three possible systems that have not yet been introduced on the market are described. Most of the cooperative systems are still in a research and development phase. The potential of the systems is considered to be large, and this is also reflected in the extensive research and development investments in the area. Furthermore, ITS as a whole, i.e. cooperative systems as well as other ITS solutions is believed to have a great potential.

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  • 26.
    Leo, Christoph
    et al.
    Vehicle Safety Institute, Graz University of Technology, Austria.
    Fredriksson, Anders
    Volvo Car Corporation, Torslanda HABVS-VAK, Sweden.
    Grumert, Ellen
    Swedish National Road and Transport Research Institute, Traffic and road users, Traffic Safety and Traffic System.
    Linder, Astrid
    Swedish National Road and Transport Research Institute, Traffic and road users, Traffic Safety and Traffic System. Mechanics and Maritime Science, Chalmers University, Sweden.
    Schachner, Martin
    Vehicle Safety Institute, Graz University of Technology, Austria.
    Tidborg, Fredrik
    Volvo Car Corporation, Torslanda HABVS-VAK, Sweden.
    Klug, Corina
    Vehicle Safety Institute, Graz University of Technology, Austria.
    Holistic pedestrian safety assessment for average males and females2023In: Frontiers In Public Health, ISSN 2296-2565, Vol. 11, article id 1199949Article in journal (Refereed)
    Abstract [en]

    Objective: An integrated assessment framework that enables holistic safety evaluations addressing vulnerable road users (VRU) is introduced and applied in the current study. The developed method enables consideration of both active and passive safety measures and distributions of real-world crash scenario parameters.

    Methods: The likelihood of a specific virtual testing scenario occurring in real life has been derived from accident databases scaled to European level. Based on pre-crash simulations, it is determined how likely it is that scenarios could be avoided by a specific Autonomous Emergency Braking (AEB) system. For the unavoidable cases, probabilities for specific collision scenarios are determined, and the injury risk for these is determined, subsequently, from in-crash simulations with the VIVA+ Human Body Models combined with the created metamodel for an average male and female model. The integrated assessment framework was applied for the holistic assessment of car-related pedestrian protection using a generic car model to assess the safety benefits of a generic AEB system combined with current passive safety structures.

    Results: In total, 61,914 virtual testing scenarios have been derived from the different car-pedestrian cases based on real-world crash scenario parameters. Considering the occurrence probability of the virtual testing scenarios, by implementing an AEB, a total crash risk reduction of 81.70% was achieved based on pre-crash simulations. It was shown that 50 in-crash simulations per load case are sufficient to create a metamodel for injury prediction. For the in-crash simulations with the generic vehicle, it was also shown that the injury risk can be reduced by implementing an AEB, as compared to the baseline scenarios. Moreover, as seen in the unavoidable cases, the injury risk for the average male and female is the same for brain injuries and femoral shaft fractures. The average male has a higher risk of skull fractures and fractures of more than three ribs compared to the average female. The average female has a higher risk of proximal femoral fractures than the average male.

    Conclusions: A novel methodology was developed which allows for movement away from the exclusive use of standard-load case assessments, thus helping to bridge the gap between active and passive safety evaluations.

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