| 1. |
- Amekudzi, A., et al.
(författare)
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Assessing extrajurisdictional and areawide impacts of clustered brownfield developments
- 2003
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Ingår i: Journal of urban planning and development. - 0733-9488 .- 1943-5444. ; 129:1, s. 27-44
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Tidskriftsartikel (refereegranskat)abstract
- Brownfields are vacant, underutilized, or abandoned industrial and commercial sites where real or perceived environmental contamination is an obstacle to development. Federal initiatives in the 1990s reduced legal liabilities associated with brownfields and provided financial incentives for development initiatives. As brownfields are often located in infill areas, they have advantages over greenfields developments in that much of the supporting infrastructure already exists and they are centrally located. However, the existing infrastructure may be deteriorated and obsolete, and brownfield developments in infill areas may require local as well as areawide transportation improvements. This paper uses a modified impact analysis approach, synthesized from regional transportation modeling and site impact analysis tools, to assess the extrajurisdictional and areawide impacts of clustered brownfield developments. The writers apply this approach to clustered brownfield developments in the City of Pittsburgh. The study results show that the synergistic effects and areawide impacts of clustered brownfield developments may not be adequately captured by traditional site impact studies. This paper is potentially useful for municipal agencies involved in assessing and planning for the transportation improvement needs of clustered brownfield developments.
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| 2. |
- Antoniou, C., et al.
(författare)
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Dynamic data-driven local traffic state estimation and prediction
- 2013
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Ingår i: Transportation Research Part C. - : Elsevier BV. - 0968-090X .- 1879-2359. ; 34, s. 89-107
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Tidskriftsartikel (refereegranskat)abstract
- Traffic state prediction is a key problem with considerable implications in modern traffic management. Traffic flow theory has provided significant resources, including models based on traffic flow fundamentals that reflect the underlying phenomena, as well as promote their understanding. They also provide the basis for many traffic simulation models. Speed-density relationships, for example, are routinely used in mesoscopic models. In this paper, an approach for local traffic state estimation and prediction is presented, which exploits available (traffic and other) information and uses data-driven computational approaches. An advantage of the method is its flexibility in incorporating additional explanatory variables. It is also believed that the method is more appropriate for use in the context of mesoscopic traffic simulation models, in place of the traditional speed-density relationships. While these general methods and tools are pre-existing, their application into the specific problem and their integration into the proposed framework for the prediction of traffic state is new. The methodology is illustrated using two freeway data sets from Irvine, CA, and Tel Aviv, Israel. As the proposed models are shown to outperform current state-of-the-art models, they could be valuable when integrated into existing traffic estimation and prediction models.
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| 3. |
- Burghout, Wilco, et al.
(författare)
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Hybrid Traffic Simulation Models : Vehicle loading at meso-micro boundaries
- 2019
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Ingår i: Transport Simulation. - : CRC Press. - 9781420095098 - 9781439808016 ; , s. 27-42
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Traffic simulation models, especially microscopic ones, are becoming increasingly popular and are being used to address a wide range of problems, from planning to operations. However, for applications with large-scale networks, microscopic models are impractical because of input data and calibration requirements. Hybrid models that combine simulation models at different levels of detail have the potential to address these practical issues. This chapter presents a framework for implementing meso-micro hybrid models which facilitates a consistent representation of traffic dynamics. Furthermore, the chapter carries out a detailed examination of an important element impacting the consistent representation of traffic dynamics, i.e., the loading of vehicles from the meso- to the micro-model. A new loading method is presented demonstrating a superior performance as compared to existing approaches. The method is useful not only in the context of hybrid models, but also for microscopic models on their own. A case study illustrates the importance of the method in improving the fidelity of both hybrid and pure microscopic models.
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| 4. |
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| 5. |
- Cats, Oded, et al.
(författare)
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Bus-Holding Control Strategies Simulation-Based Evaluation and Guidelines for Implementation
- 2012
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Ingår i: Transportation Research Record. - : National Academy of Sciences. - 0361-1981 .- 2169-4052. ; :2274, s. 100-108
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Tidskriftsartikel (refereegranskat)abstract
- Transit operations involve several inherent sources of uncertainty, including dispatch time from the origin terminal, travel time between stops, and dwell time at stops. Bus-holding control strategies are a prominent method applied by transit operators to improve transit performance and level of service. The common practice is to regulate departures from a limited number of stops by holding buses until their scheduled departure time. An analysis of the performance of a high-frequency bus line in Stockholm, Sweden, based on automatic vehicle location data showed that this control strategy was not effective in improving service regularity along the line. The analysis also indicated that drivers adjusted their speed according to performance objectives. Implications of a control strategy that regulates departures from all stops on the basis of the headways of the preceding bus and the following bus were evaluated with Bus Mezzo, a transit operations simulation model. The results suggest that this strategy can improve service performance considerably from both passengers' and operator's perspectives. In addition, the strategy implies cooperative operations, as the decisions of each driver are interdependent with other drivers' decisions, and mutual corrections can be made. Difficulties in realizing the benefits of the proposed strategy in practice, such as dispatching from the origin terminal, driver scheduling, and compliance, are discussed. The implications of several practical considerations are assessed by conducting a sensitivity analysis as part of the preparations for a field experiment designed to test the proposed control strategy.
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| 6. |
- Cats, Oded, et al.
(författare)
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Mesoscopic Modeling of Bus Public Transportation
- 2010
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Ingår i: Transportation Research Record. - : SAGE Publications. - 0361-1981 .- 2169-4052. ; :2188, s. 9-18
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Tidskriftsartikel (refereegranskat)abstract
- Analysis of public transport system performance and level of service in urban areas is essential. Dynamic modeling of traffic conditions, passenger demand, and transit operations is important to represent adequately the complexity of and the interactions between these components in modern public transportation systems. This paper presents a transit simulation model designed to support evaluation of operations planning and control, especially in the context of advanced public transportation systems. Unlike most previous efforts in this area, the simulation model is built on a platform of a mesoscopic traffic simulation model, which allows modeling or the operation dynamics of large-scale transit systems, taking into account the main sources of service uncertainty and stochasticity. The capabilities of Mezzo as an evaluation tool of transit operations are demonstrated with an application to a real-world, high-demand bus line in metropolitan Tel Aviv, Israel, under various scenarios. The application shows that important phenomena such as bus bunching are reproduced realistically. A comparison of simulated running times and headway distributions with field data shows the model is capable of replicating observed data.
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| 7. |
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| 8. |
- Cats, Oded, et al.
(författare)
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Optimizing the number and location of time point stops
- 2014
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Ingår i: Public Transport. - : Springer Science and Business Media LLC. - 1866-749X .- 1613-7159. ; 6:3, s. 215-235
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Tidskriftsartikel (refereegranskat)abstract
- Public transport service is subject to multiple sources of uncertainty that impact its reliability. Holding control strategies are a common method to prevent the deterioration of service reliability along the route. This paper expands on previous studies by considering the general case of determining both the optimal number and optimal location of the time point stops (TPS) where holding takes place, and assessing their impacts on transit performance using simulation. Holding times are determined based on a real-time headway-based holding strategy designed to improve service regularity by seeking uniform headways along the route. The evaluation of the performance of alternative TPS layouts is simulation-based, using BusMezzo, a transit operations simulation model which models the dynamic performance of bus transit systems. The proposed framework also considers the multiple objectives incorporating passenger and operator points of view. The simulation-based optimization framework was applied in a case study with one of the premium bus lines in Stockholm, Sweden, using two solution methods—greedy and genetic algorithms. A multi-objective evaluation was conducted considering both passenger and operator perspectives. The results demonstrate that transit performance varies considerably with alternative TPS layouts. The best solution obtained by the proposed methodology reduces total weighted passenger journey times and cycle times compared to both the current layout and the case of no holding control. The proposed method could assist transit agencies and operators in evaluating and recommending alternative time point layouts.
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| 9. |
- Fu, Jiali
(författare)
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Evaluating and Improving the Transport Efficiency of Logistics Operations
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The thesis focuses on evaluating and improving the transport efficiency of two types of logistics operations in the supply chain.One research area is the production of raw material in construction operations, specifically earthmoving operations. Methods and tools are developed to provide decision support in improving the transport efficiency of earthmoving at the vehicle and the systems levels. Using known road topography and a GPS unit, an optimal control problem is formulated and solved (Paper III) to determine the optimal gear shift sequence and timing in order to improve the transport efficiency at the vehicle level. For decision support at the systems level, a Fleet Performance Simulation (FPS) model is designed (Paper IV) to evaluate the transport efficiency for a given mix of construction vehicles in earthmoving. The FPS system is integrated with an optimization algorithm to solve the optimal fleet composition problem for earthmoving operations (Paper V & VI). Construction operations are dynamic and the environment is changing constantly, which bring difficulties in decision-making. Using GPS data from construction vehicles, a map inference framework (Papers I & II) is developed to automatically extract relevant input to decision support at the vehicle and the systems levels, which include the locations of various workstations, driving time distributions and road networks.The second research area is the transport efficiency of urban distribution system, which is in the final phase of the supply chain. An off-peak delivery pilot project in Stockholm is used as the background, designed to evaluate the potential for commercial vehicles to make use of off-peak hours for goods delivery. The thesis (Paper VII) evaluates the transport efficiency impacts of the off-peak pilot. An evaluation framework is defined where transport efficiency is studied in a number of dimensions. GPS data, fleet management data, and logistic information are used to assess the impacts.
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| 10. |
- Gordon, Jason B., et al.
(författare)
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Automated Inference of Linked Transit Journeys in London Using Fare-Transaction and Vehicle Location Data
- 2013
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Ingår i: Transportation Research Record. - : SAGE Publications. - 0361-1981 .- 2169-4052. ; :2343, s. 17-24
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Tidskriftsartikel (refereegranskat)abstract
- Urban public transit providers historically have planned and managed their networks and services with little knowledge of their customers' travel patterns. Although ticket gates and bus fareboxes yield counts of passenger activity in specific stations or vehicles, the relationships between these transactions-the origins, transfers, and destinations of individual passengers-typically have been acquired only through small, costly, and infrequent rider surveys. New methods for inferring the journeys of all riders on a large public transit network have been built on recent work into the use of automated fare collection and vehicle location systems for analysis of passenger behavior. Complete daily sets of data from London's Oyster farecard and the iBus vehicle location system were used to infer boarding and alighting times and locations for individual bus passengers and to infer transfers between passenger trips of various public modes, and origin-destination matrices of linked intermodal transit journeys that include the estimated flows of passengers not using farecards were constructed. The outputs were validated against surveys and traditional origin-destination matrices. The software implementation demonstrated that the procedure is efficient enough to be performed daily, allowing transit providers to observe travel behavior on all services at all times.
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| 11. |
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| 12. |
- Ma, Xiaoliang, et al.
(författare)
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A New Online Travel Time Estimation Approach using Distorted Automatic Vehicle Identification Data
- 2008
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Ingår i: PROCEEDINGS OF THE 11TH INTERNATIONAL IEEE CONFERENCE ON INTELLIGENT TRANSPORTATION SYSTEMS. - 9781424421114 ; , s. 204-209
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Konferensbidrag (refereegranskat)abstract
- Online travel time estimation is an important procedure for real-time traffic information systems (RTIS). In this paper, we describe a preliminary travel time data collection and estimation platform developed for RTIS application based on automated vehicle identification technique deployed in the Stockholm city area. The platform is composed of a client-side travel time analysis program and a database server. To obtain accurate real-time link travel times for traffic state prediction and RTIS applications, an optimal filtering algorithm is developed and evaluated using travel time data collected on urban streets in and near the city of Stockholm. The proposed algorithm shows reliable performance against the highly noisy traffic context, and is more robust than existing online travel time estimation algorithms. The estimated travel time information provides a solid basis for advanced traffic information system applications.
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| 13. |
- Ma, Xiaoliang, et al.
(författare)
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Estimation of the automatic vehicle identification based spatial travel time information collected in Stockholm
- 2010
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Ingår i: IET Intelligent Transport Systems. - : The IET: The Institution of Engineering and Technology. - 1751-956X .- 1751-9578. ; 4:4, s. 298-306
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Tidskriftsartikel (refereegranskat)abstract
- To support the implementation of real-time traffic information systems in the Stockholm city area using automatic vehicle identification (AVI) data, a preliminary travel time analysis tool has been developed. The program can manage and analyse travel time measurements in a distributed database server where both online and historical traffic information are saved. Meanwhile, several existing travel time estimation algorithms are implemented in the travel time analysis program, and are evaluated using four months of AVI data collected in the urban streets and arterials of and near the Stockholm downtown area. The advantages and disadvantages of those algorithms are also analysed using the highly noisy travel time measurements collected under the urban context. In addition, the authors have also evaluated a common statistical median filtering approach and suggested some modifications for AVI data estimation. In general, all these algorithms have the potential to be applied for real daily travel time estimation and the statistical median filter with modifications has been suggested for historical travel time estimation in real application. Finally, the authors point out an essential problem in travel time estimation and suggest a direction that may have the potential to improve the online traffic information quality.
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| 14. |
- Ma, Xiaoliang, et al.
(författare)
-
THE CAMERA BASED SPATIAL TRAVEL TIME INFORMATION : ANALYSIS PLATFORM AND ESTIMATION APPROACHES
- 2010
-
Ingår i: TRANSPORTATION AND URBAN SUSTAINABILITY. - HONG KONG : HONG KONG SOC TRANSPORTATION STUDIES LTD. ; , s. 585-592
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Konferensbidrag (refereegranskat)abstract
- To support the implementation of real-time traffic information systems in the Stockholm city area using automatic vehicle identification (AVI) cameras, a travel time analysis platform has been developed. The system is able of managing and analyzing travel time data stored in a distributed database server where information of camera stations, traffic and weather are integrated. Using Google Map API, users are able to analyze and visualize both online and historical travel time information in an intuitive way. Several existing travel time estimation algorithms are implemented in the system, and are evaluated using four months of AVI data collected in the urban streets and arterials of and near the Stockholm downtown area. The advantages and disadvantages of those algorithms are also analyzed using the highly noisy travel time measurements collected under the urban context. In general, all these algorithms have the potential to be applied for daily travel time estimation. Finally, we point out an essential research question for real-time travel time estimation and suggest a direction that may have the potential to improve the online traffic information quality.
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| 15. |
- Mishalani, R. G., et al.
(författare)
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Modeling the spatial behavior of infrastructure condition
- 2002
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Ingår i: Transportation Research Part B. - 0191-2615 .- 1879-2367. ; 36:2, s. 171-194
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Tidskriftsartikel (refereegranskat)abstract
- A new understanding of the spatial behavior of infrastructure condition is presented and a methodology for identifying this behavior is developed. Based on two deterioration mechanisms, causal and interactive, a nonstationary stochastic spatial model with a piecewise constant mean function is proposed. Based on this model, a methodology founded on nonparametric cluster analysis and dynamic programming is developed to identify the optimal spatial regions, referred to as fields, within which behavior is uniform and, consequently, condition can be estimated accurately. Validation using detailed distress data from three roadway facilities, each 15 km long, is presented. The value of the model is also demonstrated by comparing it against existing methods for characterizing infrastructure condition over space.
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| 16. |
- Moran, Carlos, 1976-, et al.
(författare)
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Congestion indicators from the users’ perspective : alternative formulations with stochastic reference level
- 2010
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Konferensbidrag (refereegranskat)abstract
- Congestion causes delays and environmental impacts. Policy makers and transport planners have used congestion indicators for monitoring traffic conditions in urban areas. These indicators require defining a reference level of congestion (based for example on free flow conditions). In most cases reported in the literature this reference point is constant and typically corresponds to speed limits. This paper proposes a methodology for the definition of congestion indicators that takes into consideration the preferences and variability across the individual commuters and hence, develops congestion indicators from the users of the system point of view. An analytical approach is developed pointing out that, as expected, for certain simple distributions of desired speed (i.e. triangular) some indicators are biased. A case study using a microscopic simulation model to study a small, dense, and very congested urban network in Stockholm illustrates the impact of applying this new definition in the calculation of congestion indicators. The results of the case study illustrate the bias of existing methods and identify indicators that are less sensitive to the distribution of the reference speed among drivers.
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| 17. |
- Moran, Carlos, 1976-
(författare)
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Relevance and Reliability of Area-Wide Congestion Performance Measures in Road Networks
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- For operational and planning purposes it is important to observe, predict and monitor the traffic performance of congested urban road links and networks. This monitoring effort describes the traffic conditions in road networks using congestion performance measures. The objective of this research is to analyse and evaluate methods for measuring congestion and congestion performance measures for monitoring purposes. For this objective, a selection of the required aspects of the performance measures in the literature is considered. The aspects to be considered can be classified into two categories: A first group relates to the statistical aspects of these indicators, i.e. reliability. The second relates to their ability to capture the impacts of congestion, i.e .relevance. The reliability and relevance of the congestion performance measures are evaluated. A recommendation of the most suitable indicator is provided at the end of the study.
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| 18. |
- Mwesige, Godfrey, 1978-
(författare)
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A methodology for operations-based safety appraisal of two-lane rural highways : Application in Uganda
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The majority of the road infrastructure in developing countries consists oftwo-lane highways with one lane in each travel direction. Operational efficiency of these highways is derived fromintermittent passing zones where fast vehicles are permitted by design to pass slow vehicles using the opposite traffic lane. Passing zonescontributeto reduction oftravel delay and queuing of fast vehiclesbehind slow vehicles. Thishoweverincreases crash risks between passing and opposite vehiclesespecially at high traffic volumesdue to reduction of passing opportunities.Reduction of passing-related crash risks is therefore a primary concern ofpolicy makers, planners, and highway design engineers. Despite the wide application of passing zones on two-lane highways, there is limited knowledge on the underlying causal mechanisms that exacerbate crash risks, and the essential tools to assess safety of the passing zones.This thesis presentsa methodology to appraisesafety of two-lane rural highways based on observed operation of passing zones.Theproposed methodology takes into accountthe impact of traffic and geometric factors onthe rate passing maneuvers end insidepassing zonesand in the no-passing zones, adequacy ofthe designpassing sight distance,and time-to-collision at the end of passing maneuvers.Thethesis is comprised offive papers addressing capacity and safety aspectsof passing zoneson two-lane rural highways. Paper Ipresents a review of the literature on capacity and safety of passing zones. Paper IIdiscusses adequacy of the design passing sight distance based on the sight distance required to complete a passing maneuverusing observed data. Paper IIIdiscusses formulation, estimation, and application of a model to predict the passing rate using geometric and traffic factors, and applications. Paper IVdiscusses risk appraisal of the passing process based on the probability to complete passing maneuvers with time-to-collision less than 3.0 seconds taking into account the accepted gap in the opposite direction and the passing duration. Paper Vdiscusses formulation and estimation of models to predict the probability and the rate at which passing maneuvers end in a no-passing zone, and applications.Resultsshow that passing zones of lengths between 1.30and 2.50km aregood for both operational efficiency and safety.Passing zones of lengths between 0.50and 1.30km exhibitincreasing crash risks resulting from delayed passing maneuvers thatend in the no-passing zone where the sight distance is limited to evadepotential collisions. Safety of these passing zones could be enhanced with additional signage to indicate the farthestpoint along a passing zone that maneuvers can be initiated so as not to end in a no-passing zone. Passing zones less than 0.50km compel drivers to commence passing maneuvers close to the beginning of the passing zone,and should be avoided during design for safety reasons.The results further show that the passing rate depends on the length of the passing zone, absolute vertical grade, traffic volume in two travel directions, directional split, 85thpercentile speed of free flow vehicles,and percent of heavy vehicles in the subject direction. The peak-passing rate also known as the passing capacity occurs at 200, 220, and 240vph in the subject direction for 50/50, 55/45, and 60/40directional splits, respectively. The rate at which passing maneuvers end in a no-passing zone increaseswith traffic volume and unequal distribution of traffic in two directions, absolute vertical grade, and percent of heavy vehiclesin the subject direction. The thesis furtherdiscusses practical applications of the study findings in highway planning and design to enhancesafety and improve operational efficiency of two-lane rural highways.
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| 19. |
- Nissan, A., et al.
(författare)
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Evaluation of recommended variable speed limits for motorway traffic control : The case of E4 in Stockholm
- 2009
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Ingår i: 16th ITS World Congress. - : World Congress on Intelligent Transport Systems (ITS).
-
Konferensbidrag (refereegranskat)abstract
- Variable Speed Limits (VSL) is a form of motorway control introduced to improve the operations of freeway facilities under congested conditions. This paper evaluates the impact of VSL on the E4 motorway in Stockholm using microsimulation. The test site is heavily congested and includes an integrated Motorway Control System with advisory VSL and Automatic Incident Detection (AID) logic. Experience indicates that the impacts of VSL on traffic condition and safety might be higher if the displayed VSL were mandatory. The objective of the study is to assess the impact of the level of driver compliance to VSL recommended speed, using microsimulation.
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| 20. |
- Rahmani, Mahmood, 1977-
(författare)
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Path Inference of Sparse GPS Probes for Urban Networks : Methods and Applications
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The application of GPS probes in traffic management is growing rapidly as the required data collection infrastructure is increasingly in place in urban areas with significant number of mobile sensors moving around covering expansive areas of the road network. Most travelers carry with them at least one device with a built-in GPS receiver. Furthermore, vehicles are becoming more and more location aware. Currently, systems that collect floating car data are designed to transmit the data in a limited form and relatively infrequently due to the cost of data transmission. That means the reported locations of vehicles are far apart in time and space. In order to extract traffic information from the data, it first needs to be matched to the underlying digital road network. Matching such sparse data to the network, especially in dense urban, area is challenging.This thesis introduces a map-matching and path inference algorithm for sparse GPS probes in urban networks. The method is utilized in a case study in Stockholm and showed robustness and high accuracy compared to a number of other methods in the literature. The method is used to process floating car data from 1500 taxis in Stockholm City. The taxi data had been ignored because of its low frequency and minimal information. The proposed method showed that the data can be processed and transformed into information that is suitable for traffic studies.The thesis implemented the main components of an experimental ITS laboratory, called iMobility Lab. It is designed to explore GPS and other emerging traffic and traffic-related data for traffic monitoring and control.
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| 21. |
- Rahmani, Mahmood, et al.
(författare)
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Requirements and Potential of GPS-based Floating Car Data for Traffic Management : Stockholm Case Study
- 2010
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Ingår i: 2010 13th International IEEE Conference on Intelligent Transportation Systems. - 9781424476572 ; , s. 730-735
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Konferensbidrag (refereegranskat)abstract
- The application of GPS probes in traffic management is growing rapidly as the required data collection infrastructure is increasingly in place in urban areas with significant number of mobile sensors moving around covering expansive areas of the road network. The paper presents the development of a laboratory designed to explore GPS and other emerging traffic and traffic-related data for traffic monitoring and control. It also presents results to illustrate the scope of traffic information that can be provided by GPS-based data, using the city of Stockholm as a case study. The preliminary analysis shows that network coverage, especially during peak weekday hours, is adequate. Further investigation is needed to validate the data, and increase its value through fusion with complementary data from other sources.
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| 22. |
- Rahmani, Mahmood, 1977-
(författare)
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Urban Travel Time Estimation from Sparse GPS Data : An Efficient and Scalable Approach
- 2015
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The use of GPS probes in traffic management is growing rapidly as the required data collection infrastructure is increasingly in place, with significant number of mobile sensors moving around covering expansive areas of the road network. Many travelers carry with them at least one device with a built-in GPS receiver. Furthermore, vehicles are becoming more and more location aware. Vehicles in commercial fleets are now routinely equipped with GPS.Travel time is important information for various actors of a transport system, ranging from city planning, to day to day traffic management, to individual travelers. They all make decisions based on average travel time or variability of travel time among other factors.AVI (Automatic Vehicle Identification) systems have been commonly used for collecting point-to-point travel time data. Floating car data (FCD) -timestamped locations of moving vehicles- have shown potential for travel time estimation. Some advantages of FCD compared to stationary AVI systems are that they have no single point of failure and they have better network coverage. Furthermore, the availability of opportunistic sensors, such as GPS, makes the data collection infrastructure relatively convenient to deploy.Currently, systems that collect FCD are designed to transmit data in a limited form and relatively infrequently due to the cost of data transmission. Thus, reported locations are far apart in time and space, for example with 2 minutes gaps. For sparse FCD to be useful for transport applications, it is required that the corresponding probes be matched to the underlying digital road network. Matching such data to the network is challenging.This thesis makes the following contributions: (i) a map-matching and path inference algorithm, (ii) a method for route travel time estimation, (iii) a fixed point approach for joint path inference and travel time estimation, and (iv) a method for fusion of FCD with data from automatic number plate recognition. In all methods, scalability and overall computational efficiency are considered among design requirements.Throughout the thesis, the methods are used to process FCD from 1500 taxis in Stockholm City. Prior to this work, the data had been ignored because of its low frequency and minimal information. The proposed methods proved that the data can be processed and transformed into useful traffic information. Finally, the thesis implements the main components of an experimental ITS laboratory, called iMobility Lab. It is designed to explore GPS and other emerging data sources for traffic monitoring and control. Processes are developed to be computationally efficient, scalable, and to support real time applications with large data sets through a proposed distributed implementation.
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| 23. |
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| 24. |
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| 25. |
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| 26. |
- Sochor, Jana
(författare)
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User Perspectives on Intelligent Transportation Systems
- 2013
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Intelligent Transportation Systems (ITS), or the advanced use of Information and Communication Technology (ICT) in the transportation context, offers new tools in the continual effort to develop an accessible, safe, and sustainable transportation system. In this thesis, focus is placed on ITS targeting individual use or the end users’ transportation experiences, e.g. video surveillance, cashless payments, pedestrian navigation, real-time information, emergency communications, and parking services. For the end user, such services can serve to enhance one’s sense of assurance by reducing uncertainty and facilitating planning and dealing with unforeseen circumstances.However, ITS and the data collection and processing upon which it is built bring their own challenges, as personal data and privacy are fundamentally intertwined. Individuals’ data is routinely collected, from which one can infer a broad range of activities and lifestyle choices, and which may have implications over time or in other contexts. Perceptions of technology and data use are contextual; what may be considered acceptable or privacy-invasive in one situation and for one purpose may not hold true for other persons, situations, or purposes. Concerns often focus on aspects of anonymity, lack of knowledge or control, function creep, etc. Furthermore, although individual, end users are affected by policies and technologies guiding data collection and processing, they are rarely involved in decision-making processes, offered realistic alternatives, or able to control their own data.The aim of this thesis is to investigate end users’ perceptions of ITS. As various contexts and factors have proven to influence perception in other research areas, the approach has been to use empirical case studies of different end user groups and ITS systems. Additionally, the case studies vary contexts and contrast potential negative consequences of ITS, such as privacy infringement, with potential positive benefits (which may depend on the circumstances of the particular user group and/or the ITS system), such as increased assurance and independence. Users are surveyed via structured interviews and questionnaires that include items addressing perceptions of benefits/risks, privacy, trust, etc. In investigating ITS from the users’ perspective, this research attempts to paint a more holistic view of the issues surrounding the use of ITS in our daily, mobile lives.The broad-spectrum conclusions are that the respondents, in general, perceive ITS as relatively beneficial, more so on a general, social level, and feel more reassured due to the systems. Privacy concerns are generally not a major barrier for acceptance in the scenarios presented, although respondents do not necessarily express high levels of trust for the data collectors or low levels of risk for data misuse. Results show that perceptions are influenced by a number of factors, such as: the targeted beneficiary; addressing a specific, personal need; perceived personal control of a situation; the actor (data collector); status within the organization; gender and parenthood. There are also indications that end users feel a sense of resignation due to lack of choice, control, or perceived influence. For example, there is no strong interest in discussing technological applications with companies, government agencies, or elected representatives, nor in searching for information about technological applications irrespective of perceived privacy infringement or acceptability. This may have broader implications, e.g. for decision-making and democratic processes, as perceived lack of influence and perceived lack of interest in participation feed back into each other.As such, recommendations include informed consent, choice (e.g. opt-in/opt-out), control over one’s personal data, ongoing, two-way dialogue between stakeholders (from the beginning of the design process), comprehensive technological assessments, as well as following through on the use of Fair Information Practices/Principles such as limitation of data collection and use, purpose specification, transparency, individual participation, etc. ITS and data collection and processing are not “silver bullets” able solve all problems via “complete and perfect” information. They are additional tools in the toolbox that bring with them their own challenges related to issues such as privacy, lack of choice/control, and technological accessibility. Thus, efforts should be made to address these new challenges, such as technological mechanisms, personal actions and user participation, and proactive organizational policy and public legislation. The research presented in this thesis serves to remind us that a coordinated effort on multiple fronts is vital in addressing users’ needs and meeting broader social goals.
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| 27. |
- Strömgren, Per
(författare)
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Modelling of Traffic Performance for Swedish Roads and Motorways
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis consists of five scientific articles oriented towards capacity. Managing capacity constraints with associated delays is a big issue at new design as well as at trimming existing traffic facilities. In larger Swedish cities these challenges have become more and more important as a result of growing traffic demand due to rapid population increase.Models for estimating capacity and delay are available, but not many are calibrated for Swedish conditions due to the high effort required. This thesis documents development and calibration of new models for motorway links, entry and exit lanes and weaving areas and an developed space-time model with the ability to calculate queue length, delay, etc.The first article is focused on identifying weaknesses in the former Swedish capacity method for motorways, and development of new models overcoming these shortcomings. The development includes new models for jam density at queue, capacity in weaving areas and fundamental flow-density relationships for 15 different highway types for inclusion in the new Swedish capacity manual.The second article describes the development of a Swedish motorway space-time model to estimate travel times and queues in oversaturated conditions based on the American FREEVAL model in Highway Capacity Manual 2010 (HCM 2010). Calibration and validation of the model has been performed with data from the Motorway Control System (MCS) in Stockholm. A good correspondence was obtained for most cases, but further calibration and validation efforts are required for entry and exit lanes.The third article describes further development of the intersection model in the Swedish microscopic model “Rural Traffic Simulator (RuTSim). This is a continuation of the work documented in the author’s licentiate thesis published in 2002. The development focused on simulation of intersections using a new concept on lane use not included in the old RuTSim model. The model describes Swedish rural intersections with flared approaches providing a non-discreet lane use due to vehicle types in queue. New data for calibration and validation data was also generated. The validation results showed good correspondence between simulated and empirical delay results. The new intersection model is now implemented in RuTSim, providing new tools for estimation of capacity, delay and queue length already included in Swedish guidelines and capacity manuals/software (Capcal).The fourth article describes the development of a new capacity model for roadwork zones. Focus is on the resulting capacity of one lane due to several reduction factors. These factors include impacts of closed road shoulders, reduction of number of lanes, diversion of traffic to the opposite carriageway, commuting traffic, length of work zone, lane width and type of road work. The first two correction factors were successfully validated in a full-scale test on the E6 motorway in Gothenburg.The fifth article describes development and implementation of a new harmonization algorithm for MCS systems on motorways designed to increase bottleneck capacity and throughput. Two different models were developed, one of which was implemented in the existing MCS system on E4 Södertäljevägen south of Stockholm. Full-scale trials were carried out with a model based on trigger levels in terms of flow. The second model based on the difference in the variance of speed during two following time periods was tested offline also with very good results.
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| 28. |
- Sundaram, Srinivasan, et al.
(författare)
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Simulation-based dynamic traffic assignment for short-term planning applications
- 2011
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Ingår i: Simulation (San Diego, Calif.). - : Elsevier BV. - 1569-190X .- 1878-1462. ; 19:1, s. 450-462
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Tidskriftsartikel (refereegranskat)abstract
- Evaluation of Intelligent Transportation Systems (ITS) at the planning level requires the use of appropriate tools that can capture the dynamic and stochastic interactions between demand and supply. The objective of this paper is to present a methodological simulation-based framework for such applications and implement it in the context of dynamic traffic assignment. The framework consists of a mesoscopic supply simulator and a demand simulator that combines OD estimation capabilities with discrete travel behavior models. Simulation-based DTA systems are particularly suited to evaluate a wide range of Advanced Traffic Management Systems (ATMS) and Advanced Traveler Information Systems (ATIS). The simulation model performance is illustrated through two large-scale case studies in Irvine, California, and Lower Westchester County, NY.
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| 29. |
- Toledo, Tomer, et al.
(författare)
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Mesoscopic simulation for transit operations
- 2010
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Ingår i: Transportation Research Part C. - : Elsevier BV. - 0968-090X .- 1879-2359. ; 18:6, s. 896-908
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a transit simulation model designed to support evaluation of operations, planning and control, especially in the context of Advanced Public Transportation Systems (APTS). Examples of potential applications include frequency determination, evaluation of real-time control strategies for schedule maintenance and assessing the effects of vehicle scheduling on the level of service. Unlike most previous efforts in this area, the simulation model is built on a platform of a mesoscopic traffic simulation model, which allows modeling of the operation dynamics of large-scale transit systems taking into account the stochasticity due to interactions with road traffic. The capabilities of Mezzo as an evaluation tool of transit operations are demonstrated with an application to a real-world high-demand bus line in the Tel-Aviv metropolitan area under various scenarios. The headway distributions at two stops are compared with field observations and show good consistency between simulated and observed data.
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| 30. |
- Tympakianaki, Athina, 1985-
(författare)
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Demand Estimation and Bottleneck Management Using Heterogeneous Traffic Data
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Congestion on urban and freeway networks has become a major problem, leading to increased travel times and reduced traffic safety. In order to suggest traffic management solutions to improve the transport system efficiency, it is important to capture the travel demand patterns, expressed as origin-destination (OD) matrices, and understand the mechanisms of traffic bottlenecks. The increasing availability of traffic data offers significant opportunities to effectively address these issues. The thesis uses heterogeneous traffic data to improve three important problems.The first problem relates to the dynamic OD estimation problem, which entails significant challenges due to its complexity. The Simultaneous Perturbation Stochastic Approximation (SPSA) algorithm has been commonly used to solve the problem, which can handle any available data that can improve the estimation accuracy. However, it encounters stability and convergence issues. The thesis proposes a general modification of SPSA, called cluster-wise SPSA (c-SPSA), that has more robust performance and finds better solutions. Its efficiency is demonstrated through simulation experiments for a network from Stockholm.The second problem focuses on the development of methods for utilizing heterogeneous traffic data for the analysis and management of freeway work zone and tunnel bottlenecks. Simulation is used as the means to evaluate and optimize various mitigation strategies for each case.The third problem analyzes multimodal impacts due to network disruptions for the case of tunnel bottlenecks, using a data-driven approach. Tunnel congestion is often dealt with temporary closures, which may cause significant disruptions. It is crucial to identify the potential multimodal impacts of such interventions so as to design efficient and proactive mitigation strategies. The thesis shows the benefits of combining multiple data sources to analyze the impacts of temporary tunnel closures for a freeway tunnel in Stockholm.
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| 31. |
- Vythoulkas, P. C., et al.
(författare)
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Modeling discrete choice behavior using concepts from fuzzy set theory, approximate reasoning and neural networks
- 2003
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Ingår i: Transportation Research Part C. - 0968-090X .- 1879-2359. ; 11:1, s. 51-73
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Tidskriftsartikel (refereegranskat)abstract
- Models of discrete choice analysis are usually based on the random utility framework. They assume that decision makers make decisions that maximize their utility. Alternative formulations of the problem have also been proposed in the literature. These approaches model the decision makers' perceptions of the attributes of the various alternatives using fuzzy sets and linguistic variables, and the decision process itself, using concepts from approximate reasoning and fuzzy control. The underlying assumption is that decision makers use a few simple rules that relate their vague perceptions of the various attributes to their preferences towards the available alternatives. The paper extends this approach by incorporating rule weights, which capture the importance of a particular rule in the decision process. It also presents an approach for calibrating the weights using concepts from neural networks. A case study, involving mode choice, is used to demonstrate the potential of the approach and compare it to alternative formulations and methodologies.
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| 32. |
- Wang, Z., et al.
(författare)
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Calibration of urban rail simulation models : A methodology using SPSA algorithm
- 2011
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Konferensbidrag (refereegranskat)abstract
- Rail simulation model calibration is a process of adjusting model parameters while comparing model output with observations from the real rail system. There is a lack of systematic methodology for calibrating urban rail simulation models. Based on a simulator developed for urban rail operations and control, the paper demonstrates a methodology of calibrating model parameters, and specifically, fine-tuning some of the simulation inputs. The calibration process is modeled as a multi-variate optimization problem and solved by the Simultaneous Perturbation Stochastic Approximation (SPSA) algorithm. A case study of the Massachusetts Bay Transportation Authority (MBTA) Red Line shows that the methodology improves the simulation model dramatically in terms of replicating the track block runtimes. At the same time, it upgrades the station specific dwell time parameters and enhances a-priori boarding rates at stations fairly effectively.
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