| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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).
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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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| 6. |
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| 7. |
- 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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