RFID-Based Vehicle Positioning and Its Applications in Connected Vehicles

This paper proposed an RFID-based vehicle positioning approach to facilitate connected vehicles applications. When a vehicle passes over an RFID tag, the vehicle position is given by the accurate position stored in the tag. At locations without RFID coverage, the vehicle position is estimated from the most recent tag location using a kinematics integration algorithm till updates from the next tag. The accuracy of RFID positioning is verified empirically in two independent ways with one using radar and the other a photoelectric switch. The former is designed to verify whether the dynamic position obtained from RFID tags matches the position measured by radar that is regarded as accurate. The latter aims to verify whether the position estimated from the kinematics integration matches the position obtained from RFID tags. Both means supports the accuracy of RFID-based positioning. As a supplement to GPS which suffers from issues such as inaccuracy and loss of signal, RFID positioning is promising in facilitating connected vehicles applications. Two conceptual applications are provided here with one in vehicle operational control and the other in Level IV intersection control

A Sigmoid-based car-following model to improve acceleration stability in traffic oscillation and following failure in free flow

This paper proposes an improved Intelligent driving model (Sigmoid-IDM) to address the problems of excessive acceleration in traffic oscillation and following failure in free flow. The Sigmoid-IDM uses a Sigmoid function to enhance the start-following characteristics, improve the output strategy of the spacing term, and stabilize the steady-state velocity in free flow. Moreover, the model asymmetry is improved by means of introducing cautious following distance, driving caution factor, and segmentation function. The anti-interference ability of the Sigmoid-IDM is demonstrated by local stability and string stability analyses.Comment: 15 pages, 51 figures

Integrated self-consistent macro-micro traffic flow modeling and calibration framework based on trajectory data

Calibrating microscopic car-following (CF) models is crucial in traffic flow theory as it allows for accurate reproduction and investigation of traffic behavior and phenomena. Typically, the calibration procedure is a complicated, non-convex optimization issue. When the traffic state is in equilibrium, the macroscopic flow model can be derived analytically from the corresponding CF model. In contrast to the microscopic CF model, calibrated based on trajectory data, the macroscopic representation of the fundamental diagram (FD) primarily adopts loop detector data for calibration. The different calibration approaches at the macro- and microscopic levels may lead to misaligned parameters with identical practical meanings in both macro- and micro-traffic models. This inconsistency arises from the difference between the parameter calibration processes used in macro- and microscopic traffic flow models. Hence, this study proposes an integrated multiresolution traffic flow modeling framework using the same trajectory data for parameter calibration based on the self-consistency concept. This framework incorporates multiple objective functions in the macro- and micro-dimensions. To expeditiously execute the proposed framework, an improved metaheuristic multi-objective optimization algorithm is presented that employs multiple enhancement strategies. Additionally, a deep learning technique based on attention mechanisms was used to extract stationary-state traffic data for the macroscopic calibration process, instead of directly using the entire aggregated data. We conducted experiments using real-world and synthetic trajectory data to validate our self-consistent calibration framework

Fundamental Diagram calibration and evaluation of the operational Level of Service on Italian motorways

Nell’analisi del deflusso autostradale trovano ampia applicazione le metodologie HCM e molti paesi, tra cui l’Italia, fanno ad esse riferimento per la valutazione delle infrastrutture esistenti e di progetto. Le norme italiane, pur citando il manuale, non esplicitano chiaramente riferimenti o procedure. Le esperienze delle Concessionarie autostradali, inoltre, mostrano dubbi sulla rappresentatività dei risultati ottenuti applicando le procedure americane, evidenziando un divario tra gli output e la percezione del reale grado di congestione. Considerando alcuni tratti autostradali italiani, la ricerca si propone di verificare l’applicabilità di procedure per la calibrazione del Diagramma Fondamentale del traffico e per la valutazione della qualità del deflusso, testando la consistenza dei risultati con gli output delle metodologie HCM2010. Rispetto agli andamenti standard, i Diagrammi ottenuti mostrano una migliore capacità di interpretare i dati sperimentali, in considerazione delle condizioni specifiche delle sezioni, delle differenze nelle caratteristiche dei veicoli o nel comportamento e nelle regole di guida. In questi termini, i modelli calibrati stimano valori di flusso e densità critici inferiori a quelli HCM2010, ma prossimi a quelli suggeriti dall’analogo manuale tedesco HBS. L'analisi comparativa, a valle della quale sono approfondite e motivate le principali differenze tra il contesto italiano, quello americano e altre situazioni internazionali, mostra come il manuale statunitense tenda ad esprimere condizioni di circolazione migliori di quelle sintetizzate con i modelli calibrati. La ricerca evidenzia, quindi, la possibilità di una sottostima della congestione sulle sezioni in esame, suggerendo un cauto e attento utilizzo delle procedure standard. I risultati ottenuti rilevano, in generale, come il mancato utilizzo di modelli calibrati e l'uso alternativo di procedure che appaiono troppo generali e provenienti da contesti eterogenei possa condizionare e penalizzare la rappresentatività dei risultati, comportando un’incoerente rappresentazione dei livelli di congestione e invalidando i requisiti di adeguatezza e di rappresentatività nella valutazione della qualità del servizio.HCM methodologies are widely used for analyzing freeways. Many countries, including Italy, refers to HCM for the assessment of existing or planned infrastructures. Although citing the manual, the Italian regulations don't make explicit references or procedures. Furthermore, the experiences of motorway operators show doubts about the representativeness of the results obtained by the American procedures, showing a gap between the output and the perception of the real level of congestion. Considering some Italian motorway sections, this research aims to analyze the applicability of a procedure for the calibration of the Fundamental Diagram of traffic flows and for the assessment of the quality of service, testing the consistency of the results with the output of HCM2010 methodologies. In comparison to standards, the calibrated Diagrams show a better match with data, due to the special conditions of the sections, the differences in vehicle characteristics or behavior and driving rules. In this way, the calibrated models estimate critical flow and density values lower than those of HCM2010, but close to the similar German manual HBS. The comparative analysis, after which the main differences between the Italian context, the American and other international situations are studied in deep and further motivated, shows as the US manual tends to give better traffic flow conditions (i.e. less congestion) than those synthesized using the calibrated models. The research remarks, therefore, the possibility of an underestimation of the congestion on the sections examined, suggesting a cautious and careful use of standard procedures. Failure to use calibrated procedures and models and the alternative use of procedures which seem too general and coming from heterogeneous contexts may affect and penalize the reliability of the results. This can result in an incoherent representation of congestion levels and may invalidate the requirements of adequacy and representativeness in the evaluation of service quality

Vehicle Longitudinal Control and Traffic Stream Modeling (Paper # 12-0156)

A simple yet efficient traffic flow model, in particular one that describes vehicle longitudinal operational control and further characterizes traffic flow fundamental diagram, is always of great interest to many. Though many models have been proposed in the past, each with their own advantages, research in this area is far from conclusive. This paper contributes a new model, i.e., the longitudinal control model (LCM), to the arsenal with a unique set of properties. The model is suited for a variety of transportation applications, among which a concrete example is provided herein