Realistic Traffic Behavior Research Articles

Framework of vehicle-bridge coupled analysis for suspension bridges under refined vehicle modeling considering realistic traffic behavior

Long-span suspension bridges experience complex dynamic interactions with stochastic traffic, which has a critical impact on the design and safety assessment of bridges. In this study, a traffic-bridge interaction (TBI) framework is proposed for suspension bridge dynamics analysis by considering realistic traffic behavior and real vehicle characteristics. A stochastic traffic simulation model aiming to faithfully reproduce realistic traffic flow is developed by integrating the Monte Carlo approach and an intelligent driving model. The key parameters of the stochastic traffic model are input into the refined vehicle model established and the bridge model is built. The vehicle and bridge models are coupled by an interface contact method to obtain a complete TBI framework. The TBI framework is applied to a prototype long-span suspension bridge to fully investigate the effect of stochastic traffic flow loads on the vertical vibration of the bridge. Furthermore, the effect of stochastic traffic flow loads on the vertical displacement of a bridge is evaluated by varying key parameters in the TBI framework, such as traffic density and road roughness. The study provides a novel perspective on the refined dynamic analysis of suspension bridges under complex traffic conditions, which can further serve as a reference for the safety assessment of suspension bridges.

Ride comfort evaluation of stochastic traffic flow crossing long-span suspension bridge experiencing vortex-induced vibration

The long-span bridge is susceptible to various wind-induced vibrations owing to its high flexibility and low structural damping, among which the vortex-induced vibration (VIV) frequently emerges in recent years resulting in considerable public concerns. Although the VIV is a limited cyclic vibration, it can cause significant negative effects on the ride comfort of vehicles crossing the bridge. Evaluating the ride comfort of vehicles crossing long-span bridges under VIV, therefore, becomes urgent to make decisions on continuing or closing the operations of bridges. In view of this, this paper presents a general ride comfort evaluation procedure for stochastic traffic flow crossing the long-span bridge under VIV, which adequately considers the realistic traffic behavior and the complex interactions among wind, vehicles (traffic flow), and bridge. The developed procedure is validated through the field-monitoring data collected in a recent VIV event of a prototype long-span suspension bridge. On this basis, the ride comfort of vehicles in different traffic flows crossing the prototype bridge under VIV is evaluated through the criteria recommended in the ISO 2631-1 standard based on the overall vibration total value (OVTV). Moreover, the effects of traffic density, traffic proportion, and road roughness on drivers’ ride comfort are studied.

Software Framework for Testing of Automated Driving Systems in the Traffic Environment of Vissim

As the complexity of automated driving systemss (ADSs) with automation levels above level 3 is rising, virtual testing for such systems is inevitable and necessary. The complexity of testing these levels lies in the modeling and calculation demands for the virtual environment, which consists of roads, traffic, static and dynamic objects, as well as the modeling of the car itself. An essential part of the safety and performance analysis of ADSs is the modeling and consideration of dynamic road traffic participants. There are multiple forms of traffic flow simulation software (TFSS), which are used to reproduce realistic traffic behavior and are integrated directly or over interfaces with vehicle simulation software environments. In this paper we focus on the TFSS from PTV Vissim in a co-simulation framework which combines Vissim and CarMaker. As it is a commonly used software in industry and research, it also provides complex driver models and interfaces to manipulate and develop customized traffic participants. Using the driver model DLL interface (DMDI) from Vissim it is possible to manipulate traffic participants or adjust driver models in a defined manner. Based on the DMDI, we extended the code and developed a framework for the manipulation and testing of ADSs in the traffic environment of Vissim. The efficiency and performance of the developed software framework are evaluated using the co-simulation framework for the testing of ADSs, which is based on Vissim and CarMaker.

Westdrive X LoopAR: An Open-Access Virtual Reality Project in Unity for Evaluating User Interaction Methods during Takeover Requests.

With the further development of highly automated vehicles, drivers will engage in non-related tasks while being driven. Still, drivers have to take over control when requested by the car. Here, the question arises, how potentially distracted drivers get back into the control-loop quickly and safely when the car requests a takeover. To investigate effective human–machine interactions, a mobile, versatile, and cost-efficient setup is needed. Here, we describe a virtual reality toolkit for the Unity 3D game engine containing all the necessary code and assets to enable fast adaptations to various human–machine interaction experiments, including closely monitoring the subject. The presented project contains all the needed functionalities for realistic traffic behavior, cars, pedestrians, and a large, open-source, scriptable, and modular VR environment. It covers roughly 25 km2, a package of 125 animated pedestrians, and numerous vehicles, including motorbikes, trucks, and cars. It also contains all the needed nature assets to make it both highly dynamic and realistic. The presented repository contains a C++ library made for LoopAR that enables force feedback for gaming steering wheels as a fully supported component. It also includes all necessary scripts for eye-tracking in the used devices. All the main functions are integrated into the graphical user interface of the Unity® editor or are available as prefab variants to ease the use of the embedded functionalities. This project’s primary purpose is to serve as an open-access, cost-efficient toolkit that enables interested researchers to conduct realistic virtual reality research studies without costly and immobile simulators. To ensure the accessibility and usability of the mentioned toolkit, we performed a user experience report, also included in this paper.

Framework of wind-traffic-bridge coupled analysis considering realistic traffic behavior and vehicle inertia force

The performance of a long-span bridge under strong wind and traffic loads is of great importance to ensure the functionality and the serviceability of the bridge as well as the safety of running vehicles. In this paper, an innovative wind-traffic-bridge (WTB) interaction model for predicting the dynamic performance of the long-span bridge and running vehicles under the crosswind is proposed, considering realistic traffic behavior and vehicle inertia force. In this regard, the LAI-E traffic simulation model aiming to faithfully reproduce realistic traffic flow is developed by integrating the kinetics theory, vehicle capabilities, and driver reactions. The results indicate that using the traditional NaSch traffic model results in a significant overestimation of the vehicle lateral response under a windy environment, whereas the LAI-E traffic model can overcome this issue by ensuring a smooth speed transition during the vehicular acceleration/deceleration process. Additionally, when the vehicle accelerates or decelerates at the emergency capability, the additional pitching moment caused by the vehicle inertia force can result in remarkable increase of vertical wheel contact forces. The present study suggests the necessity of considering both realistic traffic behavior and vehicle inertia force during the WTB analysis.

A macroscopic traffic model for traffic flow harmonization

Traffic flow will harmonize to forward conditions. The time and distance required for harmonization can have a significant effect on the traffic density behavior. The flow can evolve into clusters of vehicles or become uniform depending on parameters such as safe time headway and safe distance headway. In this paper, a new model is presented to provide a realistic characterization of traffic behavior during the harmonization period. Results are presented for a discontinuous density distribution on a circular road which shows that this model produces more realistic traffic behavior than other models in the literature.

Quality of Service Management in GPRS-Based Radio Access Networks

In this article, the performance and capacity gain achievable with quality of service (QoS) management in packet switched radio networks based on the General Packet Radio Service (GPRS) are examined. Both the functions defined in the GPRS specification for QoS support and implementation-specific strategies for subscriber- and application-based Connection Admission Control (CAC) and scheduling are introduced. The feasibility of QoS provisioning in mobile core networks with use of DiffServ compared to present IP technology realizing a pure Best-effort service is examined in addition. To achieve this, simulation results of GPRS performance and system measures for different load situations are produced with the simulation tool GPRSim that models the realistic traffic behavior of a GPRS network.

Effect of Information Quality on Compliance Behavior of Commuters Under Real-Time Traffic Information

The compliance behavior of commuters under different advanced traveler information systems (ATIS) information strategies of varying information quality and credibility is investigated. A behavioral experiment involving commuters’ departure time and route decisions in response to traffic information in a simulated traffic system is conducted by using an interactive dynamic multiuser, computer-based simulator. By actually simulating traffic conditions in response to commuter decisions, the simulator provides stimuli to the participants that are always consistent with physically realistic traffic behavior and with their previous decisions. Event-count (frequency) models and dynamic, discrete-choice models are employed to capture the principal effects of the commuters’ experience with the traffic system and with the real-time information on user compliance. The analysis reveals that the information quality of ATIS strongly affects commuters’ compliance behavior. Switching “cost” and recent experience are found to influence their trip-making behavior as well. The analysis further shows that a higher compliance rate can be achieved under prescriptive information than descriptive information. A hierarchy of achievable compliance rates appears to exist in response to the type of information supplied, under which the highest compliance is obtained for reliable, predicted information and the least compliance for random information. Moreover, by providing posttrip feedback with performance information on recommendation or ex–post-best decision, higher compliance is attained.

Some Circumstances in Which Vehicles Will Reach Their Destinations Earlier by Starting Later: Revisited

Smeed's postulate under which it is possible for a driver to depart later and arrive earlier has been modified to show that under realistic traffic behavior assumptions this phenomenon cannot occur.