Vehicular Traffic Model Research Articles

The RSU Access Problem Based on Evolutionary Game Theory for VANET

We identify some challenges in RSU access problem. There are two main problems in V2R communication. (1) It is difficult to maintain the end-to-end connection between vehicles and RSU due to the high mobility of vehicles. (2) The limited RSU bandwidth resources lead to the vehicles' disorderly competition behavior, which will give rise to multiple RSUs having overlap area environment where RSU access becomes crucial for increasing vehicles' throughput. Focusing on the problems mentioned above, the RSU access question in the paper is formulated as a dynamic evolutionary game for studying the competition of vehicles in the single community and among multiple communities to share the limited bandwidth in the available RSUs, and the evolutionary equilibrium evolutionary stable strategy (ESS) is considered to be the solution to this game. Simulation results based on a realistic vehicular traffic model demonstrate the evolution process of the game and how the ESS can affect the network performance.

Modelling interacting molecular motors with an internal degree of freedom

The mechanisms underlying the collective motion of molecular motors in living cells are not yet fully understood. One such open puzzle is the observed pulses of backward-moving myosin-X in the filopodia structure. Motivated by this phenomenon we introduce two generalizations of the ‘total asymmetric exclusion process’ (TASEP) that might be relevant to the formation of such pulses. The first is adding a nearest-neighbours attractive interaction between motors, while the second is adding an internal degree of freedom corresponding to a processive and immobile form of the motors. Switching between the two states occurs stochastically, without a conservation law. Both models show strong deviations from the mean field behaviour and lack particle–hole symmetry. We use approximations borrowed from the research on vehicular traffic models to calculate the current and jam size distribution in a system with periodic boundary conditions and introduce a novel modification to one of these approximation schemes.

Research on pricing game strategy for load-balancing in VANET

In vehicle Ad-hoc netwok (VANET), traffic load is often unevenly distributed among access points (APs). Such load imbalance hampers the network from fully utilizing the network capacity. To alleviate such imbalance, the paper introduces a novel pricing game model. The research scene is at the intersection when the traffic light is green. As vehicles are highly mobile and the network typology changes dynamically, the paper divides the green light time into equal slots and calculates APs' prices with the presented pricing game in each time slot. The whole process is a repeated game model. The final equilibrium solution set is APs' pricing strategy, and the paper claim that this equilibrium solution set can affect vehicles' selection and ensure APs' load-balancing. Simulation results based on a realistic vehicular traffic model demonstrate the effectiveness of the game method.

A Probabilistic and Traffic-Aware Bundle Release Scheme for Vehicular Intermittently Connected Networks

Delay-optimal data delivery in Vehicular Intermittently Connected Networks (VICNs) is challenging since vehicular traffic is affected by numerous recurring and completely random events. Some of these events cause breakdowns and jams while others subserve traffic stability. Researchers observed that mobile vehicles might be wisely exploited to connect two isolated, Stationary Roadside Units (SRUs). In this context, the design of effective delay-minimal data relaying strategies is receiving significant attention. However, many existing such schemes either do not adequately model vehicular traffic behaviours or adapt typical Internet packet-like forwarding protocols to VICNs. In contrast, this manuscript presents a concise, yet comprehensive study of vehicular traffic states based on which a "comme-il-faut" vehicular traffic model is established. This model captures the fundamental traffic characteristics and enables the selection of appropriate distributions for vehicular flow and speeds that parallel the realistic measurements made by traffic theorists. These distributions constitute the basis of a novel Probabilistic Bundle Release Scheme with Bulk Bundle Release (PBRS-BBR) that is proposed with the objective to minimize the average bundle delivery delay. An analytical queueing model is formulated to assess the performance of PBRS-BBR under medium-to-light vehicular traffic. Extensive simulations are conducted to prove the model's validity and accuracy.

Green- function for the highway vehicular traffic flow modeling and analysis

In the present article we offer a method for the highway traffic flow modeling, based on the Green function as a transformation tool. This approach is suitable for distributed parameter systems in order to reformulate their partial differential equation description as sets of transfer functions. The model used in our work is the macroscopic continuous Lighthill-Whitham-Richards representation. The physical phenomena characteristic for the vehicular flow on a highway section are analyzed over some important length. This implies the description of the traffic as a distributed parameter plant. We present the Green function transformation's general case and after we apply it to the considered traffic flow model in order to obtain its transfer function form. The sets of expressions obtained can be specified using concrete fundamental diagrams and data, and also can be implemented in the design of control strategies.

On the Uplink MAC Performance of a Drive-Thru Internet

As IEEE 802.11 access points (APs) open up services to mobile clients, opportunistic access to the roadside communication infrastructures from traveling vehicles has become more prominent and has drawn considerable attention. In particular, data uploading from traveling vehicles has a great potential for many vehicular ad hoc network applications, where both the intermittent connectivity and the time-varying vehicle arrivals have presented significant challenges to the current analytical models. Our focus is on the carrier sense multiple access with collision avoidance-based medium access control (MAC) layer performance in a last-hop drive-thru Internet, considering both the contention nature of the uplink and the realistic vehicle traffic model. Analytical and simulation results show the intrinsic relationships among the vehicle density and speed, the coverage of the AP, the achievable throughput, and the total amount of data uploaded by vehicles. We further investigate the efficacy of an admission control scheme by the AP for achieving an optimal operating region that has both a high throughput and a large amount of data uploaded from each drive-thru vehicle.

DORA: Dynamic Optimal Random Access for Vehicle-to-Roadside Communications

In this paper, we study random access in a drive-thru scenario, where roadside access points (APs) are installed on a highway to provide temporary Internet access for vehicles. We consider vehicle-to-roadside (V2R) communications for a vehicle that aims to upload a file when it is within the APs' coverage ranges, where both the channel contention level and transmission data rate vary over time. The vehicle will pay a fixed amount each time it tries to access the APs, and will incur a penalty if it cannot finish the file uploading when leaving the APs. First, we consider the problem of finding the optimal transmission policy with a single AP and random vehicular traffic arrivals. We formulate it as a finite-horizon sequential decision problem, solve it using dynamic programming (DP), and design a general dynamic optimal random access (DORA) algorithm. We derive the conditions under which the optimal transmission policy has a threshold structure, and propose a monotone DORA algorithm with a lower computational complexity for this special case. Next, we consider the problem of finding the optimal transmission policy with multiple APs and deterministic vehicular traffic arrivals thanks to perfect traffic estimation. We again obtain the optimal transmission policy using DP and propose a joint DORA algorithm. Simulation results based on a realistic vehicular traffic model show that our proposed algorithms achieve the minimal total cost and the highest upload ratio as compared with some other heuristic schemes. In particular, we show that the joint DORA scheme achieves an upload ratio 130% and 207% better than the heuristic schemes at low and high traffic densities, respectively.

The insights of message delivery delay in VANETs with a bidirectional traffic model

Message delivery delay is mainly caused by mobility and sparse distribution of vehicles in Vehicular Ad hoc NETworks (VANETs). It directly impacts the application design and deployments for VANETs. In this paper, we conduct an in-depth study on the insights of message delivery delay in VANETs towards the identified two major factors: (1) message delivery distance, (2) density of vehicles, based on a bidirectional vehicle traffic model. The bidirectional vehicle traffic was modeled as a combination of multiple Poisson point processes. Based on the sub-additive ergodic theory, theoretically, we found that the message delivery delay has a linear relationship with the message delivery distance. Furthermore, the upper bound of the coefficient of the linear relationship has an exponential polynomial relationship with the density of vehicles on the road and decreases with the increase of the velocity of the traffic.

Modeling and simulation of pedestrian flow through hydrodynamics

This paper proposes a pedestrian hydrodynamic model which takes a form for mass and “momentum” conservations with relaxation. The model can be viewed as an extension of the Aw-Rascle-Zhang vehicular traffic flow model, which ensures a so called “anisotropy” for traffic flow, namely, disturbance propagates only against the motion of the disturbed media. The optimal direction of motion for a pedestrian is determined by an Eikonal-type equation so that the total cost for traveling from the referred position to destination is minimized. A discontinuous Galerkin scheme is applied to solve the formulated hyperbolic system and the simulation indicates the convergence of the scheme. Moreover, numerical results demonstrate the ability of the model to depict macroscopic characteristics of pedestrian flow in normal situations, such as the formation and dissipation of congestion near the door in a walking facility.

Global solution to the Cauchy problem for discrete velocity models of vehicular traffic

This paper offers the proof of the existence for large times of the Cauchy problem for a class of vehicular traffic models with discrete velocities derived from the mathematical tools of the kinetic theory for active particles. This approach has the ability to capture some basic aspects concerning the complexity of the systems under consideration through an appropriate modeling, via stochastic games, of the interactions at the microscopic scale. The proof is related to specific aspects of the real system and hopefully can contribute towards improving the modeling approach.

On the coupling of steady and adaptive velocity grids in vehicular traffic modelling

This work deals with the derivation and the analysis of a new mathematical model for vehicular traffic along a one-way road obtained by the coupling of a uniform and an adaptive discretization of the velocity variable in the framework of the kinetic theory. Interactions are modelled by stochastic games where the output of interactions depends on the local density and is not linearly additive.

Some theoretical reasonings on the use and abuse of empirical data for vehicular traffic modelling

This paper deals with a critical analysis on the use of empirical data in the modelling of vehicular traffic dynamics. The analysis is focused on the modelling according to the macroscopic scale and the approach of the kinetic theory and aims at showing how the empirical data available in the literature can be used to derive and validate models and how these data should not be artificially plugged into models. Conceivable reasonings on the analogous problem focused on crowd modelling are proposed in the last part of this paper.

From generalized kinetic theory to discrete velocity modeling of vehicular traffic. A stochastic game approach

This work reports on vehicular traffic modeling by methods of the discrete kinetic theory. The purpose is to detail a reference mathematical framework for some discrete velocity kinetic models recently introduced in the literature, which proved capable of reproducing interesting traffic phenomena without using experimental information as modeling assumptions. To this end, we firstly derive a general discrete velocity kinetic framework with binary nonlocal interactions. Then, resorting to some ideas of stochastic game theory, we outline specific modeling guidelines for vehicular traffic, and finally we discuss the derivation of the above-mentioned vehicular traffic models from these mathematical structures.

Reversible discrete event formulation and optimistic parallel execution of vehicular traffic models

Vehicular traffic simulations are useful in applications such as emergency planning and traffic management, for rapid response and resilience. Here, a parallel traffic simulation approach is presented that reduces the time for simulating emergency vehicular traffic scenarios. We use a reverse computation-based optimistic execution approach to parallel execution of microscopic, vehicular-level models of traffic. The unique aspects of this effort are: exploration of optimistic simulation of vehicular traffic; addressing the related reverse computation challenges; achieving absolute, as opposed to self-relative, speedup. The design, development and performance study of the parallel simulation system is presented, demonstrating excellent sequential and parallel performance. A speed up of nearly 20 on 32 processors is observed on a vehicular network of 65,000 intersections and 13 million vehicles.

Stochastic Description of Traffic Flow

We propose a traffic model based on microscopic stochastic dynamics. We built a Markov chain equipped with an Arrhenius interaction law. The resulting stochastic process is comprised of both spin-flip and spin-exchange dynamics which models vehicles exiting, entering and interacting in a two-dimensional lattice environment corresponding to a multi-lane highway. The process is further equipped with a novel look-ahead type, anisotropic interaction potential which allows drivers/vehicles to ascertain local fluctuations and advance to new cells forward or sideways. The resulting vehicular traffic model is simulated via kinetic Monte Carlo and examined under both, typical and extreme traffic flow scenarios. The model is shown to correctly predict both qualitative as well as quantitative traffic observables for any highway geometry. Furthermore it also captures interesting multi-scale phenomena in traffic flows after a simulated accident which lead to oscillatory, dissipating, traffic waves with different periods per lane.

Impacts of Radio Access Protocols on Cooperative Vehicle Collision Avoidance in Urban Traffic Intersections

This paper p resents the design of a Cooperative Collision Avoidance application, and evaluates its performance with DSRC-recommended 802.11 Medium Access Control (MAC) and with a novel Vehicular Self-Organizing MAC (VeSOMAC) protocol. VeSOMAC is designed as a fully distributed TDMA protocol that relies on an in-band control exchange technique for autonomous TDMA slot allocation among vehicle-mounted wireless communication modules. A hybrid traffic and wireless network simulator has been developed for evaluating both network level and application level performance in the presence of different wireless access protocols. Detailed network and vehicular traffic simulation models have also been developed for evaluating a Cooperative Collision Control (CCA) application, operating in urban traffic intersection scenarios. Simulation results demonstrate that unlike the 802.11 style contention based protocols, a schedule based protocol such as VeSOMAC can offer better vehicle safety performance through smaller and bounded packet latency in vehicular ad hoc networks.

Balanced vehicular traffic at a bottleneck

The balanced vehicular traffic model is a macroscopic model for vehicular traffic flow. We use this model to study the traffic dynamics at highway bottlenecks either caused by the restriction of the number of lanes or by on-ramps or off-ramps. The coupling conditions for the Riemann problem of the system are applied in order to treat the interface between different road sections consistently. Our numerical simulations show the appearance of synchronized flow at highway bottlenecks.

A flow control methodology for the rapid generation of vehicle traffic models

This paper presents a conveyor-based methodology to model complex vehicle flows common to factory and distribution warehouse facilities. The AGV and human path modelling techniques available in many commercial discrete event simulation packages require extensive knowledge and time to implement even the simplest flow control rules for multiple vehicle interaction. Although discrete event simulation is accepted as an effective tool to model vehicle delivery movements, human paths and delivery schedules for modern assembly lines, the time to generate accurate models is a significant limitation of existing simulation-based optimisation methodologies. The flow control method has been successfully implemented using two commercial simulation packages. It provides a realistic visual representation, as well as accurate statistical results, and reduces the model development process cost.

The Aw–Rascle vehicular traffic flow model with phase transitions

We introduce a new model of vehicular traffic flow with phase transitions. The model is obtained by coupling together the classical Lighthill–Whitham–Richards equation with the 2×2 system proposed by Aw and Rascle. This allows us both to correct some drawbacks of the original 2×2 system, and to obtain results that fit experimental data well. We describe the solutions of the Riemann problem, and we compare the results with those obtained using other models.

On the velocity distribution at equilibrium in the mathematical theory of vehicular traffic flow

This work deals with a two-scale vehicular traffic model, where the mass conservation equation is closed by a velocity probability distribution, parameterized with respect to each density of vehicles. The above probability distribution is identified on the basis of both experimental information and theoretical conjectures.