56 research outputs found
Two-dimensional LWR model for lane-free traffic
While macroscopic models for single or multi-lane traffic flow are well
established, these models are not applicable to the dynamics and
characteristics of disordered traffic which is characterized by widely
different types of vehicles and no lane discipline. We propose a first-order
two-dimensional Lighthill-Whitham-Richards (LWR) model for the continuous
macroscopic longitudinal and lateral dynamics of this type of traffic flow. The
continuity equation is extended into two dimensions and the equation is closed
by assuming a longitudinal flow-density relationship as in traditional
one-dimensional models while the lateral dynamics is based on boundary
repulsion and a desire of a majority of the drivers to go to less dense
regions. This is equivalent to Fick's law giving rise to a lateral diffusion
term. Using the proposed model, several numerical tests were conducted under
different traffic scenarios representing a wide range of traffic conditions.
Even for extreme initial conditions, the model's outcome turned out to be
plausible and consistent with observed traffic flow dynamics. Moreover, the
numerical convergence test is performed using an analytical solution for
lateral steady-state conditions. The model was applied for bicycle simulation
and reproduced the evolution of lateral density profile with asymmetric
behavior
A two-dimensional data-driven model for traffic flow on highways
Based on experimental traffic data obtained from German and US highways, we
propose a novel two-dimensional first-order macroscopic traffic flow model. The
goal is to reproduce a detailed description of traffic dynamics for the real
road geometry. In our approach both the dynamic along the road and across the
lanes is continuous. The closure relations, being necessary to complete the
hydrodynamic equation, are obtained by regression on fundamental diagram data.
Comparison with prediction of one-dimensional models shows the improvement in
performance of the novel model.Comment: 27 page
The BGK approximation of kinetic models for traffic
We study spatially non-homogeneous kinetic models for vehicular traffic flow.
Classical formulations, as for instance the BGK equation, lead to
unconditionally unstable solutions in the congested regime of traffic. We
address this issue by deriving a modified formulation of the BGK-type equation.
The new kinetic model allows to reproduce conditionally stable non-equilibrium
phenomena in traffic flow. In particular, stop and go waves appear as bounded
backward propagating signals occurring in bounded regimes of the density where
the model is unstable. The BGK-type model introduced here also offers the
mesoscopic description between the microscopic follow-the-leader model and the
macroscopic Aw-Rascle and Zhang model
Two Lane Traffic Simulations using Cellular Automata
We examine a simple two lane cellular automaton based upon the single lane CA
introduced by Nagel and Schreckenberg. We point out important parameters
defining the shape of the fundamental diagram. Moreover we investigate the
importance of stochastic elements with respect to real life traffic.Comment: to be published in Physica A, 19 pages, 9 out of 13 postscript
figures, 24kB in format .tar.gz., 33kB in format .tar.gz.uu, for a full
version including all figures see
http://studguppy.tsasa.lanl.gov/research_team/papers
Derivation and stability analysis of macroscopic multi-lane models for vehicular traffic flow
The mathematical modeling and the stability analysis of multi-lane traffic in
the macroscopic scale is considered. We propose a new first order model derived
from microscopic dynamics with lane changing, leading to a coupled system of
hyperbolic balance laws. The macroscopic limit is derived without assuming ad
hoc space and time scalings. The analysis of the stability of the equilibria of
the model is discussed. The proposed numerical tests confirm the theoretical
findings between the macroscopic and microscopic modeling, and the results of
the stability analysis
Coordination and Analysis of Connected and Autonomous Vehicles in Freeway On-Ramp Merging Areas
Freeway on-ramps are typical bottlenecks in the freeway network, where the merging maneuvers of ramp vehicles impose frequent disturbances on the traffic flow and cause negative impacts on traffic safety and efficiency. The emerging Connected and Autonomous Vehicles (CAVs) hold the potential for regulating the behaviors of each individual vehicle and are expected to substantially improve the traffic operation at freeway on-ramps. The aim of this research is to explore the possibilities of optimally facilitating freeway on-ramp merging operation through the coordination of CAVs, and to discuss the impacts of CAVs on the traffic performance at on-ramp merging.In view of the existing research efforts and gaps in the field of CAV on-ramp merging operation, a novel CAV merging coordination strategy is proposed by creating large gaps on the main road and directing the ramp vehicles into the created gaps in the form of platoon. The combination of gap creation and platoon merging jointly facilitates the mainline and ramp traffic and targets at the optimal performance at the traffic flow level. The coordination consists of three components: (1) mainline vehicles proactively decelerate to create large merging gaps; (2) ramp vehicles form platoons before entering the main road; (3) the gaps created on the main road and the platoons formed on the ramp are coordinated with each other in terms of size, speed, and arrival time. The coordination is analytically formulated as an optimization problem, incorporating the macroscopic and microscopic traffic flow models. The model uses traffic state parameters as inputs and determines the optimal coordination plan adaptive to real-time traffic conditions.The impacts of CAV coordination strategies on traffic efficiency are investigated through illustrative case studies conducted on microscopic traffic simulation platforms. The results show substantial improvements in merging efficiency, throughput, and traffic flow stability. In addition, the safety benefits of CAVs in the absence of specially designed cooperation strategies are investigated to reveal the CAV’s ability to eliminate critical human factors in the ramp merging process
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