Car Density Research Articles

Two-dimensional traffic flow problems with faulty traffic lights.

A cellular automaton model is presented to simulate a traffic jam in a two-dimensional traffic flow with faulty traffic lights. The model is studied by computer simulations. Results show that at low car densities, faulty traffic lights speed up the overall traffic. However, the critical car density at which a serious traffic jam occurs decreases as the concentration of faulty traffic lights increases.

Phenomenological Study of Dynamical Model of Traffic Flow

We show that the Car Following Model with Optimal Velocity (Optimal Velocity Model), which was proposed in our previous paper, is a successful traffic model in reproducing the characteristic features of observed traffic flow data. In our model the transition from free flow to congested flow occurs spontaneously by the collective motion of vehicles, which obey to the same dynamical equation. The observed specific discrepancy of traffic flow vs. car density graph is well understood in terms of the phase transition in our model.

Traffic Flow Problems in One-Dimensional Inhomogeneous Media

Traffic flow problems in one-dimensional inhomogeneous media are studied using cellular automaton models. The effects of (i) a single impurity site, at which a car takes longer time to pass through, in an otherwise uniform medium, (ii) the addition of a finite concentration of overtaking sites that can accomodate two cars at the same time, and (iii) the presence of both an impurity site and overtaking sites are studied. Analytic expressions for the average car velocity and flux in the long time limit as a function of car density are derived.

Temporal Variations of Traffic Flow in the Biham-Middleton-Levine Model

The temporal variation of the average velocity of cars in the Biham-Middleton-Levine (BML) model is studied. The equations which govern the temporal variation of the car velocities for various densities of cars are derived. By utilizing these equations, the final average velocity is approximately obtained for most self-organized states.

Dynamical Phase Transition in One Dimensional Traffic Flow Model with Blockage

Effects of a bottleneck in a linear trafficway is investigated using a simple cellular automaton model. Introducing a blockage site which transmit cars at some transmission probability into the rule-184 cellular automaton, we observe three different phases with increasing car concentration: Besides the free phase and the jam phase, which exist already in the pure rule-184 model, the mixed phase of these two appears at intermediate concentration with well-defined phase boundaries. This mixed phase, where cars pile up behind the blockage to form a jam region, is characterized by a constant flow. In the thermodynamic limit, we obtain the exact expressions for several characteristic quantities in terms of the car density and the transmission rate. These quantities depend strongly on the system size at the phase boundaries; We analyse these finite size effects based on the finite-size scaling.

Traffic jam induced by a crosscut road in a traffic-flow model

Abstract A deterministic cellular automaton model is presented to simulate the traffic jam induced by a crosscut road in a two-dimensional traffic flow. The effect of a crosscut road on the traffic flow is investigated by the use of a computer simulation. The traffic jam appears when a shock (discontinuous interface of different car densities) is formed. The condition for shock formation is derived for car densities py and px of the crosscut road and its crossing streets. The phase diagram and the dependence of the traffic flow on the car densities are shown. Also, we study the shock structure and the scaling of its width. The width Δw of the shock scales with the system size L as Δw ≈ L 1 2 . We present a self-consistent mean-field theory for the traffic flow.

Effect of Jam-Avoiding Turn on Jamming Transition in Two-Dimensional Traffic Flow Model

A stochastic cellular automaton (CA) model is presented to study traffic flow in cities. In order to avoid traffic jam, cars are allowed to turn with probability p turn when cars are blocked ahead by other cars. It is found that the jam-avoiding turn has an important effect on traffic jam. With increasing car density, jamming transitions occur from a maximal velocity phase, through a homogeneously moving phase, to a jamming phase, with a critical point. Above the critical point, the jamming transition does not appear. It is shown that allowing cars to turn results in a complex phase diagram.

Traffic Jam and Shock Formation in Stochastic Traffic-Flow Model of a Two-Lane Roadway

We present a stochastic cellular automaton (CA) model to simulate the traffic jam induced by a car accident in the traffic flow of a two-lane roadway. The CA model is an extended version of the one-dimensional asymmetric exclusion model to take into account the stochastic exchange of cars between the first and second lanes. We study the traffic flow of the system when the translation invariance is broken by the insertion of a blockage which is induced by a car accident on the first lane. Using the computer simulation, it is found that the dynamical jamming transions occur successively from the phase 1, through the phase 2, to the phase 3 with increasing the density of cars. The phase 1 is characterized by the property such that no cars exist in the first lane and the cars on the second lane move with the maximal velocity. The phase 2 is characterized by the shock formation (a discontinuity of density) and the maximal current. In the phase 3, the discontinuity disappears and the traffic flow is not affecte...

Dynamical jamming transition induced by a car accident in traffic-flow model of a two-lane roadway

A deterministic cellular automaton model is presented to simulate the traffic jam induced by a car accident in a two-lane roadway. We study the traffic flow of the system when the translation invariance is broken by the insertion of a blockage which is induced by a car accident in the first lane. Using the computer simulation, it is shown that the dynamical jamming transitions occur successively from phase 1 to phase 4 with increasing the density of cars. In phase 1, no cars exist in the first lane and the cars in the second lane move with the maximal velocity. In phase 2, a discontinuity of the traffic-flow pattern appears and the cars move with the maximal current. Its discontinuity segregates system into two regions with different densities. In phase 3, the discontinuity disappears. In phase 4, the cars do not move ahead but vibrate between the first and second lanes.

Shock formation and traffic jam induced by a crossing in the 1D asymmetric exclusion model

The asymmetric simple-exclusion model on two-crossing one-dimensional lattices is considered for studying shock formation and traffic jams induced by a crossing. The condition for shock formation is derived for car densities p1 and p2 of the first and second street. The phase diagram and the dependence of the traffic current on the car densities are shown. We compare the present result with that of a car accident. Also, we investigate the shock formation induced by both a crossing and a car accident. It is found that the dynamical transitions occur successively with increasing car density. The phase diagram is shown.

1/f NOISE IN A TRAFFIC MODEL

One-dimensional traffic flow is simulated by a cellular-automaton-type discrete model. As we increase the car density, the model shows a phase transition between a jam phase and a non-jam phase. By adding random perturbations we found a 1/f power spectrum in the jam phase, whereas a white noise is observed in the non-jam phase.

Evolution of Traffic Jam in Traffic Flow Model

Traffic flow is simulated in a three-state cellular automaton model. In a two-dimensional cell without a crashed car, the ensemble average of the velocity of the cars is enhanced by the self-organization in the low-density phase of cars. In the high-density phase above p =0.5 of car density, the velocity is decreased and the system then degenerates into a global jamming phase in which all cars are stopped. A crashed car provides the seed of a jamming cluster, which grows into a global traffic jam even in the low-density phase. The growth of the jamming cluster is studied, and the time dependence of the number of jamming cars and the scaling law for the cell sizes are discussed.

Effect of traffic accident on jamming transition in traffic-flow model

A cellular automaton (CA) model is presented to simulate the traffic jam induced by a traffic accident. We investigate the effect of a traffic accident on the dynamical jamming transition in the traffic-Bow model. The dynamical jamming transition separates the moving phase in which all cars are moving and the jamming phase in which all cars are stopped. By the use of computer simulation, it is shown that the dynamical jamming transition occurs at lower density of cars with increasing delay time of a car passing over the position of the traffic accident. The phase diagram representing the moving phase and the jamming phase is shown. We also show the anisotropic effect of densities of cars on the dynamical jamming transition.

Cluster effect in initially homogeneous traffic flow.

It is shown that, in an initially homogeneous traffic flow, a region of high density and low average velocity of cars can spontaneously appear, if the density of cars in the flow exceeds some critical value. This region---a cluster of cars---can move with constant velocity in the opposite direction or in the direction of the flow, depending on the selected parameters and the initial conditions of the traffic flow. Based on numerical simulations, the kinetics of cluster formation and the shape of stationary moving clusters are found. The results presented can explain the appearance of a ``phantom traffic jam,'' which is observed in real traffic flow.

Jamming transition induced by a stagnant street in a traffic-flow model

A cellular automaton (CA) model is presented to simulate a traffic jam induced by a single stagnant street. The effect of a stagnant street on the dynamical jamming transition is investigated by the use of a computer simulation. The jamming transition describes the boundary between the moving phase in which cars are moving and the jamming phase in which all cars are stopped. It is shown that the jamming transition occurs at a lower total density of cars with an increasing local density of cars in the stagnant street. We find the phase diagram representing the moving phase and the jamming phase.

Anisotropic Effect on Jamming Transition in Traffic-Flow Model

We investigate the anisotropic effect of densities of cars on the dynamical jamming transition and self-organization in the cellular automaton model of traffic flow. By the use of computer simulation, it is shown that the traffic-jam transition occurs at higher density of cars with increasing the difference between the density of upward cars and the density of right cars. The phase diagram of the jamming transition is found. The patterns of traffic flow by self-organization of cars are shown. We find that the difference of the densities of cars has an important effect on the dynamical jamming transition. We also present a mean-field theory for the jamming transition in the traffic-flow model.

Spreading of Traffic Jam in a Traffic Flow Model

A cellular automaton (CA) model is presented to simulate the traffic jam induced by a traffic accident. The spreading of jamming cars induced by a car crash is investigated by computer simulation. An analogy is proposed between the crystal growth and the traffic-jam spreading. The scaling behavior of the traffic-jam spreading is studied. It is shown that the number N of jamming cars scales as N ≈ t 2.34±0.03 for p above the dynamical jamming transition p c =0.35 and N ≈ t 1.07 below p c where t is the time and p is the density of cars. The time constant t s , which is the time required for all cars to stop, scales as t s ≈ p -1.07±0.03 for p < p c . The following scaling form is found: p -1 N ≈( p 1.07 t ) 1.07 for p < p c .

On The Relation between Car Travel Speeds and Densities of Traffic Signals

On The Relation between Car Travel Speeds and Densities of Traffic Signals

Forest Fires: An Important Source of Benzo(a)Pyrene in the Caracas Valley

The levels of benzo(a)pyrene (BaP) were determined in downtown Caracas in order to have a first approach to the problem related to polycyclic aromatic hydrocarbons in this city. Caracas, the capital city of Venezuela is located 10.30° N and 66.77°E in a valley at an altitude of 996 m above sea level with an average temperature ranging from 18° to 23°C, and two distinctive climatic regimes, a dry and a wet season. The population is approximately 2.5 million with a car density of approximately 1000 vehicles/km2 and no industry. The valley is surrounded by mountains, the Avila National Park at the northern edge of the city with peaks of around 2200 m being the most important contribution to the green belt that has been preserved. As far as we know no other studies to determine the levels of BaP have been made in a populated urban area located near the equator.

A statistical theory of traffic flow on highways—III. Distributions of desired speeds

The development of statistical theories of traffic flow on highways has often started with a model in which each driver retains a fixed desired speed. This has been taken to mean that the distribution of desired speeds for the cars on the road at a given time was independent of density. However, it is shown that this model really implies that the desired speed distribution for the cars crossing any fixed point on the road in a certain period of time will be density-independent. The relation between the two distributions is computed, and the effect of the distinction on a theory of the density dependence of traffic behavior is discussed. The important input for a statistical theory of traffic flow seems to be a description of the desired speeds of the cars using the road in a period of time and a model of passing and queuing behavior. The number of cars crossing a fixed point in unit time appears to be more basic in such a theory than the density of cars.