Car Density Research Articles

Dieselization and Road Transport CO<sub>2</sub> Emissions: Evidence from Europe

Road transport carbon dioxide emissions were analyzed, by focusing on a panel of 14 European countries for the time span 1995-2007. We deal with the existence of contemporaneous correlation by using the Panel Corrected Standard Errors estimator. We extend the empirical literature by controlling the effect of new diesel passenger car registrations and the average power of those vehicles. The price of gasoline and income reduce road transport carbon dioxide emissions, while population density and average power of new diesel passenger cars raises those emissions. We deepen the debate about dieselization, concluding that saving emissions by using diesel tend to be surpassed by the increased kilometers driven.

Optimal Paths on Urban Networks Using Travelling Times Prevision

We deal with an algorithm that, once origin and destination are fixed, individuates the route that permits to reach the destination in the shortest time, respecting an assigned maximal travel time, and with risks measure below a given threshold. A fluid dynamic model for road networks, according to initial car densities on roads and traffic coefficients at junctions, forecasts the future traffic evolution, giving dynamical weights to a constrained K shortest path algorithm. Simulations are performed on a case study to test the efficiency of the proposed procedure.

A non-parametric CAE approach to office rents: Identification of Helsinki metropolitan area submarkets

The study attempts to identify and estimate the office rents of submarkets in the Helsinki metropolitan area. We applied a non-parametric empirical approach called the CAE method to identify six parameters: highway APD (access point distance), car traffic density, light rail APD, main retail distance, office building density and effective age. Our results suggest that car traffic density is the single most influential parameter. Office rent decreases with effective age and increases with the density of office buildings. Longer distances to highway access points and to the main retail centres decrease office rents, while shorter distances to the light rail access points increase office rents in general and particularly for locations close to highway access points. We identified local peaks by inspecting multiple graphs. The local peaks were considered evidence for the existence of commercial office submarkets within the Helsinki metropolitan area. We identified seven submarkets at different rent levels. Interpreting submarkets from the CAE graphs allowed us to recognise particular business districts in the Helsinki metropolitan area. In addition, it is of great significance that the roles of the given and estimated variables can be exchanged. The method is directly applicable in real estate studies using adapted database and prescribed smoothing parameters.

Effect of randomization in the Biham–Middleton–Levine traffic flow model

This paper studies the effect of randomization in the Biham–Middleton–Levine(BML) traffic flow model. It is found that the average velocity exhibits a first-orderphase transition from moving phase to jamming phase under periodic boundaryconditions. The intermediate stable phase identified in the original deterministic BMLmodel disappears with the introduction of randomization. The average velocityin the moving phase and the critical car density decrease as the randomizationprobability increases. We have developed a mean-field theory which successfullypredicts the average velocity in the moving phase. Under open boundary conditions,there are only two phases and the maximum current phase does not occur. Thedependence of the average velocity, the density and the flow rate on the injectionprobability in the moving phase have also been obtained through the mean-fieldtheory.

Piecewise linear concave dynamical systems appearing in the microscopic traffic modeling

Motivated by microscopic traffic modeling, we analyze dynamical systems which have a piecewise linear concave dynamics not necessarily monotonic. We introduce a deterministic Petri net extension where edges may have negative weights. The dynamics of these Petri nets are uniquely defined and may be described by a generalized matrix with a submatrix in the standard algebra with possibly negative entries, and another submatrix in the minplus algebra. When the dynamics is additively homogeneous, a generalized additive eigenvalue is introduced, and the ergodic theory is used to define a growth rate. In the traffic example of two roads with one junction, we compute explicitly the eigenvalue and we show, by numerical simulations, that these two quantities (the additive eigenvalue and the average growth rate) are not equal, but are close to each other. With this result, we are able to extend the well-studied notion of fundamental traffic diagram (the average flow as a function of the car density on a road) to the case of roads with a junction and give a very simple analytic approximation of this diagram where four phases appear with clear traffic interpretations. Simulations show that the fundamental diagram shape obtained is also valid for systems with many junctions.

A new continuum traffic model with the effect of viscosity

Through considering the connection between microscopic car-following model and macroscopic continuum model, a new viscous vehicular flow model is proposed, in which the viscosity coefficient is determined by a more realistic constitutive relationship between averaged reaction time of drivers and the car density. Further analysis indicates that two traffic sound speeds in this viscous model may determine the existence and the stability of traveling wave solutions with an analytical method.

Impacts of traffic noise on anuran and bird communities

Anurans and birds rely on sound for a number of social behaviors. Species that use roadside habitats are exposed to traffic noise that can mask important social signals and directly affect the community diversity and composition. We evaluate the impact of traffic noise on anuran and bird species richness, species occurrence, and composition in Puerto Rico, where there is a high density of highways and cars that generate high levels of noise pollution. We compared paired forest sites near (100 m, n = 20, dB > 60) and far (>300 m, n = 20, dB 80 dB), which may allow them to tolerate high levels of anthropogenic noise.

Optima and Equilibria for a Model of Traffic Flow

The paper is concerned with the Lighthill–Whitham model of traffic flow, where the density of cars is described by a scalar conservation law. A cost functional is introduced, depending on the departure and arrival times of each driver. Under natural assumptions, we prove the existence of a unique globally optimal solution, minimizing the total cost to all drivers. This solution contains no shocks and can be explicitly described. We also prove the existence of a Nash equilibrium solution, where no driver can lower his individual cost by changing his own departure time. A characterization of the Nash solution is provided, establishing its uniqueness. Some explicit examples are worked out, comparing the costs of the optimal and the equilibrium solutions. The analysis also yields a strategy for optimal toll pricing.

Splitting of Traffic Flows to Control Congestion in Special Events

We deal with the optimization of traffic flows distribution at road junctions with an incoming road and two outgoing ones, in order to manage special events which determine congestion phenomena. Using a fluid‐dynamic model for the description of the car densities evolution, the attention is focused on a decentralized approach. Two cost functionals, measuring the kinetic energy and the average travelling times, weighted with the number of cars moving on roads, are considered. The first one is maximized with respect to the distribution coefficient, and the second is minimized with respect to the same control parameter. The obtained results have been tested by simulations of urban networks. Decongestion effects are also confirmed estimating the time a car needs to cross a fixed route on the network.

SIMULATION STUDY OF TRAFFIC ACCIDENTS IN BIDIRECTIONAL TRAFFIC MODELS

Conditions for the occurrence of bidirectional collisions are developed based on the Simon–Gutowitz bidirectional traffic model. Three types of dangerous situations can occur in this model. We analyze those corresponding to head-on collision; rear-end collision and lane-changing collision. Using Monte Carlo simulations, we compute the probability of the occurrence of these collisions for different values of the oncoming cars' density. It is found that the risk of collisions is important when the density of cars in one lane is small and that of the other lane is high enough. The influence of different proportions of heavy vehicles is also studied. We found that heavy vehicles cause an important reduction of traffic flow on the home lane and provoke an increase of the risk of car accidents.

Predicting Motorway Traffic Performance by Data Fusion of Local Sensor Data and Electronic Toll Collection Data

In this article data fusion from different sources in order to improve estimation and prediction accuracy of traffic states on motorways is proposed. This is demonstrated in two case studies on an intraurban and an interurban motorway section in Austria. Data fusion combines local detector data and speed data from the Electronic Toll Collection (ETC) system for heavy goods vehicles (HGV). A macroscopic model for open motorway sections has been used to estimate passenger car and HGV density, applying a standard state-space model and a linear Kalman filter. The resulting historical database of 4 months of speed-density patterns has been used as a basis for pattern recognition. A nonparametric kernel predictor with memory length of 9 and 18 hours has been used to predict HGV speed for a prediction horizon of 15 minutes to 2 hours. The results showed a good overall prediction accuracy. Correlation analysis analysis showed little bias of predicted speed for free flow and congested time intervals, whereas transition states between free flow and congestion were frequently biases. The prediction accuracy can be improved by applying a combination of different prediction methods. However, the computational performance of the predictor needs to be further improved prior to implementation into a traffic management center.

Effect of damaged car evacuation on traffic flow behavior after perpendicular collisions in a bidirectional-lane highway with open boundaries

A new model of the perpendicular accident probability of cars in a bidirectional-lane highway with open boundaries is proposed. The numerical study is done using the Nagel–Schreckenberg (NS) model in parallel dynamics. Indeed, in addition to parallel collisions that occur in the same lane, we also take into account perpendicular accidents between cars moving in opposite directions. To be consistent with reality, we assume that those cars involved in perpendicular collision with a sufficient impact speed, V12, get damaged and must then be removed from the road. It is found that the final density of cars in lane 1 depends strongly on the threshold value V12. Besides, both the perpendicular, Pacper, and parallel, Pacpar, accident probabilities per car and per time step depend largely on the injecting rate α1, the extracting rate β1 in lane 1 and the fractions r1 and r2 in lane 2 of the injecting and extracting rates, respectively. In fact, Pacpar and Pacper show abrupt jumps that increase with increasing α1 and β1. Furthermore, Pacper increases with increasing fractions r1 and/or r2. Taking into account the braking probability P1 of the NS model, both Pacpar and Pacper decrease.

Modeling U-turn traffic flow

Median U-turns are sometimes installed to improve the traffic flow at busy intersections by eliminating left turns. Using a microscopic traffic model, we confirmed the presence of transitions from free flow to congested flow with increasing car inflow density. In addition, our proposed rules inside a U-turn curve, which accounted for safety issues and an asymmetric lane changing behavior (outer-to-inner vs. inner-to-outer lane transitions), predicted the speed distribution of cars after the U-turn curve. We found that U-turn curves installed for improving traffic flow at busy intersections produced their desired effects only when there is minimal interaction between cars.

THE EFFECT OF DAMAGED VEHICLES EVACUATION ON TRAFFIC FLOW BEHAVIOR

The effect of the damaged car evacuation on the traffic flow behavior is investigated, in the one-dimensional deterministic Nagel–Schreckenberg model, using parallel dynamics. A realistic model applied to the cars involved in collisions is considered. Indeed, in this model we suppose that the damaged cars must be removed from the ring with a probability P exit . This investigation enables us to understand how the combination of the two probabilities, namely P col and P exit , acts on density and current. It is found that the current and density at the steady state, depend strongly on the initial density of cars in the ring. However, for the intermediate initial density ρi, the current J decreases when increasing either P exit and/or P col . While, for high initial density, J increases passes through a maximum and decreases for large values of P exit . Furthermore, the current can decrease or increase with the collision probability depending on the initial density.

Resonance, criticality, and emergence in city traffic investigated in cellular automaton models

The complex behavior that occurs when traffic lights are synchronized is studied for a row of interacting cars. The system is modeled through a cellular automaton. Two strategies are considered: all lights in phase and a "green wave" with a propagating green signal. It is found that the mean velocity near the resonant condition follows a critical scaling law. For the green wave, it is shown that the mean velocity scaling law holds even for random separation between traffic lights and is not dependent on the density. This independence on car density is broken when random perturbations are considered in the car velocity. Random velocity perturbations also have the effect of leading the system to an emergent state, where cars move in clusters, but with an average velocity which is independent of traffic light switching for large injection rates.

Bivariate time-periodic Fokker-Planck model for freeway traffic

Recorded data of the density of cars and their speed from a German motorway are modeled by a bivariate Fokker-Planck equation. In order to cope with the evident diurnal variation, we assume a 24 h-periodicity in the drift and diffusion coefficients of this equation. After fitting these and smoothing them by polynomials, we validate the model by comparison of the empirical densities and densities generated by the model dynamics. We show that the time dependence of the drift field is related to a saddle-node bifurcation due to which the congested traffic state becomes stable. The separatrix between the basins of attraction is used to define flowing and jamming traffic during rush hours and characterizes the traffic dynamics together with the fixed points and the centre manifold.

Evaluating urban PM 10 pollution benefit induced by street cleaning activities

Despite their burden in urban particulate air pollution, road traffic non-exhaust emissions are often uncontrolled and information about the effectiveness of mitigation measures on paved roads is still scarce. The present study is aimed to evaluate the effectiveness of mechanical sweeping/water flushing treatments in mitigating urban road dust resuspension and to quantify the real benefit in terms of ambient PM 10 concentrations. To this aim a specific campaign was carried out in a heavily trafficked central road of Barcelona (Spain), a Mediterranean city suffering from a traffic-related pollution, both for a high car density and a frequent lack of precipitation. Several street washings were performed by means of mechanical sweepers and pressure water during night in all traffic lanes and sidewalks. PM 10 levels were simultaneously compared with four reference urban background air quality stations to interpret any meteorological variability. At the downwind measurement site, PM 10 concentrations registered a mean daily decrease of 8.8 μg m −3 during the 24 h after street washing treatments. However 3.7–4.9 μg m −3 of such decrease were due to the meteorological variability detected at the upwind site, as well as at two of the reference sites. This reveals that an effective decrease of 4–5 μg m −3 (7–10%) can be related to street washing efficiency. Mitigation of road dust resuspension was confirmed by investigating the chemical composition of airborne-PM 10 filters. Concentrations of Cu, Sb, Fe and mineral matter decrease significantly with respect to concentrations of elemental carbon, used as tracer for exhaust diesel emissions. High efficiency of street washing in reducing road dust loads was found by performing periodic samplings both on the treated and the untreated areas.

The effect of on-ramp and off-ramp on the one dimensional road with open boundaries

The effect of one on-ramp (entry) and one off-ramp (exit) is investigated numerically in a one dimensional cellular automaton traffic flow model, with open boundary conditions, using parallel dynamics. Our aim in this paper is to study how the injection rates α and α0 and the extraction rates β and β0 act on the density and flux of cars in a one dimensional road. The priority of occupation at entry site i1 (removing at exit site i2) is attributed to the particle that entered (was absorbed) the chain. Phase diagrams in (β0, α0) and (β, α0) plans are established. For α = 0.1, they show three different topologies in the flow behaviour. The first one corresponds to the presence of four regions, by varying α0, namely low-density phase (LDP), intermediate-density phase (IDP), plateau current phase (PCP), and high-density phase (HDP). In the second topology, the intermediate-density phase disappears. The third topology presents only two regions, i.e., low- and high-density phases. For small values of α, the (IDP) and (PCP) disappear, respectively, by increasing β. When increasing α, the fourth topology, corresponding to one phase (HDP), appears for low values of β and β0.

Effect of real-time information upon traffic flows on crossing roads

The effect of real-time information on the traffic flows of the crossing roads is studied by simulations based on a cellular automaton model. At the intersection, drivers have to enter a road of a shorter trip-time, by making a turn if necessary, as indicated on the information board. Dynamics of the traffic are expressed as a return map in the density-flow space. The traffic flow is classified into six phases, as a function of the car density. It is found that such a behavior of drivers induces too much concentration of cars on one road and, as a result, causes oscillation of the flow and the density of cars on both roads. The oscillation usually results in a reduced total flow, except for the cases of high car density.

Exposure of Rome City Tram Drivers to Airborne Platinum, Rhodium, and Palladium

To investigate the exposure of tram drivers of Rome to Pt, Rh, and Pd in total suspended particulate, PM10, and PM2.5 fractions. Sampling was performed on a tram running on about 15-km pathway characterized by a medium-high traffic car density. The analytical determination of metals was performed using inductively coupled plasma mass spectrometry. Mean element values (in pg/m) total suspended particulate, PM10, and PM2.5, were Pt, 20.3, 14.1, and 8.86, Rh, 3.99, 2.83, and 1.94, and Pd, 82.1, 58.0, and 15.2, respectively. Although the Pt, Rh and Pd levels in urban air were found to be still 8 to 11 orders of magnitude below the values thought to cause adverse effects on adult worker health, periodic environmental monitoring would be necessary to detect possible increments which could affect occupational exposure of tram drivers.