Traffic Flux Research Articles

Estimating spatial and temporal patterns of urban anthropogenic heat fluxes for UK cities: the case of Manchester

A model is proposed for determining the temporal and spatial patterns of anthropogenic heat fluxes in UK urban areas. It considers buildings, traffic, and metabolic heat flux sources and has been evaluated to a good accuracy against alternative data for the Greater Manchester area in the UK. Results are presented at spatial resolution of 200 × 200 m although the model itself is scalable depending on data availability. In this paper, results are generated using a set of urban morphology units so that detailed and time-consuming accounting of individual building and road emissions is not required. The model estimates a mean heat emission of 6.12 Wm-2 across Greater Manchester, with values in the region of 10 Wm-2 for non central urbanized areas and 23 Wm-2 in city center areas. Despite this difference, the results are not described by a simple distance decay function, as has been reported for other cities, due to the influence of satellite towns and the influence of the road network. Buildings are the dominant emitter, contributing some 60% of total emissions across the city compared to around 32% for road traffic and 8% for metabolic sources.

The effects of intelligent traffic light on the crossing traffic flow

Using the improved NaSch traffic model, we simulate the traffic flow on the crossroad under open boundary condition. The simulations are controled by ordinary traffic light and intelligent traffic light respectively. The results show that the average speed and the traffic flux under control of the later are greater than that controled by the former. Moreover, the vehicles controled by intelligent traffic light can cut down the unnecessary waiting time.

Health Impact of Road Traffic Emissions, Forecasted Decrease Associated to Implementation of European Standards in French Vehicle Fleet

SAB4-PD-01 Session Title: Air Pollution: Mechanisms and Health Introduction: Health Impact Assessment (HIA) of road transports emissions, based on exposure response functions (ERF) from epidemiologic studies, have influenced new European standards for terrestrial vehicles emissions. This study aims at quantifying the health impact decrease attributable to European Standards Implementation in France between 2000 and 2010. Methods: Urban exposure to road traffic emissions (RTE) was evaluated with data from French air quality-monitoring network during the year 2000. The concentrations in NO2 and PM10 were estimated by a geostatistic approach in grid cells of 4 km. Modelling the emissions of stationary and mobile sources refined this approach. The second approach allows estimating the contribution ratio of RTE in the total atmospheric concentrations. The population data in each cell and stratified by age were extracted from the 1999 French census. HIA method followed the WHO and InVS methodologic recommendations. Health impacts (HI) were estimated with European epidemiologic ERF derived for elderly, adults, and children. For children, new health outcomes such as preterm birth or childhood cancers were included. The morbidity and mortality rates for the general population came from French sanitary statistics. Comparison of the results between 2000 and 2010 made it possible to quantify the reduction associated with the introduction of new standards of emission. Results: In urban area, mean ambient concentration (all sources) should have decreased by 27% for NO2 and 28% for PM10 during the 2000 to 2010 period. However, RTE contribution rates will follow a lower decreasing trend for both pollutants (respectively 18%, 20%). In 2000, main HI due to RTE are long-term mortality (7700 cases per year), cardiovascular hospitalization (10,600), and short-term mortality in adults (3600). In children, majors HI are bronchitis (258,000), asthma attacks (47,200), and premature birth (11,765). Contribution of RTE to HI results will decrease in 2010 by 17% to 49% according to health outcomes. Conclusions: Major uncertainties, except those in the exposure assessment, come under ERF used for children. Evidence of causality between certain health effects and the air pollution has not yet been strongly shown. ERF for childhood cancer and preterm birth are based on a single epidemiologic study. Moreover, we were unable to take demographic and population health evolutions into account. HIA results plead for accompanying actions on traffic flux that will increase emissions standard benefits for population health.

Molecular motor traffic: From biological nanomachines to macroscopic transport

All cells of animals and plants contain complex transport systems based on molecular motors which walk along cytoskeletal filaments. These motors are rather small and have a size of 20–100 nm but are able to pull vesicles, organelles and other types of cargo over large distances, from micrometers up to meters. There are several families of motors: kinesins, dyneins, and myosins. Most of these motors have two heads which are used as legs and perform discrete steps along the filaments. Several aspects of the motor behavior will be discussed: motor cycles of two-headed motors; walks of single motors or cargo particles which consist of directed movements interrupted by random, diffusive motion; cargo transport through tube-like compartments; active diffusion of cargo particles in slab-like compartments; cooperative transport of cargo by several motors which may be uni- or bi-directional; and systems with many interacting motors that exhibit traffic jams, self-organized density and flux patterns, and traffic phase transitions far from equilibrium. It is necessary to understand these traffic phenomena in a quantitative manner in order to construct and optimize biomimetic transport systems based on motors and filaments with many possible applications in bioengineering, pharmacology, and medicine.

Ecological consequences of traffic organisation in ant societies

Many species of ants engage in social foraging in which traffic develops over pathways defined by pheromones or physical roads cleared through debris. Worker ants from the same colony have a common underlying evolutionary interest in their collective performance. Thus, ant traffic makes an interesting comparison to other kinds of cellular or organismal traffic composed of elements with varying degrees of shared or disparate goals. Recent studies have revealed how small-scale interactions among ants amplify to create large-scale traffic structure, such as segregation of counterflows. However, much less is known about the ecological costs and benefits of different kinds of traffic organization. The common assumption that maximum traffic flux provides maximum ecological benefit needs closer scrutiny. Ant traffic provides a potentially useful model system for experimental study of crowd panics, and for assessing the role of transport networks in creating scaling relationships between the size and activity rates of the entities they serve.

Growth and decay of shock and acceleration waves in a traffic flow model with relaxation

The usual Ficken-based constitutive relation for traffic flux is replaced with one based on the Maxwell–Cattaneo model. The resulting flux law, which now takes into account the reaction time of driver and vehicle, results in a second-order, hyperbolic generalization of Burgers’ equation as the PDE governing the traffic density. An analytical study of this equation is presented with an emphasis on shock and related kinematic wave phenomena. Specifically, the exact traveling wave solution (TWS) is derived and it is shown that shock formation is possible only if the diffusivity is non-vanishing. Using singular surface theory, exact amplitude expressions for both shock and acceleration waves are obtained and their temporal evolution determined. The exact upper bound of the reaction time parameter is established and connections between singular surface and TWS results are noted.

Carbonaceous Aerosol in the Breathable Particulate Matter (PM10) in Urban Area

Carbonaceous material is a large fraction of urban aerosol and it is classified into Elemental Carbon (EC) and Organic Carbon (OC). EC particles are emitted from combustion sources. Because most combustion sources are anthropogenic and generally EC does not undergo chemical transformations, EC is a good indicator of primary anthropogenic primary pollution. OC particles species are emitted from primary emission sources either anthropogenic or biogenic sources. In this paper we have measured the ground concentration of Particulate Matter (PM), Total Carbon (TC), EC and OC in two Monitoring Stations in Rome. The first station is situated downtown Rome (near S.M. Maggiore Cathedral) where the traffic emission flux is strong. The second station is located in the inner a green park (Villa Ada Park): this site is not directly influenced by anthropogenic emissions. The results show that in Rome the TC contribution is about 30% of PM and the OC/EC vary between 0.5 and 1.5 according to the site we are considering. About the chemical particle composition the long-chain carboxylic have been identified as major constituent of organic aerosol and a range values are reported for two important compound class, the Polyciclic Aromatic Hydrocarbons and the nitro-PAHs wich are at very low levels.

Two-Phase Fluids Model for Freeway Traffic Flow and Its Application to Simulate Evolution of Solitons in Traffic

A two-phase fluids model for mixing traffic flow on freeways has been proposed, where vehicles are decomposed into two parts (i.e., phases)—slow moving and fast moving–denoted by subscripts i=1 and 2, respectively. Based on the fact that both phases should be at rest under traffic jam conditions, it is assumed that the vehicular speeds for both phases are functions of the global traffic density, so that traffic flux can be expressed explicitly, considering that the speed of the second phase may be decreased when the mass fraction of the first phase becomes large. In addition to the relation to global density of traffic, it is assumed that the speed of vehicles in the second phase also depends on the mass fraction for the first phase. By neglecting the traffic generation rate, the governing equations from the mass conservation law were solved numerically with the Yee-Roe-Davis second-order symmetrical total variable diminishing algorithm. Two cases were considered: first, that there exists a soliton in the initial distribution of global density; second, that there is an initial uniform global density. Both cases were allowed to have a soliton in the initial density for the slowly moving vehicles. The numerical results indicate that the evolution of a soliton in traffic is quite different from those in water wave problems. The initial solitary-wave perturbation has been distorted dramatically. It was found that the presence of a soliton just in the slowly moving vehicles can increase global density, which means that traffic mixing can be viewed as a source of density wave production. Under very congested traffic flow, the speed for moving vehicles fast approaches that of vehicles in the first part.

Conceptual and Scaling Evaluation of Vehicle Traffic Thermal Effects on Snow/Ice-Covered Roads*

The potential thermal effects of traffic on road surface thermal energy balance under frost/snow cover conditions have been largely ignored in meteorological evaluations of road ice deposit conditions. Preliminary exploration of these effects, particularly for heavy traffic scenarios with calm wind conditions and an ambient temperature of 0°C, is provided in this study using a conceptual model. Observational data were used to constrain the model, and parameterizations were employed to estimate the various heat transfer processes involved. The results indicate that, for heavy traffic situations, as well as for stopped traffic at intersections, the traffic thermal flux contribution at the surface is noticeable in a wide range of possible frost/snow-covered road conditions. The sensitivity to variation in traffic density, speed, and the emissivity of vehicle radiative surfaces, among others, is evaluated. Simple quantification of these traffic thermal effects, which might be considered in operational meteorological model forecasting of icy road conditions, is offered.

Fukui–Ishibashi Traffic Flow Models with Anticipation of Movement of the Car Ahead

We propose and study new vehicular traffic flow models, incorporating the anticipation of the change in the car spacings ahead in the determination of the speed of the cars in each time step. Our models are based upon the Fukui and Ishibashi (FI) traffic flow model in which cars are allowed to move a maximum of M sites in each time step if spacing permits, together with a probabilistic delay for the cars moving at the maximum speed. By taking into account the anticipation in the change of car spacing due to movement of the car ahead, the present models give an enhanced traffic flux as compared to the FI model. The present models also give a fundamental diagram consisting of three phases – a feature consistent with traffic flow observations.

An environmental noise study in the city of Cáceres, Spain

An urban noise survey was conducted in the city of Cáceres (Extremadura, Spain). In order to select the different points where measurements were to be taken, the streets were classified according to their use in communicating the different zones of the city. The four categories considered were all through roads (service roads were excluded): arterial roads outside the central zone, arterial roads in the central zone, other two-way roads connecting different zones, other one-way roads. The first two categories were found to be statistically indistinguishable, and together with the third had the highest noise levels—median Leq above 70 dB(A). The one-way roads were some 5 dB(A) quieter. Thus the sound levels in Cáceres, a small city, are quite high, with 90% of our measurements surpassing an Leq of 65 dB(A) during working hours. Finally, relationships were established between the equivalent level, traffic flux, and the main noise level percentiles, with results in good agreement with those of other authors. We can also conclude that city noise can be usefully studied by classifying the streets according to their use.

Effects of Announcing Global Information in a Two-Route Traffic Flow Model

A two-route traffic model with a built-in decision-making process is proposed and studied numerically. The instantaneous average speeds on the routes are announced as global information. Two types of drivers, dynamic and static, are introduced. The dynamic drivers use the global information for making decisions. It is shown that announcing the instantaneous average speeds on the routes results in a better performance of the two-route system in terms of the traffic flux compared to announcing the transit time. When the static drivers randomly select a route, the presence of the dynamic drivers does not improve the traffic flux of the system. When the static drivers tend to select a particular route, the presence of dynamic drivers leads to a higher flux. Our model thus incorporates the effects of adaptability into the cellular automaton models of traffic flow.

SPVD: A magnetic vehicle detection system using a low power magnetometer

The Self Powered Vehicle Detector (SPVD) is a motor vehicle detection system, presently under development, that detects a vehicle's presence by measuring its magnetic signature in the roadway. An optimized two axis Brown fluxgate magnetometer is used as the transducer with a digital nulling loop to perform sensor offset nulling and logic functions. An FM telemetry link containing three encoded tones conveys the roadway emplanted SPVD vehicle presence and device status information to a roadside control unit which may interface with other traffic control systems. A minimum one year operational lifetime is anticipated in a roadway with a 20,000 vehicles/day traffic flux.