Aplicación del modelo de microsimulación PTV VISSIM para el cálculo de emisiones del tráfico

Aplicación del modelo de microsimulación PTV VISSIM para el cálculo de emisiones del tráfic

Modelling the effects of local emission abatement measures in hot-spots of Madrid

This work aims at estimating NOx and PM10 emissions from road traffic with high spatial and temporal resolution (seconds and meters). This is useful to understand the effect of local abatement measures and it is an essential input to microscale air quality models. For that, 1-hour representative traffic scenarios are simulated with the traffic microsimulation model VISSIM in selected hot-spots. Measured traffic data (fluxes and fleet composition) are used as inputs for the model to obtain speed-time profiles for each vehicle. These profiles are used to calculate specific emission factors for different vehicle classes according to the VERSIT+micro model through the ENVIVER interface. This modelling system allows assessing possible effects of different local scale interventions such as vehicle volume reduction, fleet composition and vehicle technology changes, etc. both on the total amount of emission amount and their spatial distribution. According to this analysis, some local measures may bring about important emission reductions in both locations, up to 28% and 23% for NOx and PM10 respectively. Such measures may therefore constitute a valuable complement for city-scale policies and measures

Comparison of Microscale Traffic Emission Models for Urban Networks

Traffic is the major source of pollution in many cities. Despite recent efforts to improve air quality, some issues (usually related to NOX and PM) remain in urban areas worldwide. Ambient air quality standards non-compliance situations are often linked to traffic-related hot-spots. The assessment of potential solutions for such locations requires very high-resolution models that can successfully capture the complexity of the processes that determine emissions from mobile sources and provide accurate inputs for highly detailed microscale air quality models. These estimations are based on acceleration-deceleration processes and speed that are significantly influenced by congestion. There are several approaches that can be used for this purpose. Among them, modal emission models are able to compute emission rates as a function of specific engine or vehicle operating modes with very high temporal resolution (seconds) being suitable for this kind of analysis. The aim of this work is to obtain detailed traffic emissions from simulated driving patterns in different typologies of complex urban network configurations in Australia and Spain. To obtain detailed traffic results, a microscale traffic flow simulation model was fed with measured traffic data. Traffic results were used as input for two microscale modal emission models (the Australian P?P and the European PHEM-light). To understand the response of these models, detailed estimation of NOX emissions and fuel consumption for diverse vehicle types were compared. In addition to differences on vehicle classification and other implementation details, large differences in the results are observed due to Power-to-Mass ratios. Therefore, it is essential to define power and load parameters as accurately as possible for each vehicle class (in addition to realistic driving patterns) to obtain accurate emissions. Our test suggest that satisfactory results can be achieved with any of the models if reliable information of vehicle fleet composition and vehicle characteristics is provided

Traffic Emission Simulation and Validation with Measured Data in South Korea

In major urban areas, air quality is directly related to traffic emissions. Major efforts have been made in recent years to compute emissions from simulated traffic conditions at microscale level in an accurate way. To validate this modelling techniques on-road air pollutant emissions of Nitrogen Oxides (NOx) estimated from mobile monitoring laboratory data are compared to the computed emissions results. The selected location is a traffic hot-spot with more than 4000 vehicles at weekday peak hours. The study area is a 300 m x 300 m domain focused on a signalized intersection of two major roads in Seoul (South Korea). For the traffic simulation, detailed information of the network (geometry, number of lines and traffic light location) is needed along with traffic light cycles. Traffic volumes, routes and fleet composition are estimated from CCTV cameras. Speed-time profiles for peak and off-peak hours on weekdays are simulated with the traffic microsimulation model PTV VISSIM. The predicted profiles are compared to the GPS data measured by the mobile laboratory in real traffic conditions. This comparison is useful to discriminate potential errors from the traffic simulation and the emission computation algorithms. Traffic emissions are computed with VERSIT+micro emission models through the TNO ENVIVER interface on a grid of 5 m x 5 m spatial resolution and temporal resolution of 1 hour along with the emission results of the individual trips. This contribution is useful to validate the emission results computed with the VISSIM-VERSIT+micro/ENVIVER modelling system

Modelling reactive pollutants dispersion in an urban hot-spot in summer conditions using a CFD model coupled with meteorological mesoscale and chemistry-transport models

Air quality assessment requires detailed studies about urban air pollution. In a city, the interaction between atmosphere and urban morphology induces complex flow pattern which leads to irregular spatial distributions of pollutants in the streets. In addition, the influence of chemical reactions and the variability of air temperature and wind make difficult to reproduce the pollutants dispersion at microscale during long periods, especially in summer conditions. The aim of this work is to simulate reactive pollutants dispersion in summer conditions in an urban hot-spot using a computational fluid dynamics (CFD) model. In summer, the high solar radiation and the high levels of O3 concentration requires introducing a chemical system in the CFD modelling. Focusing on studying the NO2 dispersion, the photostationary state is implemented in the CFD simulation. The detailed boundary conditions are obtained from the outputs of other microscale and mesoscale models. The vertical profiles of wind speed, turbulence and temperature are derived from a meteorological mesoscale simulation (WRF) and the background concentration of pollutants is obtained from a chemistry-transport (CMAQ) simulation. Additionally, the emissions of traffic-related pollutants are implemented into the CFD simulation based on the results of a microscale traffic model. Finally, the time evolution of meteorological variables and pollutants concentration resulting from the CFD simulation are thoroughly evaluated with measurements registered at several points from an experimental campaign carried out in the research area (in the framework of TECNAIRE project (S2013/MAE-2972)). Regarding the air quality assessment, the deviation of NO2 concentration including chemical reactions in the CFD simulation is quantified in comparison with a non-reactive pollutant. Likewise, the differences of assuming neutral atmospheric conditions instead of using profiles from mesoscale model for this period are analyzed through the time average concentration map at pedestrian level. In this way, the improvements included in the CFD modelling and the conclusions obtained from this analysis provide information on how to simulate reactive pollutant dispersion in an urban hot-spot in summer conditions

Development of urban air quality plans and measures in Madrid (Spain) under a multi-scale air quality modeling approach

Poor urban air quality is one of the main environmental concerns worldwide. According to WHO (WHO, 2014) outdoor air pollution caused 3.7 million premature deaths in 2012, most of them in urban areas where both, emission sources and population concentrate. Even in Europe, despite of significant efforts, exceedances of air quality standards are common in large urban areas, particularly for NO2 (EEA, 2014). Therefore, tackling urban air quality constitutes a pressing priority from the social and political point of view. However, air pollution dynamics in urban environments is extremely complex and the design and assessment of effective emission abatement plans and measures posses a major scientific challenge. Emissions of different pollutants from a variety of sources interact through intertwined atmospheric transport processes and chemical transformations involving several spatial and temporal scales. In this context, air quality modelling constitutes an essential research tool for understanding and simulating the potential effect of emission abatement measures as well as to identify the best course of action to improve air quality in cities. This contribution reflects on the inherent complexities of urban air pollution and the development of air quality plans for the Madrid city as a representative case study

High resolution emission estimation in hot-spots of Madrid (Spain)

This work aims at obtaining high resolution NOx and PM10 emissions from road traffic at hot-spots in Madrid (Spain). For that, 12 1-hour representative scenarios are simulated with the traffic microsimulation model VISSIM. Measured traffic data (fluxes and fleet composition) are used as input for the model to obtain speed-time profiles for each vehicle. These profiles are used to predict representative emission factors for different vehicle classes in the VERSIT+micro model through the ENVIVER interface. Emission factors are compared with the ones of COPERT 4, a widely used average-speed model, as a preliminary model assessment. The results are strongly influenced by low average speeds due to saturated traffic situations

High resolution emission estimation in a heavily trafficked urban area in Madrid (Spain)

This work aims to obtain high resolution NOx and PM10 emissions related to traffic activity at a hot-spot in Madrid (Spain). For that, twelve representative scenarios for a heavily trafficked roundabout are simulated with the traffic microsimulation model VISSIM. Measured traffic data (fluxes and fleet composition) are used as input for the model to obtain speed-time profiles for each vehicle. These profiles are used to predict representative emission factors for different vehicle classes in the VERSIT+micro model, through the ENVIVER interface. The emission factors are compared with the ones of COPERT IV, a widely used average-speed model, as a preliminary model assessment. The results are strongly influenced by low average speeds due to saturated traffic situations

CFD modelling of particle matter dispersion in a real hot-spot

Urban air quality is one of the main environmental concerns. The interaction between atmosphere and buildings induces complex flows within the streets and squares. This fact joint with the traffic emissions produce a heterogeneous distribution of pollutants with high gradients of concentration. The main objective of this work is to obtain high resolution maps of particle matter concentration using a CFD model so as to analyze air quality and population exposure. This study is focused on a heavily trafficked roundabout in Madrid (Fernandez Ladreda square). To achieve this objective, CFD modelling coupled with detailed emissions of PM10 and PM2.5 and outputs from WRF meteorological mesoscale model is performed. Emissions from vehicle exhaust and particle resuspension are considered with a resolution of 5 m x 5 m. The simulated mesoscale vertical profiles of wind velocity and turbulent kinetic energy, previously checked with onsite meteorological measurements, are used as boundary conditions. The effects of urban vegetation are modelled and moreover, the CFD modelling is improved implementing vehicle induced turbulence as a source of turbulence on the roads. Modelling results are evaluated for several periods of summer and winter by using data from experimental campaigns carried out in this zone in the framework of the TECNAIRE research project

Development of road traffic emission inventories for urban air quality modeling in Madrid (Spain)

Madrid is one of the many urban agglomerations that are struggling to meet NO2 air quality standards in Europe. According to previous studies, road traffic is responsible for 57% of total NOx emissions in the Madrid metropolitan area and up to 90% of NO2 ambient concentration in the city center. Therefore it is utterly important to compile reliable emission inventories for this sector so specific measures and policies can be designed and assessed. This contribution discusses a field campaign made in Madrid to produce accurate input information as well as the models and methods used to compute emissions in a consistent way. The vehicle fleet characterization study made use of already available resources of the Madrid Municipality (traffic cameras in 55 locations across the city). Information of nearly 5 million plates was captured and crossed with the database of the National Traffic Authority to map vehicles into the 199 categories considered by the COPERT 4 software (EMEP/EEA methodology). Traffic intensities and average speed were provided by the regional traffic-demand model used by the Madrid Municipality. Additional information (traffic signs, detail ed vehicle trajectories, signal lights phases, etc.) was collected to feed a microscale traffic model (VISSIM) needed to generate instantaneous speed and acceleration data for a hot-spot (a heavily-trafficked roundabout). Emissions with resolution of seconds and meters were computed with ENVIVER (emission factors from VERSIT+) for this particular area. The results were aggregated and compared with those from the mesoscale model(COPERT) as a preliminary assessment for this approach