PDF version-A +A

Traffic

 

Air pollution caused by exhaust - and non exhaust pipe emissions

Traffic induced air pollution is still responsible for the largest contribution to air pollution in our cities. Therefore our laws demand - for example in the licencing process for new roads - an Environmental Impact Assessment (EIA), containing information about the present and future air pollutant concentrations in the sphere of influence of that road.

Predictions of the modification of air pollutant concentrations are also necessary - for example in the frame of the German 23. BImSchV or the EU Air Quality Directives, in case action plans have to be developed for the decrease of air pollutant concentrations.

Examples for applications are in the frame of:

  • Design/extension for circumferencial roads, tunnels, bridges, noise barriers, dams etc.
  • Determination of hot spots of air pollutions in cities and development of action plans for 23. BImSchV and EU Air Quality Directives
  • Design and operation of underground garages, multistory car parks as well as gas stations and motorway service stations in the vicinity of living - and recreational areas
  • Design of new living - or industrial areas, inducing additional traffic volume
  • Design/extension of waterways, harbours, locks
  • Design/extension of airports

How do we do calculate air pollutant concentrations?

For the prediction of traffic induced air pollutant concentrations we offer you procedures, specific to the individual stages of the planning process. For a first estimation or in case of simple boundary conditions (for example low traffic volume and unobstructed dispersion), simple procedures can be applied. Assessments including complete road nets, complex flow conditions within city centers, dispersion in narrow valleys or in the vicinity of tunnel months usually require the application of more sophisticated methods.

Roads outside cities without or with few adjacent buildings

  • Estimation of the concentrations in the vicinity of roads without or with few adjacent buildings according to the Code of Practive RLuS.
  • Calculation of emissions and concentrations using the line source plume model PROKAS-V for road nets. PROKAS is capable to calculate concentrations by road nets including intersections, bridges and tunnels.
  • Dispersion modelling, using the Lagrangian dispersion model LASAT within areas with marked topography, if necessary including regional or local wind systems, for example valley drainage flows.

Road with major adjacent buildings, areas within cities

  • Estimation of the concentrations for locations at streets in densely built-up areas (street canyons), using PROKAS-B for defined, characteristic typs of adjacent buildings. PROKAS-B is based on the results, obtained by MISKAM for classified building configurations.
  • Calculation of the emissions and concentrations using the line source model PROKAS-V for road nets to determine the local background concentration and using MISKAM. MISKAM is a 3-dimensional numerical model to calculate the flow and dispersion in built-up areas. Buildings and other obstructions of flow are modelled by rectangular or triangular blocklike structures.
  • Calculation of the concentrations on the basis of measurements in the windtunnel using scaled physical models. These results can be combined with calculations by PROKAS.

Waterways

  • Estimation of the ship induced air pollution concentrations at waterways, using the program system LuWas, developed in our company under consideration of the influence of locks, canals, berths, waiting slots as well as 14 different types of ships

Airports

  • Emission modelling and dispersion modelling using the Langrangian model LASAT

Steps to calculate traffic induced air pollutant concentrations

First step to calculate concentrations is to determine the emissions, based on traffic volume, emission factors and characteristic driving behaviour:

  • Traffic volume (Average daily traffic, truck content)

  • Emission factors
    Determination of emission factors for the single roads on the basis of the characteristic driving behaviour (traffic situation) using the Emission Factor Handbook (UBA/INFAS, 2004)


 

  • Charasteristic driving behaviour

As interim result are obtained the emissions of the air pollutants under consideration in [mg/(ms)].

With the

  • Emission densities of the air pollutants (for each road segment) as a function of time

  • the atmospheric stability and dispersion class statistics

  • and the background concentration

the concentrations are calculated using the dispersion model and the statistics modul.

Typical results of the calculations are:

  • Prediction of the annual mean, 98-percentiles, numbers of exceedences of limit values
  •  Concentrations for single points or averaged over certain areas
  • Total emission of the road net unter consideration
  • Balancing of concentrations weighted with sensitivity criteria

The following figure displays as an example the total NO2-concentrations (98-percentile).