air quality assessment & management
Reference and User Manual
AirWare   On-line Reference Manual
  Release Level 7.0
  Revision Level beta
  Release Date 2015 03

Emission factors: traffic

Emissions for traffic sources are taken by the models from the emission data base, associated with each line source.

The emission values are either directly entered with the respective line source, or can be estimates from source specififc data (COPERT4 V8, hot emission factors) on

  • vehicle class (defined in the fleet composition object)
  • average speed over a segment
  • traffic frequency over all classes
  • road type or category and road type correction factor
  • coald start fraction and correction factor
  • data base tables of vehicle class, speed, and pollutant specific emission factors
  • correction factors for cold starts and road type.
together with the temporal emisison patterns Please note that the emission factor table can be extended and edited by the user, subject to matching pollutant names in the table and the line source emission table.

The calculation strategy

The basic emission estimates are simple: the emisison factor defines the amount of pollutant generated ( in g/km) from a single vehicle of the gfiven category in the given speed range. This is then converted to the required emission unit of g/ms per segment by correcting for the number of vehiclea and their distribution, segment length, and average speed. Optional corrections for colds start trips and road type can be applied.

The emission inventory primarily uses direct emission estimtes; If and only IF no direct emission estimate is in the data base (for any or all of the pollutants), the estimation is attempted IF and only IF all necessary data for indirect estimation are defined. Then, whenever the emission inventory is recalculated (the button: RECALCULATE) is pressed) missing, undefined emission values will be replaced with the emission factor derived estimates wherever possible. Estimated values are marked in the display of individual OBJECT (line source segments)

Emission factor editing

The Emisison factors can be edited directly in the table for each vehicle class with the standard interactive editor tool.
  • For each vehicle class (user defined in the Descriptor vehicle_class the Knowledge Base) the user can add or delete vehicle classes as required;
a matrix is defined by
  • The set of speed classes, defined by the user as upper and lower bounds in the data records;
  • The set of pollutants considered is again user defined in a Descriptor in the knowledge base. The standard set includes:

    • NOx, CO, VOC, PM10, CH4,NH3, N2O FC

The data base structure is defined as follows:

    Database:       AIR
    Table:             EMISSION_FACTOR
    ID            int(10) unsigned
    DESCRIPTOR    varchar(64)
    VALUE         varchar(255)
    primary key   (ID, DESCRIPTOR)
    Valid descriptor/ value pairs are:
    OWNER=Text (=username)
    Traffic:    CLASSID=83
       emission_factor_speed_step=int (default 30)
       Factors are stored as 'pollutant,vehicle class,speed classification (starting with 1)'
          eg."NO2,gasoline_car_pre-EURO,1, EMISSION_FACTOR"

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