air quality assessment & management
Reference and User Manual
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
The calculation strategyThe 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 editingThe Emisison factors can be edited directly in the table for each vehicle class with the standard interactive editor tool.
The data base structure is defined as follows:
Database: AIR Table: EMISSION_FACTOR Structure: ID int(10) unsigned DESCRIPTOR varchar(64) VALUE varchar(255) primary key (ID, DESCRIPTOR) Valid descriptor/ value pairs are: LOCATIONID=53 NAME=Text OWNER=Text (=username) DESCRIPTION=Text Traffic: CLASSID=83 em_factor_type=traffic emission_factor_min_speed=int emission_factor_max_speed=int 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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