Municipal authorities are forced by law to examine the concentrations of
selected air pollutants in streets. A system of measuring gauges to
ascertain these data featuring a wide spatial and temporal value range
is impossible to build not at least because of financial aspects.
Municipal authorities are imposed to take action in finding ways to
decrease high concentrations in case of detecting concentrations
exceeding concentrations defined by law. The cost efficient use of
models fits these requirements.
The program IMMISluft is particularly developed for this
purpose models the emission of motor vehicle traffic and its spreading
in the urban streets. The model is already applied by a great number of
IMMISluft models traffic induced air pollution in city
street canyons. It is based on the CPB model for street canyons and a
box model for open building structures.
A series of preprocessing programs is used to caculate the meteorology
frequency and the traffic frequency in the CPB and box model (see illustration).
Traffic and meteorology are dependent characteristics as both depend on
the time of day, for example. Dispersal conditions at night are
frequently unfavourable, but traffic is also generally lighter. The
atmosphere is more turbulent during the day and traffic is also heavier.
Because traffic and meteorology are not independent of one another, the
main relationship, namely the day-night relationship, is considered.
IMMISluft calculates air pollutant concentration levels
combining tables of coupling constants for day-night relationship from
traffic and meteorology generated statistics and from a table of the
emission factors with traffic composition statistics for particular
streets, the DTV (average daily volume of traffic) and relevant wind