The Ruhr area is the biggest German megalopolis, a conglomerate of several intertwining major cities, with more than
3.5 million inhabitants. In spite of many efforts in recent years to improve the air quality in the Ruhr area, especially residents in
street canyons with a high traffic density are still exposed to poor air quality, and meeting the limit values of European air quality
directives for PM10 and NO2 remains a challenge. In this study, the hot spots in the area have been identified by a combination of
measurements and modeling. Shares of industry, shipping, rail traffic, off-road traffic and heating were calculated. The road
network of the Ruhr area was mapped with housing data in order to identify road sections with possibly affected inhabitants. The
concentrations caused by local road traffic were then calculated with the screening model IMMISluft. Such, a road network of more
than 3000 km in length and with over 8000 inhabited sections was investigated. In quite a large number of these sections, air quality
was identified to be rather poor and measures have to be taken to improve the situation. One possible measure is the implementation
of low emission zones. In the study, effects on air quality have been calculated for different scenarios of low emission zones. Due to
the methodology, source apportionments for hot spots are easily available
