DISPERSION MODELING NEAR TUNNEL EXITS - SIMULATION AND MEASUREMENTS

Measurements of car exhaust gases were made in May/June 1995 in the vi cinity of the Bielefeld tunnel. CO and NOx from car exhausts were meas ured to allow comparison with a model simulation. Ozone was also measu red. These measurements were made using commercial continuous analyser s. A valve control system was used to investigate the dispersion of th e trace gases. This allowed measurements at up to 15 locations within a short period. Thus only one analyser was required for measurements a t all 15 points. Following the measuring campaign the topography in th e vicinity of the Bielefeld tunnel was digitized. A flow and dispersio n model called MISCAM (Micro Scale Air pollution Model) was then utili zed. Results from the simulation were compared with the measurements. Comparison of the measurements with the simulation validate the simula tion results for inert trace gases such as CO and NOx. The deviation b etween measurements and simulation is about 16%.