In this paper wind tunnel dispersion tests and accompanying numerical simulations
of the planned north section of the Budapest ring motorway M0 are reported. The investigated
suburban area is located between hills and several tunnels and viaducts are planned.
Wind tunnel tests were carried out on a 1:1000 scale model containing topography,
buildings and vegetation in a Göttingen-type wind tunnel. Road segments were modeled
as line sources, tunnel portals as point sources with horizontal momentum. Concentrations
were measured in 50
sampling points. Numerical simulations of the same case were performed using the MISKAM
code. Using both methods, large pollutant plumes near tunnel portals were observed,
reaching also populated areas far from the motorway. In consequence, extension of
the tunnel ventilation system by ventilation stacks was proposed. Effect of the stacks
was proven numerically.