Concentrations measured in the present study are lower
than those reported for the Marquês tunnel in Lisbon. Higher
traffic levels, frequent congestions, and a strong steep slope
justify the higher pollutant levels inside the tunnel of the
Portuguese capital. However, in both studies, themajor particle
components coincide and there are similarities with regard to
either the mass fractions of the various constituents in the
particulate material or the size distributions.