Over the last decade or so, epidemiologists have found increased incidence of a range of diseases, including pulmonary, cardiovascular and neurological, related to exposure to traffic-related air pollution. To obtain a better understanding of which pollutants near roadways are responsible, the UC Davis Environmental Health Science Center along with two NIEHS R21 grants supported construction of a vivarium adjacent to a traffic tunnel in the San Francisco bay area. Laboratory animals breathe air drawn from the tunnel and then are examined for a range of adverse health effects. The results of this work will identify which adverse health effects are exacerbated near roadways, which pollutants are responsible for these diseases, and how to remedy these problems.