GASEOUS EMISSIONS FROM VEHICLES IN A TRAFFIC TUNNEL IN VANCOUVER, BRITISH-COLUMBIA

In August 1995, measurements of CO, NOx, speciated nonmethane hydrocar bons (NMHC), and CO2 were made in Vancouver's Cassiar Connector, a 730 -m-long level-grade highway traffic tunnel. Two characteristics of the Vancouver setting are the presence of many propane vehicles and a man datory inspection and maintenance (I/M) program. Although the driving conditions and vehicle fleets are otherwise outwardly similar to those of recent Tuscarora-tunnel studies, CO/NOx ratios at the Cassiar Conn ector are significantly lower than those measured at Tuscarora. The Ca ssiar measurements are consistent with the MOBILE5A mobile emissions m odel predictions. The Canadian version of MOBILE5A-known as MOBILE5C-g ives nearly identical results, indicating that differences in Canadian and U.S. emission standards cannot explain differences between Cassia r and U.S. tunnels. Considering the modeling results as well as measur ed ethene/acetylene ratios indicative of noncatalyst vehicles, it appe ars that vehicle deterioration remains the major issue in in-use vehic le emissions-even in Vancouver, where there is a mandatory loaded-mode I/M program. Uncertainties in determining the ages of the vehicles in the tunnel, however, have a significant impact on the model predictio ns.