Sn. Rogak et al., GASEOUS EMISSIONS FROM VEHICLES IN A TRAFFIC TUNNEL IN VANCOUVER, BRITISH-COLUMBIA, Journal of the Air & Waste Management Association, 48(7), 1998, pp. 604-615
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.