Comparison of emission factors for road traffic from a tunnel study (Gubrist tunnel, Switzerland) and from emission modeling

The emission factors of NOx, VOC and CO of a road tunnel study performed in September 1993 in the Gubrist tunnel, close to Zurich (Switzerland) are co mpared with results of emission calculations based on recent results of dyn amometric test measurements. The emission calculations are carried out with a traffic emission model taking into account the detailed composition of t he vehicle fleet in the tunnel, the average speed and the gradient of the r oad and the special aerodynamics in a tunnel. With the exception of NOx emi ssion factors for heavy duty vehicles no evidence for a discrepancy between the results of the tunnel study and the emission modeling was found. The m easured emission factors of individual hydrocarbons of light duty vehicles were in good agreement with the expectations for most components. (C) 1999 Elsevier Science Ltd. All rights reserved.