Real-world emissions of a traffic fleet on a transit route in Austria were determined in the Tauerntunnel experiment in October 1997. The total number of vehicles and the average speed was nearly the same on both measuring days (465 vehicles 30min(-1) and 76kmh(-1) on the workday, 477 and 78 kmh(-1) on Sunday). The average workday fleet contained 17.6% heavy-duty vehicles (HDV) and the average Sunday fleet 2.5% HDV resulting in up to four limes higher emission rates per vehicle per km on the workday than on Sunday for most of the regulated components (CO2, CO, NOx, SO2, and particulate matter-PM10). Emission rates of NMVOC accounted for 200 mg vehicle(-1) km-l on both days. The relative contributions of light-duty vehicles (LDV) and HDV to the total emissions indicated that aldehydes, BTEX (benzene, toluene, ethylbenzene, xylenes), and alkanes are mainly produced by LDV, while HDV dominated emissions of CO, NOx, SO2, and PM10. Emissions of NOx caused by HDV were 16,100 mg vehicle(-1) km(-1) (as NO2). Produced by LDV they were much lower at 360 mg vehicle(-1) km(-1). Comparing the emission rates to the results that were obtained by the 1988 experiment at the same place significant changes in the emission levels of hydrocarbons and CO, which accounted 1997 to only 10% of the levels in 1988, were noticed. However, the decrease of PM has been modest leading to values of 80 and 60% of the levels in 1988 on the workday and on Sunday, respectively. Emission rates of NO, determined on the workday in 1997 were 3130mg vehicle(-1) km(-1) and even higher than in 1988 (2630mg vehicle(-1) km(-1)), presumable due to the increase of the HD-traffic. (C) 2001 Elsevier Science Ltd. All rights reserved.
