ASSESSMENT OF REAL DRIVING EMISSIONS OF A BUS OPERATING ON A DEDICATED ROUTE

Abstract

The reducing of real driving emissions from public transportation which is using intracity lines has become more important in recent years. This is because the petroleum derived fuel combustion products contributes the global warming as well as adversely the air quality. The fuel consumption perspective is another major economical concern for operating companies that should be optimized. In this context a part of Istanbul Metrobus public transportation system of which is using fully a dedicated line is assessed via on board emission and fuel metering devices for two loading conditions. The relevant vehicle and engine operating data is logged during the tests. The logged data is post processed for developing the average emission factors. The results are also analyzed from acceleration and altitude change perspective and alternative scenarios are discussed for cleaner and economic operation. Lastly the in-service conformity parameters are identified and the results are compared with homologation values. It was found that for the same velocity, acceleration affect was found significant and the critical acceleration level is determined as 0.4 m/s (2). For NOx, and CO emissions velocities smaller than 20 km/h and 40 km/h was found dominant at positive acceleration zones. Also for fuel consumption and CO2 emission levels the velocities higher than 30 km/h was found critical for all positive acceleration levels. It was shown that the real driving and emission data can be used efficiently for developing more environmentally friendly engine calibrations and decreasing fuel consumption and emissions.