ON-BOARD EMISSION MEASUREMENTS ON PETROL-DRIVEN CARS AND DIESEL CITY BUSES

Emissions of petrol cars and diesel city buses were determined using a n on-board measuring system. Six three-way catalyst (TWC) cars and one carburetted non-catalyst car were measured. In real traffic situation s, TWC cars emitted more than expected from laboratory measurements. A ggressive driving in urban and rural traffic increased the CO, HC and NOx emissions by a factor of between 1.2 and 3 compared with normal dr iving. Cars yielding low emissions during the European type approval a re not automatically low-emitting cars in real traffic. One old 'Euro- 0', two Euro-1 and two Euro-2 buses were measured on regular city line s. The CO, HC and NOx emission ranges were, respectively, 2-9, 1-3 and 16-23 g/km. The lowest CO emissions were for the Euro-2 buses. The HC emissions were lowest for the Euro-1 buses and highest for the 'Euro- 0' bus. The NOx levels were high and about equal for all buses. When c omparing the emissions of the 'Euro-0' bus with the 1990 emission fact ors of The Netherlands, the agreement was fairly good for CO and NOx e missions, but the HC emissions were only half of the emission factor.