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

Emissions of petrol cars and diesel city buses were determined using an on–board measuring system. Six three–way catalyst (TWC) cars and one carburetted non–catalyst car were measured. In real traffic situations, TWC cars emitted more than expected from laboratory measurements. Aggressive 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 driving. Cars yielding low emissions during the European type approval are not automatically low–emitting cars in real traffic. One old 'Euro–O', two Euro–l and two Euro–2 buses were measured on regular city lines. 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 comparing the emissions of the 'Euro–0' bus with the 1990 emission factors of The Netherlands, the agreement was fairly good for CO and NO, emissions, but the HC emissions were only half of the emission factor.