REALISTIC DRIVING CONDITIONS FOR MEASUREM ENT OF POLLUTION EMISSIONS AND FUEL CONSUMPTION OF PASSENGER VEHICLES ON A CHASSIS DYNAMOMETER

Fuel consumption and pollutant emissions from vehicles are mainly a fu nction of the vehicle's use (journey type. frequency, etc...) and of t he vehicle's operating conditions (speed, engine speed, rates of accel eration, temperature conditions, etc...) and depend on both the traffi c conditions and the individual behaviour of the driver. Thus, a reali stic assessment of emissions, pollution reduction methods and the effe ctiveness of emission control technologies cannot be carried out witho ut taking into account the actual operating conditions of the vehicles . For that reason, a project modem (Modelling of Emissions and Fuel Co nsumption in Urban Areas - DRIVE project UI053) has been carried out w ithin the EC DRIVE (Dedicated Road Infrastructure for Vehicle Safety i n Europe - EEC research programme - DGXIII) programme to develop model s of vehicle emissions in terms of traffic operations. Part of the pro ject was a large scale experiment to measure engine and vehicle operat ing conditions during normal driving. A total of 58 private cars were equipped with sensors and data acquisition systems to record details o f their use by their owners over a period of about 1 month. Over 8200 trips were monitored, covering more than 73 000 km of travel, during w hich the vehicle speed, engine speed, temperatures and other variables were recorded at 1-s intervals. 'Kinematic sequences' were defined as the periods between two successive stops of the vehicle and these wer e used to characterize the traffic conditions, which were assumed to b e homogeneous throughout each 'sequence'. The main categories of seque nces (urban, non-urban and motorway) were identified by factorial anal ysis and classifying techniques and each sequence was assigned to a ca tegory. An analysis of the way in which the sequences were linked duri ng a trip and statistics on trip lengths were used to develop realisti c and statistically significant test cycles representing different urb an traffic conditions. The cycles were created by recombining real seq uences, randomly selected in accordance with the results of the statis tical analyses. These cycles were then used on a chassis dynamometer f or accurate measurements of exhaust emissions and fuel consumption on a large sample of vehicles. This paper describes the statistical analy sis of the vehicle operation data and the development of the test cycl es.