On-Road Vehicle Testing and Characterization

Vehicle testing for fuel economy and emissions is typically performed indoors over standard dynamometer drive schedules to minimize variability and maximize repeatability of the results. In contrast, during on-road operation, operational parameters such as vehicle speed and acceleration and environmental factors such as temperature and wind will change unpredictably. These factors influence vehicle fuel economy and emissions, making on-road operation much more variable than dynamometer results. However, even though on-road conditions may be unpredictable, the on-road operational data can still be used to characterize vehicle performance. This paper describes the development of an on-road vehicle test methodology, with a focus on accounting for on-road factors with a high degree of accuracy while requiring only an achievable and reasonable amount of data. To develop this methodology, a 2016 Honda Civic was instrumented and driven multiple times over a route covering urban, rural, and freeway segments. Vehicle operational data, environmental conditions, fuel consumption, and emissions were recorded. The route was divided into segments and drive cycle parameters were calculated for each segment. Simple empirical equations were developed for this vehicle correlating fuel consumption with drive cycle parameters and the environmental conditions. The empirical models were compared to fuel consumption data from dynamometer tests with good results. Criteria pollutants (CO, NOx, and THC) were also measured and compared to dynamometer data. Finally, the amount of testing and data required to adequately characterize vehicle performance is discussed.