Real-world automotive emissions: Monitoring methodologies, and control measures

Vehicular emissions make significant contribution to the total ambient airborne pollutants. Global warming and human health concerns are motivating researchers to come out with newer ways of controlling air pollution effectively. On the other hand, there are significant challenges in complying with current and upcoming vehicle emission regulations, which are quite stringent. It is therefore quite important to monitor vehicular emissions closely, which can facilitate adopting effective control measures when necessary, and also in predicting the impact of vehicular emissions on ambient air quality. Traditionally, dynamometers (both engine and chassis) testing has been used extensively to measure and monitor vehicular emissions, and the database generated has been used as input in modeling the traffic-related air quality impact. Even though standard driving cycles are followed in dynamometer tests attempting to closely replicate real-world driving conditions, they may not necessarily represent actual real-world driving conditions and emissions thereof. Therefore, in recent years, significant scientific efforts have been directed to measure and analyze real-world driving emissions (RDE) from vehicles. In this paper, the state-of-the-art techniques and methods for vehicular emissions monitoring under real-world driving conditions are reviewed and discussed in detail. Different vehicle emissions monitoring methods are presented in comparison to dynamometer-based measurements. Several influencing factors which affect on-road and in laboratory measurements are identified and discussed. Potential applications of different emission control strategies are reviewed. Finally, guidelines are formulated for effective vehicular emissions monitoring, and to minimize discrepancies between on-road and laboratory based measurements, in order to have a sustainable road transport system in future.