Identifying NOx Hotspots in Transient Urban Driving of Two Diesel Buses and a Diesel Car

Abstract

NO x emissions from vehicles have been a substantial cause for concern due to their impact on urban air quality. In particular, despite reducing levels of permitted emissions legislatively, such reductions have not been observed in the real world. In this work, NO x emissions from three vehicles-a Euro 5 car, a Euro V hybrid bus, and a Euro VI-bus have been measured in real driving conditions (and in the case of the buses-in full passenger service). A recently developed high spatio-temporal resolution technique combining very fast (10 ms) NO x measurement with differential GPS accurate to 1 cm allows these emissions to be resolved to a distance of less than 10 cm (worst-case-dependent on vehicle speed). The results show that acceleration events for the vehicles play a significant part in their total NO x emissions. In addition, standard events such as a speed bump and a bus stop are analysed. The temperature of any aftertreatment (catalytic converter) to reduce NO x emissions is also observed to be of substantial significance. At idle, the passenger car was observed to near-double its NO x emissions when the air conditioning was switched on. Finally, the real driving conditions are compared to the legislative compliance cycles for the certification of the buses, and those results used to further understand the observed NO x emissions.

Impacts of emergency health protection measures upon air quality, traffic and public health: evidence from Oxford, UK

“…Decreases in activity levels from other combustion sources, such as power plants and industry may have contributed to the decline in NO 2 emissions, but the relatively small and non-significant (deweathered, detrended) decline in NO concentrations at the urban background site suggests these were not substantial for this location. In this study we did not consider the influences of driving behaviour such as mean speeds or acceleration events upon NO 2 emissions (Leach et al, 2020); research which considers these factors could provide further relevant insights at the studied location.…”

Assessment of Gaseous and Particulate Emissions of a Euro 6d-Temp Diesel Vehicle Driven >1300 km Including Six Diesel Particulate Filter Regenerations

“…In most cases, though, the engine and the after-treatment systems calibration was mainly covering the laboratory homologation test conditions but not other conditions typically encountered on the road. On-road calibration has to cover a wide range of ambient conditions (temperature, altitude) and driving events (e.g., speed bumps, traffic, higher vehicle dynamics, altitude) [27][28][29], and is therefore more demanding. The widespread introduction of Selective Catalytic Reduction for NO x (SCR) systems using urea to reduce NO x [30] and proper optimization for a big part of the engine map, has resulted in low NO x emissions.…”

Alternative Exhaust Emission Factors from Vehicles in On-Road Driving Tests

“…In the work of Leach et al [12], NO x emissions from three vehicles (a Euro 5 car, a Euro V hybrid bus, and a Euro VI) were measured under real driving conditions. The results show that vehicle acceleration events play a significant role affecting their total NO x emissions.…”